Mardi 06 juillet
10:30

Mardi 06 juillet

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A1
10:30 - 12:00

Ouverture
Accueil - Mot de présentation - Conférence inaugurale

10:35 - 10:40 Introduction par la Présidente de la SFµ. Catherine VENIEN-BRYAN (Professor) (Paris)
10:30 - 10:35 Mot d'accueil d'un représentant de l'Université de Reims.
10:40 - 10:55 Introduction par le Président du Comité Local d'Organisation. Jean MICHEL (Reims)
10:55 - 11:40 Voyage au cœur d’une flûte de champagne. Gérard LIGER-BELAIR (Equipe Effervescence, Champagne et Application, GSMA)
Depuis quelques années maintenant, le champagne et les vins à bulles au sens large connaissent un essor sans précédent. La valse des bulles dans une flûte n’est pas étrangère à cet incroyable engouement. L’effervescence qui agite votre verre engendre une kyrielle de phénomènes d’une complexité insoupçonnée, qui met en éveil tous vos sens. Nous proposerons une vue d’ensemble des phénomènes qui accompagnent une dégustation de champagne, depuis le débouchage de la bouteille, jusqu’à l’éclatement d’une bulle, en passant par le rôle essentiel du verre en dégustation. Profondément inscrite dans l’imaginaire collectif, la bulle de champagne devient prétexte à une flânerie scientifique qui nous entraîne dans le monde fascinant des gaz dissous, des changements de phase et des fluides en mouvement.

Gérard Liger-Belair est professeur à l'université de Reims Champagne-Ardenne, où il dirige un laboratoire de recherche dévolu à l’étude des bulles et des gaz dissous. Il est l'auteur d'une centaine d'articles de recherche et d'une dizaine d'ouvrages universitaires et à destination du grand public.
11:40 - 12:00 Discussion.
Room 1
12:10 Pause
13:10

Mardi 06 juillet

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SC1
13:10 - 15:45

Symposium Commun 1
Avancées instrumentales et développements méthodologiques

Modérateurs : Florent HOUDELLIER (IR) (CEMES, Toulouse), Wai-Li LING (IBS, Grenoble)
Les développements instrumentaux et méthodologiques récents en microscopie touchent aussi bien les applications dans la science de la vie que dans la science des matériaux. La volonté d’étudier des échantillons sensibles, tout en augmentant les limites de résolution et de détection des instruments actuels, poussent les développements vers de nouveaux détecteurs plus sensibles, des méthodes d’acquisitions et de traitements plus rapides mais aussi de nouvelles méthodes de préparation et d’analyse des matériaux en utilisant des sources innovantes. Les sujets de ce symposium incluent, mais sans s'y limiter, de nouveaux algorithmes et méthodes pour augmenter l’efficacité et repousser les limites des microscopes tel que la détection pixélisée en STEM, des balayages non conventionnels, des nouveaux modes optiques comme l’utilisation de déflecteurs ultra-rapides dans le cas des approches pompe-sonde, l’automatisation du microscope, etc.
13:10 - 13:40 FIB from cold atoms. Matthieu VITEAU (Orsay Physics)
Charged particle beams of controlled energy and strong focusing are widely used tools in industry and science. Focused Ion Beam (FIB) column combine with a Scanning Electron Microscope (SEM) provide full control of nanofabrication or nanolithography processes. Ion energy can be varied typically in the 0.5–30KeV range, with an energy-dependent resolution attaining the nanometer range. State-of-the-art FIBs commercially available are based mainly on plasma, liquid metal tip or helium ion sources for large, intermediate, and low currents, respectively. Despite the very high technological level of the available machines, research of new ion sources allowing even higher resolution and a wider choice of atomic or molecular ions for new and demanding application is very active.
As an example, the world of electronic components evolves regularly towards the miniaturization by integrating a number of transistors more and more important. The dimensions being smaller and smaller (technology 7 nm, 5 nm even 3-2 nm), nowadays the instruments of analysis used, like the conventional FIB, reach their limit. Thus it’s necessary to realize a technological breakthrough to be able to observe, analyze and modify components and structures on the scale of the nanometer. The performances of a focused particules beam (FIB or SEM) are mainly given by the source.
After more than 10 years of research and developpement, the idea to cool down atoms and ionize them for the production of a charged beam with a high brightness is quite mature.
In this presentation I’ll introduce the principel of these cold sources and discuss the status of differents cold atoms sources for ions, and focus on our prototype [1].


References:
[1] L. Antoni-Micollier, et al., Optics letters, Vol. 43, No. 16 (2018), p.3937
13:40 - 13:50 Discussion.
13:50 - 14:20 Two-photon optogenetics, shaping light for the precise study of neuronal circuits and deep brain structures. Nicolò ACCANTO (Institut de la Vision, Paris)
In recent years the use of light has established itself as one of the most prominent tools for the study of the brain: genetically encoded calcium indicators enable to image neurons firing [1], while optogenetics has provided the key to activate neurons with light [2]. To date, optogenetics has been mainly used to activate entire brain regions, thus unveiling the links between neural activity and behaviour in different areas of the brain [3]. However, to really decrypt the neural code, we now need to understand how the spatial and temporal organization of neural activity at the single cell level influences brain computation.
Such a shift of paradigm, from the study of entire brain areas to that of single neurons and single neuronal circuits, can only occur with a parallel advancement of the optical technologies used to study the brain. Today, we need advanced optical methods capable of (1) precisely targeting hundreds of neurons at will with high spatio-temporal precision; (2) reaching very
deep brain regions while maintaining high performances.
To reach these objectives, in our group we combine two-photon (2P) light shaping with optogenetic photo-stimulation and the use of optical micro-endoscopes that can relay these techniques to deep brain regions. Recently, we demonstrated multiplexed temporally focused light shaping (MTF-LS), a technique capable of simultaneously generating hundreds of 2P excitation patterns in large volumes, suitable for the precise optogenetic photo stimulation of many neurons in the three dimensions [4]. Next, we extended MTF-LS to a micro-endoscope based on the use of a gradient index (GRIN) lens, which constitutes an important step for the precise optical study and manipulation of deep brain circuits [5].
In this talk I will detail our latest works and give a perspective on future studies.

References
1. Knöpfel (2012), Nat. Rev. Neurosci., 13, 1, DOI: 10.1038/nrn3293 2. Deisseroth (2011), Nat. Methods, 8, 26, DOI: 10.1038/nmeth.f.324 3. Jennings et al. (2013), Nature, 496, 224, DOI: 10.1038/nature12041 4. Accanto et al. (2018), Optica, 5, 1478, DOI: 10.1364/OPTICA.5.001478 5. Accanto et al. (2019), Sci. Rep., 9, 7603, DOI: 10.1038/s41598-019-43933-w
14:20 - 14:30 Discussion.
14:30 - 14:45 #26203 - Imagerie vectorielle tridimensionnelle des polaritons de phonons de surface.
Imagerie vectorielle tridimensionnelle des polaritons de phonons de surface.

Xiaoyan Li *, Georg HaberfehlnerUlrich HohenesterOdile StéphanGerald KothleitnerMathieu Kociak,

  • Université Paris-Saclay, CNRS, Laboratoire de Physique des Solides, 91405 Orsay. France.
  • Institute of Electron Microscopy and Nanoanalysis, Graz University of Technology, Steyrergasse 17, 8010 Graz, Austria.
  • Institute of Physics, University of Graz, Universitätsplatz 5, 8010 Graz, Austria.
  • Université Paris-Saclay, CNRS, Laboratoire de Physique des Solides, 91405 Orsay. France.
  • Institute of Electron Microscopy and Nanoanalysis, Graz University of Technology, Steyrergasse 17, 8010 Graz, Austria.
  • Université Paris-Saclay, CNRS, Laboratoire de Physique des Solides, 91405 Orsay. France.


Surface phonon polaritons (SPhPs) are mixed electromagnetic and optical phonons waves that propagate at the surface of ionic materials [1]. They strongly influence the optical and thermal behavior of nanomaterials. For example, they are responsible for highly coherent emission of SiC upon heating, in stark contrast with the conventional incoherent black-body radiation [2). They also induce enhanced thermal conduction in thin membranes [3] or heat transfer between two nanosurfaces [4]. These applications rely on the nanostructuration of the electromagnetic field in the vicinity of surfaces of metamaterials or nanoparticles. Designing or even engineering the electro-magnetic local density of states (EMLDOS) for specific functionalities require therefore the unambiguous visualization of such field modulations at the nanometer scale. Recently, EELS in a scanning transmission electron microscope (STEM) made it possible to measure phonons spectra at the nanometer [5, 6], then atomic scales [7]. Nevertheless, they were restricted to 2D imaging, and not able to reveal the complete three-dimensional vectorial picture of their electromagnetic density of states. Using a highly monochromated electron beam in a scanning transmission electron microscope, we could visualize varying SPhPs signatures from nanoscale MgO cubes as a function of the beam position, energy-loss and tilt angle, see Fig 1. Following early works on plasmons [8,9], the SPhPs response was described in terms of eigenmodes and used to tomographically reconstruct the phononic surface electromagnetic fields of the object [10]. Such 3D information promises novel insights in nanoscale physical phenomena and is invaluable to the design and optimization of nanostructures for fascinating new uses. Références/References : [1] Kliewer, R. Fuchs, Theory of dynamical properties of dielectric surfaces, vol. 27 (1974). [2] J. Greffet, et al., Nature 416, 61 (2002). [3] Y. Wu, et al., Science Advances 6 (2020). [4] B. Song, et al., Nature Nanotechnology 10, 253 (2015). [5] O. L. Krivanek, et al., Nature 514, 209 (2014). [6] M. J. Lagos, et al., Nature 543, 529 (2017). [7] F. S. Hage, et al., Science 367, 1124 (2020). [8] Nicoletti et al., Nature 502, 7469 (2013). [9] Hörl et al., Nature Comm. 8, 1 (2017). [10] X. Li et al., Science 371, 6536 (2021).
Yi XIAOYAN (Orsay)
14:45 - 14:55 Discussion.
14:55 - 15:10 #26204 - La microscopie électronique à transmission ultra-rapide pour l'étude des nanomatériaux.
La microscopie électronique à transmission ultra-rapide pour l'étude des nanomatériaux.

Matthieu PICHER *, Yaowei HuShyam Kanta SinhaJun SunAmir KhammariMarlène PalluelNathalie DaroGuillaume ChastanetNgoc Minh TranEric FreyszFlorian Banhart,

  • Institut de Physique et Chimie des Matériaux, CNRS UMR 7504, 67034 Strasbourg, France
  • CNRS, Univ. Bordeaux, ICMCB, UPR 9048, F-33600, Pessac, France
  • Laboratoire Ondes et Matière d’aquitaine (LOMA), 33405 Talence, France


Dynamic processes at the nanoscale are not accessible by conventional TEM because they happen at much shorter timescales than the millisecond. This restriction is nowadays being overcome by developing ultrafast TEMs working with short electron pulses. In this approach, the transformation of interest is triggered by a short photonic pulse. Then, a short electron pulse probes the sample after an adjustable delay, which allows collecting pieces of information about the reaction process along its advancing at precise time steps, that is, with high temporal resolution [1,2]. Behind such a particular setup which brings into play ultrafast lasers with a transmission electron microscope stands a remarkable instrumental opportunity to study light/matter interactions within the typical high spatial resolution of electron microscopy. Here, we present two examples of investigations that have been carried out with the UTEM in Strasbourg. 1. A non-time-resolved TEM study of the laser-induced amorphization of metal nanocrystals: an infrared nanosecond laser pulse leads to fast melting of the metal nanocrystal which then dissolves carbon atoms from surrounding graphitic species, and is followed by fast cooling. This rapid quenching does not allow structural ordering and leaves a metastable amorphous metal-carbon phase. This shows how short IR pulses irradiating encapsulated metal nanocrystals can be a route towards the fabrication and stabilization of otherwise unfavorable amorphous metal or metal-carbon phases. ([3], Fig1) 2. A temporally resolved study of Spin Crossover (SCO) switching phenomena, carried out with nanosecond pulses in a stroboscopic approach. Here, individual SCO nanoparticles encapsulating gold nanorods were subjected to IR pulses, which lead to plasmonic heating of the Au rods and consequently to the thermal spin transition of the SCO associated with a significant length change. This correlated elongation was monitored with nanosecond and nanometer resolutions, and compared with time-resolved optical measurements previously acquired on a large ensemble of SCO. (Fig2) Remerciements Funding by the Agence Nationale de Recherche (ANR-11-EQPX-0041,ANR-17-CE09-0010), by the University of Strasbourg Institute of Advanced Studies (USIAS), and the METSA Institute are gratefully acknowledged. Références [1] M.Picher, K.Bücker, T.LaGrange, F.Banhart, Ultramicroscopy,188,(2018),p41 [2] SK.Sinha, A.Khammari, et al., Nature Communications,10,(2019),p3648 [3] J.Sun, SK.Sinha, et al., Carbon,161,(2020),p495-501
Matthieu PICHER (Strasbourg)
15:10 - 15:20 Discussion.
15:20 - 15:35 #26209 - Sonder les interactions entre les bulles d'air et les (bio)-interfaces à l'échelle moléculaire en utilisant la technologie FluidFM.
Sonder les interactions entre les bulles d'air et les (bio)-interfaces à l'échelle moléculaire en utilisant la technologie FluidFM.

Understanding the molecular mechanisms underlying bubble-(bio)surfaces interactions is currently a challenge that if overcame, would allow to understand and control the various processes in which they are involved. Atomic force microscopy is a valuable tool to measure such interactions, but it is limited by the large size and instability of bubbles that can be attached on surfaces or on AFM cantilevers. To overcome these challenges, we here develop a new method to probe more accurately the interactions between bubbles and (bio)-interfaces by taking advantage of the fluidic force microscopy technology (FluidFM) that combines AFM with microfluidics. In this system, a micro-sized channel is integrated into an AFM cantilever and connected to a pressure controller system, thus creating a continuous and closed fluidic conduit that can be filled with a solution, while the tool can be immersed in a liquid environment [1]. An aperture at the end of the cantilever allows liquids to be dispensed locally. In this study, we use FluidFM in an original manner, to produce microsized bubbles of 8 µm in diameter, directly at the aperture of the microchanneled FluidFM cantilevers. For that, as shown in Figure 1 instead of liquid, the cantilever is filled with air and immersed in a liquid environment. By applying a positive pressure inside the cantilever, we succeeded in forming bubbles of controlled size directly at its aperture. Because the same pressure is maintained in the cantilever during the experiment, the dissolution of the gases from the bubble is compensated, which allows keeping the size of the bubble constant over time. After the characterization of the bubbles produced using this method, their interactions with hydrophobic surfaces were probed, showing that bubbles behave like hydrophobic surfaces. Thus they can be used to measure the hydrophobic properties of microorganisms’ surfaces, but in this case the interactions are also influenced by electrostatic forces. Finally we developed a strategy to functionalize their surface, thereby modulating their interactions with microorganisms’ surfaces. This new method provides a valuable tool to understand bubble-(bio)surfaces interactions but also to engineer them. 


Irem DEMIR (Toulouse)
15:35 - 15:45 Discussion.
13:10 - 15:45 Introduction.
Room 1
15:40 Pause
16:00

Mardi 06 juillet

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AG
16:00 - 16:40

Assemblée Générale - General Assembly

16:00 - 16:40 Présentation - Rapport Moral. Catherine VENIEN-BRYAN (Professor) (Paris)
16:00 - 16:40 Rapport Financier. Ilse HURBAIN (Ingénieur de Recherche) (Bures-sur-Yvette)
16:00 - 16:40 Rapport Financier. Katia MARCH (Orsay)
16:00 - 16:40 Bourses et soutiens. Catherine VENIEN-BRYAN (Professor) (Paris)
16:00 - 16:40 Changements de statuts. Catherine VENIEN-BRYAN (Professor) (Paris)
16:00 - 16:40 Prix de l'année. Catherine VENIEN-BRYAN (Professor) (Paris)
16:00 - 16:40 La vie des revues (BOC, EPJAP). Suzanne GIORGIO (Pr) (Marseille)
16:00 - 16:40 Notre implication avec les sociétés savantes. Catherine VENIEN-BRYAN (Professor) (Paris)
16:00 - 16:40 Appel à candidature pour le Colloque de 2023. Catherine VENIEN-BRYAN (Professor) (Paris)
16:00 - 16:40 Nomination du membre d'honneur. Catherine VENIEN-BRYAN (Professor) (Paris)
16:00 - 16:40 Questions diverses issues des adhérents. Catherine VENIEN-BRYAN (Professor) (Paris)
Room 1
16:50

Mardi 06 juillet

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A2
16:50 - 18:15

Remise des Prix
Prix Favard et Prix Castaing

Membre du bureaus : Suzanne GIORGIO (Pr) (Marseille), Catherine VENIEN-BRYAN (Professor) (Paris), Jean-Marc VERBAVATZ (IJM CNRS UMR 7592, Paris)
16:50 - 17:15 Prix Favard - Sciences de la Matière. Clément LAFOND
17:20 - 17:45 Prix Favard - Sciences de la Vie : Microscopie par génération de second harmonique (SHG) résolue en polarisation linéaire et circulaire pour caractériser l'organisation 3D du collagène. Margaux SCHMELTZ
17:50 - 17:56 Prix Castaing - Sciences de la Matière. François VURPILLOT (Rouen)
17:57 - 18:03 Prix Castaing - Sciences de la Vie. Graça RAPOSO
18:04 - 18:15 Présentation du Membre d'Honneur. Virginie SERIN (Prof.) (Toulouse Cedex), Didier BLAVETTE (Professor) (Saint-Étienne-du-Rouvray)
Room 1
Mercredi 07 juillet
09:40

Mercredi 07 juillet

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SC2
09:40 - 12:15

Symposium Commun 2
Méthodes d’imagerie volumique (SBEM, AT, FIB-SEM)

Modérateurs : Nicolas BROUILLY (IBD, Marseille), Williams LEFEBVRE (GPM, Rouen)
Les contributions concerneront des travaux menés par toute technique d’imagerie tridimensionnelle opérant depuis le micromètre jusqu’à l’échelle atomique et utilisée pour résoudre des problématiques liées au domaine du vivant ou des matériaux inorganiques. L’accent sera mis sur les cartographies tridimensionnelles de propriétés, l’imagerie 3D résolue en temps, la corrélation de données tridimensionnelles, l’analyse d’échantillons à plusieurs échelles au moyen de protocoles expérimentaux parfois périlleux et souvent originaux et toutes les approches émergentes dans le domaine de l’imagerie volumique.
09:40 - 10:10 The 3D approach in electron holography. Christophe GATEL (CEMES, Toulouse)
L’holographie électronique est une technique interférométrique permettant d’enregistrer le déphasage de l’onde ayant traversé l’échantillon. Ce déphasage permet d’obtenir des cartographies quantitatives à l’échelle du nanomètre des potentiels/champs électriques et magnétiques et d’accéder ainsi aux propriétés électromagnétiques locales du nanosystème étudié. Cependant ce déphasage provient d’une intégration le long du trajet électronique des potentiels et l’image finale obtenue n’est que la projection bidimensionnelle de configurations électromagnétiques tridimensionnelles. Il faut ainsi tenir compte des variations d’épaisseur, des champs rayonnés, d’artefacts de préparation et de l’effet de charge du faisceau électronique afin d’interpréter pleinement les résultats obtenus. Dans cet exposé, je montrerai les paramètres dont il faut tenir compte et les approches que nous avons développées pour reconstituer les configurations électromagnétiques tridimensionnelles des systèmes étudiés. Ces approches permettent à l’holographie électronique d’être considérée directement ou indirectement comme une méthode d’imagerie volumique.
10:10 - 10:20 Discussion.
10:20 - 10:50 Les techniques basées sur le MEB pour l’acquisition de larges volumes en science de la vie. Christel GENOUD (PME UNIL, Lausanne, Suisse)
Les MEB sont utilisées désormais de manière routinière pour acquérir des images sériées d’échantillons biologiques. Grâce au FIBSEM, de petits volumes sont acquis à haute resolutions. Trois exemples vont illustrer les apports de cette technique pour explorer des échantillons au niveau cellulaire. Le microtome-SEM permet de très grandes et longues acquisitions. L’exemple d’un organisme complet acquis et de la corrélation avec des données génétiques illustrera cette technique. Finalement, l’essor de l’”array tomography”, technique non-destructive, permet de détecter des événements rares et de combiner l’analyse 3D ultrastructurelle avec des immunomarquages.
10:50 - 11:00 Discussion.
11:00 - 11:15 #26228 - Imagerie FIB-SEM et reconstructions 3D pour étudier le phytoplancton.
Imagerie FIB-SEM et reconstructions 3D pour étudier le phytoplancton.

Phytoplankton encompasses a huge diversity of eukaryotic unicellular organisms, issued by multiple endosymbiosis events, and belonging to distinct taxa. Their heterogeneous origin has led to a large biodiversity of phytoplankton, which comprises cells with different morphologies and sizes. Although they are exposed to extremely variable environments, phytoplankton cells are on average fast growing, suggesting that their metabolism should be highly flexible. However, we still do not know if these original metabolic strategies are linked to singular cell topological arrangements, due to the lack of high resolution imaging studies. 

We have developed a FIB-SEM–based workflow (Fig. 1) to generate 3D reconstructions of different eukaryotic microalgae representing major oceanic phytoplankton lineages suitable for quantitative morphometric analysis (surfaces and volumes) of organelles and subcellular structures. 

Cells were cryo-fixed using high-pressure freezing followed by slow freeze substitution and resin embedding. FIB-SEM datasets were processed to 3D models using open-access software. We obtained complete 3D models of entire cells including quantification of cellular and subcellular volumes, surfaces and interactions between compartments (Fig. 2).

By revealing evolutionarily-conserved topologies of energy-managing organelles, and their role in phytoplankton acclimation, this work deciphers phytoplankton responses at subcellular scales [1]. 

[1] Uwizeye, C., al. (2021) Morphological bases of phytoplankton energy management and physiological responses unveiled by 3D subcellular imaging. Nat Commun 12, 1049. https://doi.org/10.1038/s41467-021-21314-0.


Clarisse UWIZEYE (Grenoble)
11:15 - 11:25 Discussion.
11:25 - 11:40 #26231 - Analyse quantitative 3D de la structure et de la morphologie de la boehmite hiérarchique.
Analyse quantitative 3D de la structure et de la morphologie de la boehmite hiérarchique.

Boehmite (AlOOH) is considered as an important precursor to γ-Al2O3 which when calcinated undergoes topotactic transformation to form the latter.1,2 Alumina has extensive applications in fields such as catalysis, abrasives, cosmetics and many more. Boehmite falls under the category of hierarchical structures whose structural and textural properties are a result of its compositional and porous hierarchy. Although research has been carried out exquisitely to understand the complete representation of its structure, a true morphological model is an important key to understand and fully explain its transport properties during catalytic processes.3,4

3D electron microscopy in TEM or STEM modes helps us to dive deeper into the different hierarchical entities of boehmite, bridging the gaps between the models and assumptions made using the traditional characterisation techniques such as N2 Physisorption, Hg Porosimetery, X-Ray Diffraction (XRD), Dynamic Light Scattering (DLS) and Small angle X-Ray Scattering Techniques (SAXS). We present here deeper insight into the structural and morphological parameters of different commercial boehmites (Disperal 40, Dispal 10F4, Catapal 200 and Pural TH500) using 3D-TEM. The extraction of quantitative descriptors of the hierarchical entities and their comparison to bulk analyses provide a truthful and detailed insight into such microstructures. We show how seamingly identical grades of boehmite differ by their varying homogeneity of entity sizes and more particularly by different platelet interaction configurations giving rise to different pore types (Figure.1). The interaction between the different crystallographic planes - (200), (020) and (002) is found to be different from one sample to another giving rise to the uniqueness in its different compositions within its aggregates and the combination of four different morphologies quantified was different from aggregates of one boehmite grade to another (Figure.2).

References:
[1] Christoph, G. G. Clays Clay Miner. 27, 81–86 (1979).
[2] Wilson, S. J. J. Solid State Chem. 30, 247–255 (1979).
[3] Karouia, F. Powder Technol. 237, 602–609 (2013).
[4] Wang. H. J. of Microscopy. 260, pp. 287–301(2015).


Nivedita SUDHEER (Strasbourg)
11:40 - 11:50 Discussion.
11:50 - 12:05 #26232 - Méthode de reconstruction 3D de cellules par STEM en phase liquide vers l'étude des interactions cellule-biomatériaux.
Méthode de reconstruction 3D de cellules par STEM en phase liquide vers l'étude des interactions cellule-biomatériaux.

The successful development of new implants relies on a better understanding of the interactions between cells and biomaterials [1]. Cell adhesion onto the biomaterial is a key step to predict the future of an implant in the human body. Cell adhesion is involved in many cellular processes such as proliferation, migration and differentiation. Recent studies have shown that the substrate on which cells are cultured can lead to different cell morphologies, which is linked to the expression of specific genes [2]. Cell adhesion is widely studied through focal adhesion labelling in confocal microscopy. The morphological analysis is mostly done in 2D using high vacuum scanning electron microscopy, a label-free technique requiring heavy sample preparation including dehydration. To reduce changes during sample preparation, a solution may be the use of liquid-phase SEM (LPSEM) analysis. A home-made scanning transmission electron microscopy (STEM) tomography device, specific to LPSEM, has previously been developed to study aqueous suspensions in 3D [3]. In this work, we further develop the device and propose a 3D analysis method to study whole cells in 3D close to their native state. We will show that Liquid-Phase electron tomography in ESEM enables the 3D analysis of whole hydrated cells without any heavy sample preparation. We will first present the technical settings used for image acquisition on hydrated biological objects. Then, we will show complementary volumes reconstructed from BF and HAADF tilt image series (see figure 1 A and B). Morphological parameters describing cell parts, such as the filopodia, will be extracted. The limits of the technique will be explored in terms of culture medium, cell thickness, spatial resolution and electron dose received by the sample. Complementary topographic results of cells/thick substrates will also be analysed. Such development opens the way towards 3D analysis of intact cells in environments mimicking their native environment. Another targeted application is the 3D study of the morphological interactions between cells and biomaterials.

[1] Cells Mater., 3, (1993) p.141–150.
[2] Nat. Commun., 11, (2020) p 1–13.
[3] Microsc. Microanal., 20, (2014) p.366–375.


Akkiz BEKEL (Lyon)
12:05 - 12:15 Discussion.
Room 1
12:10 Pause
13:10

Mercredi 07 juillet

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SDV2
13:10 - 15:45

Symposium Sciences de la Vie 2
Cryométhodes 2 : Cellulaires / Tissulaires : applications et développements

Modérateurs : Amélie LEFORESTIER (Chargée de Recherche) (Paris-Saclay), Patrick SCHULTZ (IGBMC, Strasbourg)
Les développements récents des cryo méthodes cellulaires et tissulaires offrent la possibilité de décrire leur organisation au niveau moléculaire. Un ensemble de technologies à basse température doit être combiné pour préserver au mieux l’ultrastructure cellulaire par cryo fixation, amincir la cellule par cryo-coupe ou fabrication de cryo-lamelles, reconstruire le volume cellulaire par cryo tomographie électronique et déterminer la nature, la structure et les interactions des molécules présentes dans ce volume. L’opportunité de visualiser des molécules en action dans leur contexte cellulaire sans avoir à les purifier et donc les séparer de leurs partenaires est une révolution majeure dans le domaine de la biologie. De nombreuses difficultés techniques restent à surmonter pour démocratiser ces approches, reconnaitre sans ambiguïtés les machines moléculaires de petite taille ou peu abondantes, ou encore améliorer la résolution des reconstructions tridimensionnelles. L’ambition de cette session est de présenter l’état de l’art et d’illustrer les développements par des applications biologiques représentatives des progrès les plus récents.
13:10 - 13:40 Towards a mechanistic understanding of ciliary assembly by CLEM and cryo-ET. Gaia PIGINO (MPI-CBG, Dresden, Allemagne)
Research in my lab aims at understanding the molecular principles and processes that drive the self-organization of complex cellular machines, which are relevant for human health and disease. In this talk I will show how we combine EM and molecular cell biology methods to obtain a mechanistic understanding of the molecular machineries required for the assembly and the function of cilia/flagella: conserved organelles that are fundamental for most eukaryotic cells.
Assembly of the cilium requires the rapid bidirectional intraflagellar transport (IFT) of building blocks to and from the site of assembly at its tip. This bidirectional transport of IFT trains is driven by the anterograde motor kinesin-2 and the retrograde motor dynein-1b, which are both bound to a large complex of about 25 IFT adaptor proteins. We developed a millisecond resolution 3D correlative light and electron microscopy (CLEM) approach to show that the spatial segregation of oppositely directed IFT trains on the two microtubules of each axonemal doublet ensures a collision free transport in the cilium. Then, it remained to be explained how competition between kinesin and dynein motors, both found on anterograde IFT trains, is avoided. In other bidirectional transport systems in the cell the presence of opposing motors leads to periodic stalling and slowing of cargos moving along the microtubule. No such effect occurs in IFT. To address this question, we used cryo-electron tomography and sub-tomogram averaging to resolve the 3D structure of IFT train complexes in the cilia/flagella of Chlamydomonas cells. We showed that a tug-of-war between kinesin-2 and dynein-1b is prevented by loading dynein-1b onto anterograde IFT trains in an inhibited conformation and by positioning it away from the microtubule track to prevent binding. We also show that dyneins are released from the train at the ciliary tip, but how this happens and how these motors are activated to power retrograde IFT is not yet understood. Protein complexes that form specialized structures at the ciliary tip are thought to be involved in this process. By mechanically manipulating IFT trains in the cilia/flagella of Chlamydomonas cells, we showed that the structures of the ciliary tip are not necessary for the conversion from anterograde to retrograde IFT. Thus, the conversion process is an intrinsic, calcium-optional ability of IFT machinery. Other research lines of the Pigino Lab aim at understanding the role of tubulin posttranslational modification for the assembly and the mechanics of cilia and flagella, and the structure, composition and function of primary cilia.
13:40 - 13:50 Discussion.
13:50 - 14:20 Structural biology of prokaryotic cell surface proteins. Tanmay BHARAT (Bacterial Biofilms, Oxford Univ., Royaume-Uni)
My laboratory studies how molecules on the surface of prokaryotic cells mediate cellular interaction with the environment, enabling cellular motility, initiating cellular adhesion to surfaces, and facilitating biofilm formation. For our work, we leverage our expertise in electron cryotomography (cryo-ET) in situ imaging, together with ongoing method development in subtomogram averaging approaches for structure determination of macromolecules in their native context. We combine cryo-EM with FIB milling of specimens and cryo-light microscopy to study molecules on prokaryotic cells.
14:20 - 14:30 Discussion.
14:30 - 14:45 #26368 - HEMNMA-3D: a new method for continuous conformational variability analysis of macromolecules. Application to cryo electron tomography of nucleosomes in situ.
HEMNMA-3D: a new method for continuous conformational variability analysis of macromolecules. Application to cryo electron tomography of nucleosomes in situ.

Cryogenic electron tomography (Cryo-ET) allows in situ structural determination of macromolecules. Its potential to provide information on macromolecular dynamics is still largely unexploited due to data analysis challenges represented by 1) low signal-to-noise ratio and 2) spatial anisotropies due to the limited tilt angle of Cryo-ET (missing-wedge).

Conventional subtomogram analysis techniques simplify macromolecular conformational variability to discrete rather than continuous solutions using 3D-subtomogram classification and class averaging.

We present HEMNMA-3D [1], the first method for analyzing subtomograms for macromolecular continuous conformational changes. HEMNMA-3D uses elastic and rigid-body alignments of a flexible 3D-reference (atomic structure or a density map) to match the macromolecule's conformation, orientation, and position in each subtomogram. The elastic matching combines molecular mechanics simulation (Normal-Mode-Analysis of the reference) and subtomogram data analysis. The rigid-body alignment includes compensation for the missing wedge. The conformational parameters (amplitudes of normal modes) of the macromolecules in subtomograms obtained through the alignment are processed to visualize the distribution of conformations in a space of lower dimension (2D or 3D) referred to as space of conformations. This allows a visually interpretable insight into macromolecular dynamics, by calculating 3D-averages of subtomograms with similar conformations from selected (densest) regions and recording movies of the 3D-reference's displacement along selected trajectories through the densest regions.

In this presentation, we describe HEMNMA-3D and show its application on an experimental dataset describing in situ nucleosomes.

HEMNMA-3D software is available freely as part of the ContinuousFlex plugin of Scipion-V3.

[1] Harastani M, Eltsov M, Leforestier A, Jonic S. HEMNMA-3D: Cryo Electron Tomography Method Based on Normal Mode Analysis to Study Continuous Conformational Variability of Macromolecular Complexes. Front. Mol. Biosci, in press.

Acknowledgments:

We acknowledge the support of the French National Research Agency—ANR (ANR-20-CE11-0020-01 to A.L., ANR-20-CE11-0020-02 to M.E., ANR-20-CE11-0020-03 and ANR-19-CE11-0008-01 to S.J.); German Research Foundation (DFG EL 861/1 to M.E.); La Société Française des Microscopies (2019 Master internship grant to M.H.); the Sorbonne University (2019 ""Interface pour le Vivant"" PhD scholarship grant to M.H.); and the access to the HPC resources of CINES and IDRIS granted by GENCI (2019-A0070710998, AP010712190, AD011012188 to S.J.).


Mohamad HARASTANI (Paris)
14:45 - 14:55 Discussion.
14:55 - 15:10 #26357 - Microtubule lattice organization in Xenopus laevis egg cytoplasmic extract.
Microtubule lattice organization in Xenopus laevis egg cytoplasmic extract.

Our current knowledge on microtubule structure is essentially derived from the numerous studies that have been performed on microtubules assembled in vitro from purified tubulin. However, little is known concerning the structure of microtubules in cells, and more specifically on the organization of the tubulin heterodimers within their lattice. 

To tackle this matter, we have used Xenopus egg cytoplasmic extracts that can recapitulate the events of the cell cycle [1], and thus constitute a convenient close-to-cellular open system where proteins can be either added or depleted. Here, we used the motor domain of kinesin that binds every tubulin dimer to decorate microtubules in the egg cytoplasm. Dual-axis cryo-electron tomographic data were taken so that all microtubules could be analyzed irrespective of their orientation with respect to the tilt axes [2] (Fig. 1). We then used a segmented sub-tomogram averaging approach to analyze the organization of the tubulin molecules within all microtubules (Fig. 2).

We found that the vast majority of the microtubules are made of 13 protofilaments with 3-start lateral helices. Tubulin molecules engage homotypic lateral interactions of the B-type along the 3-start helices, except at a unique region of the A-type, called the seam. Yet, we observed exceptions such as microtubules segments built from different protofilaments number (e.g. 12 and 14), as well as fully helical 13 protofilaments microtubule segments with 4-start lateral helices. We also found that the seam location can vary within individual microtubules, which implies the presence of holes inside their wall. In parallel, we have analyzed the structure of microtubules assembled in vitro from pure tubulin and discovered that they are much more structurally heterogeneous, both in terms of protofilament and seam numbers, as well as in lattice type transition frequency (~40 times higher in vitro than in Xenopus egg cytoplasm). Altogether, our data suggest that microtubule architecture is tightly regulated in cells to avoid the formation of lattice defects commonly observed in microtubules assembled in vitro from purified tubulin. 

References:

[1] Gibeaux R. and R. Heald. Cold Spring Harb. Protoc. (2019), doi:10.1101/pdb.top097048 

[2] Guesdon A. et al. J. Struct. Biol., 181 (2013), p. 169–78.


Charlotte GUYOMAR (Rennes)
15:10 - 15:20 Discussion.
15:20 - 15:35 #26359 - Sparse cryo-STEM tomography for biological samples.
Sparse cryo-STEM tomography for biological samples.

Cryo-electron tomography (Cryo-ET) enables to recover 3D information of cryo-fixed samples in a near-native state [1] with a thickness up to ~250 nm [2]. Thicker samples (up to 1 µm) can be studied in scanning transmission electron microscopy (STEM) [3][4]. At equivalent electron dose, STEM induces less radiation damage to the sample than classical transmission electron microscopy (TEM) [5] and is able to image micrometer thick cryo-fixed biological samples in 3D (Fig. 1) [6]. However, in order to image thicker specimens or to reach higher magnifications we need to increase the dwell time or to sample the specimen more densely, respectively. This will inevitably increase the electron dose and the beam damage proportionally. The need to further reduce the electron dose emerges. 

In this work, we present a sparse cryo-STET acquisition scheme. Instead of collecting a full frame for each tilt-angle, we collect only a fraction of the pixels. This permits to reduce the electron dose received by the sample on each frame and across the full tilt-series. Multiple sparse data collection schemes have been previously investigated at our lab [7] (Fig. 2). A pre-processing inpainting step, using discrete cosine transform (DCT) [8] or shearlets transform [9], is necessary prior tilt-series alignment to recover the missing information due to the data sparsity. Then the 3D volume can be reconstructed using classical methods like WBP [10] or iterative algorithms such as SIRT [11]. 

To demonstrate the advantages of a sparse cryo-STET acquisition scheme, we applied our method on a sample that is too thick (>1µm) to be studied using conventional TEM methods.

References 

[1] Lučić et al., J. Cell Biol., 202(2013), pp.407–419.

[2] Aoyama et al., Ultramicroscopy, 109(2008), pp.70–80.

[3] Midgley & Weyland, Ultramicroscopy, 96(2003), pp.413–431.

[4] Pennycook, Ultramicroscopy, 123(2012), pp.28–37.

[5] Wolf et al., Nat. Methods, 11(2014), pp.423–428.

[6] Trépout, J. Struct. Biol. X, 4(2020), p.100033.

[7] Trépout, Materials, 12(2019), p.2281.

[8] Garcia, Stat. Data Anal., 54(2010), pp.1167–1178.

[9] Kutyniok et al., GAMM-Mitteilungen, 37(2014), pp.259–280.

[10] Radermacher, in Electron Tomography, Springer, (2006), pp.245–273.

[11] Gilbert, J. Theor. Biol., 36(1972), pp.105–117.


Antoine COSSA (Paris-Saclay)
15:35 - 15:45 Discussion.
Room 1

Mercredi 07 juillet

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SDM3
13:10 - 15:45

Symposium Sciences de la Matière 3
Cristallographie, structures et microstructures

Modérateurs : Emmanuel BOUZY (LEM3, Metz), Christine LEROUX (IM2NP, Toulon)
La cristallographie est à la base de l'élaboration de tous les nouveaux matériaux. En effet, afin d'optimiser et de développer de nouvelles fonctionnalités, l'arrangement atomique, les orientations, les déformations élastiques des cristaux et les défauts qu’ils présentent doivent être étudiés dans l'espace réel et/ou dans l'espace réciproque, et ce à différentes échelles. Pour ce faire, que ce soit en MEB ou en MET, différentes techniques de diffraction et d'imageries sont utilisées parmi lesquelles : EBSD, TKD, ECCI, HRTEM, ACOM, PED, NBED, CBED, STEM in SEM, STEM in TEM… Ce symposium se veut général et regroupe les études de structure et microstructure de matériaux sous forme massive, de poudres ou de couches minces, qui font appel aux techniques ci-dessus ou à toutes autres techniques relatives à la cristallographie. Les contributions qui établissent un lien certain entre l'étude structurale et microstructurale et les propriétés du matériau sont les bienvenues.
13:10 - 13:40 ANALYSE MICROSTRUCTURALE DES SUPERALLIAGE BASE NICKEL POLYCRISTALLINS POUR DISQUES DE TURBINE. Nathalie BOZZOLO (CEMEF, Paris)
Les superalliages polycristallins sont utilisés pour la fabrication des disques de turbine de motorisation aéronautique. Les alliages employés aujourd’hui et pour les quelques décennies à venir sont de type γ-γ’. La microstructure des disques forgés doit répondre à un cahier des charges strict pour atteindre les propriétés requises pour cette application parmi les plus exigeantes. Aussi le développement des gammes de fabrication suppose la parfaite connaissance des mécanismes et cinétiques métallurgiques à l’œuvre au cours des opérations de forgeage à chaud.
Ainsi l’optimisation de la tenue en service de ces alliages passe par l’analyse fine des microstructures en cours de mise en forme et par l’analyse des mécanismes de recristallisation qui contrôlent la taille de grains finale. La cartographie d’orientations par EBSD est une technique phare dans ce domaine.
Les superalliages γ-γ’ présentent des difficultés particulières liées notamment à la similitude cristallographique de la matrice austénitique et de la phase secondaire de structure L12 et au caractère multi-échelle des populations de précipités. Différentes approches possibles pour contourner ces difficultés et obtenir des cartographies d’orientation discriminant les deux phases seront présentées (variantes de la technique EBSD et techniques alternatives) [1,2].
Par ailleurs l’analyse quantitative des microstructures visant à l’évaluation de l’énergie stockée, pilote de la recristallisation, sera également illustrée et discutée [3,4].

Références:
[1] Charpagne M.-A., Vennéguès P., Billot T., Franchet J.M. & Bozzolo N., Journal of Microscopy, 263:1 (2016) p.106-112
[2] Vernier S., Franchet J.M., Lesne M., Douillard T., Silvent J., Langlois C. & Bozzolo N., " Materials Characterization, 142 (2018) p. 492-503
[3] Seret A., Moussa C., Bernacki M., Signorelli J. & Bozzolo N., Journal of Applied Crystallography, 52 (2019) p.548-563
[4] Nicolay A., Franchet J.M., Cormier J., Mansour H., De Graef M., Seret A. & Bozzolo N., " Journal of Microscopy, 273:Issue 2 (2019) p.135-147
13:40 - 13:50 Discussion.
13:50 - 14:20 Measuring local lattice parameters by Precession Electron Diffraction: an opportunity to give a personal overview of Electron Crystallography. Jean-Luc ROUVIÈRE (Docteur) (LEMMA, Grenoble)
In this presentation, I will start recalling what is crystallography and explain why some of my work - in particular strain measurement by electron diffraction with or without precession (Fig. 1) - can be related to crystallography. After recalling this strain measurement work, I will show some appealing recent publications on electron crystallography and will take this opportunity to give a non-crystallographer and thus partial overview of the evolution of Electron Crystallography.

Figure 1 gives an overview of local strain measurements by N-PED (Nano-beam Precession Electron Diffraction). Diffraction Maps (DM), also called 4D-STEM experiments, are performed by scanning in 2 directions an electron beam of about 1 nm in diameter, and at each position a diffraction pattern (DP) is recorded and numerically analysed. Using simple filtering and autocorrelation, the relative local lattice parameters can be measured accurately; by using a reference pattern either locally in the same map or in a second map obtained on a reference sample of known lattice parameter absolute measurements can be obtained with an accuracy approaching 10-4, and a spatial resolution of about 1 nm [1]. When the sample contains only homethetic diffraction patterns, like in a SiGe/Ge multilayer (Fig. 1a), the strain formula is straightforward. When the sample contained different phases like in a GaN layer deposited on Si [3] (Fig. 1b), the strain formula involves several matrix multiplications.
This method has been applied to study strain in different semiconductor nanostructures [1-8] but it could be applied in any crystalline nomaterial, where 2D-projected strain maps bring useful information on the structure.

Références/References :
[1] J.-L. Rouviere et al. Appl. Phys. Lett., vol. 103, no 24, (2013)
[2] S. Reboh et al., Appl. Phys. Lett., 112 (2018) p. 051901
[3] N. Mante et al., Journal of Applied Physics, 123 (2018) p. 215701
[4] T. Cerba et al. Thin Solid Films, vol. 645 (2018) p. 5 9
[5] S.-T. Zhang et al., Materials & Design, 132 (2017) p. 518
[6] B. Haas et al., Appl. Phys. Lett. 110 (juin 2017) p. 263102,
[7] D. Cooper et al., Appl. Phys. Lett. 110 (2017) p. 223109
[8] J. Aubin et al., Semiconductor Science and technology 32, no 9, (2017)
14:20 - 14:30 Discussion.
14:30 - 14:45 #26401 - An original homography-based approach for high-angular resolution EBSD and TKD: principle and examples.
An original homography-based approach for high-angular resolution EBSD and TKD: principle and examples.

Digital image correlation (DIC) techniques usually performed on deforming speckle patterns are transferred to electron microscopy in order to map grain internal disorientation with high angular resolution, as well as geometrically necessary dislocation densities (GND) and elastic strains.The developed method analyses electron diffraction patterns as a whole through a unique and large region of interest for which the relative deformations are described by a linear homography [1]. Such a geometric transformation is often met in photogrammetry to model projections. It is here measured by means of a numerically efficient inverse-compositional Gauss-Newton algorithm (IC-GN). The latter integrates a correction of optical distortions caused by the camera lenses, avoiding thus a time-consuming patterns straightening step [2]. A global cross-correlation based initial guess step pre-aligns the  patterns so that the IC-GN algorithm convergences despite the presence of disorientations up to 10°. The method is implemented in ATEX-software [3], developed at our lab, and applied to a semi-conductor and a deformed metal. First, the elastic strain field in the vicinity of a screw dislocation in GaN single crystal is investigated using EBSD. It reproduces very well the theoretical elastic strain field (Fig. 1). Then, the DIC analysis is coupled with the recent on-axis Transmission Kikuchi Diffraction (TKD) configuration to characterise a nanocrystalline aluminium obtained by severe plastic deformation. The dislocation structures are highlighted by the GND density maps (Fig.2). Thanks to this coupling, high-spatial (3-6 nm) and high-angular (0.01°) resolutions are simultaneously achieved in the scanning electron microscope [4].

References:

[1] C. Ernoud et al., Acta Materialia 191 (2020), p.131-148

[2] C. Ernoud et al., Ultramicroscopy, 221 (2021), p.113158

[3] B. Beausir, J.-J. Fundengerger, Analysis Tools for Electron and X-Ray Diffraction, ATEX - Software, Université de Lorraine, Metz, 2017.

[4] C. Ernoud et al., Scripta Materialia, 185 (2020), p.30-35

Figure 1: (a) Forward Scatter Detector (FSD) image of a screw dislocation in GaN and (b-d) elastic strain maps obtained by the HR-EBSD method.

Figure 2: On-axis HR-TKD characterization of a nanocrystalline aluminium and comparison with a standard indexation-based analysis.


Clément ERNOULD (Metz)
14:45 - 14:55 Discussion.
14:55 - 15:10 #26412 - Low-dose imaging of metal-organic frameworks and study of their electron-beam stability.
Low-dose imaging of metal-organic frameworks and study of their electron-beam stability.

Metal-organic frameworks (MOFs) are hybrid (organic/inorganic) crystalline porous materials intensively studied for their potential in several applications related to energy, environment or health. Diffraction-based techniques are the methods of choice for the crystal structure determination of MOFs, providing a better understanding of their unique properties. However, the information obtained is the averaged periodic structure, while in some cases - such as adsorption and catalysis - the local structural features (ie., crystal surfaces, interfaces, the presence of guest molecules or defects) are key elements. In this regard, high-resolution TEM methods provide the opportunity to probe/visualize such details [1]. However, MOFs are among the most beam-sensitive materials and can be easily damaged after exposure to few electrons/Å2. Therefore, there are only a few studies where HRTEM imaging was successful, so far. Most of them focus on a few MOFs that were found to be relatively stable under the electron beam [1]. These recent studies have demonstrated that using a direct detection electron counting camera (DDEC) allows performing HRTEM imaging of MOFs with extremely low dose rates (as low as 4 e−/Å2.s) [2].

The prediction of the electron-beam stability of a MOF nanocrystal is a difficult task since many structural, morphological or instrumental parameters can be taken into account and could have interconnected effects. This work aims at identifying these parameters and assessing their influence on the stability of these objects under the beam. Several known MOFs were successfully imaged by low-dose HRTEM (Figure 1) enabling the investigation of the effect of the voltage, the particle size and orientation, the presence of guest molecules, as well as the nature of the organic and the inorganic moieties. Additionally, low-dose HRTEM imaging has been for the first time applied on new in-house nano-sized MOFs (Figure 2), where important structural information was extracted and confirmed by complementary techniques [1].

Acknowledgement :

The authors acknowledge the Region Ile-de-France in the framework of DIM ResPore for funding.

Références/References :

[1] L. Liu, D. Zhang, et al., Communications Chemistry (2020), 3, 1–14.

[2] Y. Zhu, J. Ciston, et al., Nature materials (2017), 16, 532–536.


Asma MANSOURI (Paris)
15:10 - 15:20 Discussion.
15:20 - 15:35 #26413 - Combined Electron Diffraction and Chemical Contrast Imaging Studies : Identification of Nanometric Inclusions in Annealed (Eu,Tb) Doped ZnO/Si Junction.
Combined Electron Diffraction and Chemical Contrast Imaging Studies : Identification of Nanometric Inclusions in Annealed (Eu,Tb) Doped ZnO/Si Junction.

(Tb,Eu) doped ZnO films annealed at 1100°C showed intense photoluminescense (PL) emission from Eu and Tb ions [1]. The high temperature annealing led to a chemical segregation and a secondary Zn free phase formation that is suspected to be responsible for the high PL intensity. Large faceted inclusions of rare earth silicates of a size of few hundred nanometers were observed (Figure 1). Owing to various advanced electron microscopy techniques, a detailed microstructural study of these nanometric inclusions combining atomic Z contrast imaging (STEM) and precession electron diffraction tomography (PEDT) data was carried out and concluded to the formation of a hexagonal P63/m-type (Tb,Eu)9.43(SiO4)6O2-δ structure related to an oxyapatite structure [2]. Simulated atomic imaging and chemical analyses from spectroscopic data (EDX mapping and EELS) at the atomic scale (Figure 2)  have confirmed this result and showed that both rare earth (RE) elements sitting on two independent atomic sites have three-fold oxidation states while refinements of their occupancy sites from PEDT data have evidenced preferential deficiency for the first one. The deduced RE-O distances and their corresponding bond valences are discussed with the efficient energy transfer from Tb3+ towards Eu3+.

References :

[1] Davesnne, C.; Ziani, A.; Labbé, C.; Marie, P.; Frilay, C.; Portier, X. Energy Transfer Mechanism between Terbium and Europium Ions in Zinc Oxide and Zinc Silicates Thin Films. Thin Solid Films 2014, 553, 33–37.

[2] Leroux, Chris; Guillaume, Clement; Labbe, Christophe; Portier, Xavier and Pelloquin, Denis. Identification of (Tb,Eu)9.43(SiO4)6O2-delta Oxy-Apatite Structures as Nanometric Inclusions in Annealed (Eu,Tb)-Doped ZnO/Si Junctions: Combined Electron Diffraction and Chemical Contrast Imaging Studies. Inorganic chemistry 2021, 60,7, ‏  4508-4516 


Denis PELLOQUIN (Caen)
15:35 - 15:45 Discussion.
Room 2
15:40 Pause
16:00

Mercredi 07 juillet

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POS1
16:00 - 18:00

Session Posters 1

16:00 - 18:00 #26224 - STEM-in-SEM FOR LOW COST STRUCTURAL BIOLOGICAL STUDIES AT ROOM TEMPERATURE.
STEM-in-SEM FOR LOW COST STRUCTURAL BIOLOGICAL STUDIES AT ROOM TEMPERATURE.

Marie Laure SGARRA *, Aurelie DELIOTFranck CHARLESSergio MARCO

  • Sanofi Pasteur, Analytical Sciences, 1541 avenue Marcel Merieux, 69280 Marcy l’Etoile.
  • JEOL Europe SAS. 1 Allée de Giverny, 78290 Croissy sur Seine.


Ultrastructural studies of proteins, viral particles and resin embedded cells by negative staining are often performed by transmission electron microscopy (TEM). TEMs, in general, require a significant investment and maintenance cost having limited possibilities to program an automatic data acquisition flow from several grids inserted at once. STEM-in-SEM microscopes [1] are low cost solution compared to TEMs for acquisition, operation and maintenance. It offers the advantage of a multi-EM-grids holders (up-to 12 TEM-standard 3mm-grids) automatic management becoming a valuable alternative to address the aforementioned issues. In addition, they are easier to use not requiring additional protocols for sample preparation for negative staining or resin-embedding samples such as they are equal to those used for TEM. We aim here to demonstrate how STEM-in-SEM can be an alternative to make it available for a maximum number of laboratories. All the biological structural studies which can be performed at room temperature from cells to viruses and proteins including 2D-single-particle analysis (2D-SPA) which would be the maximum analytical limit of this technique as it requires the maximum achievable resolution. We have compared two studies with the same ~650 kDa oligomer performed by SPA using the same grids by MET and STEM-in-SEM. Raw images examples shown in figure 1 depict the ability of STEM-in-SEM to generate data suitable for 2D-SPA. We will introduce a full comparative study performed on these images’ sets. In addition, we will illustrate the use of STEM-in-SEM of large resin embedding samples study, without heavy metals post-embedding contrasting, at high magnification by stitching. In this last case, no charging phenomena were observed with a good enough contrast to get access to subcellular structures. In summary, STEM-in-SEM allows the negatively stained samples study, being even suitable for 2D single particle analysis, as well as for ultrastructural studies of large areas of resin embedded samples. STEM-in-SEM becomes a powerful and economic alternative to TEM for ultrastructural biological studies at room temperature. References: [1] Woolf et al., A transmission stage for the scanning electron microscope, J. Phys. E, 5 (1972), p. 230-23
Marie Laure SGARRA (Sanofi Pasteur)
16:00 - 18:00 #26225 - Real-time drift correction for EELS hyperspectrum acquisition.
Real-time drift correction for EELS hyperspectrum acquisition.

Marcel Tencé *, Xiaoyan LiAlexandre GloterMichael Walls

  • LPS Orsay (CNRS)


We present a novel approach for drift correction in real time during EELS hyperspectrum (HS) acquisition, taking advantage of the high-speed and noiseless readout characteristics of newly available direct electron detectors. These enable several HS to be recorded in sequence while adjusting the scanned area between each HS to remain on the same area of the sample. To achieve this, the cross-correlations between successive HAADF images (acquired simultaneously with the HS) are used to estimate the drift occurring during each scan. With our Medipix3RX Merlin EM detector, nominal dwell times as low as 100µs are currently attainable if one-bit counting is used. For quantitative, linear counting this limits the counts per channel per scan to somewhat less than the number of channels over which the spectrum signal is spread in the non-dispersive direction (about 150 in our case). But in the core-loss region such low count rates are typical using sub-millisecond dwell times. This approach eliminates the need for a separately defined drift-calculation image as is commonly used at present but which often presents difficulties, since a suitable region is not always available. Figure 1 shows an HAADF image and elemental maps of the of the Sc L (ca. 400eV) and Dy M (ca. 1300eV) signals from a conventional HS acquisition without drift correction on an ScDyO3 crystal oriented along the [100] pseudo-cubic axis. The dwell time was 20ms, giving a total acquisition time of 444s. Considerable drift occurred, producing distortions in the images. Figure 2 shows the equivalent results using our approach. Here, 100 HS each with a nominal pixel dwell time of 200µs were collected from the same area and summed. The total signal acquisition time is thus the same as in Figure 1 and the count levels were similar. However, the resulting image and maps are essentially free of drift distortion. We believe this method is the way forward for EELS HS acquisition. We thank Quantum Detectors for implementing TCP streaming speed improvements in the Merlin software, and ESTEEM3 (Europe), METSA (France) and the “Equipex” project TEMPOS (France) for financial support.
Marcel TENCÉ (ORSAY)
16:00 - 18:00 #26226 - Orientation mapping of bio-inspired alumina down to 1 kV.
Orientation mapping of bio-inspired alumina down to 1 kV.

C. LafondT. DouillardH. SaadS. DevilleS. MeilleP. SteyerS. CazottesC. Langlois *

  • Univ Lyon, INSA Lyon, UCBL, CNRS, MATEIS, UMR5510, 69621 Villeurbanne, France
  • Laboratoire de Synthèse & Fonctionnalisation des Céramiques, UMR3080 CNRS-Saint-Gobain CREE, Saint-Gobain Research Provence, Cavaillon 84306, France
  • Univ Lyon, Université Claude Bernard Lyon 1, CNRS, Institut Lumière Matière, 69622 Villeurbanne, France


Mapping the grain orientations of polycrystals brings crucial information when studying the relationships between microstructure and properties. Among different orientation mapping approaches, Electron Back Scattered Diffraction (EBSD) in a Scanning Electron Microscope (SEM) has been a milestone in the development of crystallographic characterizations. Nevertheless, efforts are still needed to improve the technique toward a better spatial resolution. One strategy is to decrease the accelerating voltage in order to reduce the interaction volume under the probed surface. However, the Kikuchi pattern quality decreases rapidly and the standard indexation routine fails. The actual limit found in the literature is 5kV [1]. Orientation mapping using the eCHORD approach [2] is not subjected to such limitations: it has been shown that the channeling of back scattered electrons (BSE), was still present at low voltages. In the current work, we show for the first time that orientation mapping at 1 kV is possible. The test material was a bio-inspired alumina presenting a lamellar structure mimicking the shell nacre, developed to improve the resistance to crack propagation. EBSD and eCHORD results about the local crystallographic texture are in very good agreement. This preliminary result paves the way for addressing samples sometime difficult to map by conventional EBSD like deformed crystal, nanocrystalline grains or subgrains, and insulating materials. Acknowledgments Thanks are due to the CLYM (www.clym.fr) for access to the ZEISS NVision 40 scanning electron microscope. C. Lafond thanks the French Ministry of Higher Education and Research for his PhD grant. We are also grateful for the financial support from the Agence Nationale pour la Recherche (ANR-16-CE08-0006 BICUIT, program DS0303-2016). References: [1] Singh, S., Guo, Y., Winiarski, B., Burnett, T. L., Withers, P. J., & De Graef, M. (2018). High resolution low kV EBSD of heavily deformed and nanocrystalline Aluminium by dictionary-based indexing. Scientific reports, 8 (2018), 10991 [2] Lafond C., Douillard T., Cazottes S., Steyer P. and Langlois C. (2018) Electron CHanneling ORientation Determination (eCHORD): An original approach to crystalline orientation mapping. Ultramicroscopy, 186 (2018), p.146-149
Clément LAFOND ()
16:00 - 18:00 #26227 - Characterisation of PAN and PES polymeric filtration membranes for microalgae valorization using 3D FIB/SEM.
Characterisation of PAN and PES polymeric filtration membranes for microalgae valorization using 3D FIB/SEM.

Hélène Roberge *, Philippe MoreauEstelle CouallierPatricia Abellan

  • Institut des Matériaux Jean Rouxel de Nantes
  • Laboratoire de Génie des Procédés, Environnement et Agroalimentaire, GEPEA, Saint Nazaire


Membrane filtration processes allow concentrating, separating and purifying the components from a complex mixture in a liquid phase. Recently, they have been adapted for microalgae valorization, where filtration employing nanoporous polymer membranes is used to separate and recover lipids and proteins from ground microalgae aqueous extracts. The biomolecules can be used in pharmaceutical industry, cosmetics, food supplements or biofuel industry [1]. The performance of the membrane is related to the size and density of its pores, but also to the selective layer thickness (a thin layer placed in contact with the fluid to be filtered), as shown by Poiseuille’s law [2]. During filtration, the unwanted accumulation of biomolecules at the surface and in the pores, termed fouling, hampers membrane performances. A detailed characterization of the pore structure, firstly in clean membrane, is essential to understand the fouling. 3DFIB/SEM allows characterizing the 3D structure of the material with a few nanometers resolution. Data acquisition is particularly challenging with polymer membranes constituted of amorphous materials presenting little contrast and a strong sensitivity to the electron and ion beams. Moreover, 3D reconstructions of porous media present a common issue: the shine through artefact, (material from subsequent slices is imaged through the pores), leading to a pores deformation in the FIB-milling direction [3]. We tested two widely used polymer membranes: PAN (polyacrylonitrile) and PES (polyethersulfone), with a respectively nominal pore size of their selective layer of 30 nm and 100 nm. We developed a 3D FIB/SEM method to obtain quality 3D reconstructions with a 5 nm voxel size and overcoming beam sensitivity and artefact difficulties. In this presentation, the sample preparation as well as the optimization of acquisition and reconstruction parameters will be described. We will present a method for identifying the selective layer in polymer filtration membranes using FIB/SEM. The quantitative analysis of pore size distribution, porosity, connectivity and tortuosity (figure 1) will be discussed. The properties-structure relationships will be analyzed, by linking these results with the theory of Hagen-Poiseuille on the porous media flow calculation. References: [1] Rivera et al., PB (2020) [2] AIMAR et al., TI, (2010) [3] Terao et al., JPS 347 (2017)
Hélène ROBERGE (Nantes, Saint Nazaire)
16:00 - 18:00 #26234 - 3D Microstructure Study of Li1.5Al0.5Ge1.5(PO4)3 Solid electrolyte pellets using FIB/SEM Tomography.
3D Microstructure Study of Li1.5Al0.5Ge1.5(PO4)3 Solid electrolyte pellets using FIB/SEM Tomography.

Sorina Cretu *, Linh Lan NguyenVincent SeznecArash JamaliLoic DupontArnaud DemortièreMartial Duchamp

  • Laboratoire de Réactivité et Chimie des Solides, UMR CNRS 7314, 33 Rue Saint Leu, 80039 Amiens, France
  • Réseau sur le Stockage Electrochimique de l’Energie (RS2E), FR CNRS 3459, 80039 Amiens, France
  • School of Materials Science and Engineering, Nanyang Technological University, 50 Nanyang Technological University, Singapore 639798, Singapore


Inorganic solid electrolytes (SE)[1] represent an advantageous future technology due to their non-flammable nature, good stability with high voltage cathode materials and extended temperature opration ranges. Li1.5Al0.5Ge1.5(PO4)3 (LAGP) [2], oxide SE gained attention due to its wide electrochemical window, high moisture stability and high ionic conductivity which can be obtained by sintering them at high temperature. The total conductivity of LAGP pellet has an inverse relationship with the amount of grain boundaries of the inside electrolyte pellet since Li+ ions are conducted relatively slower at at the grain boundaries due to solid-solid interface. SE pellets with different densities were prepared by Spark Plasma Sintering (SPS) and investigated using techniques such as Potentiostat Electrochemical Impedance Spectroscopy (PEIS), Focused Ion Beam/ Scanning Electron Microscopy (FIB/SEM) tomography and SEM-Energy Dispersive X-rays (EDX) analysis in order to get a better understanding better of the link between the amount of grain boundaries and ionic conductivity. FIB/SEM tomography analysis (Fig.1a) using a Dual Crossbeam 540 Zeiss microscope offered insights into the 3D morphology of solid electrolyte pellets and revealed unexpected presence of an extra phase at LAGP grain boundaries (Fig.1c). The back-scattered SEM images were segmented using a Random Forest approach with WEKA FIJI plugin allowing us to identify each phases (LAGP, extra-phase and porosity). The quantitative image process of 3D volume allowed us to extract porosity distribution, tortuosity and phase-to-phase surface area. Tomographic data displayed a lower presence of the grain boundary phase for high compact pellets indicating a clear correlation between the extra phase and the total ionic conductivity, which is consistent with PEIS analysis. SEM-EDX analysis showed that the extra phase located at the grain boundaries contained less germanium compared to the pure LAGP SSE. [1] Zhang, Z. et al. Energy Environ. Sci. 11, 1945–1976 (2018). [2] Delaizir, G. et al.. Adv. Funct. Mater. 22, 2140–2147 (2012).
Sorina CRETU (Amiens)
16:00 - 18:00 #26229 - FIB-SEM to study the Intraflagellar transport.
FIB-SEM to study the Intraflagellar transport.

Adeline Mallet *

  • Institut Pasteur


Cilia and flagella are essential organelles composed in general of 9 doublet microtubules. They can adopt different configurations from one species to the other, or even from one cell type to the other in the same organism. Their construction is mainly done by addition of new subunits at the distal end. Precursors are transported by Intraflagellar transport (IFT), the movement of trains composed of protein complexes between the flagellar membrane and the microtubule doublets driven by molecular kinesin and dynein motors. Despite high train frequency in both anterograde and retrograde directions (1-3 trains per second), collisions are extremely rare. We proposed three hypotheses to explain this phenomenon based on differential localisation for anterograde and retrograde trains. The localisation of IFT trains within flagellum was not precisely determined so far. We studied the localisation of IFT trains in the flagellum of the protist Trypanosoma brucei. Thanks to FIB-SEM, a three-dimensional electron microscopy approach, we established that IFT trains are localised specifically on only 4 microtubule doublets out of the 9 available. This was confirmed both in vitro and ex vivo using parasites developing in the tsetse fly. Comparison of the results with the literature reveals that IFT transport adopts different configuration depending on the anatomy of cilia and flagella. This raises the question of the evolution of the transport system in association with that of organelle structure. Two intriguing possibilities will be discussed.
Adeline MALLET (Institut Pasteur)
16:00 - 18:00 #26230 - Field Evaporation Energy Loss Spectroscopy.
Field Evaporation Energy Loss Spectroscopy.

Loïc ROUSSEAU *, Felipe F. MORGADOLeigh STEPHENSONConstantinos HATZOGLOUKambiz TEHRANIAntoine NORMANDBaptiste GAULTFrançois VURPILLOT

  • Groupe Physique des Matériaux, Université de Rouen, Normandie, France
  • Max-Planck Institut für Eisenforschung GmbH, D-40237 Düsseldorf, Germany
  • Norges teknisk-naturvitenskapelige universitet (NTNU), Trondheim, Noway
  • ESIGELEC
  • Groupe Physique des Matériaux, Université de Rouen, Normandie, France


The design of new materials requires an in-depth exploration of their physical, or structural properties. Deciphering their structure and composition at the atomic scale is a real challenge. Atom Probe Tomography (APT) allows to map 3D composition of a specimen near the atomic scale for a wide range of materials. However, in APT, the information is restricted to the list of coordinates of atoms in the probed volume, with elemental information get from time-of-flight mass spectrometry. No real local chemical information is extracted from the data. To access it, APT data have been recently indirectly mined looking at the mechanism of field evaporation of atoms in thermoelectric and phase change materials[1]. Field evaporation is the fundamental mechanism involved to peel off the sample atom by atom. Deep inspection of the dynamic of field evaporation showed some differences from one sample to another related to the nature of the atomic bonding, which could help to explain their properties[2]. However, this information remained global and very indirect. In this paper, we show how energetic considerations in the field evaporation process are in fact intrinsically present within the data, but have until now been ignored or even consciously suppressed using ion optics devices. This information is indeed embedded inside mass spectra. Based on an analytical model and robust simulations, we confirm the validity of our method and document this parameter for a series of different materials. We finally demonstrate how this information can be mapped in 3D with nanometric resolution. A grain boundary example in a pure Al dataset and the case of recrystallisation of amorphous FeBSi metallic glasses will be presented (fig.1,2). We term this new approach ""Field Evaporation Energy Loss Spectroscopy"". FEELS can be adapted to any straight flight path APT using voltage pulses, and can even be used on the thousands of existing data sets to retrieve further information. [1] T. Ohnuma, Microsc. Microanal., pp. 1–7, 2021, doi: 10.1017/S1431927621000155. [2] M. Raghuwanshi et al., Nano Lett., vol.20, no.1, pp.116–121, 2020, doi: 10.1021/acs.nanolett.9b03435.
Loïc ROUSSEAU (Saint Etienne du Rouvray)
16:00 - 18:00 #27024 - THERMAL PROBE MICROSCOPY: TOWARD A THERMAL ANALYSIS OF NANOMATERIALS.
THERMAL PROBE MICROSCOPY: TOWARD A THERMAL ANALYSIS OF NANOMATERIALS.

Nathaly Chaaraou*, Patricia Al Alam, Nathalie Trannoy*, Jaona Randrianalisoa

University of Reims Champagne Ardenne, IThMM, Reims, 51687, France 



Nanotechnology requires characterization technics for nanosystems and nanomaterials. Since twenty years, Nanotechnology reveals new needs in understanding and management of heat distribution at micro/nanoscale and in nanoscale structures. Development in new materials requires advanced knowledge of nanoscale heat transfer and thermal properties of nanostructured materials. Scanning thermal microscopy (SThM) based on Atomic Force Microscopy (AFM) technique is a promising tool for investigating material’s thermal measurements and heat transfer mechanisms at the micro/nanoscale [1, 2]. This project aims to investigate temperature and/or thermal properties of the studied material using a SThM probe with thermal sensor (thermoresistive, thermocouple etc.) at the tip. This thermal tip allows us obtaining topographic and thermal images simultaneously with micrometer and sub-micrometer spatial resolution. In this matter, Wollaston is used as a resistive probe in order to: (i) study the influence of sample structure on the thermal signal of the probe, (ii) characterize and estimate the effect of probe volume on the thermal conductivity measurements. For that, samples composed of buried silicon steps under polished CVD SiO2. A well-defined heat transfer numerical model was developed for the probe-sample system with the surrounding medium using COMSOL Multiphysics based on finite element method. This simulation allows comparison between measured results and the model developed with all physical aspects considered. A 3D realistic geometry of the Wollaston probe is modelled in contact operation mode in order to obtain probe temperature behavior (Fig.1(a,b)). The probe/sample numerical model reveals the evaluation of the dissipated flux by the thermal resistive wire (platinum-rhodium wire) and into the sample. By comparing the experimental measurements with the simulation, it is clearly shown that the developed models are in good agreement with experiment results (Fig.2(a,b)) . In other words, the developed models are capable to rebuild experimental thermal profiles. More worthwhile , this study proofs the sensitivity of the thermal signal to the internal nanostructure of the investigated samples. Références/References: [1] Majumdar, Lai, Chandrachood, Nakabeppu, Wu and Shi, Thermal imaging by atomic force microscopy using thermocouple cantilever probes, 1995 [2] F.A. Guo, N. Trannoy, J. Lu, Analysis of thermal properties by scanning thermal microscopy in nanocrystallized iron surface induced by ultrasonic shot peening, Materials Science and Engineering: A, 2004.
Nathaly CHAARAOUI (Reims)
16:00 - 18:00 #26241 - Using Convolutional Neural Network for segmenting the nano-XCT Images of battery materials.
Using Convolutional Neural Network for segmenting the nano-XCT Images of battery materials.

Zeliang Su *, Etienne DescencièreTuan-Tu NguyenVincent De AndradeAlejandro A. FrancoArnaud Demortière

  • Laboratoire de Réactivité et Chimie des Solides (LRCS), CNRS UMR 7314, Université de Picardie Jules Verne, Hub de l’Energie, Rue Baudelocque, 80039 Amiens Cedex, France.
  • MINES ParisTech – PSL Research University, CMM, Center for Mathematical Morphology, 35 rue Saint Honoré, Fontainebleau, France
  • Argonne National Lab, Advanced Photon Sources Beam line, Bldg. 401/Rm A4115, Argonne National Laboratory 9700 S. Cass Ave. Argonne, IL 60439, USA.


X-ray tomography has been widely used in battery research in recent years for understanding the impact of the microstructure and the dynamics of the batteries. However, every experiment generates up to dozens of gigabytes, the quantity of image data is challenging for the segmentation. Additionally, for the nano-XCT data, where a high signal-to-noise ratio is challenging to obtain and a wide variety of artifacts is present, the traditional grayscale thresholding approach is not efficient enough for complex composite battery materials. Up to date, the task of segmentation is still tedious work. We, therefore, investigated in the Convolutional Neural Network (CNN Figure 1). We decrypted the working mechanism of an in-house CNN by visualizing the outputs of each unit and its gradients during the training. We reexamined the influence of each hyperparameter to determine the parameter tuning priority. The segmentation efficiency has been successfully demonstrated by giving only one example to train the CNN. And high accuracies have been obtained for various cathode material datasets for Li-ion and Li-O2 batteries[1][2]. To further reduce the computation time, we have also shown that transfer learning (using a well-trained CNN on a new dataset) could improve the convergence. A roof of accuracy has been observed during our experiments. Such a limit likely depends on the quality of the tomography and the experimenter. To figure out the impact of segmentation on the material properties determination, we used a simulation and statistical approach. Lastly, we have embedded our findings and CNN methods in open-source graphical software (Figure 2) to allow a broader community can benefit from training CNNs without knowing coding basics. Références/References : [1] Nguyen et al. Adv.Energy Mat. (2021) p. 2003529 [2] Su et al. ACS Appl. Energy Mater. 3 (2020), p.4093−4102 Figure 1: Raw nano-XCT volume of an NMC cathode material and the rendering of the segmentation results by CNN. At the bottom, slices of raw XCT-image a ground truth, and a prediction are showcased. Figure 2: The user-friendly interface of the open-source software SegmentPy for XCT segmentation
Zeliang SU (Amiens)
16:00 - 18:00 #26371 - IN SITU ANALYSIS OF THE PROTEIN CORONA BY CRYO-TRANSMISSION ELECTRON MICROSCOPY.
IN SITU ANALYSIS OF THE PROTEIN CORONA BY CRYO-TRANSMISSION ELECTRON MICROSCOPY.

Jéril DEGROUARD *, Laurent MARICHALStéphanie DEVINEAUGaël GIRAUDON-COLASYves BOULARDJean-Philippe RENAULTSerge PIN

  • Université Paris-Saclay, CNRS, UMR 8502, Laboratoire de Physique des Solides, 91405 Orsay Cedex, France
  • Université de Paris, BFA, UMR 8251, CNRS, F-75013 Paris, France
  • Université Paris-Saclay, CEA, CNRS, NIMBE, Gif-sur-Yvette 91190, France


In a biological environment, the adsorption of proteins on nanoparticles (NPs) is an early process that leads to major changes of the physicochemical properties and the biological effects of NPs. The formation of the so-called protein corona drives NP-cell interaction, NP biodistribution, and NP toxicity in vivo. However, few experimental techniques allow for the analysis of the protein corona in situ. As a result, little is known on its structure. Using silica NPs and a library of purified hemoproteins with sizes ranging from 2.8 to 22 nm in diameter (17 to 3,600 kDa in MW), we investigated the effect of protein size on the protein corona assembly by cryo-TEM. Our observations revealed that larger proteins, composed of more than a hundred subunits, form open networks with NPs rather than a homogeneous monolayer of proteins decorating the surface as observed for smaller ones (Figure 1) [1]. The ability of each protein to bind to several NPs drives the formation of novel supramolecular assemblies, while preserving protein structure and function, here in terms of oxygenation properties. By combining cryo-TEM and synchrotron radiation circular dichroism, we further showed that NPs can stabilize partially unfolded protein conformations, thereby driving the formation of a ‘soft protein corona’ consisting of small weakly bound proteins directly adsorbed to the surface, a dynamic process associated with the partial loss of protein structure and stability (Figure 2) [2]. These results highlight the need for in situ analytical approaches to investigate the structuring and driving forces of protein adsorption on nanomaterials to better our understanding of their effects in biologically relevant conditions. Acknowledgements: Cryo-TEM experiments were supported by the METSA network (Proposal FR3507) and by the French Investissements d’Avenir LabEx PALM (ANR-10LABX-0039- PALM). References : [1] From Protein Corona to Colloidal Self-Assembly: The Importance of Protein Size in Protein−Nanoparticle Interactions. Marichal L. et al. Langmuir (2020) 36, 8218-8230. [2] In situ analysis of weakly bound proteins reveals molecular basis of soft corona formation. Sanchez-Guzman D. et al. ACS Nano (2020) 14, 9073-9088.
Jéril DEGROUARD (Orsay)
16:00 - 18:00 #26374 - Structure determination of an artificial virus made of self-assembling cyclodextrin and dsDNA by cryo-EM.
Structure determination of an artificial virus made of self-assembling cyclodextrin and dsDNA by cryo-EM.

Mauricio G.S. Costa *, Zakaria L DahmaniCharline FagnenCarlos A.H. FernandesLeonid LavnevichCatherine Vénien-BryanMatthieu Sollogoub

  • Sorbonne Université, Muséum National d'Histoire Naturelle, Institut de Minéralogie, Physique des Matériaux et Cosmochimie, IMPMC, UMR 7590, CNRS, Paris, France
  • Sorbonne Université, Faculté des Sciences et d’Ingénierie, Institut Parisien de Chimie Moléculaire, Paris, France


Therapeutics based on siRNA are very promising. siRNA are very short double-stranded RNA with the ability to specifically inhibit the expression of a gene. This discovery is promising but meets some difficulties to be applied. One of the major obstacles is relative to their use as drugs, they need an efficient and non-toxic vector to let the siRNA reach its target and plays its role. A key challenge for their development is the design of sophisticated, safe and effective delivery methods. However, the development of such vectors for therapeutics on an industrial scale remains complicated and very expansive. Thus the imitation of their self-assembled highly cooperative structure with artificial systems is a real challenge. Taking into consideration this fact, we synthetized an artificial virus inspired by the tobacco mosaic virus to bring the siRNA to the targeted cell. Complexes cyclodextrin/siRNA (CD-siRNA) and CD-dsDNA were realized in fiber form. Our goal is to understand the assembly mechanism between the cyclodextrin and the cdDNA, for that an electron microscopy study has been led on this complex to resolve this structure at high-resolution. The complexation of CD-dsDNA was checked by electrophoresis studies. The fiber synthetized is a polymer of very big molecur weight. In order to determine the 3D structure of the complex, it is necessary to choose a method able to deal with big sizes systems. It is for this reason that cryo-EM was chosen to build the structure in 3D to understand the assembly mechanism of the complex CD-dsDNA. The 3D structure of these fibers made of CD-dsDNA at high resolution was calculated from cryo-EM images combined witrh image analysis. This structure gives some clues on the organization of the cyclodextrins and their interaction with the siRNA. Reference: 1. Kanasty, R., et al.. Delivery materials for siRNA therapeutics. Nat Mater 12, 967–977 (2013)
Mauricio G.s. COSTA (Sorbonne Université)
16:00 - 18:00 #26375 - Combined Hamiltonian Monte Carlo and Normal Mode Flexible Fitting.
Combined Hamiltonian Monte Carlo and Normal Mode Flexible Fitting.

Rémi Vuillemot *, Slavica JONIC

  • IMPMC - UMR 7590 CNRS, Sorbonne Université, MNHN, Paris, France


Density volumes obtained by three-dimensional reconstruction of biomolecular complexes from cryogenic electron microscopy (cryo-EM) images (also known as cryo-EM maps) can be interpreted in terms of atomic positions by flexible fitting. The fitting modifies an available atomic structure to match the target EM map. The most accurate fitting methods are based on atomic-coordinate degrees of freedom (e.g. Molecular Dynamics (MD), Monte-Carlo Simulation) but come with high computational cost for large required displacements. To reduce the computational cost, methods based on Normal Modes Analysis (NMA) decrease the number of degrees of freedom to only several collective motions (described by normal modes). The NMA-based methods are well-suited for global atomic displacements (large collective motions) but are suboptimal regarding local atomic displacements. To take advantages of both methods, we propose to combine them. More precisely, we combine Hamiltonian Monte Carlo and normal mode flexible fitting. We tested our method using synthetic and experimental cryo-EM maps of several complexes with large-scale conformational changes. Fig.1 shows the result of the fitting of a synthetic cryo-EM map of p97 ATPase. It shows that the combination of both approaches efficiently performs global and local atomic displacements and that it is more efficient and precise than any of the two approaches alone. The presentation will include experimental cryo-EM map fitting examples. To the best of our knowledge, this is the first flexible fitting method combining a Bayesian approach based on Hamiltonian Monte Carlo sampling and normal mode analysis.
Rémi VUILLEMOT (Paris)
16:00 - 18:00 #26376 - Tundra Cryo-TEM: Cryo-TEM that is cost effective and easy to use, bringing cryo-electron microscopy to every biochemistry laboratory.
Tundra Cryo-TEM: Cryo-TEM that is cost effective and easy to use, bringing cryo-electron microscopy to every biochemistry laboratory.

Massimiliano Maletta *

  • TFS


One of the primary challenges of investigating dynamic biological processes, and how they fail in disease, is the complexity inherent to biological machinery. Large and/or dynamic protein systems present a unique challenge to traditional methods of scientific inquiry, which study these systems either indirectly or in isolation. Fortunately, cryo-electron microscopy (cryo-EM) single particle analysis (SPA) has emerged as a well-suited approach for the direct determination of native function and dynamics in complex biological systems. Single particle analysis can validate your biochemistry work by showing the molecular details that underlie the interactions between proteins, small molecules, and post-translational modifications in large and dynamic protein systems at near native conditions. These molecular details confirm the mechanism of action by which complex biological systems (e.g. membrane proteins, protein complexes, and macromolecular machines such as viruses, ribosomes, and proteasomes) contribute to human health and disease. For example, the human GABAA (gamma-aminobutyric acid type A) receptor is a small membrane protein and ligand-gated chloride-ion channel that mediates inhibitory neurotransmission. GABAA receptors are important therapeutic targets as their various conformations affect a variety of important signaling pathways. Due to GABAA's conformational flexibility, traditional methods have been unable to reveal its molecular mechanism of action. The ability of cryo-EM to image large, biologically complex structures has, meanwhile, allowed researchers to see the molecular details that underpin the allosteric modulation of this important receptor. With the Tundra Cryo-TEM, more scientists can have access to this type of information for their complex biological systems. Our applications scientists have used the Tundra Cryo-TEM to determine a 3D structure of GABAA to ~4-5 Å resolution. At this resolution, molecular details such as individual alpha helices and beta sheets are clearly visible, molecular structures can be docked, and molecular interactions modeled. Additionally, the Tundra Cryo-TEM was able to achieve 3 Å resolution for the rigid benchmark protein apoferritin. At this resolution, the protein backbone can be traced, and major amino acid side chains are clearly visible, making de novo model building possible. Data at these resolutions helps you understand how proteins function, how to modify genes, and how to design drugs accordingly.
Max MALETTA (, )
16:00 - 18:00 #26377 - Cryo-EM structure of the yeast SWI/SNF complex.
Cryo-EM structure of the yeast SWI/SNF complex.

Maximilien Werderer *, Adam Ben-ShemGabor PapaiCorinne CrucifixPatrick Schultz

  • Institut de Génétique et de Biologie Moléculaire et Cellulaire (IGBMC), Illkirch, France


Diploid human cells contain 2 meters of DNA condensed within a 5 μm nucleus. This condensed DNA is not accessible to the transcription machinery, and must be spatially organised to allow the decompaction and expression of specific genes when deemed necessary by the cell. DNA is packaged into chromatin and its level of compaction is regulated by protein complexes called chromatin remodelers. One of these chromatin remodeling complexes is the switching defective/sucrose nonfermenting (SWI/SNF) complex. It is highly conserved from yeast to human and regulates many critical cellular processes, including gene expression, cellular differentiation and DNA repair by using the energy of ATP to remodel the structure of the chromatin. SWI/SNF has recently been identified as a tumor suppressor in human malignancies as proteomics studies revealed that the complex subunits of the complex are mutated in almost 20% of all human tumors leading to aberrant SWI/SNF complexes [1]. However, the mechanical details of the SWI/SNF remodelling activity remain poorly understood, hindered by the lack of high resolution structure of the complex. Cryo-Electron Microscopy (Cryo-EM) is used to investigate the structure of proteins and complexes by imaging hydrated samples in vitrous ice in a transmission electron microscope. Recent advances in hardware and software allows Cryo-EM to image multi-protein complexes at sub-nanometer resolution and solve their atomic structure. Here we present the structure of the yeast SWI/SNF complex from the yeast Pichia pastoris obtained through Cryo-EM at near atomic resolution (Fig. 1). The high degree of structural conservation between yeast and human allow us to map mutations identified in human cancers and provides new insight into mechanistic implication of these mutations (Fig. 2). References: [1] Kadoch, C., Hargreaves, D. C., Hodges, C., Elias, L., Ho, L., Ranish, J., & Crabtree, G. R. (2013). Proteomic and bioinformatic analysis of mammalian SWI/SNF complexes identifies extensive roles in human malignancy. Nature Genetics, 45(6), 592–601. https://doi.org/10.1038/ng.2628
Maximilien WERDERER (Illkirch)
16:00 - 18:00 #26378 - Structural insights into how bS1 promotes translation.
Structural insights into how bS1 promotes translation.

Gaetano D'Urso *, Sophie ChatReynald GilletEmmanuel Giudice

  • Université Rennes, CNRS, Institut de Génétique et Développement de Rennes (IGDR) UMR 6290, Rennes, France


In prokaryotes, the initiation of the translation is known to be directed by the mRNA Shine – Dalgarno (SD) sequence [1]. However, some mRNAs contain a weak or even no SD [2]. In these cases, the bS1 protein has been show to efficiently promote the initiation of translation [3, 4]. bS1 is a bacterial ribosomal protein composed of six domains (D1 to D6). The N-terminal end (D1 – D2) interacts with the 70S [4-6] while the rest of the protein (D3 to D6) forms a flexible arm catching mRNAs [7]. In the present study we characterized, using cryo-EM, the role of E. coli bS1 protein during the initial steps of translation (Figure 1). In agreement with the previous founding, the interaction is primarily based on the stacking between bS1 and 70S uS2 (Figure 1). Surprisingly, the D2 assumes a new conformation thanks to a partial misfolding of the helix connecting the two domain, placing an hydrophobic pocket just upstream the SD – anti SD base pairing. These results suggest the involvement of D2 in the correct positioning of mRNA into the ribosome and in the stabilization of the SD – anti SD base pairing, as well as its fundamental role in contacting the ribosome. References: [1] Shine J, Dalgarno L. Proc Natl Acad Sci USA. 71 (1974), p. 1342-6 [2] Marzi, S. et al. Myasnikov, A. G., Serganov, A., Ehresmann, C., Romby, P., Yusupov, M., Klaholz, B. P. Cell Press. 130 (2007), p. 1019-1031 [3] Irina V. Boni, Dilara M. lsaeva, Maxim L. Musychenko, Nina V. Tzareva, Nucleic Acids Research, 19 (1991), p. 155–162 [4] Salah P, Bisaglia M, Aliprandi P, Uzan M, Sizun C, Bontems F. Nucleic Acids Res. 37 (2009), p. 5578-88. [5] Loveland, A. B., Korostelev, A. A. Methods. 137 (2018), p. 55-66 [6] Byrgazov K, Grishkovskaya I, Arenz S, Coudevylle N, Temmel H, Wilson DN, Djinovic-Carugo K, Moll I. Nucleic Acids Res. 43 (2015), p. 661-73 [7] Duval, M., Korepanov, A., Fuchsbauer, O., Fechter, P., Haller, A., Fabbretti, A., Choulier, L., Micura, R., Klaholz, B. P., Romby, P., Springer, M., Marzi, S. PLOS Biology. 11 (2013), e1001731
Gaetano D'URSO (Rennes)
16:00 - 18:00 #26381 - Mode de processivité de la formine mDia1 aux extrémités barbées des filaments d'actine élucidé par microscopie électronique.
Mode de processivité de la formine mDia1 aux extrémités barbées des filaments d'actine élucidé par microscopie électronique.

Julien Maufront *, LuYan CaoBérengère GuichardDaniel LevyAntoine JégouGuillaume Romet-LemonneAurélie Bertin

  • Institut Curie UMR168
  • Institut Jacques Monod


Les Formines stimulent la nucléation et l'élongation rapide des filaments d'actine non branchés dans les cellules. À l’échelle moléculaire, elles constituent des homodimères capables d’interagir avec les extrémités barbées des filaments d’actine en élongation via leurs domaines FH2. Bien que les changements conformationnels impliqués dans ce processus n'aient jamais été observés directement, des études suggèrent que le dimère de FH2 se déplace pas à pas à l'extrémité barbée à travers un équilibre entre deux états dits « fermé » et « ouvert ». Plusieurs modèles ont pu être proposés pour décrire ces deux états conformationnels ainsi que la transition de l’un vers l’autre comme le modèle de la « marche enjambée » ou le modèle du « saut enclenché ». Aucune structure en microscopie électronique n’avait été obtenue jusqu’à présent pour lever ces interrogations. En effet, rapidement, en présence de formines, de longs filaments d’actine sont générés et ne permettent pas l’obtention d’une densité élevée de courts filaments coiffés de formines, nécessaire à une analyse en particules isolées. Un goulot d'étranglement a donc dû être surmonté afin de rendre possible une telle analyse avec notamment le choix d’une approche par sonication. Deux structures 3D du complexe bout barbé - formine dans sa conformation majoritaire et minoritaire ont pu être déterminées en coloration négative. Ces deux conformations correspondent respectivement aux états « ouvert » et « fermé » décrits par le modèle de la « marche enjambée » et confortent ainsi ce dernier modèle. Des variations conformationnelles au sein de l’état « ouvert » ont également pu être mise en évidence au cours d’une analyse 2D focalisée. Ces observations ont permis de proposer l’existence d’un chemin d’interaction à l’issu duquel le dimère de FH2 encercle le corps du filament d’actine, en amont de l’extrémité. Cette hypothèse a pu être validée par une analyse 2D suivie d’une reconstruction 3D. La transposition de ces résultats à une approche par cryo-microscopie a été entreprise via l’utilisation de grilles recouvertes d’oxide de graphène. Une quantité limitée d’extrémités a pu être analysée en 2D et 3D confirmant à minima la nature non artéfactuelle des résultats précédents.
Julien MAUFRONT (Paris)
16:00 - 18:00 #27356 - Structural study of the tail tip of siphophage T5.
Structural study of the tail tip of siphophage T5.

Romain LINARES, Grégory EFFANTIN, Charles-Adrien ARNAUD, Claudine DARNAULT , Elisabetta BOERI ERBA , Guy SCHOEHN, Cécile BREYTON

Institut de Biologie Structurale, 71 avenue des Martyrs, CS 10090, 38044 Grenoble Cedex 9, FRANCE



The vast majority (96%) of bacteriophages - bacterial viruses - possess a tail that allows host recognition, cell wall perforation and safe viral DNA channelling from the capsid to the cytoplasm of the infected bacterium. The majority of tailed phages, the Siphoviridae, bear a long flexible tail formed of stacked tail tube proteins (TTP) that polymerise around and along the tape measure protein (TMP). At the distal end of the tail, the tail tip complex harbours the receptor binding protein·s (RBP). Interaction between the RBP with the host surface triggers cell wall perforation and DNA ejection, but little is known on these mechanisms for Siphoviridae. We aim at characterising the mechanism of cell wall perforation and DNA ejection in the siphocoliphage T5. We have determined the structure of T5 TTP and tail tube, before and after interaction with its E. coli receptor, and shown that host binding information is not propagated to the capsid by the tail tube [1]. We now focus on the structure of the tail tip complex, and we will present high-resolution structures of T5 tail tip complex, determined by cryo-electron microscopy and single particle reconstruction on purified T5 tails. We could trace 6 of the 7 proteins that compose it [2, 3], and we will discuss the structural homology with other phages and phage-derived complexes Références/References : [1] Arnaud C-A, Effantin G, Vivès C, Engilberge S, Bacia M, Boulanger P, Girard E, Schoehn G and Breyton C, Bacteriophage T5 tail tube structure suggests a trigger mechanism for Siphoviridae DNA ejection Nat Com, 8, 1953 (2017) [2] Zivanovic, Y, Confalonieri, F, Ponchon, L, Lurz, R, Chami, M, Flayhan, A, Renouard, M, Huet, A, Decottignies, P, Davidson, AR, Breyton, C, and Boulanger, P, Insights into bacteriophage T5 structure from the analysis of its morphogenesis genes and protein components. J. Virol. 88:1162-74 (2014) [3] Flayhan, A, Vellieux, FMD, Lurz, R, Maury, O, Contreras-Martel, C, Girard, E, Boulanger, P, and Breyton, C Crystal structure of pb9, the distal tail protein of bacteriophage T5: A conserved structural motif among all siphophages. J. Virol. 88, 820-8 (2014)
Romain LINARES (Grenoble)
16:00 - 18:00 #26356 - ORGANISATION SUPRAMOLECULAIRE DANS LES FIBRES DE COLLAGÈNE.
ORGANISATION SUPRAMOLECULAIRE DANS LES FIBRES DE COLLAGÈNE.

Amélie LEFORESTIER *, Gervaise MOSSERJéril DEGROUARDJean CHARVOLINJean-François SADOC

  • Université Paris-Saclay, CNRS UMR8502, Laboratoire de Physique des Solides, 91405, Orsay, France
  • Sorbonne Université, CNRS UMR 7574, Laboratoire de chimie de la matière condensée de Paris, 75005 Paris


Le collagène est le principal polymère de la matrice extracellulaire chez les vertébrés. Il joue un rôle essentiel dans l’intégrité des tissus, dans leurs propriétés mécaniques (peau, tendon, cartilage) ou optiques (cornée). La matrice de collagène présente une structure hiérarchique : les triples hélices forment des fibrilles striées de diamètre variable (20-200 nm), qui elles-mêmes présentent différents types d’arrangements supra-fibrillaires. Malgré de nombreuses études, la structure des fibrilles est très mal connue. Le modèle d’organisation longitudinale échelonnée [1], explique de façon simple les striations du collagène de type I, mais ne contribue pas à une description de l’organisation 3D. Différents modèles théoriques ont été proposés, sans que la diffusion des rayons X ne permette de trancher, du fait d’une coexistence structurale d’ordre et de désordre : i) Une organisation poly-cristalline de micro-fibrilles pentagonales aplaties avec des lignes de dislocations radiales [2]. ii) Une organisation phyllotactique [3] (Figure 1A) qui présente une coexistence ordre-désordre intrinsèque et assure une densité optimale par ses lignes de dislocations circulaires (cercles verts et bleues). En nous appuyant sur un ensemble de techniques de microscopie, nous analysons l’organisation du collagène au sein des tendons de souris. En particulier, nous analysons l’organisation latérale des triples hélices au sein des fibrilles en utilisant la cryo microscopie électronique de sections vitreuses (CEMOVIS). Nous montrons que les triples hélices de collagène peuvent être ainsi visualisées (Figure 1C, D). Un ordre hexagonal local est mis en évidence (Figure 1C, C’). Nous analysons le facettage des fibrilles, l’ordre local et la torsion entre molécules. A plus long terme, les impacts de différentes pathologies sur ces organisations pourraient être mise en évidence et révéler ainsi des déstructurations aux échelles nanométriques. Références : [1] Petruska J.A., Hodge A.J. (1964) Proc. Natl. Acad. Sci. USA 51, 871. [2] Hulmes D.J. (2002). J. Struct. Biol., 137, 2-10. [3] Charvolin J., Sadoc J.F. (2014) Biophysical Reviews and Letters, 9, 225-238 ; Charvolin J., & Sadoc J.F. (2013) Biophysical Reviews and Letters, 8, 33-49.
Amélie LEFORESTIER (Paris-Saclay)
16:00 - 18:00 #26358 - Order and disorder in DNA toroids analyzed by cryo electron tomography.
Order and disorder in DNA toroids analyzed by cryo electron tomography.

Kahina VERTCHIK *, Cédric MESSAOUDISylvain TREPOUTAmélie LEFORESTIER *

  • Université Paris-Saclay, CNRS, Laboratoire de Physique des Solides, 91405 Orsay, France.
  • Multimodal Imaging Center, Centre Institut Curie, PSL Research University, CNRS, Université Paris-Saclay, INSERM, 91401 Orsay, France.


DNA toroids are complex nanometer-scale liquid crystalline objects that combine properties of both biological and material sciences objects. They spontaneously form in vitro in the presence of spermine 4+ that condenses DNA in solution. In these condensates, DNA strands locally organize with hexagonal packing, but topological constraints impose the existence of defects. Deviation from hexagonal order arise from the continuity of the DNA chain that creates crossover defect [1] and from the competition between twist induced by the DNA helices and the parallelism of hexagonal lattice which creates frustration [2]. In order to investigate the links between the macroscopic and microscopic structure of toroidal condensates, DNA toroids obtained from bacteriophage ejecting their genome in the presence of spermine [3] were investigated using cryo electron tomography. Tomogram reconstruction allowed a direct visualization of the hexagonal lattice of the DNA helices. However, Bragg contrast precludes unambiguous analyses in most regions. We therefore analyze local order in 2D images extracted from the tilt series in relationship with the overall shape of the condensate obtained in the reconstructed tomogram. Segmentation of the toroids reveals the existence of a disordered region, less dense that hexagonally packed regions. These regions could be related to bridge defects predicted by simulations [4] and/or concentration of DNA ends. A faceting of toroids is also highlighted. We analyze the relationship between the rotation of the lattice [2] and the faceting of the toroid. References: [1] Hud N.V., Downing K.H. (2001) Proc. Natl. Acad. Sci. USA 98, 14925-14930. [2] Leforestier A., Livolant F. (2009) Proc. Natl. Acad. Sci. USA, 106, 9157-9162. [3] Barberi L., Livolant F., Leforestier A., Lenz M. (2020) Nucleic Acid Res., in press. [4] Dey A., Reddy G. (2017) J. Phys. Chem B, 121, 9291.
Kahina VERTCHIK (Orsay)
16:00 - 18:00 #26360 - Deciphering chromatin organization in situ using cryo-electron tomography and image denoising techniques.
Deciphering chromatin organization in situ using cryo-electron tomography and image denoising techniques.

Fadwa FATMAOUI *, Diana GREWEAmelie LEFORESTIERMikhail ELTSOV

  • Institut de Génétique et de Biologie Moléculaire et Cellulaire (IGBMC), Illkirch
  • Buchmann Institute for Molecular Life Sciences, Frankfurt
  • Laboratoire de Physique des Solides, Orsay


Cryo-electron tomography (cryo-ET) has recently emerged as one of the main methods for high-resolution characterization of biological structures. While single-particle approaches require averaging images of a number of identical structures, cryo-ET allows direct three-dimensional imaging of biological structures with nanometer resolution in situ, which is particularly advantageous for studying complex pleomorphic structures. We apply in situ cryo-ET to analyze chromatin, which exhibits a high degree of heterogeneity at all levels of its organization, starting with nucleosome particles [1]. Tomographic resolution is directly dependent on sample thickness, so we use vitreous cryosectioning (CEMOVIS, [2]) to obtain < 100 nm thick slices from vitrified Drosophila embryos to provide visualization of fine structural details (Figure 1).The second major obstacle to the structural interpretation of tomographic reconstructions is the very low signal-to-noise ratio. The conventional solution to this problem is based on averaging of subvolumes to remove noise, but it cannot be applied to pleomorphic chromatin fibers. We demonstrate that recent denoising algorithms based on deep learning [3] can effectively deal with noise in our cryo-ET data, thereby providing visibility of fine structural details of in situ chromatin organization (Figure 2). Acknowledgements: We acknowledge the support of the French National Research Agency (ANR-20-CE11-0020-02 to ME, ANR-20-CE11-0020-01 to AL); German Research Foundation (DFG EL 861/1 to ME). References: [1] Eltsov et al., Nucleic Acids Research, 46 (2018), p. 9189–9200 [2] Al‐Amoudi et al., EMBO Journal, 23(2004), p. 3583-3588 [3] Tegunov and Cramer, Nature Methods, 16(2019), p. 1146–1152
Fadwa FATMAOUI (Illkirch)
16:00 - 18:00 #26361 - Nanometric Probes for Cryo-Tomography Analysis.
Nanometric Probes for Cryo-Tomography Analysis.

Victor Hanss *, Guy ZuberMikhail EltsovPatrick Schultz

  • Institut de Génétique et de Biologie Moléculaire et Cellulaire (IGBMC), Integrated Structural Biology, Centre National de la Recherche Scientifique (CNRS), UMR 7104, Institut National de la Santé et de la Recherche Médicale (INSERM), U1258
  • Ecole Supérieure de Biotechnologie Strasbourg (ESBS), Biotechnologie et Signalisation Cellulaire, Centre National de la Recherche Scientifique (CNRS), UMR 7242, Université de Strasbourg, lllkirch, France.


In vitro macromolecular structure analysis methods do not represent the macromolecules architecture under cellular constrains. We therefore aim at observing biomolecules within vitrified cellular sections by cryo electron tomography. However, transient molecular partners, which can be small and rare, are difficult to identify. To overcome this barrier, we want to label macromolecules of interest within human cells with antibodies conjugated to gold nanoparticles (AuNp) before cell vitrification. Structure studies on in vivo labelled molecules requires the following steps (Fig. 1). First, electron dense AuNps are conjugated to a probe and electroporated into cells [1]. Cryo-fixation is then performed by plunge freezing or high pressure freezing. Since only less than 300 nm thick samples can be used for sub-molecular structure analysis, the sample needs to be thinned [2]. : Cryo-EM of vitreous sections (CEMOVIS) generates thin sections of the cryo-fixed sample [3]. Alternatively focused ion beam (FIB) thinning mills thin lamellae of the vitrified samples directly on the EM grid [2]. Here we show preliminary data of antigen binding fragment (Fab) conjugated with 2,4 nm diameter AuNps directed towards the Human RNA polymerase DNA dependant II C-terminal domain (RNAPII-CTD). In order to control the fab conjugate efficiency and specificity we fixed, permeabilized and incubated Hela cells with anti RNAPII-CTD mice Fabs (fab@RNAPII-CTD). A fluorescent detection in immunohistochemistry was performed with a second antibody coupled to the Alexa488 fluorophore (@mouse-Alexa488). The Alexa488 signal from the fab incubated Hela cells overlaps with Hoechst’s nucleus stain (Fig. 2, 1 b,e) while the weak signal from buffer incubated cells is not (Fig. 2, 1 d,f). The same was observed after silver enhancement of AuNps within incubated Hela cells (Fig. 2, 2). Fab@RNAPII-CTD incubated cells show a strong nuclear signal after silver enhancement. These preliminary data suggest that the gold-conjugated fab kept its specificity towards RNAPII-CTD after AuNp conjugation. References: [1] N. Groysbeck et al., Nanotechnology, vol. 30 (2019) p. 184005 [2] M. Schaffer, et al., Journal of Structural Biology, vol. 197 (2017) p. 73‑82 [3] A. Al-Amoudi et al., EMBO J, vol. 23 (2004) p. 3583‑3588
Victor HANSS (Illkirch)
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Jeudi 08 juillet
10:00

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SC3
10:00 - 12:10

Symposium Commun 3
Nouvelles microscopies : Microscopies de phase, Champ proche et Sonde locale, Super résolution optique

Modérateurs : Damien JACOB (UMET, Lille), Elisabeth WERKMEISTER (Institut Pasteur, Lille)
Les dernières avancées technologiques concernant les microscopes et les détecteurs font de la microscopie de phase, la microscopie à sonde locale et la microscopie photonique super résolution, des outils en pleine évolution pour étudier à l’échelle atomique les matériaux et leurs propriétés ainsi que des échantillons biologiques à des résolutions allant jusqu’au nanomètre. En sciences de la vie, les techniques sont de plus en plus résolutives et rapides et sont adaptées à l’imagerie de compartiments subcellulaires. Ce symposium permettra de montrer l’évolution de ces différentes techniques et leur intérêt dans le domaine des sciences de la vie ou de la matière au travers de la présentation d’applications récentes.
10:00 - 10:30 3D nanoscale imaging using single-objective light-sheet microscopy. Jean-Baptiste SIBARITA (IINS, Bordeaux)
Assessing protein organization and dynamics in their native cellular context provides invaluable insights into their activities and functions. Fluorescence microscopy has drastically improved and diversified over the last 20 years, allowing major discoveries in cell biology, neuroscience and developmental biology. Single molecule localization microscopy (SMLM) allows monitoring the evolution of fluorescent markers with down to single molecule spatial resolution. However, it remains limited in its throughput, its capability to investigate 3D biological samples, and the quantifications that can be obtained.
In order to overcome these limits, we have developed a single objective Selective Plane Illumination Microscope (soSPIM) [1], as well as several popular point-cloud analysis methods dedicated to SMLM data [2, 3]. soSPIM is a light-sheet microscopy technique operating on a standard inverted microscope equipped with high NA objectives, compatible with single molecule imaging. It relies on dedicated microchips embedding arrays of microwells flanked with 45° micro-mirrors acting as light guides and culture vessels. In this talk, I will present our recent acquisition and analysis workflow to perform quantitative single cell 3D nanoscopy of membrane receptors, and discuss the challenges for its broad adoption by the scientific community.

[1] R. Galland, G. Grenci, A. Aravind, V. Viasnoff, V. Studer, J.B. Sibarita, 3D high- and super-resolution imaging using single-objective SPIM, Nat Methods, 12 (2015) 641-644.
[2] F. Levet, E. Hosy, A. Kechkar, C. Butler, A. Beghin, D. Choquet, J.B. Sibarita, SR-Tesseler: a method to segment and quantify localization-based super-resolution microscopy data, Nat Methods, 12 (2015) 1065-1071.
[3] F. Levet, G. Julien, R. Galland, C. Butler, A. Beghin, A. Chazeau, P. Hoess, J. Ries, G. Giannone, J.B. Sibarita, A tessellation-based colocalization analysis approach for single-molecule localization microscopy, Nature communications, 10 (2019) 2379.
10:30 - 10:40 Discussion.
10:40 - 11:10 En quête de sources brillantes : une source ponctuelle d'électrons isolant/conducteur. Evelyne SALENÇON (CINaM, Marseille)
Le développement de sources brillantes permet des ruptures technologiques, notamment dans le domaine de la microscopie. Cela passe par un contrôle et une compréhension très avancés des mécanismes d’émission.
Dans le cas de sources brillantes d’électrons, un microscope à projection fournit, à partir d'une pointe à émission de champ, une image interférentielle qui correspond à un enregistrement holographique. La reconstruction des images peut être effectuée numériquement pour former une image « réelle » de l’objet. Mais, l’obtention d’images interférentielles n’est possible qu’avec une source « ponctuelle, et, monochromatique » : souvent, une pointe ultrafine de tungstène dont le rayon de courbure est de l’ordre de 10nm.
La résolution ultime de ce type de microscope, mettant en œuvre une projection, ne dépend que de la taille de la source apparente (1). C’est pourquoi nous utilisons un microscope à projection pour caractériser une source dans son intégralité : l’analyse du contraste interférentiel permet d’estimer la taille de la source, par exemple.

Nous montrerons ensuite qu'il n'est pas indispensable de recourir à des pointes ultrafines en tungstène pour obtenir des sources brillantes. En appliquant des tensions induisant un champ électrique macroscopique faible (<1V/μm), nous avons en effet observé de l'émission de champ, intense à partir de cristaux isolants, microniques, déposés sur des conducteurs à fort rayon de courbure (>10μm)! De surcroît par l’analyse des hologrammes nous avons mesuré la taille de source et avons démontré que la brillance de ces nouveaux émetteurs égalait la brillance des sources à émission de champ classiques (2).

1. W. Stocker, H.W. Fink, and R. Morin. Low-energy electron and ion projection microscopy. Ultramicroscopy, 31 (379), 1989.
2. E. Salançon, Alain Degiovanni, Laurent Lapena, Mehdi Lagaize, and Roger Morin. Preparing a celadonite electron source and estimating its brightness. Journal of visualized experiments: JoVE, 153, 2019.
11:10 - 11:20 Discussion.
11:20 - 11:40 #26235 - Capacité Invasive de Cellules Gliales modulées par des Nanoparticules d'or-gadolinium.
Capacité Invasive de Cellules Gliales modulées par des Nanoparticules d'or-gadolinium.

Glioblastoma are characterized by an invasive phenotype, which is thought to be responsible for recurrences and the short overall survival of patients. In last decade, the promising potential of ultrasmall gadolinium chelatecoated gold nanoparticles (namely Au@DTDTPA(Gd)) was evidenced for image-guided radiotherapy in brain tumors. Considering the threat posed by invasiveness properties of glioma cells, we were interested to further investigate the biological effects of Au@DTDTPA(Gd) by examining their impact on GBM cell migration and invasion. In our work, exposure of U251 glioma cells to Au@DTDTPA(Gd) led into high accumulation of gold

nanoparticles, that were mainly diffusely distributed in the cytoplasm of the tumor cells. Experiments pointed out a significant decrease in glioma cells invasiveness when exposed to nanoparticles. As the proteolysis activities were not directly affected by the intracytoplasmic accumulation of Au@DTDTPA(Gd), the anti-invasive effect cannot be attributed to a matrix remodeling impairment. Rather, Au@DTDTPA(Gd) nanoparticles affected the intrinsic biomechanical properties of U251 glioma cells, such as cell stiffness, adhesion and generated traction forces, and significantly reduced the formation of protrusions, thus exerting an inhibitory effect on their migration capacities. These results highlight the interest of Au@DTDTPA(Gd) nanoparticles for the therapeutic management of astrocytic tumors, not only as radio-enhancing agent but also by reducing invasive potential of glioma cells.


Alexandre BERQUAND (Reims)
11:40 - 11:50 Discussion.
11:50 - 12:00 Axia ChemiSEM : new and fully integrated SEM EDS workflow - Thermo Fisher Scientific. Stefan SCHWARZMUELLER (Allemagne)
12:00 - 12:10 Discussion.
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13:10

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SDV3
13:10 - 15:45

Symposium Sciences de la Vie 3
Imageries, spectroscopies en applications biomédicales
sdv3

Modérateurs : Emmanuel BEAUREPAIRE (Polytechnique, Paris), Ignacio IZEDDIN (Institut Langevin, ESPCI, Paris)
Ce symposium explorera le domaine très actif de la microscopie optique multidimensionnelle, des microscopies multiphotoniques, à super-résolution, à feuille de lumière, et d'autres nouvelles modalités, ainsi que leurs applications biologiques et médicales. Nous espérons que le large éventail de sujets pertinents présentés lors de cette conférence encouragera l'interaction entre les experts en instrumentation, en gestion et analyse d’images, et les chercheurs dans les différents domaines d'application.Nous vous invitons à présenter des contributions portant sur tous les domaines de développement et d'application des d’approches telles que :
- imagerie optique à super-résolution (PALM, STORM, STED, SIM, etc)
- l'imagerie à feuille de lumière de spécimens biologiques complexes ou de grande taille (SPIM et dérivées)
- microscopies multiphotoniques de tissus biologiques (2PEF, 3PEF, SHG, THG, CARS, SRS, etc)
- microscopies de phase ou de polarisation
- microspectroscopies
- Modalités FRET-FLIM et de fluorescence avancées
- développements instrumentaux
- applications à la biologie cellulaire, à la biologie du développement, aux neurosciences, aux modèles animaux
- applications cliniques
13:10 - 13:40 Enregistrement de l’activité neuronale à haute cadence chez la souris non-contrainte par imagerie confocale de fluorescence. Cathie VENTALON (ENS PSL, Paris)
Grâce au développement de l’optogénétique et en particulier de sondes calciques génétiquement encodées permettant la mesure de l’activité neuronale par imagerie de fluorescence, les méthodes optiques sont devenues des outils majeurs pour les études de neuroscience intégratives. Néanmoins, l'imagerie de l’activité neuronale chez la souris libre de se mouvoir est difficile en raison de contraintes de miniaturisation sévères. Ainsi, les méthodes utilisées actuellement présentent des limitations importantes : les microscopes large-champ conventionnels miniatures sont limités par un fort arrière-plan flou, et les microscopes à 2 photons miniatures souffrent de petits champs de vue ou de faibles cadences d’acquisition. Dans ce projet, nous avons mis au point un nouveau fibroscope permettant l’imagerie de l’activité neuronale par microscopie confocale de fluorescence à haute cadence (100 Hz), sur un champ de vue de 230 µm chez la souris non-contrainte.
Le dispositif est composé d'un microscope confocal couplé à l'animal avec un guide d’image et un micro-objectif. Le rapport signal sur bruit des enregistrements d’activité étant un paramètre critique, nous avons optimisé l’efficacité de détection de la fluorescence :
- Au sein du microscope, des lignes d’illumination sont créées par un DMD, tandis que les lignes (« pinholes ») de détection sont créées directement sur une caméra sCMOS fonctionnant en mode « feuille de lumière ». Ces deux lignes sont balayées simultanément.
- Nous avons développé de nouveaux micro-objectifs à haute ouverture numérique (0.7) permettant de gagner un facteur 2 à 3 sur le signal par rapport à des micro-objectifs à lentilles GRIN commerciaux
Nous avons appliqué le fibroscope à l’imagerie de l’activité neuronale dans l’hippocampe de souris non contraintes. L’hippocampe est l’une des régions du cerveau impliquées dans le codage de l’espace, et il contient en particulier des cellules de lieu, codant pour des positions précises de l’animal dans son environnement. Nous avons réalisé des sessions d’enregistrement de l’activité neuronale à 100Hz pendant 1.5h, en alternant des périodes de repos et de navigation sur une piste linéaire. Ces sessions sont reproduites chaque semaine, de façon à suivre l’évolution du codage spatial au cours du temps. Les premières analyses ont montré que le fibroscope permettait de suivre l’activité de 50 à 100 cellules de lieu dans chaque souris, et il devrait être donc un outil pertinent pour étudier le codage spatial à la fois sur des échelles de temps très courtes et très longues.
13:40 - 13:50 Discussion.
13:50 - 14:20 Multi-scale imaging using the soSPIM technology (single-objective Selective Plane Illumination Microscopy). Rémi GALLAND (IINS, Bordeaux)
Light microcopy offers to the cell biologists the capability to monitor living samples in conditions similar to their native environment. Combined with fluorescent probes, it opened the unique opportunity to image proteins of interest with a very high specificity and in a minimally invasive manner within 3D living samples. Since about fifteen years, 3D fluorescence microscopy for biology is undergoing an in-depth revolution with the advent of Light-Sheet Fluorescence Microscopy (LSFM or SPIM) technics which enable to tackle many limitations of standard 3D imaging technics in term of photo-toxicity, speed and sensitivity. Common LSFM implementation use at least two objective lenses positioned perpendicularly one from the other to create a thin sheet of light and collect the fluorescence signal respectively. However, this multi-objective architecture comes with some drawbacks. It prevents the possibility to use bulky high numeral aperture objective and limits the achievable imaging throughput due to complex sample mounting.
To overcome those limitations, we developed an alternative architecture, called soSPIM (single-objective Selective Plane Illumination Microscope), which uses a single objective to create both the excitation light-sheet and collect the fluorescent signal. It relies on the integration of 45° mirrors directly into the imaging devices in place of the excitation objective along with a laser beam steering unit. I will discuss the multiscale imaging capability of the soSPIM technology which allows to image the nanoscale organization of proteins within single cells up to the development of living 3D organoids by varying the size and design of the imaging devices. Especially, I will present the recently engineered multiwell devices, named JeWells, that enable to turn the soSPIM system into a high-content screening platform of living 3D cellular cultures (spheroids/organoids) greatly improving the imaging throughput of 3D imaging technics.
14:20 - 14:30 Discussion.
14:30 - 14:45 #26362 - Towards automation of mechanobiological measurements by atomic force microscopy (AFM).
Towards automation of mechanobiological measurements by atomic force microscopy (AFM).

Atomic force microscopy (AFM) has proven to be a powerful tool for performing biomechanical force measurements on living cells. However, this technology requires methodological improvements to be applied realistically to the medical field. To perform statistically relevant experiments, we need to automate AFM force measurements on living cells. A first strategy has been developed on C. albicans cells and we now want to be able to apply it to human cells. The strategy consists of two phases: patterning of cells in a defined network; measurement of mechanobiological properties by force spectroscopy.

To create the cells arrays, we pattern fibronectin by microcontact-printing (µCP) according to specific geometrical features and spacing. The master molds are designed and fabricated in LAAS-CNRS cleanroom facilities and µCP is performed automatically by Innostamp40TM (innovation of the joint lab between LAAS and Innopsys: BIOSOFT). Innostamp40TM prints fibronectin arrays by physical contact between a microstructured and inked PDMS stamp and a glass slide. Finally, the cells are seeded on the fibronectin array and organize themselves in the form of an ordered matrix (Fig. 1).

We need to automate biomechanical AFM measurements on each spot of the array occupied by a cell. To reach this goal we are developing and adapting an algorithm based on a Jython script [1]. The script needs the centre coordinates of the first and last cell of the matrix and the number of cells between them, which allows calculating the distance between each cell. Then the AFM tip indents the first cell and then automatically moves to the next, recording force curves on each cell (Fig. 2). The aim of automation is to be able to analyse cell populations, instead of the usual few tens of cells. We applied this methodology to PC3 and RWPE-1 cells (grade IV prostate adenocarcinoma cell line derived from bone metastases and immortalized normal prostate cell line). The results obtained on the two cell lines will be compared by conventional analysis of cell stiffness and stress and by using supervised machine learning algorithms.

Reference:

[1] Severac et al. Automation of Bio-Atomic Force Microscope Measurements on Hundreds of C. albicans Cells. JOVE, (2020)


Ophélie THOMAS-CHEMIN (Toulouse)
14:45 - 14:55 Discussion.
14:55 - 15:10 #26363 - Individual characterization of drug nanocarriers for a comprehensive analysis of their degradation mechanisms.
Individual characterization of drug nanocarriers for a comprehensive analysis of their degradation mechanisms.

Over the last two decades, a plethora of drug nanocarriers have been developed to improve the therapeutic effect of their cargo. As “smart” vehicles, they enable the delivery of the intact drug across biological barriers such as cellular membranes. Recently, there has been an increasing interest for hybrid nanocarriers named nanoscale metal-organic frameworks (nanoMOFs). [1] Built by the self-assembly of metal clusters and organic linkers, these nanoparticles exhibit a highly porous structure allowing the incorporation of a wide variety of chemical species. Taking advantage of their versatile composition, their physicochemical properties can be customized with respect to the drug to be incorporated and to the biological target. Among nanoMOFs families, MIL-100(Fe) (MIL standing for Material of Institute Lavoisier) were among the most studied drug nanocarriers due to their biocompatibility, biodegradability and hydrophilic/hydrophobic inner microenvironment, which combined to their high surface area (~1700 m2/g), ensure elevated drug payloads, together with nearly 100% loading efficiency. [2] After injection, the drug release, enabled by the nanoMOFs structure degradation, is triggered by interactions with the biological environment. Recent studies have demonstrated the role of phosphate molecules, but the related mechanisms are still to be uncovered. [3,4]

To fully understand and control these interactions, spectromicroscopies constitute ideal tools for individual and label-free analysis at a nanoscale resolution. In this regard, STEM-EELS and AFM-IR appear to be remarkable and complementary high-resolution approaches. While STEM-EELS provides valuable chemical information on the inorganic part (Fig. 1), AFM-IR identifies the chemical signature of the organic part (Fig. 2). [5] Both were employed in our studies to characterize the physicochemical properties of individual nanoMOFs and to investigate their interactions with cellular media, their biodistribution and biomodification upon cellular incubation. In the future, we will aim to optimize the design of drug nanocarriers to target specific cells and organs to improve their therapeutic efficiency. 

References :

[1] Horcajada et al., Nat. Mater. 9 (2010), 2.

[2] Li et al., ChemMedChem 15 (2020), 274.

[3] Christodoulou et al., Nanomaterials 11 (2021), 3.

[4] Li et al., Sci. Rep. 7 (2017), 1.

[5] Pancani et al., Part. Part. Syst. Charact. 35 (2018), 1700457.


Maeva CHAUPARD (Paris-Saclay)
15:10 - 15:20 Discussion.
15:20 - 15:35 #26364 - 3D characterization of cardiac fibrosis in dystrophic rat : collagen SHG imaging on CUBIC cleared heart.
3D characterization of cardiac fibrosis in dystrophic rat : collagen SHG imaging on CUBIC cleared heart.

Duchenne muscular dystrophy (DMD) is a neuromuscular disease caused by mutations in the gene encoding dystrophin. It leads to progressive muscle weakness and premature death of patient. A dystrophic (DMDmdx) rat model has been described as reflecting the muscle lesions and functional abnormalities observed in patients [1]. These muscle impairments are coupled with increases of connective tissue defined as the excessive or dysregulated deposition of extracellular matrix components. This fibrosis, particularly collagen accumulation, is a crucial component in the DMD pathogenesis. Interfering with regeneration by altering muscle architecture and function, it could also play a role as potential obstacle to cell therapies. Thus, a better understanding of fibrosis development is essential. Three-dimensional (3D) collagen organization detected by second harmonic generation (SHG) microscopy was already described as highly informative to investigate fibrotic network in tissue [2].

Here, we combine for the first time tissue clearing with SHG microscopy to characterize in depth the 3D cardiac fibrosis network from DMDmdx rat model. Heart sections (1mm thickness) from one-year-old WT and DMDmdx rat were cleared using CUBIC protocol.

We identified a massive fibrosis network in all DMDmdx rat sections compared to WT ones. We observed a distinct pattern of SHG+-segmented objects in DMDmdx animals compared with WT ones, with a decrease of the elongative shape and increase of density. Based on the orientation of SHG+-collagen fibers, we identified two distinct profiles in DMDmdx rat sections that could correspond to the natural course of fibrosis development. A relative alignment of SHG+-collagen fibers was observed in WT rat in comparison to a profound disorganization observed in severe DMDmdx rats.

The current work highlights the interest to combine multiphoton microscopy and tissue clearing for 3D collagen network characterization in label free organ. It could be a relevant tool to characterize the natural course of the disease or to evaluate efficacy of therapeutic strategies in preclinical studies in DMD model or others fibrotic cardiomyopathies.

References :

[1] PLoS One. 2014 Oct 13;9(10)

[2] Sci Rep. 2016 Jul 20;6:29863.


Julien PICHON (Nantes)
15:35 - 15:45 Discussion.
Room 1

Jeudi 08 juillet

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SDM2
13:10 - 15:45

Symposium Sciences de la Matière 2
Microscopies In-situ et in-operando
sdm2

Modérateurs : Damien ALLOYEAU (CNRS scientist) (LMPQ, Paris Diderot), Renaud PODOR (Group leader) (ICSM, Marcoule)
Compte tenu des liens étroits entre la structure atomique et les propriétés physico-chimiques de la matière, on ne peut pas développer des matériaux fonctionnels efficaces si on ne connait pas leur dynamique structurale dans leur milieu d’application. Pour répondre à ce challenge, les microscopes électroniques et champs proches ont été transformés en véritables nano-laboratoires afin d’étudier le comportement des (nano)matériaux dans des environnements liquides ou gazeux bien contrôlés et/ou en réponse à des excitations électriques, thermiques, mécaniques et optiques. Ces analyses in situ ou operando ont ouvert des champs d'investigation immenses aussi bien en chimie des matériaux (synthèse des nanomatériaux, électrochimie, catalyse, géosciences) qu’en physique des matériaux (électronique, optique, mécanique). Ce symposium vise à montrer des applications de plateformes in situ qui mettent en lumière les transformations structurales et chimiques des matériaux en fonctionnement, mais aussi des solutions innovantes pour minimiser les artéfacts expérimentaux et optimiser le traitement des données.
13:10 - 13:40 Microscopie électronique en transmission in situ appliquée à l’étude des nanomatériaux : état de l’art et perspectives. Ovidiu ERSEN (Professor) (IPCMS, Strasbourg)
L’étude à haute résolution spatiale des propriétés et de l’évolution structurale des matériaux nanostructurés à l’état d’équilibre ou dans des environnements représentatifs de leur formation ou de leur utilisation dans des applications est un enjeu majeur. Cette étude est indispensable pour comprendre les phénomènes physiques et chimiques qui gouvernent les propriétés d’intérêt, en permettant ainsi de résoudre des questions à fort impact sociétal telles que la catalyse du futur et les nouvelles formes de stockage ou de conversion de l’énergie. Grâce à sa résolution, la microscopie électronique est la technique de choix ; cependant, utilisée de manière classique par l’acquisition d’une image de l’échantillon qui se trouve dans le vide du microscope, elle est souvent insuffisante pour résoudre ses propriétés et sa dynamique structurale lorsqu’il est soumis à une contrainte environnementale spécifique. En utilisant des méthodologies d’analyse nouvelles et des conditions expérimentales s’éloignant du vide des microscopes, il est maintenant possible de se donner les moyens de se rapprocher de conditions de température et d’environnement dans lesquelles ces matériaux sont synthétisés, modifiés ou utilisés (mode operando). L’une de possibilités est l’utilisation des cellules environnementales fermées pour insérer les échantillons dans le microscope, ce qui permet de les étudier sous gaz et à haute température ou encore en milieu liquide. Il faut de plus pouvoir les exposer à des contraintes électrique, mécanique, chimique ou optique afin de récolter les informations nécessaires à la compréhension de leur comportement en conditions « réalistes ».
Cet exposé se propose de résumer les récents progrès dans le domaine de la microscopie électronique en transmission in situ et operando à travers quelques études types, allant de l’étude in-situ de la croissance des nanomatériaux, à leurs transformations structurales en fonction de la contrainte appliquée ou encore à leur évolution dans des conditions « operando ». Les domaines concernés sont nombreux, la synthèse des matériaux par voie chimique, la catalyse hétérogène, l’électrochimie, les processus de biominéralisation etc., et plus généralement tous les processus qui impliquent des réactions à l’interface « gaz-solide » ou « liquide-solide ». La quantification des résultats obtenus est aussi un aspect essentiel en microscopie environnementale, pour être capable d’extraire des paramètres physiques pertinents, tel que par exemple l’énergie d’activation de la diffusion d’une nanoparticule ou d’un atome individuel. Le concept d’étude de l’objet unique basé sur le couplage de la microscopie in-situ avec d’autres techniques appliquées au même objet est aussi important, sinon l’interprétation des résultats peut s’avérer compliquée en raison de la diversité en taille, en forme et en structure des nano-objets.
Dans la dernière partie de l’exposé, plusieurs nouveaux développements et perspectives d’évolution de la microscopie électronique in situ et operando seront présentés. Pour l’acquisition, au-delà du développement de nouveaux détecteurs plus sensibles et plus rapides, il s’agira de concevoir et utiliser des logiciels spécifiques permettant d’automatiser le protocole d’acquisition des données in-situ, d’enregistrer des données sous-échantillonnées pour diminuer la dose totale d’électrons sur l’échantillon et ainsi minimiser l’influence du rayonnement électronique dans le processus étudié, ou encore de développer de nouveaux porte-objets pour pouvoir appliquer une contrainte supplémentaire comme, par exemple, une excitation optique durant le suivi in-situ de l’objet. Du point de vue des traitements de données, plusieurs méthodologies sont en cours de développement pour permettre l’analyse des données acquises de manière corrélative ou encore l’utilisation des approches de type apprentissage profond qui sont essentielles pour extraire des paramètres statistiquement pertinents et qui seront sans doute indispensables dans les années à venir pour traiter la grande quantité des données générées par les microscopies in-situ.
13:40 - 13:50 Discussion.
13:50 - 14:20 Application of Liquid-Phase Electron Microscopy in materials science. Karine MASENELLI-VARLOT (Professeur) (MATEIS, Lyon)
Understanding and optimizing materials structures and properties implies the development of characterization techniques with which materials can be studied in conditions close to their native state, avoiding, therefore, possible artifacts due to sample preparation. Moreover, characterizing materials in situ during use, under conditions close to or mimicking real conditions, brings crucial information on the mechanisms involved. In this context, Liquid-Phase Electron Microscopy (LPEM) has become a key modality for the study of hydrated samples as well as liquid suspensions and mixtures.
Two different configurations are available: in closed cells or in dedicated environmental microscopes. Closed cells can be used in Scanning Electron Microscopes (SEMs) or Transmission Electron Microscopes (TEMs) operating under vacuum as the sample is protected by membranes. They can be used to study a large range of liquids, including corrosive ones. Specific set-ups in TEM include sample holders and external controllers. They allow tests at temperatures up to 100°C and quantitative electrochemistry experiments.
On the contrary, in dedicated environmental microscopes, the sample is preserved in the liquid state without any encapsulation. Actually, the sample temperature and the surrounding gas pressure are set in order to stay at the liquid-vapor equilibrium. Although several liquids can be studied this way, such solution is mainly used to study hydrated samples and aqueous suspensions. It is noteworthy that the gas pressure can be changed to induce in situ hydration- dehydration cycles. Up to now, the developments have mainly been carried out in ESEM, where a Peltier stage can be placed in the large sample chamber.
Within a brief introduction to the basic principles of LPEM, several examples using both configurations will be shown in order to illustrate its capabilities in materials science. Several detailed examples will be given using LPEM in ESEM. Fully hydrated materials and liquid suspensions will be used to discuss the choice of the configuration and the subsequent sample preparation, if needed, and the extracted data will show how the species evolve and interact in liquid. In situ water condensation will also be shown on dry samples. The latest developments of electron tomography in LPEM will finally be exposed.
14:20 - 14:30 Discussion.
14:30 - 14:45 #26430 - Exceptional reactivity of ultra-small gold nanoparticles under H2 at atmospheric pressure revealed by environmental TEM.
Exceptional reactivity of ultra-small gold nanoparticles under H2 at atmospheric pressure revealed by environmental TEM.

L'origine de l’activité catalytique remarquable des NPs Au demeure mal définie, en particulier celle des NPs inférieures à 5 nm [1]. Cette activité est généralement attribuée aux atomes sous-coordinés d’arêtes et de coins de nanoparticules de formes cristallines supposées statiques et parfaites dans les conditions de réaction. Dans cette contribution, en étudiant à l’échelle atomique la dynamique structurale sous H2 de NPs d’Au de taille inférieure à 7 nm par MET in situ, nous montrons que cette vision est erronée pour les NPs « ultrapetites » (~3 nm), avec la mise en évidence de la grande mobilité des atomes d'or à la fois en surface et en volume.

La figure 1 montre l’évolution structurale de deux NPs Au supportées sur anatase TiO2, l’une petite (~4,5 nm) et l’autre ultrapetite (~3 nm), initialement sous 40 Pa d’Argon à 400°C , puis pendant le refroidissement de 400 à 25 °C sous 105 Pa de H2. Les deux NPs ont une structure CFC et une morphologie de type octaèdre tronqué sous Ar (Fig 1.a et d). Sous H2, la petite NP d’Au conserve sa structure cristalline, sa morphologie et son orientation par rapport au support, même jusqu’à 25°C (Fig 1.b et c). A l’inverse, l’ultrapetite NP d’Au évolue vers une structure présentant un ordre icosaèdrique dès l’introduction de H2 à 400°C (Fig 1.e et f). La caractérisation MET ex situ des NPs Au traitées sous H2 dans un réacteur à lit fixe dans des conditions de pression et de température proches des observations in situ confirme la dépendance en taille de la réactivité des NPs Au sous H2 (Fig 2). Si les NPs de taille supérieure à 4 nm présentent très majoritairement une structure CFC (Fig 2.a et c), les structures des NPs de taille inférieure à 4 nm sont différentes de CFC et variables (principalement des structures icosaèdriques et déformées) (Fig 2.e-h). Les observations MET in situ et ex situ concordantes ont été corroborées par des études de dynamique moléculaire ab initio qui seront également présentées.

[1] Catalysis by Gold G.C. Bond, C.Louis, D.Thompson, Imperial College Press, 2006.


Abdallah NASSEREDDINE (MPQ, Paris)
14:45 - 14:55 Discussion.
14:55 - 15:10 #26434 - PLASMA-ENHANCED CVD IN A TEM?
PLASMA-ENHANCED CVD IN A TEM?

In plasma-enhanced chemical vapour deposition (PECVD), the radicals and atoms generated by the plasma have the effect, among others, of changing the surface energies of the growing materials, which allows one to prepare objects that would not stabilise in other conditions. This is the case of the Sn-Cu-catalysed Si nanowires (NWs) we present in this talk: without plasma, the liquid Sn, used by the vapour-liquid-solid mechanism [1], is so unstable that no growth is allowed, while in presence of the H atoms generated by the plasma,  the Sn droplet stabilises and growth can start [2]. Yet, this method is up to now the only way of growing 2H SiNWs (a metastable polytype with interesting optical properties [3]) (Fig. 1) [4]. The goal of our present in-situ study is to understand how this metastable phase can be preferred to the stable one (the 3C polytype).

However, no electric field is compatible with HRTEM, which forbids plasma under the beam. To circumvent this incompatibility, we implemented, on the H2 line of our in-situ TEM (“NanoMAX”, a modified Thermo Fisher Titan Environmental TEM), an electron-cyclotron-resonance plasma source (Aura-wave from SAIREM), to remotely generate the H atoms necessary for the growth. Thanks to this unique setting, we obtained Sn-Cu-catalysed SiNWs in-situ, with 2H regions (Fig. 2) [5]. 

The talk presents the effect on NW growth of switching the plasma on and off, and shows movies of the nucleation of the Si 2H metastable polytype recorded at atomic resolution.

Acknowledgements:

This work was funded by the ANR: TEMPOS-NanoMAX (ANR-10-EQPX-50); HexaNW (ANR-17-CE09-0011). We kindly thank P. Roca i Cabarrocas, M. Foldyna (LPICM), F. Glas, F. Panciera (C2N), for fruitful discussions, and also the CIMEX at École polytechnique.

References:

[1] R.S. Wagner, W.C. Ellis, Appl. Phys. Lett. 4 (1964), p. 89

[2] S. Misra, et al., J. Phys. D: Appl. Phys. 47 (2014), p. 393001

[3] M. Amato, et al., Nano Lett. 16 (2016), p. 5694

[4] W. Wang, PhD thesis, Institut Polytechnique de Paris, École polytechnique (2021)

[5] É. Ngo, PhD thesis, Institut Polytechnique de Paris, École polytechnique (2021)


Jean-Luc MAURICE (Palaiseau)
15:10 - 15:20 Discussion.
15:20 - 15:35 #26439 - In-situ biasing in 4D-STEM experiments to measure electric fields in p-n junction semiconducting nanowires.
In-situ biasing in 4D-STEM experiments to measure electric fields in p-n junction semiconducting nanowires.

The advance of fast pixelated detectors has allowed performing 4D-STEM, where by measuring the shift of the transmitted beam, the electric field distribution inside the sample can be accessed, as demonstrated for p-n junctions in lamella specimens prepared from bulk or thin-film semiconductor samples [1-3]. However, the detection of the transmitted beam can be affected by diffraction contrast. In thin semiconducting nanowires (NWs) a rotation of the crystal is often present and this change in orientation of the crystal across the NW modifies the diffraction condition, potentially affecting the algorithms used to detect the beam shift. 

Here, we present in-situ biasing 4D-STEM experiments to study the electrical properties of n-i-p/p+n+/n GaN NW photodetectors grown by MBE [4]. We show that artefacts due to crystal rotation in the NWs can be reduced or removed by a combination of in-situ biasing, different algorithms to detect the beam shift, and orienting the sample off-axis to reduce diffraction contrast. We were able to measure electric fields on the order of few MV/cm in a tunnel junction (p+/n+) with high spatial resolution, consistent with doping levels around 〖10〗^19 〖cm〗^(-3). The electric field profiles are compared to 3D finite element calculations and electron beam induced current (EBIC) maps, which also reflect the internal field distribution. We measure the current-voltage (IV) response of the NW at different stages of the experiment to better understand the effect of the electron beam exposure on the electrical properties.

This work illustrates the potential of 4D-STEM measurements combined with in-situ biasing to reveal the internal electric field quantitatively, which is linked with the electrically active doping concentrations and surface band bending. These properties are otherwise difficult to access in semiconductor NWs at nm length scales, and are crucial for development of new devices with carefully designed electrical properties.

Acknowledgements: ERC, CNRS, CEA

References:

[1] N. Shibata et. al., Scientific Reports 5 (2015), 10040.

[2] L. Bruas et. al., Journal of Applied Physics, 127 (2020), 205703.

[3] A. Beyer et. al., Nano Letters, 21 (2021), 2018-25.

[4] S. Cuesta et al. Nano Letters, 19 (2019), 5506-5514.


Bruno C. DA SILVA (Grenoble)
15:35 - 15:45 Discussion.
Room 2
15:40 Pause
16:00

Jeudi 08 juillet

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SDV1
16:00 - 18:55

Symposium Sciences de la Vie 1
Cryométhodes : Particules isolées : applications et développements
sdv1

Modérateurs : Irina GUTSCHE (IBS, Grenoble), Célia PLISSON-CHASTANG (LBME, Toulouse)
La cryo-microscopie électronique a vécu une véritable révolution ces dernières années puisqu’elle permet maintenant couramment de déterminer la structure 3D de divers complexes biologiques à une résolution atomique. La taille des complexes macromoléculaires accessibles aux études par cryo-MET ne cesse de baisser, la flexibilité de ces objets devient un atout pour des analyses dynamiques plutôt qu’une entrave à la résolution, et l’hétérogénéité compositionnelle n’est plus une véritable contrainte puisque les images correspondant à chaque type objet peuvent être distinguées et traitées séparément. Au travers de cette session, il est proposé un éventail de ce qui se fait actuellement en cryo-MET, des développements récents de la cryo-MET 3D à l’apport de la cryo-MET à des problématiques biologiques diverses.
16:00 - 16:30 Novel algorithms for cryo-electron tomography. Dimitry TEGUNOV (MPIBPC, Göttingen, Allemagne)
While single-particle analysis of in vitro samples made major advances over the past decade to achieve atomic resolution, the analysis pipeline for tomographic in situ data has lagged behind. With the recent development of Warp and M, we were able to close the gap in processing, obtaining residue-level resolution for ribosomes images inside cells for the first time. In my talk, I will highlight our recent results and the underlying ideas, and discuss how new deep learning-based algorithms allow to further make sense of in situ data.
16:30 - 16:40 Discussion.
16:40 - 17:10 Phage revenge: allosteric inhibition of CRISPR-Cas9 by the anti-CRISPR protein AcrIIA6. Adeline GOULET (AFMB, Marseille)
Bacteriophages (phages) and their preys are engaged in an endless evolutionary arms race. Bacteria have evolved sophisticated defense mechanisms to thrive in virus-rich ecosystems, including the well-known CRISPR-Cas9 immune system. In parallel, phages have developed counter-attack strategies to overcome their host’s defenses, including anti-CRISPR proteins. The striking sequence diversity of anti-CRISPR proteins and the lack of homology with proteins of known function raise questions relating to their modes of action. Moreover, anti-CRISPR proteins, as natural CRISPR-Cas9 inhibitors, hold great promise as biotechnological tools to fine-tune CRISPR-Cas9-based gene edition, and as useful addition to phage therapy.
In this context, we embarked on the structural and functional characterization of the anti-CRISPR protein AcrIIA6, discovered in virulent phages infecting Streptococcus thermophilus, combining cryo-electron microscopy and single particle analysis, in vitro analyses of macromolecular interactions, and functional cellular assays. The AcrIIA6 molecular mechanism is unique: we showed that AcrIIA6 acts as an allosteric inhibitor and induces St1Cas9 dimerization. AcrIIA6 affects St1Cas9 conformational dynamics, which reduces St1Cas9 binding affinity for DNA and prevents St1Cas9 binding to its target within cells. Interestingly, these findings led us to identify a natural variant of St1Cas9 resistant to AcrIIA6, illustrating anti-CRISPR-driven mutational escape and molecular diversification of Cas9 proteins.
17:10 - 17:20 Discussion.
17:20 - 17:35 #26369 - How to get the maximum out of your cryo-EM data collection session.
How to get the maximum out of your cryo-EM data collection session.

Single-particle cryogenic transmission electron microscopy (cryo-EM) can be used to elucidate the 3D structure of macromolecular complexes. The sample is embedded in a thin layer of vitreous ice and maintained at liquid nitrogen temperature. It is then imaged directly in the microscope and a 3D reconstruction may be calculated from projections of individual macromolecular complexes by determining the orientations of the projections. For many years cryo-EM was limited to low-resolution, but driven by technological breakthroughs in electron microscope and electron detector developments coupled with improved image processing procedures,  cryo-EM is now a method of choice for the determination of high-resolution structures, termed as “The Resolution Revolution” [1].

These developments deeply modified the way of collecting cryo-EM data. Currently, after only a few hours of setup, data collection can run in a fully unattended and automated way for several days, producing high quality dataset of thousands of micrographs. These improvements led to new challenges in term of session setup, microscope alignments and acquisition parameters and new strategies were required to tackle these questions. This communication will present how high-end data collection is performed at the EMBL Heidelberg cryo-EM platform using SerialEM (Fig. 1) [3], insisting on some of the key steps of the workflow: Microscope alignments allowing a small electron beam and aberration-free beam shift/image shift [2]; pixel size choice for optimized data collection; alternative collection strategies for samples with very low concentration and uneven spreading on the grid [4]; ice thickness characterisation for optimal holes selection.

References :

[1] W Kühlbrandt, Science 343 (2014), p. 1443.

[2] F Weis and WJH Hagen, Acta Crystallogr D Struct Biol 76 (2020), p. 724.

[3] DN Mastronarde, J Struct Biol 152 (2005), p. 36.

[4] M Schorb et al, Nat Methods 16 (2019), p. 471.


Felix WEIS (Heidelberg, Allemagne)
17:35 - 17:45 Discussion.
17:45 - 18:00 #26370 - Structural characterization of a human Kir potassium channel and its involvement in Andersen syndrome.
Structural characterization of a human Kir potassium channel and its involvement in Andersen syndrome.

Inward rectifier potassium (Kir) channels belong to a family of integral membrane proteins that selectively control the K+ ions permeation at the cell membranes of various tissues and regulate the membrane electrical excitability [1]. The Kir channels gating is essentially modulated by phosphatidylinositol-4,5-bisphosphate (PIP2), although a full description of PIP2 role requires more details [1]. Genetically-inherited defects in Kir channels are responsible for several rare human diseases, including Andersen-Tawil syndrome (AS), a muscular disease that causes episodes of muscle weakness, arrhythmia, and developmental abnormalities, which the available treatments are inefficient [2]. Two-third of the mutations that causes this syndrome are situated on the PIP2 binding site [2]. 

Here, we present a 3.5 Å resolution cryo-EM map of the human Kir2.1 channel (Fig. 1). The data were collected on a Titan Krios TEM (FEI) operating at 300 kV equipped with a Gatan K2 Summit DED and Cs corrector. After micrographs selection based on visual quality inspection, it was obtained 7,188 images and 837,808 particles. All data was processed using Relion 3.0.

This is the first structural data of the whole human Kir2.1 channel, which can reveal useful insights about selectivity filter gate. The near-atomic resolution of the obtained cryo-EM map can provide a complete description of the PIP2 binding site in the Kir2.1 channel and the understanding of the clinically-relevant disease-causing mutations impact on the Kir channels function and dynamics. Molecular dynamis simulations performed with the final cryo-EM structure can provide the understanding of the full gating mechanism of human Kir2.1 channel and the PIP2 role on the dynamics of this channel.

References

[1] Suh et al. Curr. Opin.Neurobiol. v.15 (2005), p. 370-378.

[2] Andersen et al. Acta Paediatr. Scand. v.60 (1971), p. 559-564.

[3] Donaldson et al. Neurology v.60 (2003), p.1811-1816.

Figure 1: Structure of the human Kir2.1 channel. (A) Representative cryo-electron micrograph; (B) Representative 2D class averages of the particles; (C) Fourier Shell Correlation (FSC) curve indicating the map overall resolution; (D) Cryo-EM map obtained at 3.5 Å resolution highlighting the PIP2 binding site between cytoplasmic and transmembrane domains and including a map detailed view at the transmembrane domain. 


Carlos A. H. FERNANDES (Bioinformatique et BioPhysique (BIBIP))
18:00 - 18:10 Discussion.
18:10 - 18:25 #26372 - A hybrid approach to analyze continuous conformational variability of single particles based on deep learning.
A hybrid approach to analyze continuous conformational variability of single particles based on deep learning.

Cryo-electron microscopy (cryo-EM) allows high-resolution 3D reconstruction of biomolecular structures from highly noisy 2D parallel-beam projection images containing tens of thousands of copies of the same macromolecular complex but at different random orientations and positions. However, biomolecular complexes are not rigid but flexible entities that change their conformations gradually (continuous transition with many intermediate states) to accomplish biological functions (e.g., DNA replication, protein synthesis, etc.). The determination of the full distribution of conformations (conformational space or landscape) from cryo-EM images is challenging but could provide insights into working mechanisms of the complexes. In this presentation, we describe a method for conformational space determination, which uses deep learning in combination with cryo-EM image analysis and normal mode analysis [1,2] (Fig. 1), where the amplitudes of normal modes are the parameters of the elastic conformations of complexes. We show the performance of this new method

using synthetic cryo-EM data (Fig. 2). The conformational space predicted using the proposed method (Fig. 2(a)) allows obtaining molecular movies of the conformational transition (Fig. 2(b)).

Acknowledgment:

We acknowledge the support of the French National Research Agency — ANR (ANR-19-CE11-0008-01 and ANR-20-CE11-0020-03 to SJ) and the access to the HPC resources of CINES and IDRIS granted by GENCI (2019-A0070710998, AP010712190, AD011012188 to S.J.).

References :

[1] Harastani M, Sorzano COS, Jonic S, Hybrid Electron Microscopy Normal Mode Analysis with Scipion. Protein Sci 29 (2020), p. 223-236.

[2] Jin Q, Sorzano CO, de la Rosa-Trevin JM, Bilbao-Castro JR, Nunez-Ramirez R, Llorca O, Tama F, Jonic S, Iterative Elastic 3D-to-2D Alignment Method Using Normal Modes for Studying Structural Dynamics of Large Macromolecular Complexes. Structure 22 (2014), p. 496-506.


Ilyes HAMITOUCHE (Paris)
18:25 - 18:35 Discussion.
18:35 - 18:45 CRYO TEM: Latest improvements on throughput & resolution - JEOL. Guillaume BRUNETTI (Responsable Marketing) (JEOL EUROPE)
18:45 - 18:55 Discussion.
Room 1

Jeudi 08 juillet

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SDM1
16:00 - 19:05

Symposium Sciences de la Matière 1
Microscopies des matériaux/nanomatériaux et applications
sdm1

Modérateurs : Caroline ANDREAZZA (Professor) (ICMN, Orléans), Virgile ROUCHON (IFPEN, Lyon)
Les nanomatériaux sont au cœur de l’innovation technologique du XXIème siècle avec une grande variété d’applications, allant des domaines tels que l’énergie, les transports, l’environnement, le bâtiment à ceux de la santé ou de l’électronique. Cet essor des nano-objets est permis grâce à l’amélioration des méthodes de caractérisation qui permettent à la fois de décrire ces systèmes à l’échelle de l’atome et également d’analyser leurs propriétés fonctionnelles. La microscopie est un axe de développement central pour les nanomatériaux puisqu’elle permet de révéler à la plus fine échelle spatiale les informations bi- et tri- dimensionnelles nécessaires à l’optimisation de leur synthèse, leur fonctionnalisation, leur mise en forme et par voie de conséquence leurs comportements et performances.
Cette session interdisciplinaire vise à présenter les approches innovantes des techniques de microscopie à résolution nanométrique et sub-nanométrique, telles que la microscopie électronique à transmission ou à balayage ou encore la microscopie photonique hyper résolutive, pour l’étude de nanomatériaux (nanoparticules, nanofils, matériaux poreux et/ou nanostructurés, couches ultra-minces, …). Les développements techniques et méthodologiques, que ce soit d’un point de vue des performances instrumentales, des approches de microscopies corrélatives et multimodales (imagerie, spectroscopie, diffraction, …), ou du traitement de données seront mises en avant de façon à démontrer comment les informations obtenues contribuent au développement des nouveaux matériaux nanostructurés. Les domaines d’application des matériaux étudiés peuvent être très larges et englober des approches de développement durable (énergies renouvelables, conversion de l’énergie, dépollution, recyclabilité …) ou des questions de toxicité, de biosécurité ...
16:00 - 16:30 Highly doped Si nanostructures for infrared plasmonics. Caroline BONAFOS (CEMES, Toulouse)
The appearance of Localised Surface Plasmon Resonances (LSPR) in highly doped Si nanostructures opens a new field of applications, with Si-based plasmonic tunable over a wide infrared range [1]. However, doping low dimensional silicon remains a challenge due to self-purification mechanisms [2]. To circumvent this problem, we recently proposed a top down approach consisting at optimizing the doping of thin silicon layers, by means of P low energy ion implantation (LE-II) and further Laser Thermal Annealing (LTA), in which nanometer size disks are produced by electron beam lithography. The melting regimes and the regrowth processes as well as the redistribution of P in the top Si amorphized layer were studied as a function of the P content by coupling HRTEM and STEM-EDX. The results highlight the crucial role of the thin crystalline Si layer preserved after amorphization, which provides nucleation seeds for the liquid phase recrystallisation. FTIR measurements demonstrate that the Si overlayers can be massively doped over a wide range of active dopant concentrations. By processing these hyper-doped overlayers, we realized all-silicon-based plasmonic metasurfaces formed by submicrometer doped-Si nanodisks and demonstrated that such nanostructures support LSPR tunable between 2.5 and 5 µm via the free carrier density of the silicon [3].
In a second part of this talk, preliminary results on a bottom-up approach consisting of doping smal (3 nm) Si nanocrystals (SiNCs) synthesised by LE-II in a silica matrix will be presented. Atom Probe Tomography analysis clearly shows the dopant insertion in the SiNC volume. The decrease of the SiNC photoluminescence intensity after dopant insertion due to Auger quenching likely evidences its electrical activation. Finally, the first demonstration of LSPR from these small embedded P doped SiNCs has been obtained provided the passivation of surface defects.
This work was partly funded by ANR DONNA (ANR-18-CE09-0034).
References:
[1] D. J. Rowe et al. Nano Lett. 13 (2013), p. 1317
[2] J. P. Petropoulos, et al. Nanotechnology 22, (2011) p. 245704
[3] J. M. Poumirol, ACS photonics (2021) https://doi.org/10.1021/acsphotonics.1c00019
16:30 - 16:40 Discussion.
16:40 - 17:10 Contribution de la microscopie électronique au développement des électrodes de pile à combustible de type PEMFC et à la compréhension de leurs mécanismes de dégradation. Laure GUETAZ (LITEN, Grenoble)
Les piles à combustible de type PEMFC pour « proton exchange membrane fuel cell » permettent de générer de l’électricité à partir des deux réactions électrochimiques que sont l’oxydation de l’hydrogène et la réduction de l’oxygène. Elles sont principalement développées pour répondre au besoin de moyen de transport décarboné. Leurs performances actuelles sont suffisantes pour avoir permis la commercialisation des premiers véhicules à pile à combustible. Cependant leur coût et leur durabilité sont encore les deux verrous qui limitent l’extension de ce marché. Pour lever ces verrous, il est encore nécessaire d’optimiser les composants et la structure des électrodes et de mieux comprendre leurs mécanismes de dégradation.
Les électrodes sont un milieu poreux nano-composite composé de particules de carbone (30-50 nm) supportant des nanoparticules de Pt (2-5 nm) qui catalysent les réactions et entourées d’une fine (5-8 nm) couche de ionomère qui joue le rôle d’électrolyte mais aussi de liant. Pour analyser ces différents composants, la microscopie électronique et ses différentes techniques sont alors devenues des outils indispensables. Ainsi, le STEM/EDS ou STEM/EELS ont largement contribué au développement de nouveaux catalyseurs d’alliage de Pt plus performants et à la compréhension de leurs mécanismes de dégradation. Plus récemment la tomographie électronique a révélé que des carbones supports poreux pouvaient permettre de confiner les nanoparticules de Pt à l’intérieur des pores et ainsi limiter leur dégradation par le mécanisme de maturation électrochimique d'Ostwald. La répartition du ionomère au sein de l’électrode reste aujourd’hui encore mal connue et est pourtant un paramètre important à optimiser car d’elle dépend le taux d’utilisation des catalyseurs et la diffusion des gaz au sein de l’électrode. Ainsi, la visualisation en 3D du ionomère semble essentielle mais reste encore un défi. Des techniques de tomographie associant les signaux de plusieurs détecteurs pourraient être prometteuses.
17:10 - 17:20 Discussion.
17:20 - 17:35 #26352 - UNVEILING NANOSCALE OPTICAL PROPERTIES OF 2D SEMICONDUCTORS USING ELECTRON SPECTROSCOPY.
UNVEILING NANOSCALE OPTICAL PROPERTIES OF 2D SEMICONDUCTORS USING ELECTRON SPECTROSCOPY.

In this contribution, we will present results on the optical and the structural properties of a monolayer of semiconducting transition metal dichalcogenide (TMD) encapsulated with hexagonal boron-nitride (h-BN), at the tens of nanometers scale. In this work we the correlate optical spectra at the nanoscale with structural and chemical maps. In this way, we connect the information usually available separately from optical diffraction-limited techniques, such as photoluminescence (PL) [1], and from high-resolution techniques, such as electron microscopy [2] or scanning tunneling microscopy [3].

To achieve this, we used combined high spatial and spectral resolution techniques in a scanning transmission electron microscope (STEM), such as illustrated in Fig. 1. Electron energy loss spectroscopy (EELS) was used to obtain optical absorption (low-loss range) and chemical analysis (core-loss range). Cathodoluminescence (CL), a nanoscale coun-terpart of PL [4], was used to measure light emission at the tens of nanometers scale. The two types of spectral data were acquired in the same regions. This gave access to, for example, the local Stokes shift (SS), which is the difference between absorption and emission energies. This quantity gives information about the physical mechanism in-volved in the absorption and emission processes [1]. In addition to these spectral meas-urements, spatial structural information was gathered using either atomically-resolved imaging or diffraction mapping for local strain measurements. Moreover, chemical maps were measured using core-loss EELS.

Using these combined techniques, we detected spatially localized emission from excitonic complexes in WS2 monolayers maintained at 150 K, with bright spots as small as few tens of nanometers (Fig. 2). The presence of such bright spots was linked to the chemi-cal environment, displaying small patches of contaminants (such as C, O, N, or Si), prob-ably coming from sample preparation [5].

References
[1] Kolesnichenko et al. 2D Mater. 7 025008 (2020)
[2] Chang et al. Appl. Miscosc. 49, 10 (2019)
[3] Schuler et al. Sci. Adv., 6, eabb5988 (2020)
[4] Kociak and Zagonel, Ultramicroscopy, 176, 112-131 (2017)
[5] Bonnet et al. arXiv :2102.06140 [cond-mat.mes-hall]


Noémie BONNET (LPS - STEM, Paris)
17:35 - 17:45 Discussion.
17:45 - 18:00 #26354 - Mapping Built-in electric field in nanowires and in-situ biasing by 4D scanning electron transmission microscopy.
Mapping Built-in electric field in nanowires and in-situ biasing by 4D scanning electron transmission microscopy.

Today's progress in semiconductor technology and electronic device miniaturization, necessitate the exact estimation of electrostatic properties like local electric field and electronstatic potential to enhance the performance and functionality of nano-devices. Though, the direct observation and precise measurements of local electric fields are still quite challenging, 4D scanning transmission electron microscopy (4D STEM) technique is known as a sensitive detection tool to map the internal electric fields arising from nanoscale features like p-n junctions [1-4]. Moreover, the development of fast pixelated detectors based on direct electron detection technology, has improved the feasibility of 4D STEM through their higher acquisition speed, high dynamical range and fast readout. 

In this work, we aim to map the internal electric field of highly doped (1019 atom/cm3) Ge p-n junction nanowires prepared by gold catalyzed chemical vapour deposition (CVD). 4D-STEM measurements with careful tuning of the parameters, with/without precession and in different crystal orientation, are applied to get the maximum spatial resolution, necessary for the built-in electric field detection in the junction. Also, for the first time, in-situ electrical measurements are exploited to monitor the I-V characteristics of the nanowires during different steps of the 4D STEM experiments to verify if the system is electrically modified during 4DSTEM data acquisition. Moreover, reverse and forward biased data are acquired to separate the contribution of electrical characteristics and the ones due to artifacts in the reconstructed data. MerlinEM fast pixelated detector is used for STEM data acquisition. Post-acquisition data analysis is performed by Python and MATLAB based scripts to reconstruct the STEM images from the data sets and investigate the effect of experimental parameters. Moreover, scanning electron microscopy (SEM) based Electron beam Induced current (EBIC) is also used to verify the position of the junction and compared with the STEM data. Also, the data from EBIC can be exploited to acquire higher resolution data by 4D STEM, focusing on the small region of the nanowire containing the field. Different methods for data analysis, including Center of Mass (CoM) and template matching (TM) is applied on the data and pros and cons of each method will be investigated.


Zahra SADRE MOMTAZ (Grenoble)
18:00 - 18:10 Discussion.
18:10 - 18:25 #27017 - Individual magnetic moments in assemblies of magnetic nanoparticles in a ferrofluid.
Individual magnetic moments in assemblies of magnetic nanoparticles in a ferrofluid.

Ferrofluids, which are suspensions of magnetic nanoparticles in a liquid, have many current and potential applications in the biomedical field (e.g. improved MRI agents, magnetic hyperthermia) and in the technological industry (e.g. permanent magnets, magnetic memory). When the nanoparticles have a large enough magnetic moments, magnetic dipole interactions give rise to different assemblies of nanoparticles. Indeed, theoretical simulations [1] have predicted the existence of nanoparticles assembled in chains, rings, or a combination of both. These assemblies modify the macroscopic properties of the ferrofluid significantly. Thus, in order to achieve a better understanding of these materials, we aim to study the correlation between the magnetic properties and the self-organisation. To that goal, we have used Cryogenic Transmission Electron Microscopy (Cryo-TEM) and Electron Holography to study a suspension composed of nanoflowers of cobalt ferrite with 25nm diameter, which are known to present a large magnetic anisotropy and their ferrofluidic solution in water have shown efficient magnetic hyperthermia [2]. 

Cryo-TEM allows visualising the self-organisation of the ferrofluid. By rapidly plunge-freezing a drop of the sample in liquid ethane, we show the theoretically predicted assemblies (fig. 1) and establish the statistical occurrence of each shape. Several assemblies were further investigated by Electron Holography, a TEM-based technique, that allows retrieving the magnetic induction at the nanoscale by interfering the transmitted electron beam with a reference beam and measuring the phase shift. We quantitatively mapped the in-plane magnetic induction within several assemblies and deduced the magnetization orientation of each particle (fig 2.). While dipolar magnetic interactions are expected to align dipolar moments top to tail within a chain, we show that the relative orientation of particle magnetization varies from parallel to anti-parallel configuration, suggesting a significant contribution of the particle’s magnetic anisotropy. This contribution cannot, therefore, be neglected when performing Monte-Carlo simulations of magnetic properties for ferrofluids presenting such a large magnetic anisotropy.


Malika KHELFALLAH (IMPMC)
18:25 - 18:35 Discussion.
18:35 - 18:55 Distinguer les phases à l'aide de l'EBSD - Oxford Instruments. Brooke JABLON (Applications and Field Service Engineer FRANCE)
18:55 - 19:05 Discussion.
Room 2
Vendredi 09 juillet
09:40

Vendredi 09 juillet

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SC4
09:40 - 12:15

Symposium Commun 4
Assistance machine pour acquisition, analyse, interprétation/modélisation de données de microscopies

Modérateurs : Arnaud DEMORTIÈRE (chargé de recherche CNRS - CR1) (UPJV, Amiens), Perrine PAUL-GILLOTEAUX (IRS, Nantes)
Le numérique a pris aujourd’hui une place prépondérante en microscopie, que ce soit dans le domaine des sciences des matériaux, de la médecine ou de la biologie. L’utilisation d’approches en apprentissage profond (“deep learning”) est devenue une solution incontournable dans le traitement et l’analyse des données massives acquises en microscopie. Elles permettent leur classification ou leur modélisation sur la base de lois statistiques, et peuvent également nous assister dans la prise de décision et la visualisation de ces données. Les algorithmes “ad hoc” et les approches de “deep learning” démontrent depuis quelques années leur capacité à pouvoir aider à la prise de décision sur les paramètres d’acquisition à choisir et viennent même dans certain cas remplacer l'opérateur. Par exemple, l’analyse des images au cours de l’acquisition peut aider à décider de la suite et guider le microscope, ou permettre de rechercher les événements rares de manière automatique. Ils permettent également d’extraire de l’image des informations qui n’y semblaient pas présentes, en utilisant une connaissance a priori, formalisée ou non, comme dans le cas du débruitage, de correction d’artefact ou d’amélioration de la résolution de l’image. Ils sont aussi capables d’extraire des données de phénotypages ou caractérisation de manière automatique et sans comparaison de vitesse avec un opérateur humain, avec un biais de quantification reproductible, par la segmentation, le tracking, ou l’analyse des signaux et les mesures dérivées. La mise au point de ces algorithmes et en particulier des modèles de machine learning pour toutes ces applications requièrent le partage de données annotées afin de les mettre au point, ce qui appelle également à de nouvelles solutions de partage et d’annotation.
09:40 - 10:10 Microscopy Image Analysis: The Shift to Deep Learning. Daniel SAGE (EPFL, Lausanne, Suisse)
The quantification of microscopy images require automatic tools to extract relevant information from complex data. To tackled this task, numerous image analysis algorithms have been designed, commonly based on prior knowledge and on physical modeling. However, the recent success of the deep learning (DL) in computer science have drastically changed the bioimage analysis workflows to a data-centric paradigm. While this DL technology remains relatively inaccessible to end-users, recent efforts has been proposed to facilitate the deployment of DL for some bioimage applications through new open-source software packages.
Here, we present a set of user-friendly tools that allows to test DL models and to gain proficiency in DL technology: the centralized repository of bioimage model (Bioimage Model Zoo), the readytouse notebooks for the training, and the plugin deepImageJ that can run a DL model in ImageJ.
We provide also good practice tips to avoid the risk of misuses. We address some practical issues such as the availability of massive amount of images, the understanding of generalizability concept, or the selection of the pre-trained models. The shift to deep learning also questions the community about the trust, the reliability and the validity of such trained deep learning models.
10:10 - 10:20 Discussion.
10:20 - 10:50 From regularized methods to deep learning in imaging sciences. Nelly PUSTELNIK (Chargée de recherche CNRS CRCN) (ENS, Lyon)
During the last 20 years, imaging sciences, including inverse problems or segmentation, have known two major revolutions: (i) sparsity and proximal algorithms and (ii) deep learning. Non-smooth convex optimization became the main thrust behind significant advances in signal processing, image processing, and machine learning. Behind non-smooth functions, there is the concept of sparsity which is central in the contributions in inverse problems and compressed sensing but also proximal algorithms allowing to handle with large scale data. These concepts will be described as well as the objective functions relying on it, going from Mumford-Shah model to the most advanced restoration and segmentation methods. Ten years after the start of proximal revolution, deep learning has started to provide a new framework for solving imaging problems going from agnostic techniques to models combining deep learning with standard regularized formulations. The second part of the talk will be dedicated to these recent advances in the specific context of image restoration.
10:50 - 11:00 Discussion.
11:00 - 11:15 #26238 - Utilisation d’outils d’intelligence artificielle pour la segmentation d’images 3D d’ovaire de poisson.
Utilisation d’outils d’intelligence artificielle pour la segmentation d’images 3D d’ovaire de poisson.

L’analyse quantitative du contenu cellulaire d’organes entiers par microscopie permet de comprendre leur organisation en conditions physiologiques ou pathologiques. Dans certains cas, l’analyse exhaustive est essentielle pour évaluer par exemple l’impact d’une mutation sur la mise en place d’une fonction biologique clé. 

Chez le médaka (Oryzias latipes), un poisson modèle classiquement utilisé pour l’étude de la reproduction, la fertilité des femelles est directement dépendante de la croissance asynchrone des follicules ovariens. Recrutés à partir de pools de cellules germinales, les ovocytes évoluent, en fonction de leur stade de développement, au sein de follicules de différentes classes de tailles (de 20um à plus de 1000um). Chaque jour, une vingtaine d’œufs sont ainsi pondus dans des conditions de photopériode contrôlée. Pour étudier cette dynamique de croissance, notamment dans le cas d’une lignée mutante présentant une fertilité réduite (miR-202-5p Knock-out), nous cherchons à dénombrer et mesurer l’ensemble des follicules contenus dans les ovaires des femelles juvéniles et adultes.

A partir d’images d’ovaires en 3D de médaka obtenus en microscopie confocale à fluorescence, nous avons mis en place une séquence d’analyse qui s’appuie sur des réseaux de neurones pré-entraînés accessibles en opensource. La segmentation 3D des follicules a été réalisée avec l’algorithme Cellpose, récemment développé par Stringer.C et al [1], et ce sans nécessiter une étape d’apprentissage sur nos images. Une étape de débruitage appliquée en amont via l’outil Noise2void [2] a également permis d’augmenter la qualité de la segmentation. Grâce aux récents développements des approches de « deep-learning » appliqués aux données de microscopie, nous avons ainsi obtenu des données quantitatives tridimensionnelles jusqu’alors inaccessibles avec des méthodes classiques (Figure 1).

Ces nouveaux outils, rendus de plus en plus disponibles aux non-spécialistes du domaine, ont ainsi ouvert la voie à un phénotypage cellulaire profond, dès les stades larvaires précoces chez les femelles invalidées pour le miR-202.

Références:
[1] Stringer, C., Wang, T., Michaelos, M. et al. Cellpose : a generalist algorithm for cellular segmentation. Nat Methods 18 (2021), p.100–106. https://doi.org/10.1038/s41592-020-01018-x
[2] Krull, A., Buchholz, T. O., & Jug, F. Noise2void-learning denoising from single noisy images (2019). arXiv:1811.10980v2.


Manon LESAGE (Rennes)
11:15 - 11:25 Discussion.
11:25 - 11:40 #26239 - Méthodes d’imagerie computationnelle par ptychographie 3D et hyperspectrale par contraste de phase : algorithmes et applications.
Méthodes d’imagerie computationnelle par ptychographie 3D et hyperspectrale par contraste de phase : algorithmes et applications.

Les valeurs de résolution spatiale les plus élevées dans les microscopies aux rayons-X et électronique d'aujourd'hui sont obtenues par ptychographie[1]. Cette nouvelle méthode de nanoimagerie computationnelle ne repose pas sur l'utilisation de lentilles, qui sont remplacées par l’ordinateur et des algorithmes avancés de récupération de phase. Différemment d’autres méthodes, la résolution spatiale dans la ptychographie ne dépend pas de la taille de sonde et le faisceau incident n’a pas besoin d’être une onde plane sans aberrations, ce qui allège les contraintes sur l'optique du microscope.

Nous présentons ici cette méthode innovante ainsi que ses algorithmes de reconstruction. Elle peut être réalisée soit dans le régime holographique[2] soit dans le régime de champ lointain[3,4]. Quatre informations quantitatives sont obtenues à partir d’une seule expérience : les images d’absorption et de contraste de phase de l’échantillon, ainsi que l’amplitude et phase du faisceau incident (sonde)[5]. En combinaison avec la tomographie, nous présentons comment la tomographie ptychographique aux rayons X (PXCT) a révolutionné la caractérisation des matériaux hétérogènes (Fig.1). En fournissant une carte 3D quantitative de l'indice de réfraction du matériau, des informations chimiques locales sur l’échantillon peuvent être obtenues[3]. Pour compléter, nos derniers développements méthodologiques combinent la ptychographie avec des méthodes spectroscopique dans une méthode la nanoimagerie hyper spectrale pour extraire la localisation et état chimique des éléments chimique d’intérêt dans l’échantillon.

Pour finir, nous discuterons nos outils open-source d’analyses de données en Python sur lesquelles nous travaillons : (i) Ptypy : un framework computationnel pour la reconstruction ptychographique optimisé pour les calculs en parallèle ou sur GPUs (Fig.2a) ; (ii) Toupy : une librairie d’outils pour de reconstruction tomographique qui comprend des algorithmes de déroulage de phase, correction de la rampe de phase, alignement de projections basée sur la consistance tomographique, et la reconstruction tomographique (Fig.2b).

Références :
[1] da Silva & Menzel, Optics Express 23 (2015), p. 33812-33821.
[2] Gussone, et al., Applied Materails Today 20 (2020), p. 100767.
[3] da Silva, et al., Langmuir 31 (2015), p. 3779-3783.
[4] da Silva, et al., ChemCatChem 7 (2015), p. 413-416.
[5] da Silva, et al., Optica 4 (2017), p. 492-495.


Julio DA SILVA (Grenoble)
11:40 - 11:50 Discussion.
11:50 - 12:05 #26240 - Développement de simulation de microscope électronique en transmission pour l’optimisation des expérimentations.
Développement de simulation de microscope électronique en transmission pour l’optimisation des expérimentations.

Le microscope électronique en transmission est un instrument extrêmement puissant et flexible, capable d’explorer la matière à des échelles inférieures au nanomètre, mais aussi de sonder des propriétés spécifiques, comme les états magnétiques ou les détails de la microstructure. Sa complexité d’utilisation le rend cependant difficile à maîtriser, pour le débutant comme l’expert. Cela signifie un coût financier et de temps de formation, mais aussi une perte d’efficacité pour l’expérimentateur, qui ne peut pas utiliser le microscope comme il le souhaite, ni au maximum de ses capacités.

Ce problème est une conséquence du manque d'information accessible sur la configuration optique du microscope. N'ayant accès simplement qu’à l'image produite en sortie, le microscopiste doit faire appel à des stratégies, ou méthodes d'alignements, pour manipuler l'état optique de l'instrument.

Nous proposons ici d’introduire un paradigme différent, basé sur  représentation fidèle de l’état optique interne. Nous avons ainsi développé deux simulations complémentaires du microscope I2TEM [1, 2] du CEMES :  une pour des trajectoires électroniques exactes à l'aide du logiciel SIMION [3] et une autre basée sur l’approximation paraxiale à l’aide d’une bibliothèque python.Les champs électriques et magnétiques du microscope sont préalablement simulés à partir de la forme exacte des pièces par SIMION. Les simulations se synchronisent en temps réel avec le microscope. La mise en place de ces simulations pour d’autres microscopes est également facilitée grâce à un logiciel d'automatisation réalisé aussi en interne.

Cependant les résultats de telles simulations optiques sont complexe à visualiser. Nous  avons ainsi développé une interface dédiée en collaboration avec des étudiants et chercheurs en Interaction Homme-Machine, de l'équipe SINA de l'ENAC.

Ce système, qui s'adresse tant au novice qu'à l'expert, offre la possibilité de rendre plus accessible la réalisation d'expériences complexes, de les  préparer en amont, et fournit un outil pédagogique innovant pour la formation et la vulgarisation.

Références
[1] Y. Kubo, C. Gatel, E. Snoeck, et F. Houdellier, Ultramicroscopy, 175 (2017).
[2] J. Dupuy, Contrôle dynamique et optimisation des observations en microscopie électronique en transmission, Thèse de doctorat, Université de Toulouse (2021).
[3] David A. Dahl, International Journal of Mass Spectrometry, 200 (2000).


Julien DUPUY (Toulouse)
12:05 - 12:15 Discussion.
Room 1
12:15 Pause
13:00

Vendredi 09 juillet

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POS2
13:00 - 15:00

Session Posters 2

13:00 - 15:00 #26242 - IN SITU GROWTH AND SHAPE TRANSFORMATION OF Co NANOPARTICLES AND Co-Ni NANOALLOYS.
IN SITU GROWTH AND SHAPE TRANSFORMATION OF Co NANOPARTICLES AND Co-Ni NANOALLOYS.

Arthur MOISSETChristophe PETITPascal ANDREAZZADamien CHAUDANSONOlivier MARGEATSuzanne GIORGIO *,

  • Sorbonne Université,CNRS, MONARIS, UMR 8233, 4 place Jussieu, 75005 Paris
  • Université d’Orléans, CNRS, ICMN, UMR 7374, 1 rue de la Ferollerie, 45100 Orléans
  • Aix-Marseille Université, CNRS, CINaM, UMR 7325, Campus de Luminy, 13288 Marseille


The control of the shape and structure of metal nanoparticles or nanoalloys is important for applications. It mainly depends on the crystal growth mechanism. Co nanoparticles (NPs) and Co-Ni nanoalloys, grown from solution, exhibited a shape transformation from nanospheres to nanorods [1]. The growth mechanism from nanospheres to nanowires as in figure 1, was studied by the association of two in situ techniques, liquid microscopy and SAXS. In situ SAXS measurements have shown a textured media between the oleylamine (OAm) and the cobalt precursor. The shape transformation of pure Co NPs and Co-Ni nanoalloys was observed by TEM in a drop of OAm solution diluted in toluene or heptane, encapsulated between graphene layers, as described in previous works [2]. The growth of the NPs and alloys in an OAm visquous solution allows a growth mechanism by direct adsorption of the monomers and an homogeneous size and shape distribution, as seen in figures 2 a-c (a), after 5mn (b), 15 mn(c) . At RT, after the growth of NPs in the encapsulated solution, the OAM has a tendency to texture while the metal NPs are dissolved (figure 2d-e, 17 mn (d) and 18 mn (e)). Then, Co re-crystallizes as nanorods as in figures 2 f-g-h (19 mn (f), 23 mn (g), 27 mn (h)). The same mechanism was observed with Co-Ni nanoalloys. Careful observation of NPs in diluted OAm during the NPs dissolution in the electron beam, shows residual metal clusters with sizes below 1 nm, as in figure.2i (scale bar 50 nm). By the following, these remaining small clusters are the results of the beginning of the Co NRs’ formation and tend to align along the OAm texture then, they grow as nanorods. Références: [1] L.Meziane, C.Salzemann, C.Aubert, H.Gérard, C.Petit , M.Petit, Nanoscale, 8 (2016), p.18640 [2] De Clercq, W. Dachraoui, O. Margeat; C.R.Henry, S.Giorgio; J. Phys. Chem. Letters, 5 (2014) p.2126 [3] A. Vivien, M. Guillaumont, L. Meziane, C. Salzemann, C. Aubert, S. Halbert, H. Gérard, M. Petit and C. Petit, Chem.Mater., 31, 3, (2019), p. 96
Suzanne GIORGIO (Marseille)
13:00 - 15:00 #26243 - Phase evolution in Si-graphite electrodes mapped by VEELS in the transmission electron microscope.
Phase evolution in Si-graphite electrodes mapped by VEELS in the transmission electron microscope.

Jianhan XIONGNicolas DUPREPhilippe MOREAU *, Bernard LESTRIEZ

  • Université de Nantes, CNRS, Institut des Matériaux Jean Rouxel, IMN, F-44000 Nantes, France


Negative electrodes based on silicon have been considered for some time (due to their theoretical high capacity) [1], but present long term performance not meeting the current requirements. This is due to the large change of volume of the material with its reaction with lithium ions and its unstable passivation against the electrolyte. In order to mitigate this downfall evolution, mixtures of silicon with graphite (a long used and efficient material) are now being developed and studied [2]. This is the objective of the ANR project SILMARILION concerning the negative electrode of the complete lithium-ion battery to be produced. Since interactions between the different constituents of the composite electrode (Si, graphite, binder) are essential to the behaviour during cycling and occurs at very small scale, (S)TEM experiments are quite useful. In this study, we have used valence electron energy-loss spectroscopy to map the different constituents of the pristine electrodes as well as the reaction products along cycling. The use of this method was shown [3] to be very effective even on highly beam sensitive materials such as lithium fluoride or polymeric entities. Thanks to a method developed by M. Boniface in his PhD thesis [4], it was even possible to grasp the evolution of these constituents along cycling in a quantitative way. To that end, the Gatan 969 spectrometer (equipped with a K2) of the Nant’Themis, some PCA post-processing and MLLS fitting routines were used. They allow identifying and, visualising the role of the PAA polymer binder (Figure 1) and the presence of a hairy silicon (Figure 2) as soon as 30 cycles, despite the presence of graphite [5].
Philippe MOREAU (IMN, Nantes)
13:00 - 15:00 #26246 - Defect creation in Transition Metal Dichalcogenides by Ion Bombardment and further characterization by Scanning Tunneling Microscopy.
Defect creation in Transition Metal Dichalcogenides by Ion Bombardment and further characterization by Scanning Tunneling Microscopy.

Pedro Lourenco *, Nadine WITKOWSKIGeoffroy PRÉVOTHervé CRUGUELRomain BERNARD

  • Institut de Nanosciences de Paris, Sorbonne Université, Paris, France


Transition-metal dichalcogenides (TMDC), such as WS2 and WSe2, are layered two dimensional materials, having a wide number of applications in optoelectronics, energy storage or catalysis. Epitaxial films are usually synthesized by chemical vapor deposition (CVD), leading to high-quality stoichiometric crystals with large domain sizes. Recently, there have been efforts to synthesize high-quality WS2 and WSe2 films through the use of reactive magnetron sputtering,[1] a versatile physical vapor deposition (PVD) process already implemented in the semi-conductor industry. As compared to CVD, more structural defects and smaller domain sizes are however observed. This could be explained by the impact of energetic species at the surface of the film during the growth. These structural defects play an important role in the characteristics of the TMDC. For example, chalcogenide vacancies are known to decrease the carrier mobility and thus to deteriorate the device performance. [2] To better understand the impact of energetic particles on the TMDC surface, we have generated single defects on the surface of WS2 and WSe2 crystals using low energy (50 eV to 500 eV) Ar+ ions with a controlled fluence. The irradiated samples were then analyzed by Scanning Tunneling Microscopy (STM). When imaged at negative sample bias, the defects appear as a bright protrusion due to the presence of a localized electronic state, associated with chalcogenide vacancies (see Fig. 1). Whereas a strong dependance with Ar+ energy of the probability of defect creation is observed, the shape and size of each defect, when imaged by STM, appears to be independent of the energy (see Fig. 1). In order to have an atomistic view of the collision phenomena, we have performed Molecular Dynamics (MD) simulations. These simulations show that there is a higher probability of creating defects at higher Ar energies, agreeing with the experimental results. They also show that there are more defects created which are located into the layers underneath the surface due to the collision cascade. This might explain why there is no clear difference in defect morphology with varying Ar+ energy, as the effect of the generated structures in the layers underneath cannot be fully probed by STM. Références/References : [1] Villamayor, M. et al, Vacuum, 188 (2021). [2] Yu, Z. et al. , Nat Commun 5, 5290 (2014)
Pedro LOURENCO (Paris)
13:00 - 15:00 #26349 - In-situ TEM techniques of magnetic nanotubes for 3D spintronics.
In-situ TEM techniques of magnetic nanotubes for 3D spintronics.

Mahdi Jaber *

  • Univ. Grenoble Alpes / CEA / CNRS, SPINTEC, France.
  • CEA, IRIG/MEM, France.


A major driving force in applied spintronics is magnetic memories. While existing products rely on uniformly-magnetized elements, data storage using the motion of magnetic domain walls in two-dimensional strips using spin-polarized current is also investigated [1]. The three-dimensional geometry like in cylindrical nanowires and nanotubes is researched [2]. Magnetic domain walls in the latter are distinct from those in flat films and strips, opening perspectives for new physics. In comparison to cylindrical nanowires, isolated ferromagnetic nanotubes have given rise to relatively few experimental reports. Here, we describe the characterization of high-aspect ratio CoNiB nanotubes, grown chemically by electroless plating, using various TEM techniques such as Energy-dispersive X-ray spectroscopy EDX, Electron energy-loss spectroscopy EELS, and in-situ Electron Holography. Previous experimental studies revealed the possibility for orthoradial magnetization (i.e. azimuthal domains), a phenomenon not expected by theory, but interesting for the application side [3] (Figure 1.a,b). Based on that, we performed TEM electron holography to explore the magnetic configuration in nanotubes, as well as their magnetic history under applied fields (Figure 1.c,d). We also evidence that Nickel tends to segregate on both side of the CoNi layer, which is supposed to affect the system magnetic behavior (Figure 2). To help the physical and the theoretical interpretation of the measurements, reasonable efforts on data analysis and micromagnetism simulations will be made. As a result, a deeper understanding of the spin textures in nanotubes will contribute to enhance the productivity in spintronics. References: [1] J. Hurst et al. Theoretical study of current-induced domain wall motion in magnetic nanotubes with azimuthal domains. Phys. Rev. B 103, 024434 (2021). [2] Magnetic nanowires and nanotubes, M. Staňo, O. Fruchart, Handbook of Magnetic Materials. Ed. Ekkes Brück vol. 27, 2018, Pages 155-267 [3] Staňo, M. et al. Imaging magnetic flux-closure domains and domain walls in electroless-deposited CoNiB nanotubes. SciPost Phys. 5 (2018) p 038.
Jaber MAHDI (CEA, Grenoble)
13:00 - 15:00 #26247 - CONTROLLING POROSITY IN CONDUCTING POLYMER CRYOGEL VIA THE ICE-TEMPLATING METHOD.
CONTROLLING POROSITY IN CONDUCTING POLYMER CRYOGEL VIA THE ICE-TEMPLATING METHOD.

Naoures HMILI *, Swapneel THAKKARQuentin WEINBACHPatrick allgayerMarc SCHMUTZLaure BINIEKAlain CARVALHO

  • CNRS – Institut Charles Sadron – 23 Rue du Lœss 67034 Strasbourg, France.


Porous bulk polymers are of great interest for their advantageous properties like low bulk density, flexibility and high surface area. These properties among many others, open new doors for diverse applications such as the hot topic of thermoelectricity. In that field, the porous polymer should be electrically conductive and thermally isolating. Ideally, an anisotropic structure with well oriented pores is crucial to reach high thermoelectric efficiency. Porous conducting polymers can be prepared by freeze-drying a hydrogel (PEDOT:PSS) leading to a porous cryogel. But, with a classic flash freeze-drying a non-controlled porous structure is obtained as shown in the SEM image (fig.1) (taken by Hitachi SU 8010 Ultra High Resolution Field Emission Scanning Electron Microscope). In this project, our team applies the ice templating technique [1] on PEDOT:PSS gels to control the porous structure. This involves the unidirectional growth of ice crystals in the gel as a texturing agent for the porosity. We demonstrate by cryoSEM that while freezing, the ice crystals grow and push apart the polymer fibers to create the walls of the pores. Once freezing is complete, the sample is dried by sublimation. A porous cryogel is then obtained in which the pores are the replica of the ice crystals. Via this method, and by controlling the cooling rate and temperature [2], we have succeeded to channel the pores and obtain a well aligned honeycomb structure as seen in fig.2 (a) and (b). Finally, the pore size as well as the directionality of the channelled pores were analysed by ImageJ (using respectively “analyse particles” and the plug-in “orientation J”). References: [1] Deville, S. (2013). Ice-templating, freeze casting: Beyond materials processing. Journal of Materials Research, 28(17), 2202–2219. doi:10.1557/jmr.2013.105 [2] S. Deville, Ice-Templating: Processing Routes, Architectures, and Microstructures. 2017. This Master internship work has been supported by a Sfμ grant.
Naoures HMILI (Strasbourg)
13:00 - 15:00 #26350 - Highlights of 15R crystal phase in Au-catalyzed ZnS nanowires.
Highlights of 15R crystal phase in Au-catalyzed ZnS nanowires.

Sumit Kumar *, Frédéric FossardGaëlle AmiriJean-Michel ChauveauVincent Sallet

  • GEMaC, CNRS - UVSQ, Université Paris-Saclay
  • LEM, ONERA-CNRS, Université Paris-Saclay


Unique growth mechanisms involved in semiconductor nanowires (NWs) pave the way to the achievement of new crystallographic phases and remarkable material properties. Interestingly, in the case of 1D nanostructures, polytypism can arise due to the particular growth mode below a catalyst droplet, which may induce stacking faults along the length of the nanowire. Moreover, these stacking faults can be correlated and form ordered arrays, until giving rise to new phases (polytypes) with distinct properties[1]. Hence, 4H, 6H, 8H, and 10H (so-called high order polytypes) can be observed in nanowires[2]. Hence, studying polytypism in semiconductor NWs arouses a strong interest for the next generation of electronic and photonic applications. In this framework, ZnS is an important II-VI semiconductor that has a wide range of optoelectronic applications including luminescent devices, infrared windows, and UV-photodetectors[3]. In this work, Au-assisted ZnS nanowires were grown by MOCVD on GaAs (111B) substrate (VLS mode or VSS mode). The idea is to provide a change in the growth mechanism via the physical state of catalyst droplets (liquid or solid) and hence, study the induced polytypism in ZnS nanowires. ZnS nanowires with length up to 1.4 µm and diameter in the range 10–34 nm was successfully achieved. The obtained morphologies and densities of the NWs have been systematically inspected by scanning electron microscopy (SEM) directly on the substrate (illustrated in Fig 1). Transmission Electron Microscopy has been also used to investigate the crystallographic structures and compositions of both catalysts and nanowires. HRTEM observations revealed that the NWs exhibits periodic stacking faults, and the resulting structure was accurately identified as 3 sequences of 5 planes ABCBA-BCACB-CABAC (i.e. 5th order superstructure), giving rise to an astonishing 15R crystal structure (Fig 2)[4]. This structure is highlighted for the first time in ZnS nanowires. We modeled this 15R structure in the framework of the classical nucleation theory and axial-next-nearest-neighbour-Ising model (ANNNI). References [1] G. Priante et al. Phys Rev B. 89 (2014) 241301 [2] Y. Jiang et al. Adv. Mater. 15 (2003) 1195 [3] S. Premkumar et al. Sci. Rep. 9 (2019) 18704 [4] S. Kumar et al. Nano Res. (2021) https://doi.org/10.1007/s12274-021-3487-8
Sumit KUMAR (Paris-Saclay)
13:00 - 15:00 #26347 - Impact of irradiation and nano-oxides dispersion on alpha prime phase formation in Oxide Dispersion Strengthened steels: a combined TEM and APT study.
Impact of irradiation and nano-oxides dispersion on alpha prime phase formation in Oxide Dispersion Strengthened steels: a combined TEM and APT study.

Marie-Jose SALEH AFIF *, Stephanie JUBLOT-LECLERCJoel RIBISAurelie GENTILSMarie LOYER-PROST

  • Université Paris-Saclay, CEA, Service de Recherches de Métallurgie Physique, 91191 Gif-sur-Yvette, France
  • Université Paris-Saclay, CNRS/IN2P3, IJCLab, 91405 Orsay, France


Because of industrial development and the growth of the world population, nuclear reactors are developed to cover the increase in energy consumption. The nuclear energy produced through fission and fusion reactions is indeed capable of producing a very large amount of electrical power. One of the problems encountered during these nuclear reactions is the irradiation swelling of fuel cladding materials. Hence nanostructured materials such as Oxide Dispersion Strengthened (ODS) steels were especially developed to resist to irradiation [1] and high temperature [2]. These steels are composed of a metallic body-centered cubic matrix (FeCrW or FeCrMo) reinforced with nano-oxides of titanium and yttrium. As the ODS steel matrix is mainly a Fe-Cr system, a Cr-rich phase, alpha’, can precipitate under irradiation [3] and brittle the system. This study focuses on the impact of the nano-oxides dispersion and the irradiation conditions on the formation of the alpha’ phase in an ODS steel: MA957 [4]. A MA957 steel and a corresponding steel without nano-oxides are irradiated on the JANNuS platform [5] at 400°C with Fe ions at different damage doses (from 0,5 to 9 dpa). Samples are characterized at the nanometric scale using Transmission Electron Microscopy (TEM), Energy Filtered TEM (EFTEM) and Atomic Probe Tomography (APT). The drastic impact of the nano-oxide distribution and the influence of injected ions on the alpha’ distribution are revealed and discussed. References: [1] R.L. Klueh et al., Journal of Nuclear Materials 341 (2005), p.103 [2] T.R. Allen et al., Journal of Nuclear Materials 375 (2008), p. 26 [3] N.A. Bailey, Journal of Nuclear Materials 459 (2015), p. 225 [4] J. Ribis et al., J. Mater. Res. 30 (2015), p.2210 [5] A. Gentils, C. Cabet, Nucl. Instrum. Methods B 447 (2019), p.107
Marie-Jose SALEH AFIF (Orsay)
13:00 - 15:00 #26248 - Quantitative STEM imaging: from the SiGe model toward application to interfacial phase-change memories (iPCMs).
Quantitative STEM imaging: from the SiGe model toward application to interfacial phase-change memories (iPCMs).

Vitomir Sever *, Nicolas BernierPierre NoéJean-Luc Rouvière

  • Université Grenoble Alpes, CEA, LETI, F-38000 Grenoble


GeTe-Sb2Te3 superlattices (SL’s) are the most promising materials for iPCMs, but the physical switching mechanism is still under debate. To improve this emerging technology, it becomes mandatory to describe the iPCMs structures at an atomic scale since the involved mechanism upon switching is expected to rely on local atomic motion. Using atomic resolution HAADF STEM images, acquired on a FEI Titan Themis microscope, two analyses were performed. However, before studying the more complex case of iPCM SL’s, we explored the experimental approaches on a reference Si-SiGe multilayer sample calibrated by XRD. Various sets of data were acquired and analyzed using Python programming. First, images recorded with an HAADF detector were interpreted quantitatively by means of comparison between experimental and simulated intensities. We used the STEMsim software from the Rosenauer’s group [1] for HAADF image simulations. From this comparison, the local thickness can be obtained. If the thickness is known, the unknown chemical concentration of a single element can be measured. Here, PACBED measurements give the thickness and Ge concentration in SiGe layers was extracted [1]. Additionally, the position of atomic columns can be precisely determined utilizing a template-matching approach [2]. After acquiring a stack of low-dose images, rigid and non-rigid alignments were performed using the SmartAlign software. Then the center of gravity method is used to find the precise position of the correlation peaks between a template and an experimental image. Hence, a reference lattice can be calculated. Therefore, atomic displacements and strain maps were obtained on the same reference sample. For robust and fast analysis, two Python libraries have been developed and corresponding notebooks were deployed at the CEA Grenoble. After validating these methods on the reference sample, these analyses were applied to numerous HAADF images of iPCM SL’s and the first results on Sb2Te3 blocks will be presented. References: [1] Rosenauer et al., Ultramicroscopy 111 (2011), p.1316-27. [2] Zuo et al., Ultramicroscopy 136 (2014), p. 50-60
Vitomir SEVER (Grenoble)
13:00 - 15:00 #26244 - Segregation in Au-Cu nanoparticles: a theoretical and experimental approach.
Segregation in Au-Cu nanoparticles: a theoretical and experimental approach.

Grégoire Breyton *, Hakim AmaraJaysen NelayahDamien AlloyeauGuillaume WangJérôme CreuzeChristian Ricolleau

  • MPQ, Univ. de Paris
  • LEM, CNRS / ONERA
  • ICCMO, Univ. Paris Saclay


Nanoparticles (NPs) are primarily known for their high surface to volume ratio making them perfect candidate as catalyst for reactivity process. Another attractive aspect of these nano-objects lies in the unexpected reactivity of some materials. For example, gold is known to be inert at bulk scale but very reactive in small sized nanoparticles (< 5 nm) for the CO to CO2 transformation [1]. Interestingly, this phenomenon is enhanced by alloying gold with copper [2]. However, little is known on the surface structure of the Au-Cu alloy and more precisely of their surface composition which plays a crucial role during reactivity process. In this context, our work aims at characterizing the AuxCu1-x nanoparticles structure in order to highlight surface segregations or not by using both a theoretical and experimental approaches. Atomic scale Monte Carlo simulations based on semi-empirical potential [3] have been performed (Fig 1 Left). A strong segregation of gold over the entire surface is observed whatever the size of octahedron NPs (Fig 1 Middle). Simulations of nanocubes seem to strengthen these results where only (100) facets are present. Experimentally, octahedron NPs and nano-cubes have been synthesized by Pulsed Laser Deposition (PLD) on a substrate of NaCl. This substrate has a cubic structure which favors cubo-octaedron morphologies. Their chemical analysis and structural characterization on an aberration corrected JEOL ARM 200F in TEM and STEM modes are still ongoing (Fig 1 Right). References: 1. Lopez Nuria et al. Journal of Catalysis223.1 (2004): 232-235. 2. Liu Xiaoyan et al. Catalysis today 160.1 (2011): 103-108. 3. Rosato Vittorio et al. Philosophical Magazine A59.2 (1989): 321-336.
Grégoire BREYTON (Paris)
13:00 - 15:00 #26355 - Wave contrast analysis in High Resolution TEM : Rhombohedral Pr5Co19 structure and polytypes.
Wave contrast analysis in High Resolution TEM : Rhombohedral Pr5Co19 structure and polytypes.

Farah Chafaï *, Loïc PatoutKhalid HoummadaLotfi BessaisNajeh MlikiAhmed Charaï,

  • Université de Tunis El Manar, Faculté des Sciences de Tunis, Laboratoire Matériaux Organisation et Propriétés, 2092, Tunis, Tunisie
  • Aix-Marseille Université, CNRS, Université de Toulon, IM2NP - Campus de St Jérôme, 13397 Marseille cedex 20, France
  • ICMPE UMR CNRS 7182 – Université Paris Est Créteil, 94320, Thiais, France


Les intermétalliques à base de terre-rares (RE) et d’éléments de transition sont parmi les meilleurs candidats pour une utilisation comme aimants permanents. Les composés nanocristallins ont été très étudiés notamment par rapport aux techniques de préparation et l’état approprié du matériau pour obtenir le champ coercitif optimisé [1]. En particulier, le composé Pr5Co19 constitue un alliage attractif dû à ses propriétés significatives donnant lieu à une grande variété d’applications technologiques telles que la réfrigération magnétique à haute température [2]. Quelques travaux montrent l’importance de réduire les défauts microstructuraux qui peuvent influencer localement les forces de pinning [3]. Une poudre nanocristalline Pr5Co19 de structure rhomboédrique a été préparée par fusion à arc et broyage à haute énergie. Les analyses MET montrent une structure en forme de plaquettes avec des alternances de contraste séparées par des distances non périodiques le long de l’axe c (c = 48,75 Å). Une projection HREM [100] tiltée le long de c* met en évidence des décalages d’empilement de part et d’autre des plaquettes sombres qui sont en partie intrinsèques à la structure (Fig. 1). En effet, l’analyse des empilements dans une image en axe de zone [210] et des réflexions FOLZ dans la FFT correspondante montrent que des fautes apparaissent dans la séquence des blocs A-B-C (ou 3R) (Fig. 2). La présence de polytypes, notamment les structures hexagonales Pr5Co19 et Pr2Co7, forment des structures d’inter-croissance où un bloc est retiré pour former localement des séquences bicouches de blocs A-B (ou 2H). Ces défauts semblent difficiles à éviter dû à la gamme de solubilité solide très limitée de la phase Pr5Co19 dans le système binaire et aux très faibles différences d’énergie entre les différentes stœchiométries et entre les structures stables 3R et métastables 2H. References [1] R. Fersi, et al.. J. Alloys Compd. 522 (2012) 14-18 [2] V. K. Pecharsky, et al. Phys. Rev. B, 64 ; 144406, 2001 [3] M. Duerrschnabel, et al. Nat. Commun. 8 (2017) 54
Farah CHAFAÏ ()
13:00 - 15:00 #26416 - Quantitative study of temperature effects on the nucleation and growth of gold nanocrystals in water.
Quantitative study of temperature effects on the nucleation and growth of gold nanocrystals in water.

Temperature is a crucial parameter in the liquid-phase synthesis of metal nanoparticles (NPs) that directly impacts all the atomic-scale processes that drive the size dispersion of colloidal assemblies and the shape of nanostructures1-2. As the temperature concomitantly affects the kinetics of chemical reactions and the thermodynamic equilibrium of nanomaterials in solution, the full understanding of thermal effects on the nucleation and growth processes requires direct in situ observations at the nanoscale.   

Here, we exploit for the first time temperature controled liquid-cell TEM to study thermal effects on the radiolysis-driven formation of gold nanocrystals in water between 25 °C and 85 °C (Figure 1)3. The huge impacts of temperature on the nucleation and growth rates of nanostructures measured using automated video processing are quantitatively explained in the framework of the classical theories. Thus, we show that the increase of molecular diffusion and nanoparticle solubility governs the drastic changes in the formation dynamics of nanostructures in solution with temperature. In contradiction with the common view of coarsening processes in solution, we also demonstrate that the dissolution of nanoparticles and thus the Ostwald ripening are not only driven by size effects (Figure 2). Furthermore, visualizing thermal effects on faceting processes at the single nanoparticle level reveals how the competition between the growth speed and the surface diffusion dictates the final shape of nanocrystals. Our method and data-analysis workflow can be applied to other dynamical processes in nanochemistry where temperature plays an important role.

Acknowledgments:

We gratefully acknowledge the help of Maxime Moreaud in the processing of our videos using the PlugIM plateform developed at IFPEN. 

References:

[1] N. T. Thanh, N. Maclean and S. Mahiddine, Chemical reviews, 2014, 114, 7610-7630.

[2] X. Xia, S. Xie, M. Liu, H.-C. Peng, N. Lu, J. Wang, M. J. Kim and Y. Xia, Proceedings of the National Academy of Sciences, 2013, 110, 6669-6673.

[3] A. Khelfa, J. Nelayah, G. Wang, C. Ricolleau, D. Alloyeau, JOVE Vis. Exp. (168), e62225, doi:10.3791/62225 (2021).


Abdelali KHELFA (Paris)
13:00 - 15:00 #26418 - Morphological and structural thermal stability of Pt-based hollow nanoparticles under different environments.
Morphological and structural thermal stability of Pt-based hollow nanoparticles under different environments.

Josephine REZKALLAH *, Simona MOLDOVANBernhard WITULSKIXavier SAUVAGE

  • GPM Laboratory, CNRS UMR 6634, Rouen University, Normandy
  • LCMT Laboratory, CNRS UMR 6507, ENSICAEN & Caen University, Normandy.


Owing to their high reactivity, Pt nanoparticles (NPs) are commonly used in catalysis.[1,2] Shape, size, morphology and catalytic performance of NPs can be engineered by different synthetic methodologies;[3] and one of the strategies aiming at the active surface maximization is the use of hollow nanospheres.[4] Since catalytic reactions often occur under a well-controlled environment including conditions of high temperature and high pressure, a deeper knowledge on the catalytic materials behavior is necessary to understand, control and improve materials properties under reaction conditions. In this context, the approach proposed herein concern the use of Environmental TEM to probe microstructural changes in real time and under real-life conditions with notably atomic resolution. Two syntheses that differ each other in the well-defined ratio of Pt salts (H2PtCl6) and Co nanoparticles as precursors have been carried out for the elaboration of discrete Pt hollow nanospheres. [4] From a morphological point of view, the Pt-based NPs are spherical with a diameter of 15-20nm. They exhibit a core-shell structure with a polycrystalline shell (Fig. 1a and 2a). The chemical composition of these NPs was measured by EDX (Fig. 1(d-g) and 2(d-g)). It is strongly influenced by the Pt/Co ratio during the synthesis. The cobalt content of these hollow-sphere NPs produced from a Pt/2Co = 1.5 and a Pt/2Co = 0.75 ratio is 10% and 20%, respectively. Here we report on the influence of temperature, pressure and exposed gas (H2, Ar) on the morphological (coarsening, agglomeration and/or collapsing) and structural stability (phase transformation) of those hollow-sphered Pt nanoparticles. A windowed gas cell in-situ TEM holder (atmosphere-Protochips) was used in the 20-300°C temperature range and up to 1 atm pressure for this study. Acknowledgment The authors acknowledge the financial support of the French Agence Nationale de la Recherche and LabEx EMC3 through the Project ZeoMah (Grant No. ANR-10-LABX-09-01) References: [1] T.S. Ahmadi et M.A. El-Sayed, Science, 272 (1996), 1924. [2] Z. Zhou et Q. Xin, Chem.Commun., (2003). [3] T. Altantzis and S. Bals, Nano Letters, 19 (2019), 477. [4] H.‐P. Liang and C.‐L. Bai, Angew. Chem. Int. Ed., 43 (2004),1540.
Josephine REZKALLAH (Rouen)
13:00 - 15:00 #26419 - Investigation of the elastic properties of Au nanoparticles by in-situ TEM nanocompression experiments and Brillouin spectroscopy.
Investigation of the elastic properties of Au nanoparticles by in-situ TEM nanocompression experiments and Brillouin spectroscopy.

Mariana Timm *, Rongrong ZhangKarine Masenelli-VarlotJérémie MargueritatLucile Joly-Pottuz

  • Univ-Lyon, INSA, UCBL, CNRS, MATEIS UMR 5510, 69621 Villeurbanne, France
  • Institut Lumière Matière, Université de Lyon, Université Claude Bernard Lyon 1, UMR CNRS 5306, 69622 Villeurbanne, France


The mechanical behavior of materials at the nanometer scale is strongly different from the one observed in bulk materials [1]. However, the measurements at the nanoscale remain extremely challenging, and the same is true concerning their interpretation. Thus, we combine two different techniques, nanocompression and Brilloun spectroscopy, on the same system to reach a high characterization level. Initially, the elastic properties of monocrystalline Au nanoparticles with sizes around 100 nm was assessed with low-frequency Raman/Brillouin spectroscopy using the dependency of the acoustic vibrational modes. The measurement of acoustic vibrational modes is fundamental to the full comprehension of the mechanical properties of nano-objects, since they are connected to the intrinsic characteristics of the material, such as crystallinity, size, shape and elasticity [2]. We show that changes in the environment around the particles modify the distribution of the electrical field inside the NPs, therefore affecting their acoustic response. The same particles were submitted to nanocompression in the TEM to characterize their deformation behavior and to obtain the stress-strain curve. The in-situ nanocompression experiments were performed with a Cs-corrected FEI-Titan microscope using a Hysitron pico-indenter. Finally, using the pico-indenter sample-holder adapted to the Brillouin experimental set-up, the measurement of the acoustic vibrational modes of single Au NPs was performed during compression tests. References : [1] O. Kraft et al., Annu. Rev. Mater. Res 40 (2010) 293-317 [2] Hodak, J. H.; Martini, I.; Hartland, G. V. J. Phys. Chem. B 102 (1998), 6958−6967
Mariana TIMM (Lyon)
13:00 - 15:00 #26420 - In situ nanocompression tests in an environmental TEM to study plasticity of cerium oxides.
In situ nanocompression tests in an environmental TEM to study plasticity of cerium oxides.

Rongrong ZHANG *, Lucile Joly-PottuzGaëtan LaurensTristan AlbaretEpicier ThierryKarine Masenelli-Varlot

  • Univ Lyon, INSA-Lyon, MATEIS
  • Univ Lyon, UCB Lyon 1, ILM


As one of the most important ceramic materials, cerium oxide is widely used in many applications, such as in solid oxide fuel cell electrodes, catalysis, and is also used as superior abrasive particles in chemical mechanical planarization [1]. Ceria is sensitive to electron beam irradiation leading to a reduction [2]. Nevertheless, the use of the environment allows to control or avoid this reduction [publi Matthieu]. It is, thus, possible to test a CeO2 structure or a structure CeOx (1.5
Rongrong ZHANG (Lyon)
13:00 - 15:00 #26421 - Multimodal study of dis-sodiation mechanism within individual Na3V2(PO4)2F3 cathode crystals using 4D-STEM-ASTAR & STXM-XANES.
Multimodal study of dis-sodiation mechanism within individual Na3V2(PO4)2F3 cathode crystals using 4D-STEM-ASTAR & STXM-XANES.

Nicolas Folastre *, Kirill CHEREDNOCHENKO François CADIOU Matthieu BUGNET Edgar RAUCH Jacob OLCHOWKAStefan STANESCUSufal SWARAJ Rachid BELKHOU Antonella IadecolaChristian MASQUELIER Laurence CROGUENNEC Arnaud DEMORTIERE

  • Laboratoire de Réactivité et de Chimie des Solides (LRCS), CNRS UMR 7314, Amiens, France
  • MATEIS Laboratory – CNRS UMR 5510/University of Lyon, Lyon, France
  • Laboratoire Science et Ingénierie des Matériaux et Procédés (SIMaP) – Grenoble INP/CNRS/UJF, Saint Martin D’Hères, France
  • Institut de Chimie de la Matière Condensée de Bordeaux (ICMCB), CNRS/Université de Bordeaux, Pessac, France
  • SOLEIL Synchrotron - Science Division - Gif-sur-Yvette, Ile-de-France, France
  • Laboratoire de Réactivité et de Chimie des Solides (LRCS), CNRS UMR 7314, Amiens, France
  • Institut de Chimie de la Matière Condensée de Bordeaux (ICMCB), CNRS/Université de Bordeaux, Pessac, France


In situ liquid electrochemical TEM [1] is one of the most powerful analytical tools allowing to follow structural and chemical transformations in Li-ion battery active materials at nanoscale with high spatial resolution and in conventional liquid electrolytes. For instance, very recently, the changes in the unit cell structure of cathode materials (LFP) during electrochemical cycling in liquid electrolyte were determined using in situ electron diffraction tomography [2]. The same compound was earlier comprehensively studied by 4D-STEM ASTAR (parallel beam) [3] and other techniques as electron ptychography [4]. Sodium vanadium (III) fluorophosphate, Na3V2(PO4)2F3 (NVPF) is attracting great interest as a potential positive electrode for Na-ion batteries due to its exceptional rate and electrochemical cycling capabilities. During the charging process, the disinsertion of two Na+ ions leads to the change of vanadium oxidation state and corresponds to structural transformations which can be registered with 4D-STEM ASTAR system. In our work we employed Poseidon in situ electrochemical liquid cell TEM holder (Protochips) and TEM equipped with Oneview camera (GATAN) and 4D STEM ASTAR system. Thanks to 4D-STEM system we succeeded to follow the structural and, thus, phase transformations of NVPF grains during the charge/discharge process in coin-cell battery. The results of obtained phase mapping are in good agreement with corresponding galvanostatic curves and available X-ray diffraction synchrotron data. More recently, we mapped by STXM-XANES (SOLEIL, beamline HERMES) (energies of V and O) then by STEM-EELS (energies of Na) the same individual grains of NVPF de-sodiated ex-situ at different charge states[5] (Fig. 1). These results Added to 4D-STEM mappings will provide some answers concerning the (dis)-sodiation mechanisms in the NVPF material. Based on this multimodal study, we correlated structural and chemical behaviors in high resolution maps to improve reliability and draw evidence of Na diffusion pathway inside single grains. References: [1] Protochips, Micros. Today. 25 (2017) 13–13. [2] O.M. Karakulina, et al. , Nano Lett. 18 (2018) 6286–6291. [3] E.F. Rauch et al. Zeitschrift Für Kristallographie. 225 (2010). [4] Y. Jiang et al. Nature. 559 (2018) 343–349 [5] S. Adams, et a. Springer Berlin Heidelberg, Berlin, Heidelberg, 2014: pp. 129–159.
Nicolas FOLASTRE (Amiens)
13:00 - 15:00 #26429 - In situ liquid TEM experiments for material dissolution kinetics investigation: application to Li-ion battery materials.
In situ liquid TEM experiments for material dissolution kinetics investigation: application to Li-ion battery materials.

Julie Poulizac *, Adrien BoulineauEmmanuel BillyKarine Masenelli-Varlot

  • CEA Grenoble
  • MATEIS Lyon


Liquid in situ TEM is a powerful technique to observe various phenomena in their native environment such as nanoparticles nucleation and growth, alive biological samples or battery cycling, with high spatial and temporal resolution [1]. In this study, we applied this technique to investigate the dissolution kinetics of LiFePO4 cathode material for Li-ion battery recycling by hydrometallurgy. As the specimen studied here is a highly agglomerated powder, we applied the ultramicrotomy technique to prepare samples for the in situ experiment in order to control the sample size and avoid breaking the Si/SiN liquid cell. Thanks to this sample preparation method, we were able to observe in situ a complete dissolution of LiFePO4 by sulfuric acid, as shown in figure 1. We used BF-STEM technique to image the dissolution and the resulting images were post-processed with ImageJ software [2] to extract the reaction kinetics (figure 2). In parallel, ex situ dissolution experiments were done on LiFePO4 in order to obtain the ex situ reaction kinetics. Both ex situ and in situ kinetics were compared. Even though the in situ kinetics appears to be much slower than the ex situ one, by taking into account the samples geometry (spheres vs. disks) and the reacting surfaces, we show that the reaction kinetics are equivalent and could be overlaid. We demonstrate here that we are able to investigate in situ dissolution kinetics by the combination of the sample preparation method and image-processing routine. References : [1] S. Pu, C. Gong, and A. W. Robertson, “Liquid cell transmission electron microscopy and its applications,” R. Soc. open sci., vol. 7, Jan. 2020. [2] M. D. Abràmoff, P. J. Magalhães, and S. J. Ram, “Image Processing with ImageJ,” Biophotonics international, vol. 11, 2004.
Julie POULIZAC (Grenoble)
13:00 - 15:00 #26431 - Unveiling MoS2 behavior in biomimetic and biological media: In situ and ex vivo complementary study.
Unveiling MoS2 behavior in biomimetic and biological media: In situ and ex vivo complementary study.

Nathaly ORTIZ PEÑA *, Kondareddy CHERUKULAAlberto BIANCOCecilia MENARD-MOYONFlorence GAZEAUDamien ALLOYEAU

  • Laboratoire Matériaux et Phénomènes Quantiques, UMR 7162 CNRS/Université Paris Diderot, 75013 Paris, France
  • Laboratoire Matière et systèmes complexes, CNRS UMR 7057, Université de Paris, Paris Cedex 13, 75205, France
  • CNRS, Institut de Biologie Moléculaire et Cellulaire, Laboratoire d'Immunopathologie et Chimie Thérapeutique, 67084 Strasbourg, France


In the booming of 2D materials for a variety of applications, transition metal dichalcogenides, in particular molybdenum disulfide, have raised as an attractive subject thanks to their exceptional electronic, optical, mechanical and chemical properties.1 Notably, the large surface area with tunable electronic properties, the intercalable layers and the readiness for functionalization makes them good candidates for biomedical proposes such as biosensing, bioimaging, and drug delivery, among others. Furthermore, MoS2 have shown to have a better biocompatibility and stability in comparison with their carbon-based analogues. Prior publications assessing the degradation products from the biotransformation of MoS2 point to the oxidation of the sheets leading to the formation of free Mo+4 ions and molybdenum oxides.2 Such degradation process appears to be innocuous for the cell life. Nonetheless, additional insight in the biotransformation mechanism of exfoliated MoS2 nanosheets is key in the assessment of its viability for biomedical applications. Herein, we have implemented a complementary approach by using in situ liquid phase transmission electron microscopy and ex-vivo studies to unveil a new aspect of the behavior of MoS2 patches in conditions mimicking those within cells, in particular those with high concentrations of ROS and H2O2. We have observed in direct the scrolling of MoS2 sheets in situ and verified the presence of the same structures ex vivo (Figure 1-2). Additionally, we determined that freestanding unrolled sheets can undergo oxidation and etching. The oxidized fragments were found in post-in situ samples and extra-cellular vesicles recovered from ex vivo experiments. Further studies enquiring on the effect of the scrolling in the stability of the nanoscrolls should be conducted in order to prove that this can constitute a protective mechanism of the structure. We would like to acknowledge the financial support of the French national research agency for the CYCLYS project. References: (1) Bazaka, K.; Levchenko, I.; Lim, J. W. M.; Baranov, O.; Corbella, C.; Xu, S.; Keidar, M. J. Phys. D. Appl. Phys. 2019, 51, 1–39. (2) Kurapati, R.; Muzi, L.; de Garibay, A. P. R.; Russier, J.; Voiry, D.; Vacchi, I. A.; Chhowalla, M.; Bianco, A. Adv. Funct. Mater. 2017, 27.
Nathaly ORTIZ PEÑA (Paris)
13:00 - 15:00 #26433 - The role of functionalized organic surfaces in metal biomineralization: insights from liquid-cell STEM experiments.
The role of functionalized organic surfaces in metal biomineralization: insights from liquid-cell STEM experiments.

Nathaly ORTIZ PEÑA *, Charlotte DEJEANBenedicte MENEZCyril GADALDamien ALLOYEAUAlexandre GELABERT

  • Laboratoire Matériaux et Phénomènes Quantiques, UMR 7162 CNRS/Université Paris Diderot, 75013 PARIS, France
  • Université de Paris, Institut de physique du globe de Paris, CNRS UMR 7154, Paris, France


Recent direct observations in liquid phase of mineral nucleation and growth on bacterial cells highlighted, at the nanoscale, the critical role of chemical functions in cell surfaces and exopolymers in metal biomineralization [1]. Harnessing the possibilities of liquid-cell scanning transmission electron microscopy (LC-STEM), and using the incident electron beam to trigger and observe the precipitation of Mn-bearing minerals, differences in the morphology and distribution of Mn precipitates were observed. Differences in nucleation site density and accessibility on bacterial cell surfaces and exopolymers were correlated to the in situ observations. Herein, we use functionalized polystyrene beads of 1 µm diameter as simple analogues of bacteria cells, in order to better understand and characterize independently the role of the various chemical functions encountered on biological surfaces on Mn precipitation. Ten representative types of functionalization were selected for LC-STEM experiments, ranging from basic ones, like carboxylic groups (–COOH) or amine functions (–NH ), to chelating agents like nitrilotriacetic acid (NTA) or to protein compounds like streptavidin. This allows to characterize the specific impact of individual chemical function taken independently. Manganese mineralization was tracked for each type of functionalized beads, displaying significant difference in growth rates and mineralization patterns. As illustrated in figure 1, at the same electron dose rate, Mn precipitation for COOH-bearing beads is much faster (Figure 1b), compared to non-functionalized beads (Figure 1a) and, exhibit massive dendritic precipitates at the bead surface. Bulk measurements of electrophoretic mobility for each type of bead will be use to correlate surface charge to mineral growth rate on beads. The bulk surface charge explains only partially Mn mineralization properties at the beads surface but other parameters like steric effect need to be explored. We would like to acknowledge the financial support of the French national research agency for the MAMBA project. References [1] Couasnon, T., Alloyeau, D., Ménez, B., Guyot, F., Ghigo, J. M., & Gélabert, A. (2020). In situ monitoring of exopolymer-dependent Mn mineralization on bacterial surfaces. Science advances, 6(27), eaaz3125
Nathaly ORTIZ PEÑA (Paris)
13:00 - 15:00 #26435 - Growth of MgO Nanocrystals by self-assembly in Molten Salts.
Growth of MgO Nanocrystals by self-assembly in Molten Salts.

Isabel Gómez-Recio *, Ram KumarDris IhiawakrimAlmudena Torres-PardoJose M. González-CalbetOvidiu ErsenDavid Portehault

  • Sorbonne Université, CNRS, Laboratoire Chimie de la Matière Condensée de Paris (LCMCP), 4 place Jussieu, 75005 Paris, France
  • Institut de Physique et Chimie des Matériaux de Strasbourg (IPCMS), UMR 7504 CNRS-Université de Strasbourg, BP 43 Strasbourg Cedex 2, France
  • Dpt. of Inorganic Chemistry, Faculty of Chemistry, Universidad Complutense de Madrid, Madrid (28040) Spain


Metal oxides exhibit a wide range of properties combined to stability under ambient conditions that have given rise to an extensive range of applications. The decrease of oxides particle size at the nanoscale is well known to modify or enhance their properties. Developing synthesis methods is then important to widen the compositional range of oxides accessible at the nanoscale. Among several strategies, synthesis in molten salts is particularly appealing as a liquid-mediated pathway that allows extensive nucleation with limited grain growth to enable particle size control.[1] Nonetheless, the reaction mechanisms underlying molten salts syntheses are currently unknown. Real time observations of nucleation and growth steps can unveil the key mechanisms of nanocrystals formation, as well as provide guidelines towards selected morphologies. [2] Of particular interest is the search of self-assembly processes driving the crystallization and that could play an essential part of the toolkit for designing inorganic nanocrystals. In situ techniques, as in situ transmission electron microscopy, strongly contribute to the advancement of such knowledge, but have never been applied to the specific conditions of molten salts syntheses that encompass high temperatures and liquid phase. In this work the self-assembly is suggested to be one of the MgO crisytallization mechanisms in molten salts. Oriented attachment is a characteristic feature of colloidal syntheses, never observed before in molten salts medium. This growth mechanism gives rise to enthalpy drops in a thermodynamic spontaneous process due to crystal surface energy reduction. [3] TEM low magnification images evidence that the number of primary nanoparticles belonging to a cluster increase over the reaction time (Fig. 1), and that particle attachment occurs preferentially face-to-face. TEM images (Fig. 2) show the same crystallographic orientation at both sides of primary nanoparticles boundary. This information is complemented by in situ TEM studies which allow direct monitoring of MgO crystallization. For the in situ TEM study an environmental gas holder (Atmosphere from Protochips) was used.
Isabel GÓMEZ-RECIO (Paris)
13:00 - 15:00 #26436 - The influence of organic molecules on the mineralization of calcium carbonate by Liquid Phase Transmission Electron Microscopy (LPTEM).
The influence of organic molecules on the mineralization of calcium carbonate by Liquid Phase Transmission Electron Microscopy (LPTEM).

Vinavadini Ramnarain *, Nathaly ORTIZ PEÑADris IHIAWAWKRIMMariana LONGUINHOTristan GEORGESThierry AZAISClément SANCHEZOvidiu ERSEN

  • Institut de Physique et Chimie des Matériaux Strasbourg (IPCMS)
  • CBPF, Rio de Janeiro, Brasil
  • Laboratoire de Chimie de Matière Condensé de Paris, Sorbonne Université, Paris, France
  • USIAS, Université de Strasbourg, France


Biominerals have complex hierarchical structures, often combined with exceptional properties, such as high mechanical, electrical or magnetic properties, which are achieved under the direct control of biomolecules. This level of control originates from an intimate association of an organic matrix comprised of macromolecules and inorganic components in a localized environment of the organisms1. Thus, scientists seek inspiration from the properties of biominerals to produce advanced materials by means of biomimetic material design. The key factors which influence the final properties of the crystal are predominantly proteins of the organic matrix which may consist of various amino acids2. Whilst several studies have been carried out on the growth of biominerals controlled by macromolecules, the early steps before growth are not fully understood. Therefore, it is of great interest to study the impact of these amino acids on the early nucleation stages of biomineralization and to provide a direct mechanistic insight into these phenomena. Herein, we present the study of the mineralization processes of calcium carbonate. This system is chosen because of its abundance in nature and it is a relatively simple model. Furthermore, we have investigated the role of L-Aspartic acid on biomineralization. We have used the Liquid Phase Transmission Electron Microscopy to assess the incipient steps of mineralization within a liquid environment confined between two silicon nitride windows. In this study, we have been able to unravel, in real time, novel visual insights on the incipient steps, that is pre-nucleation and nucleation of CaCO3. In particular, we could experimentally determine the presence of pre-nucleation clusters and their dynamic behavior (Fig 1), Moreover we could observe a real time nucleation taking place where the pre-nucleation species are transformed to liquid nanodroplets upon crossing a binodal limit (Fig 2). The liquid nanodroplets further aggregated to form hydrated amorphous calcium carbonate by an annealing process. These results allowed us to understand the influence of organic matter during biomineral formation and hence establish a mechanistic picture. References: [1] Weiner, S.; Addadi, L. Annu. Rev. Mater. Res. 2011, 41 (1), 21–40. [2] Tavafoghi, M.; Cerruti, M. J. R. Soc. Interface 2016, 13 (123), 20160462
Vinavadini RAMNARAIN (Strasbourg)
13:00 - 15:00 #26437 - Probing and mapping the structural and electronic evolution of metal/insulating V2O3 nanodomains by electron spectromicroscopy under variable temperatures.
Probing and mapping the structural and electronic evolution of metal/insulating V2O3 nanodomains by electron spectromicroscopy under variable temperatures.

Ibrahim Koita *, Xiaoyan LiLuiz H. G. TizeiJean-Denis BlazitNathalie BrunEtienne JanodJulien TranchantBenoît CorrazeLaurent CarioMarcel TencéOdile StéphanLaura Bocher

  • Université Paris-Saclay, CNRS, Laboratoire de Physique des Solides, 91405, Orsay, France
  • Institut des Matériaux Jean Rouxel (IMN), Université de Nantes, CNRS, 2 Rue de la Houssinière, 44322 Nantes, France


V2O3 présente différentes transitions métal-isolant (TMIs) induites en température, sous pression ou par dopage chimique[1]. Ces TMIs présentent des scenarii complexes du point de vue de leurs évolutions électronique et structurale qui rendent encore leurs compréhensions incomplètes[2]. Lorsqu’il est refroidi en dessous de 160 K, V2O3 subit une transition structurale (rhomboédrique vers monoclinique) et une TMI avec une hausse de résistivité de 7 ordres de grandeur. Cette TMI activée en température a été largement étudiée à l’échelle macroscopique (Fig.1a)[1], récemment la coexistence de domaines isolant/métallique (I/M) a été cartographiée in situ par photoémission[3] et nano-IR[4] avec une résolution respective de 1 µm et de 25 nm au mieux. Or cette séparation de phases électroniques peut être due localement à des mécanismes structuraux d’où la nécessité de coupler cartographies structurale et électronique à l’échelle locale et sous températures variables. Ici nous avons réalisé des expériences STEM/EELS monochromatées de ultra-haute résolution spectrale sur le NION CHROMATEM 200 MC associé au porte-objet cryo double-tilt Henny Z refroidi à l’azote et utilisant des MEMS (Fig.1b) pour accéder à des conditions de températures variables à partir de 120 K. Lors des cycles thermiques à travers la TMI, les spectres EELS acquis dans le domaine des pertes proches présentent une signature plasmonique caractéristique à 1.1eV uniquement pour la phase métallique (Fig.2a)[5]. A température intermédiaire, la coexistence de nanodomaines I/M est cartographiée à l’échelle nanométrique (Fig.2b et 2c). Des analyses par K-means clustering confirment l’homogénéité électronique de chaque domaine (Fig.2d). En parallèle, des expériences 4DSTEM de nanodiffraction permettent de révéler l’évolution structurale des domaines I/M en température. Ces expériences visent à sonder localement les mécanismes physiques mis en jeu lors de la transition et en particulier la relation entre les degrés de libertés structuraux et électroniques. Les auteurs remercient l’EDPIF, l’ANR IMPULSE No. ANR-19-CE42-0001 et le programme de futur investissement TEMPOS No. ANR-10-EQPX-50. References: [1] McWhan, et al., PRB,2 (1970), 3734 [2] Kalcheim, et al., PRL.,122 (2019), 057601. [3] Lupi,et al., Nat. Commun.,1(2010),105. [4] McLeod, et al., Nat. Phys.,13 (2017),80. [5] Abe, et al., Jpn. JAP., 37 (1998), 584
Ibrahim KOITA (Paris-Saclay)
13:00 - 15:00 #26438 - Modeling electric fields in nanocapacitors observed by operando electron holography.
Modeling electric fields in nanocapacitors observed by operando electron holography.

Kilian Gruel *, Raphaël SerraAurélien MasseboeufChristophe Gatel *, Martin Hÿtch *

  • CEMES-CNRS, Toulouse, France
  • Université de Toulouse, Toulouse, France


Electron holography has the potential to become a powerful technique to measure electric fields in microelectronics devices such as capacitors during their operation. However, we first need to show that measurements can be performed quantitatively, and in operando conditions, for model systems [1]. The experimental results need to be compared with modeling that takes into account factors such as specimen geometry, FIB damage, stray fields and charging [2]. The model dielectric capacitor that has been studied experimentally is composed of an insulating layer of silicon nitride (Si3N4) between a bottom electrode (substrate) of highly P-doped silicon (Si) and a top electrode of deposited titanium (Ti). Electron holography experiment has been performed on this sample using the I2TEM microscope (Hitachi HF3300-C) operating at 300 kV whilst applying different voltages from – 10V to 10V. Finite element method (FEM) was used to model the electrostatic potential (COMSOL Multiphysics). Parameters were adjusted to produce an excellent fit with the experimentally measured phase shift (Figure 2). The curvature of the phase in the electrodes is well reproduced and is caused by the stray field around the sample. In the silicon nitride, there is a slight disagreement with the experimental curvature and can be modelled by introducing charges in the insulating layer. This work was supported by the French national project IODA (ANR-17-CE24-0047). The research leading to these results has received funding from the European Union Horizon 2020 research and innovation programme under grant agreement No. 823717 – ESTEEM3. Références/References : [1] AC Twitchett et al., Phys. Rev. Lett. 88 (2002), p. 238302 [2] S Yazdi et al., Ultramicroscopy 152 (2015), p. 10
Kilian GRUEL (Toulouse)
13:00 - 15:00 #26440 - New insights into the growth mechanism of WO3 gels by in-situ liquid-phase TEM and time-resolved DLS.
New insights into the growth mechanism of WO3 gels by in-situ liquid-phase TEM and time-resolved DLS.

Charles Sidhoum *, Mateusz OdziomekDris IhiawakrimDoru ConstantinFrançois SchosselerClément SanchezOvidiu Ersen

  • Institut de Physique et Chimie des Matériaux de Strasbourg, 23 rue du Lœss, BP 43, Strasbourg Cedex 2, France
  • Laboratoire de Chimie de Matière Condensé de Paris, Sorbonne Université, Paris, France
  • Institut Charles Sadron, UPR22, 6 rue Boussingault, 67083 Strasbourg cedex, France


The electrochromic and photocatalytic properties of tungsten oxide (WO3) find broad applications in display devices, smart windows or degradation of pollutants. The synthesis of WO3 does not require high temperatures, and soft methods fitting into “chimie douce” concept are well-established. Following the sol-gel routes, it is possible to obtain WO3 gels by acidification of tungsten salt solutions. The acidification leads to hydrolysis and consecutive condensation first to polyoxotungstate species and further to gel-like structure. Although the process has been studied by various techniques1, we still lack the understanding on how the charged polyoxometallate species react with each other and form a gel. Several models have been proposed, based on the condensation of a hypothetical “zero-charge complex” by hydroxylation and oxolation2. The recent developments in TEM, in particular the emergence of the in-situ Liquid Phase TEM (LP-TEM), may provide new insight into the nucleation and growth processes of WO3-based nanostructures, with a particular focus on the early steps of gel formation. Herein, using the ability of LP-TEM to monitor nanometric processes in real space, we report a first picture of the growth of WO3 gels. This in situ analysis highlights several possible pathways for the growth mechanism, including the diffusion-limited cluster aggregation process. Indeed, a closer look into the reaction environment (Figure 1) reveals the presence of well-defined clusters, with a nanometric size, which apparently plays the role of elemental bricks for gel formation3. To further improve the comprehension of the first growth events, we have also carried out time-resolved DLS measurements for different tungsten salt concentration. As expected, a decrease in concentration (Figure 2b) leads to a decrease in intensity but, at the same time, we find similar sizes (Figure 2a), indicating the presence of precursors of few nm. In complement to DLS data obtained during the first 30 minutes, cryo-TEM studies are ongoing in order to complete the mechanistic picture and to provide a complete description of the growth process. References: [1] Pope, M. T.Heteropoly and Isopoly Oxometalates;Springer:Berlin, 1983. [2] J-P. Jolivet. (2015). De la solution à l’oxyde. EDP Sciences [3] Chemseddine, A. J. Solid State Chem. 2008, 2731–2736.
Charles SIDHOUM (Strasbourg)
13:00 - 15:00 #26402 - Kinetics of the parent grain growth in a 20MND5-type bainitic steel with micro-segregations.
Kinetics of the parent grain growth in a 20MND5-type bainitic steel with micro-segregations.

Suzanne Vernier *, Pierre JolyLydia LaffontEric Andrieu

  • CIRIMAT - INPT
  • FRAMATOME
  • CIRIMAT - INPT/ENSIACET


L’acier 20MND5 (0,2%C-1,4%Mn-0,7%Ni-0,5%Mo) est un acier faiblement allié utilisé dans l’industrie nucléaire pour fabriquer des générateurs de vapeur. Ces pièces en 20MND5 sont obtenues par forgeage de lingots de très grandes dimensions qu’il est difficile d’homogénéiser chimiquement. Ainsi, des micro-ségrégations, héritage des ségrégations entre bras de dendrite secondaires, sont classiquement observées dans ces pièces. Les micro-ségrégations sont responsables de la microstructure en « bandes » obtenue après un refroidissement de l’acier à vitesse modérée [1] : des bandes de bainite supérieure (matrice non ségrégée) alternent avec des bandes de bainite inférieure (micro-ségrégation) (Figure 1). La structure en bandes de l’acier 20MND5 est suspectée d’être à l’origine d’une dispersion des valeurs de résilience à basse température, en particulier dans la zone de transition ductile-fragile. Or, l’étude de la microstructure a montré que les grains parents, c’est-à-dire les anciens grains austénitiques, sont plus gros dans les micro-ségrégations que dans la matrice non ségrégée. Cette plus grande taille de grains austénitiques combinée à la ségrégation des éléments d’alliage et des impuretés pourrait expliquer une plus grande fragilité des micro-ségrégations à basse température. Afin de comprendre les raisons d’une telle croissance des grains austénitiques dans les micro-ségrégations, l’évolution de la taille des grains parents a été suivie dans chaque type de zone au cours d’un traitement d’austénitisation (montée lente puis maintien en température – Figure 2.a). Des images en microscopie optique et électronique, des essais de micro-dureté et des analyses EBSD ont été réalisés à différentes étapes du traitement (Figure 2). En particulier, les analyses EBSD ont permis de reconstruire les cartographies des grains parents en se basant sur la relation d’orientation entre grains enfants et grains parents [2]. Ainsi, il est apparu que l’écart de taille de grains entre les deux types de zone se creuse une fois la transformation austénitique terminée, lors du maintien en température. Des nitrures d’aluminium de taille nanométrique pourraient être à l’origine du ralentissement de la croissance des grains dans la matrice non ségrégée. Références : [1] R.A. Grange, Metall. Trans., vol. 2 (1971), p. 417 [2] T. Nyyssönen, Metall. Mater. Trans. A, vol. 49 (2018), p. 6426
Suzanne VERNIER (CIRIMAT INPT)
13:00 - 15:00 #26404 - Low Dose Electron Diffraction Tomography (LD-EDT) in TEM: Application on a hydrated Al arsenate mineral.
Low Dose Electron Diffraction Tomography (LD-EDT) in TEM: Application on a hydrated Al arsenate mineral.

Emre Yörük *, Holger KleinStéphanie Kodjikian

  • CNRS Néel Institute, University of Grenoble Alpes


3D electron diffraction (3D ED) has recently emerged as an alternative to x-ray diffraction to elucidate atomic structures of nano-sized crystals [1]. High scattering cross-sections of electrons allows for a diffraction data quality on par with synchrotron x-rays, albeit at a reduced cost. However, electron beam damage is still a major issue in the 3D ED field [2], and exposure conditions need to be optimized for beam sensitive compounds. LD-EDT [3] is a low dose 3D ED technique for ab initio structure determination of beam sensitive crystals such as hydrated minerals or MOFs. High quality diffraction data can be obtained from individual single crystalline particles in a powder without damaging the structure, and a precise sampling of the reciprocal space is assured by beam precession. We recently applied LD-EDT on Bulachite [4], a hydrated Al arsenate mineral, and solved its atomic structure. Difficulties related to the small size of crystals as well as beam sensitivity due to the presence of H2O molecules inside the lattice were overcome by LD-EDT, where synchrotron x-ray powder diffraction previously failed. The resulting structure [5] is comprised of layers containing edge-sharing Al-O octahedra, inter-connected with As-O tetrahedra by corner sharing. The localization of light atoms in the lattice showcases the potential of electron crystallography for yielding high quality diffraction data even under low dose conditions. References : [1] M. Gemmi et al., ACS Cent. Sci., 5 (2019), p. 1315−1329. [2] J. Hattne et al., Structure, 26 (2018), p. 759-766. [3] S. Kodjikian, H. Klein, Ultramicroscopy, 200 (2019), p. 12-19. [4] K. Walenta, Aufschluss., 34 (1983), p. 445-451. [5] I.E. Grey., E. Yoruk et al., Mineralogical Magazine, 84 (2020), p. 608-615.
Emre YÖRÜK (Grenoble)
13:00 - 15:00 #26411 - NANOSTRUCTURED LaFeO3 THIN FILMS GROWN ON SILICON.
NANOSTRUCTURED LaFeO3 THIN FILMS GROWN ON SILICON.

Christian Turquat *, Mateusz JĘDRUSIKŁukasz CIENIEKAgnieszka KOPIAChristine LEROUX

  • Université de Toulon, AMU, CNRS, IM2NP (UMR 7334), CS 60584, Toulon, F- 83041, France
  • Wydział Inżynierii Metali i Informatyki Przemysłowej, Akademia Górniczo – Hutnicza, al. Mickiewicza 30, 30-059 Kraków, Polska


In this paper, our attention has been focused on lanthanum iron oxide (LaFeO3) as thin films because of its potential in silicon microelectronics-based gas sensing technologies [1]. More precisely, the purpose of this research is to investigate the influence of process temperature on the morphology and crystallographic structure of LaFeO3 (LFO) thin films obtained by a Pulsed Laser Deposition (PLD) method on silicon (Si) substrates, in particular the nature of the exposed crystallographic facets. Three deposition temperatures, 750°C, 850°C, and 1000°C were investigated. Morphologic information was secured via Scanning Electron Microscopy and Atomic Force Microscopy while crystallographic information was gained via grazing incidence X-ray Diffraction and Transmission Electron Microscopy. At all temperatures, the films are crystallized in the Pnma orthorhombic structure. Thin films with a temperature deposition of 750°C and 850°C exhibit a microstructure of columnar grains with different LFO thicknesses, respectively 80 and 150 nm, and a similar intriguing surface structuration (see Figure 1). However, films grown at 750 °C show cracks, which disqualify them for applications. Two types of columnar grains are observed, with a tip termination and a columnar width from 15 to 20 nm, and broader flat terminated grains (see Figure 2). They correspond to two different growth direction [101] (flat) and [200] (tip), but in both cases {101} facets are exposed. The microstructure of the sample with a temperature deposition of 1000°C contrasts with the lower temperature samples and shows an active layer thickness of around 130 nm with a random arrangement of grains. HREM evidenced a reaction between the silicon substrate and the LaFeO3 layer, with the formation of La2Si2O7, indicating diffusion of Si through the native SiO2 barrier. This phenomenon was also observed in LaCoO3/Si [2]. These disparities will be discussed in terms of the structure and composition variation with the LFO layer. Références/References: [1] H. Zhu, P. Zhang, S. Dai, ACS Catalysis, 5 (2015) 6370-6385. [2] M. Jedrusik, Ł. Cieniek, A. Kopia, Ch. Turquat, Ch. Leroux, Arch. Metall. Mater. 65 (2020), 793-797
Christian TURQUAT (Toulon)
13:00 - 15:00 #26414 - eCHORD as a tool to characterize internal misorientation of strained samples.
eCHORD as a tool to characterize internal misorientation of strained samples.

Romain Facchinetti *, Cyril LangloisSophie CazottesThierry DouillardClaire MauriceJuliette ChevyChristine Nardin

  • MATEIS – Institut National des Sciences Appliquées (INSA Lyon) - Lyon – France
  • Mines Saint-Etienne, Univ Lyon, CNRS, UMR 5307 LGF, Centre SMS, F-42023 Saint-Etienne France
  • Constellium – Voreppe - France


Understanding the relationship between microstructure and properties is a necessary step for the improvement of existing materials or the development of new materials. The microstructure can be characterised using orientations maps, from which information like grain size distribution and deformation state can be extracted. Apart from EBSD (Electron Backscattered Diffraction), a promising approach to obtain orientation maps with the SEM (Scanning Electron Microscope) is the eCHORD method [1], which is based on electron channelling contrast. This method has the advantage that the sample tilt is only about 10°, and that the accelerating voltage can be lowered to a few kV, resulting in an improved spatial resolution. A series of BSE images is recorded during the rotation of the sample around its tilted normal direction, from which the intensity profiles of each pixel can be extracted as a function of the rotation angle. By comparing the obtained intensity profiles with the one calculated from ECP (Electron Channelling Patterns) simulations [2], the orientation of each pixel can be determined. The angular resolution achieved on Aluminium alloys is about 0.1°. In addition to orientation maps, we present here an original method to characterize the local misorientation using eCHORD. One objective is to determine the fraction of recrystallized grains in a partially recrystallized Aluminium. In fact eCHORD identify the internal misorientation by comparing the distances between profiles of adjacent pixels, without the need to compute pixels orientation. The results are compared with EBSD Kernel maps obtained on Aluminium with different levels of strain and different fractions of recrystallized grains. Références/References : [1] C.Lafond, T.Douillard, S.Cazottes, P.Steyer, and C.Langlois. Electron CHanneling Orientation Determination (eCHORD): An original approach to crystalline orientation mapping. Ultramicroscopy, 186 :146–149, (March 2018). [2] Singh, S., Ram, F., & De Graef, M. EMsoft: Open source software for electron diffraction/image simulations, Microscopy and Microanalysis, 23(S1), 212-213. (July 2017)
Romain FACCHINETTI (Lyon)
13:00 - 15:00 #26415 - FAST AND AUTOMATED ACQUISITION OF THE RECIPROCAL SPACE FOR MONOCRISTAL STRUCTURE DETERMINATION.
FAST AND AUTOMATED ACQUISITION OF THE RECIPROCAL SPACE FOR MONOCRISTAL STRUCTURE DETERMINATION.

Nicolas Gautier *, Anne-Claire Gaillot

  • Institut des Matériaux Jean Rouxel (IMN), UMR6502 CNRS, 2 rue de la Houssinière BP32229, 44322 Nantes cedex3, France


Depuis une dizaine d’années, la résolution de la structure d’un monocristal par diffraction électronique s’est fortement développée [1]. Différentes techniques ont été mises au point, basées sur la diffraction électronique en mode tomographie (EDT), associée ou non à la précession électronique, permettant un meilleur échantillonnage du réseau réciproque en ne se limitant plus aux principaux axes de zones [2]. Des programmes tels que PETS2, implémenté dans Jana2006, permettent de résoudre et d’affiner les structures cristallines à partir des données de diffraction électronique en mode tomographie avec précession (PEDT) en prenant en compte également les effets dynamiques [3]. Mais les techniques classiques d’EDT sont difficilement applicables aux cristaux très sensibles au faisceau d’électrons. Des conditions d’acquisition spécifiques doivent être mises en œuvre pour limiter le courant du faisceau d’électrons (« low dose ») ou augmenter la vitesse d’acquisition pour limiter le temps d’exposition. C’est ce que permet le script “Continuous Rotation movie acquisition” (CRmov) intégré au programme libre SerialEM [4]. CRmov permet de contrôler la platine goniométrique pour tourner le porte-objet à l’angle de départ, collecter une série de clichés de diffraction en continu jusqu’à l’angle final et sauvegarder les données automatiquement en quelques minutes. Les données acquises sur un monocristal peuvent ensuite être traitées à l’aide de logiciels tels que PETS2 et JANA, afin de déterminer les paramètres de maille du composé, jusqu’à la résolution structurale. Installé sur Nant’Themis (S/TEM ThermoScientific Themis Z), ce dispositif nous a permis grâce à cette rapidité d’acquisition, de collecter des données de diffraction électronique en mode tomographie avec précession (PEDT) sur des échantillons organiques. Il a également été mis à profit sur des échantillons moins sensibles sous le faisceau, pour enregistrer dans un temps limité plusieurs jeux de données dans des conditions expérimentales différentes. Références : [1] Gemmi et al. ACS Central Science 2019, 5 (8), p.1315– 1329, [2] Kolb et al., Ultramicroscopy 107 (2007) 507–513 [3] Palatinus, L., Petricek, V. & Correa, C. A. (2015). Acta Cryst. A71, 235-244 [4] De la Cruz et al., Ultramicroscopy, 201 (2019), 77-80
Nicolas GAUTIER (Nantes)
13:00 - 15:00 #26382 - Analytical TEM Radiation-Induced Segregation (RIS) study at grain boundaries of a baffle-former bolt irradiated up to 45dpa coming from a French Pressurized Water (nuclear) Reactor (PWR).
Analytical TEM Radiation-Induced Segregation (RIS) study at grain boundaries of a baffle-former bolt irradiated up to 45dpa coming from a French Pressurized Water (nuclear) Reactor (PWR).

Priscille Cuvillier *, Eric DerniauxRémi MercierYannick ThébaultMarylou BoissonRoch MenandVirginie Boulay

  • EDF – DI, CNPE de Chinon - BP23 - 37420 Avoine, France
  • EDF – DI, 2 rue Ampère – 93206 Saint-Denis, France
  • EDF UNIE, 1 place Pleyel 93200 Saint-Denis, France
  • EDF – DT, 19 rue Pierre Bourdeix – 69007 Lyon, France


Radiation-Induced Segregation (RIS), causing in particular Cr depletion at grain boundaries (GB), is a phenomena suspected in the embrittlement of nuclear component during service [1]. RIS in a bolt stayed 26 years under neutron irradiation in a civil nuclear reactor (PWR) has been studied by TEM using a FEI TECNAI Osiris equipped with a energy dispersion X-ray spectrometers (four SDD detectors). This is the first time EDF investigates a deposited baffle-former bolt from PWR at such levels of irradiation (≈ 45dpa) [2] thanks to new sampling preparation [3] using a FIB-SEM Lyra3 TESCAN in a high-activity cell [4] making it possible to prepare remotely lamellae from an initially highly radioactive sample. The bolt, with no indication of cracking, and its anti-rotation lock-bar (Figure 1) are respectively in a 316L and 304L austenitic stainless steel. As RIS is subjected to be affected by several parameters such as dose, temperature, material composition or crystallographic orientation of the GB, three samples at different pairs of dose/temperature, in different material and for different disorientation of GB have been studied: 45dpa/295°C (304L anti-rotation strip), 40dpa/305°C (316L bolt head) and 24dpa/340°C (316L bolt shank). Depletions of Cr, Fe, Mn and Mo and enrichment of Ni and Si have been observed at GB and maximum Cr depletion reaches ΔCr≈6 wt% (Figure 2). Some GB decorated with precipitates (probably γ’ (Ni3Si) or G (M6Ni16Si7) phases) are also observed. RIS is larger for the pair “higher” dose / “lower” temperature and seems to be more pronounced for highly disoriented GB and more disadvantageous for 316L than 304L (initially richer in Cr). Further work on higher dose and cracked bolts is planned to better understand the evolution of RIS and its influence on GB embrittlement. References: [1] A. J. Ardell and P. Bellon, Solid State and Materials Science 20 (2016), p. 115-139 [2] É. Fargeas et al, Fontevraud 9, (2018) [3] L. Legras et al., European Microscopy Congress (2016) p. 443-444 [4] S. Miloudi et al., European Microscopy Congress (2016) p. 368 The authors would like to thank all the persons of EDF hot laboratory that contributed to the examinations.
Priscille CUVILLIER (Avoine)
13:00 - 15:00 #26383 - STEM-EELS investigation of c-Si/a-AlOx interface for solar cell applications.
STEM-EELS investigation of c-Si/a-AlOx interface for solar cell applications.

Guillaume Noircler *, Fabien LebretonEtienne DrahiPatricia De CouxBénédicte Warot-Fonrose

  • CEMES-CNRS
  • Total SA
  • Institut Photovoltaïque d’Ile-de-France (IPVF)
  • LPICM


Amorphous aluminum oxide (a-AlOx) capped with amorphous silicon nitride (a-SiNx:H) is nowadays a common passivation stack for p-type silicon surfaces and is a good candidate to passivate the rear side of two-terminal perovskite/silicon tandem cells. The combination of atomic layer deposition (ALD) for a-AlOx with plasma-enhanced chemical vapor deposition (PECVD) for the capping made its success. Chemical passivation is insured by hydrogen from a-SiNx:H that can easily diffuse to the c-Si/AlOx interface. The field effect passivation is provided by a-AlOx which contains a high negative fixed charge density. The origin of the latter one is still a matter of debate and therefore requires additional research to be more controlled. 3 different samples have been studied with different process for the annealing step and a-SiNx:H composition (figure 1). In an attempt to better understand these negative fixed charges, local scale investigation by STEM-EELS has been performed at the c-Si/a-AlOx interface on 3 different samples. However, the extreme sensitivity of a-AlOx and a-SiNx:H to the electrons beam has led us to carry out a detailed study of the electron irradiation process. The c-Si/a-AlOx interface can undergo several electron-beam irradiation damage like sputtering, knock-on or radiolysis which have a direct impact on the structure and the chemical composition if precautions are not taken. We have shown that the radiolysis process was the dominant radiation damage and that it could drastically be limited by reducing the acceleration voltage and by modifying the scan orientation. Once the radiation damage has been understood and brought under control, STEM-EELS analysis has been done using Si and Al L2,3 and O K edges to determine the composition of the c-Si/a-AlOx interface (figure 2). Just above the c-Si, an ultrathin a-SiOx layer was found. Between the latter and the a-AlOx, a non-stoichiometric aluminum silicate has been characterized containing tetrahedrally coordinated Al in its first layers. The tetrahedral coordination of Al is known to have a net negative charge and high catalytic activity. Thus, this coordination could strongly participate in the production of negative fixed charge which improves the field effect passivation of this amorphous stack.
Bénédicte WAROT-FONROSE (CEMES, Toulouse)
13:00 - 15:00 #26387 - Spectral unmixing of EELS spectrum-images.
Spectral unmixing of EELS spectrum-images.

Nathalie Brun *, Guillaume LambertLaura Bocher

  • CNRS Université Paris Saclay Laoratoire de Physique des Solides
  • Université Paris Saclay M1 Mathématiques Appliquées


Le développement de la microscopie électronique analytique en mode STEM banalise l'acquisition de spectres-images représentant un grand volume de données, de l'ordre de 10k pixels x 1000 canaux en énergie. Il est possible d'appliquer les techniques classiques de traitement des données EELS à chaque spectre. Toutefois il est préférable de considérer le spectre-image comme un tout et d'exploiter le caractère redondant de l'information. Les techniques d'analyse statistiques commencent ainsi à être couramment utilisées, notamment l'analyse par composantes principales (ACP) mise en œuvre par l'intermédiaire de la Toolbox Hyperspy [1]. Néanmoins l'ACP est en général utilisée pour débruiter le spectre-image, auquel on applique ensuite le processus classique (soustraction du fond continu/somme des canaux correspondants au seuil caractéristique). En effet le but du traitement est de passer d'un cube de données difficilement visualisable à des données 2D exploitables sous forme de cartes. Le moyen d'obtenir directement ces cartes en exploitant pleinement l'information contenue dans le spectre-image est d'utiliser des techniques de démélange spectral [2]. Le démélange spectral repose sur l'hypothèse que chaque spectre individuel d'un spectre-image peut être décrit comme une combinaison linéaire d'un petit nombre de n spectres représentatifs des composants présents dans l'échantillon. Le spectre-image peut être alors complètement décrit par ces n composantes et les n cartes correspondantes. Outre d'être souvent beaucoup plus rapides, ces méthodes ont l'avantage de s'affranchir de problèmes tels que la superposition de seuils ou la difficulté de soustraire le fond continu, voire de cartographier indirectement certains éléments dont le seuil n'est pas détecté avec la dispersion utilisée. Je montrerai des exemples obtenus avec différentes techniques de démélange; on s'intéressera en particulier à l'intérêt de l'utilisation du Deep Learning pour ce type de problème. Références: [1] https://hyperspy.org/index.html [2] Dobigeon, N., & Brun, N. Spectral mixture analysis of EELS spectrum-images. Ultramicroscopy, 120 (2012) p.25-34. Remerciements : nous remercions André Thiaville (LPS, Orsay), William Legrand, Nicolas Reyren et Vincent Cros (UMP CNRS/Thales, Palaiseau) pour l’échantillon Pt/Co/Ru.
Nathalie BRUN (Paris-Saclay)
13:00 - 15:00 #26388 - Probing Whispering Gallery Mode Resonators With Electron Beams.
Probing Whispering Gallery Mode Resonators With Electron Beams.

Yves Auad *, Cyrille HamonMarcel TencéVahagn MkhitaryanOdile StephanJavier Garcia de AbajoLuiz Galvão TizeiMathieu Kociak

  • Laboratoire de Physique des Solides, Orsay
  • ICFO, Barcelona


Whispering gallery mode resonators confine light using total internal reflection and take advantage of its several and narrowband circulating resonances for applications in optomechanics [1], quantum electrodynamics [2] and sensing [3]. The spherical symmetry and the low radiation loss make them difficult to study under free-space light. The ability of fast electrons to excite confined light modes in the near-field of photonic objects paves the way to probe these circulating modes with high spatial resolution. Electron Energy Loss Spectroscopy (EELS) has already been performed in small ( 1 μm) silica spheres with high quality factors. References: [1] Tobias Kippenberg et al. Analysis of radiation-pressure induced mechanical oscillation of an optical microcavity. Physical Review Letters, 95, 2005. [2] D. Vernooy et al. Cavity qed with high-q whispering gallery modes. Physical Review A, 57, 1998. [3] Yu Zheng et al. Sensing and lasing applications of whispering gallery mode microresonators. Opto-Electronic advances, 1, 2018. [4] Jerome Hyun et al., Measuring far-ultraviolet whispering gallery modes with high energy electrons. Applied Physics Letters, 12 2008. [5] Ofer Kfier et al. Controlling free electrons with optical whispering-gallery modes. Nature, 2020.
Yves AUAD (Orsay)
13:00 - 15:00 #26389 - Multi-phase nucleus inside a spheroidal graphite nodule analyzed by STEM-EDS.
Multi-phase nucleus inside a spheroidal graphite nodule analyzed by STEM-EDS.

Alessandro PUGLIARA *, Lydia LAFFONTTeresa HUNGRIAClaudie JOSSEJacques LACAZE

  • CIRIMAT-ENSIACET, Université de Toulouse, Toulouse, France
  • Centre de Microcaractérisation Raimond Castaing, Université de Toulouse, UPS – CNRS – Toulouse INP – INSA, Toulouse, France


Spheroidal graphite cast irons are alloys with excellent ductility (mechanical characteristics close to those of mild steels). In these alloys, spheroidizing and inoculation treatments, using Fe-Si-Mg and Fe-Si alloys respectively, interact to give the final particles acting as nuclei for generating the spheroidal graphite nodule [1]. Many observations of these nuclei reported the presence of multi-phase nanometric structure containing oxides, sulfides, oxysulfides [1], and sometimes nitrides [2, 3]. Accordingly, the chemical characterization of nuclei is of prime importance to establish the sequence of phase transformations leading to the formation of spheroidal graphite nodules. Scanning transmission electron microscopy (STEM) coupled with energy dispersive X-ray spectroscopy (EDS) is carried out on a thin diametric section of a graphite nodule. Bright field (BF) STEM image shows the presence of a nucleus in the middle of the graphite nodule (Fig. 1a). This nucleus appears composed of two parts: a round head loosely connected to an elongated tail (Fig. 1b). High-angle annular dark-field (HAADF) STEM images evidence the presence of at least one element much heavier than carbon in both parts (Fig. 1c). Moreover, the presence of different contrasts in the head indicates a multi-phase nature with a fan-like faceted precipitate (Fig. 1d). STEM-EDS cartography shows that the tail is composed of Al, Mg, Si and N, with however a few isolated small iron rich precipitates. In contrast, the head exhibits at least four different phases: 1) an inner facetted center rich in Fe; 2) a shell rich in S and Mg surrounding the center; 3) the fan-like precipitate mainly composed of Ti and developing outwards from this shell; and 4) a structure having the same composition as the elongated tail (Fig. 2). In this study, transmission and analytical electron microscopy allowed determining an organized multi-phase graphite nucleus at nanometric scale in a spheroidal graphite cast irons and a formation sequence could be proposed [4]. References: [1] T Skaland, Metall Trans A, 24A (1993), p. 2321 [2] H Nakae, Mater Trans, 43 (2002), p.2826 [3] JK Solberg, Mater. Sci. Tech., 17 (2001) p.1238 [4] L Laffont, J Mater. Res. Technol., 9 (2020) p.4665
Alessandro PUGLIARA (Toulouse)
13:00 - 15:00 #26391 - Dynamic effect of field evaporation on the distribution of the light emitted by a quantum well analyzed witin a photonic atom probe.
Dynamic effect of field evaporation on the distribution of the light emitted by a quantum well analyzed witin a photonic atom probe.

Eric Maximilian Weikum *, Georges BeainyJonathan HouardIvan BlumSimona MoldovanJean-Michel ChauveauMaxime HuguesDenis LefebvreNolwenn le BiavanAngela Vella Lorenzo Rigutti

  • UNIROUEN, CNRS, Groupe de Physique des Matériaux, Normandie Université, 76000 Rouen, France.
  • Centre de Recherche sur l’Hétéro-Epitaxie et ses Applications, UPR10 CNRS, 06560 Valbonne, France.


The Photonic Atom Probe (PAP) [1] uses the pulsed laser of a Laser-assisted Atom Probe Tomograph (La-APT) to excite electronic states in semiconductor materials. The radiation caused from the relaxation of these excited electronic states is analyzed by a Photoluminescence (PL) set-up. Simultaneously the sample can be field-evaporated by the La-APT set-up. This destructive analysis method offers compositional information on the atomic scale. The combination of both analysis methods allows to correlate the PL spectra with the evaporation state of the sample. This instrument allows performing super-resolution PL analysis correlated with 3D chemical mapping [2] and stress measurements on tip specimens [3]. In this contribution we report about the effect of the dynamical development of the tip specimen morphology during evaporation on intensity of the collected PL. The experiment shows indeed that the collected PL intensity from a single MgZnO/ZnO-QW (quantum well) shows a dependence on the amount of field-evaporated atoms. Using the FTDT method of the LUMERICAL software (Fig. 1), the emission of PL was simulated for different evaporation states of the tip and compared to the experiment. The calculation was performed taking into account the microscopic APT-reconstruction of the tip, which allows determining the location, the composition and the geometry of the light-emitting quantum well (Fig. 2). The numerical results show that the change in the tip’s geometry, due to the removal of atoms by field evaporation, leads to a change in the spatial distribution of the emitted light, resulting in a change in the measured PL intensity. A good agreement between experimental and numerical results is observed. In addition to the analysis of the intensity as a function of the evaporation state, the Polarization dependence of the measured data was compared to the simulated results. It was found experimentally that the emission from the ZnO-QW shows a different favored Polarization direction (σ) than the MgZnO-barrier (π), which is not to be expected, since the ZnO-QW shares its Wurzite crystal structure with the MgZnO-barrier. References [1] Review of Scientific Instruments 91.8 (2020): 083704. [2] Nano Letters 20.12 (2020): 8733-8738. [3] Physical Review Applied 15.2 (2021): 024014.
Eric Maximilian WEIKUM (Rouen)
13:00 - 15:00 #26390 - Characterization STEM/XPS of a passive film formed on additive manufactured 17-4PH stainless steel.
Characterization STEM/XPS of a passive film formed on additive manufactured 17-4PH stainless steel.

Lydia Laffont *, Adrien BarrouxThomas DuguetNadège DucommunEric NivetJulien DelgadoChristine Blanc

  • CIRIMAT/Toulouse INP-Ensiacet
  • CIRIMAT/CETIM Nantes
  • CETIM Nantes


L’acier inoxydable martensitique 17-4PH (17%Cr, 5%Ni, 5%Cr) est utilisé dans l’industrie nucléaire, aéronautique et biomédicales en raison d’une bonne résistance à la corrosion intergranulaire et de très bonnes propriétés mécaniques (précipités nanométriques riches en Cu). Ces pièces sont obtenues par forgeage (REF) mais depuis quelques années par fusion laser sur lit de poudre (procédé de fabrication additive métallique -FA) [1]. La microstructure de ces pièces obtenues après le traitement thermique de référence H900 est équivalente mais présente néanmoins des différences en ce qui concerne la quantité d’austénite, la taille des lattes de martensite et celle des précipités de NbC (Figure 1) [2]. Dans cette étude, la spectroscopie de photoélectrons (XPS) et la microscopie électronique en transmission (MET/STEM) associée à la spectroscopie de dispersion en énergie des rayons X (EDS) ont été utilisés afin de caractériser le film passif nanométrique formé après immersion en milieu NaCl sur l’acier obtenu par FA en comparaison à l’acier de référence. Ce film présente une structure duplex constituée d’hydroxydes/oxydes de Fe et de Cr suivie d’une couche intermédiaire enrichie en Cr, Cu et Ni. La couche d’oxyde externe est composée principalement d’oxy/hydroxydes de fer alors que la couche interne est enrichie en chrome au niveau de l’oxyde de fer (Figure 2). Des différences significatives au niveau de l’épaisseur et de la distribution en chrome dans le film passif ont été observées pour les deux aciers. De plus, un film d’oxyde particulier est formé sur les précipités de NbC présents à la surface. Ces différences de composition chimique et de structure au niveau du film passif pour ces deux aciers permettent d’expliciter les différences de comportement en corrosion obtenues en ce qui concerne la résistance à la corrosion par piqûres [3]. Références : [1] X. Lou J. Nucl. Mater. vol. 499 (2018) p.182 [2] A. Barroux, Corr.Sci., vol. 169 (2020), p. 108594 [2] A. Barroux, Surf Int., vol. 22 (2021), p. 100874
Lydia LAFFONT (Toulouse)
Room 1
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Vendredi 09 juillet

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SDV4
15:15 - 17:05

Symposium Sciences de la Vie 4
Imageries, spectroscopies en applications environnementales (Ecotoxicologie, Sols, Végétaux, milieux aquatiques)

Modérateurs : Arash JAMALI (UPJV, Amiens), Corentin SPRIET (TISBIO, Lille)
Le thème de ce symposium est large et couvre les développements récents et l'application des techniques de microscopie et de spectroscopie en sciences de l'environnement, leurs défis actuels et les solutions possibles.
La science de l'environnement est l'étude multidisciplinaire des environnements physiques, chimiques et biologiques de la terre. Les sujets englobent donc de nombreux domaines, notamment les sciences du sol, de l'eau et de l'atmosphère, l'écologie, l'écotoxicologie, les sciences végétales et animales, leurs sous-domaines, leurs processus et leurs interactions. La diversité et la complexité de ce domaine nécessitent souvent une approche et une expertise multidisciplinaire. L'utilisation de diverses techniques de microscopie et de spectroscopie contribue à la recherche environnementale en fournissant à la fois des informations qualitatives (identification) et quantitatives.Ce symposium est l'occasion de présenter des résultats de recherche originaux et exploratoires, ainsi que le développement, la validation et l'évaluation d'outils ou de méthodes innovants en recherche environnementale. Les modalités comprennent, mais sans s'y limiter, la microscopie photonique, électronique, et les méthodes d’analyses spectroscopiques associées.
15:15 - 15:45 La paroi secondaire décryptée par la microscopie optique multimodale. Guy COSTA (LCSN, Limoges)
Le bois est un matériau composite constitué principalement de cellules mortes. Le bois, ou xylème pourrait se réduire à l’étude de paroi secondaire des plantes. Paroi secondaire qui est constituée de lignines (polymère de phénol), de cellulose (polymère de ß-glucose) et dans une moindre mesure d’hémicelluloses (polymère de ß-galactose, ß-mannose, etc…). Usuellement, l’analyse de la composition pariétale nécessite l’utilisation de techniques de biochimie souvent complexe, consommatrice de temps et destructrices d’informations inhérentes aux méthodes biochimiques utilisées. La microscopie optique multimodale (immunomarquage, microscopie infrarouge, microscopie RAMAN, microscopie CARS, microscopie multiphotonique) offre alors des alternatives permettant une analyse fine de la paroi sans provoquer aucune modification des polymères pariétaux.
Les travaux présentés ici, visent à montrer en quoi l’imagerie optique multimodale permet d’analyser la distribution des polymères pariétaux. Pour ce faire, nous comparerons les résultats d’immunomarquage de la paroi avec des études d’imageries sans marquage, comme la microscopie vibrationelle CARS (Coherent Anto-Stokes Raman Scattering microscopy). Cette technique ne pouvant certainement pas à elle seule expliquer l’organisation et la distribution des biomolécules dans la paroi, elle sera complétée par de nouvelles approches comme la microscopie biphotonique, et la SHG.
15:45 - 15:55 Discussion.
15:55 - 16:25 Explore the functional organization of the vacuolar system by multiscale 3D reconstruction. Romain LE BARS (I2BC, Paris-Saclay)
The secretory glands of carnivorous plants undergo major remodeling when they enter a digestive process, making them an ideal model to study the morphodynamics of the endomembrane system (reticulum, Golgi apparatus, vacuoles). Understanding the functional mechanics of these changes requires the use of high-resolution techniques and 3D visualization of the entire secretory apparatus. To study how the vacuolar system adapts to this situation, electron microscopy studies allowed us to characterize morphologically these modifications. Nevertheless, the quantification of this process was not achievable as the vacuolar system is a very complex tridimensional network of interconnected compartments. To overcome this challenge we decided to combine electron microscopy sample preparation, light microscopy imaging and machine learning based image segmentation to generate 3D models of the vacuolar system. This complete workflow allowed us to quantify the vacuolar system evolution and is also a great alternative for any laboratory to reach high resolution at the sub-cellular scale on complex and challenging tissues.
16:25 - 16:35 Discussion.
16:35 - 16:55 #26366 - Investigation of the methylmecury detoxification into nano-HgSe in subantartic seabirds tissues.
Investigation of the methylmecury detoxification into nano-HgSe in subantartic seabirds tissues.

Mercury is a global contaminant which readily bioaccumulates in aquatic organisms and biomagnifies in marine food webs mainly as neurotoxic methylmercury (MeHg). Being high in the food webs, large seabirds are particularly exposed to MeHg. Because mercury has huge affinity for selenium, resistance to high amounts up to 1500 ppm of toxic mercury is thought to be achieved by detoxification in association with Se through biomineralization as HgSe, similarly to marine mammals, though no direct proof of such precipitates in birds was brought. To assess the Hg exposure risk, the Hg:Se ratio in cells is widely used as it is related to the capacity to detoxify MeHg which becomes more hazardous when Hg:Se≥1. But this approach relies on the hypothesis that the cells contain no other selenious form of Hg than HgSe.

This hypothesis was tested on the southern giant petrel Macronectes giganteus. The Hg speciation in dead-birds tissues was determined by coupling Hg L3-edge X-ray absorption spectroscopy with scanning transmission electron microscopy (STEM) using a Cs-probe-corrected and monochromated Themis-Z-G3.

STEM imaging at 80 kV using a High-Angle-Annular-Dark-Field detector (HAADF) allowed imaging for the first time large aggregates (up to 1 µm) of HgSe nanoprecipitates  with a grain size between 5 nm in kidneys and pectoral muscles, up to 40 nm in the liver (Figure 1). A 80 kV voltage with a curent of ~100 A was chosen to maximize the X-rays emission for EDS elemental mapping while preserving at most the beam-sensitive organic tissues. It confirmed the precipitates composition with a Hg:Se~1. No selenium was found in the HgSe pecipitates vicinity. High-resolution (HR) TEM images of individuel gains in liver and kidneys were aquired to explore the crystal structure at the atomic scale, using a 300 kV to maximize the phase contrast. Fast-Fourier transform (FFT) images and electron diffraction of large HgSe aggregates demontrate their cubic F43m structure (a = 6.08 Å). HR images of the more challenging muscle sample were obtained in STEM-HAADF at 300 kV, 60 pA current and -170°C. A collection of 80 images (0.1 sec/frame) were drift-corrected and summed, confirming a similar cubic structure.


Anne-Claire GAILLOT (NANTES Cedex 3)
16:55 - 17:05 Discussion.
Room 1

Vendredi 09 juillet

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SDM4
15:15 - 18:10

Symposium Sciences de la Matière 4
Spectroscopies, analyses et imageries chimique multi-échelles

Modérateurs : Philippe MOREAU (IMN, Nantes), Michaël WALLS (LPS, Orsay)
La puissance de la microscopie dans sa capacité d’interprétation des phénomènes à différentes échelles réside souvent de son association possible à une spectroscopie. Des analyses et/ou cartographies chimiques peuvent alors être produites, sur des dimensions micrométriques comme sub-nanométriques. La diversité des spectroscopies permet d’obtenir différentes informations qu’elles soient vibrationnelles, élémentaires ou donnant accès au type de liaison chimique, par exemple. La même diversité existe sur les types de microscopie (électronique, photonique, à sonde locale…) ce qui donne un caractère très ouvert et général à ce symposium. Les contributions présentant un caractère multi-échelle fort seront donc privilégiées, notamment en montrant l’intérêt de la complémentarité des techniques et les différences/similarités constatées aux différentes échelles. Les apports respectifs des analyses quantitatives précises et des cartographies de phases pourront être mises en avant. Les réflexions sur les résolutions spatiales adaptées en fonction de la technique, de l’information recherchée et de l’échantillon considéré sont aussi les bienvenues.
15:15 - 15:45 Modeling vibrational EELS of a single point defect. Guillaume RADTKE (CNRS Senior Researcher) (IMPMC, Paris Sorbonne)
Vibrational excitations are now accessible to high-energy-resolution electron- energy-loss spectroscopy (EELS) in a growing number of materials [1]. Combined with the very high spatial resolution of transmission electron microscopy, this technique therefore opens exciting perspectives for investigating the vibrational properties of condensed matter systems down to the atomic scale. In this context, EELS brings a direct insight into localized modes associated with structural defects, which strongly influence the macroscopic properties of materials and in particular, heat transport.
Most of these systems however, display complex atomic structures whose dynamics can seldom be understood using empirical models or through simple comparisons with known references. A proper assessment of the origin of the different structures observed experimentally therefore relies both on first-principles calculations and on an accurate description of the scattering process [2,3].
The major part of this talk will be devoted to the modeling of atomic-resolution vibrational EELS acquired on point defects in graphene [4]. After discussing the general features of impurity-induced vibrational modes in solids and the insights EELS could provide in this field, we will present state-of-the art DFT calculations carried out on the particular case of a trivalent substitutional impurity of silicon. Results obtained from first- principles on supercells as large as 96 x 96 (18432 atoms) graphene unit cells, required to isolate the substitutional silicon atom, show how resonant modes result from the hybridization of local impurity modes with the continuum of “bulk” graphene. We will show how the projected phonon density of states (PPDOS) mimics the dominant features of atomically-resolved “dark EELS” spectra and appears in this context as a simple and useful quantity to interpret qualitatively experimental spectral features. Finally, these results will be compared to those obtained theoretically on other point defects and their impact on the lifetime of “bulk” phonons in graphene, and thus on the thermal pransport properties of this material, will be discussed.

[1] O.L. Krivanek, T. C. Lovejoy, N. Dellby, T. Aoki, R.W. Carpenter, P. Rez, E. Soignard, J. Zhu, P. E. Batson, M.J. Lagos, R.F. Egerton and P.A. Crozier, Nature 514 (2014) 209.
[2] G. Radtke, D. Taverna, M. Lazzeri and E. Balan, Phys. Rev. Lett. 119 (2017) 027402.
[3] G. Radtke, D. Taverna, N. Menguy, S. Pandolfi, A. Courac, Y. Le Godec, O. L. Krivanek, and T. C. Lovejoy, Phys. Rev. Lett. 123 (2019) 256001.
[4] F. S. Hage, G. Radtke, D. M. Kepaptsoglou, M. Lazzeri and Q. M. Ramasse, Science 367 (2020) 1124.
15:45 - 15:55 Discussion.
15:55 - 16:25 Séparation de phases dans des minéraux complexes grâce à des techniques de "machine learning". Cécile HÉBERT (Prof.) (EPFL, Lausanne, Suisse)
16:25 - 16:35 Discussion.
16:35 - 16:50 #26385 - A Photonic Atom Probe allowing for super-resolution photoluminescence spectroscopy and 3D microscopy of nanoscale light emitters.
A Photonic Atom Probe allowing for super-resolution photoluminescence spectroscopy and 3D microscopy of nanoscale light emitters.

The laser pulses controlling the ion evaporation in Laser-assisted Atom Probe Tomography (La-APT) can simultaneously excite photoluminescence in semiconductor or insulating specimens [1]. An atom probe equipped with approriate focalization and collection optics can thus be coupled with an in-situ micro-photoluminescence (µPL) bench [2] that can be operated even during APT analysis. Our team has recently developed a coupled µPL-APT instrument operating at 400 kHz, controlled by 150 fs laser pulses tunable in energy in a large spectral range (spanning from deep UV to near IR). Micro-PL spectroscopy is performed using a 320 mm focal length spectrometer equipped with a CCD camera for time-integrated and with a streak camera for time-resolved acquisitions. Such a Photonic Atom Probe (PAP) has been applied to the study of the optical properties of nanoscale emitters in an in-situ correlative microscopy approach. The evolution of the PL signal during the APT analysis is an original source of information. In this work we analyzed specimens containing ZnO/(Mg,Zn)O quantum wells (QWs) of different thicknesses, and we show that it is possible to distinguish the optical signatures of separate QWs distant as few as 20 nm – well below the diffraction limit of the laser [3]. This information is then correlated with the chemical 3D distribution obtained by APT. The analysis of the PL spectral shifts during the APT analysis also allows determining the stress state induced by the electrostatic field [4].

[1] Mancini, Lorenzo, et al. ""Carrier localization in GaN/AlN quantum dots as revealed by three-dimensional multimicroscopy."" Nano letters 17.7 (2017): 4261-4269.

[2] Houard, Jonathan, et al. ""A photonic atom probe coupling 3D atomic scale analysis with in situ photoluminescence spectroscopy."" Review of Scientific Instruments 91.8 (2020): 083704.

[3] Di Russo, Enrico, et al. ""Super-resolution Optical Spectroscopy of Nanoscale Emitters within a Photonic Atom Probe."" Nano Letters 20.12 (2020): 8733-8738.

[4] Dalapati, P., et al. ""In Situ Spectroscopic Study of the Optomechanical Properties of Evaporating Field Ion Emitters."" Physical Review Applied 15.2 (2021): 024014.


Lorenzo RIGUTTI (Rouen)
16:50 - 17:00 Discussion.
17:00 - 17:15 #26392 - Quantification of hydrogen in nanoscale structures using correlative TEM, SIMS and APT analysis.
Quantification of hydrogen in nanoscale structures using correlative TEM, SIMS and APT analysis.

Transmission Electron Microscopy (TEM) is a widely used technique for atomic scale imaging and chemical analysis of materials [1]. However, the analysis of elements in trace concentrations, low-Z elements and isotopic selectivity are very difficult or impossible using the typical chemical analysis techniques available in a TEM such as Energy Dispersive X-ray Spectroscopy (EDS) or Electron Energy-Loss Spectroscopy (EELS). Atom Probe Tomography (APT) allows 3D nanoscale chemical imaging and it is capable of distinguishing isotopes. However, the analysed volume is small (~ 10^6 nm^3) and the data is prone to artefacts. Specifically, a precise 3D APT reconstruction requires the local morphology of the sample tip at each instance in time which is often lacking. Furthermore, limited mass resolution and differences in the field evaporation of different elements can also introduce artefacts in the APT data. Secondary Ion Mass Spectrometry (SIMS) is a high-sensitivity technique to detect concentrations down to the ppm range. Moreover, all elements and isotopes in the periodic table can be analysed. However, the main limitation of SIMS is that the quantification is difficult because of matrix effects (i.e. strong variations in ionization yields depending on matrix elements). Relatively large volumes (~ 10^3 um^3) are typically analysed in SIMS and the lateral resolution in SIMS imaging is fundamentally limited to ~ 10 nm by the ion-solid interaction volume. To overcome the limitations of the individual techniques, we present a correlative TEM-APT-SIMS method [2] for the quantification of hydrogen, deuterium and other trace elements (dopants) in passivating contact layers used in silicon photovoltaics. The analysis and data treatment methodologies will be discussed in detail and other new methods to quantify SIMS images will also be briefly introduced [3, 4]. 

This work was partially funded by the Luxembourg National Research Fund (FNR) by the grants C18/MS/12661114 (MEMPHIS) and INTER/SNF/16/11536628 (NACHOS).

References:

[1] D. B. Williams & C. B. Carter, Transmission Electron Microscopy, Springer, US 2009

[2] S. Pal et al, Appl. Surf. Sci, 555, 149650, 2021

[3] S. Eswara et al, MRS Comm., 9, 916–923, 2019

[4] L. Yedra et al, J. Anal. Atom. Spectrom., 36, 56-63, 2021


Santhana ESWARA (Esch-sur-Alzette, Luxembourg)
17:15 - 17:25 Discussion.
17:25 - 17:40 #26394 - Low-Energy Excitations in Transition-Metal Oxides by STEM-EELS Spectromicroscopy.
Low-Energy Excitations in Transition-Metal Oxides by STEM-EELS Spectromicroscopy.

The transition metal oxides exhibit a variety of interesting properties, such as ferroelectricity, superconductivity, etc. The atomic structural degrees of freedom and the electron’s degrees of freedom (charge and spin) lead to various phenomena through phase transitions. All these orders can be studied through collective excitations. By scanning transmission electron microscopy (STEM) with monochromator, the energy resolution can go as low as 5meV [1], and such low-energy excitations can thus be investigated by electron energy-loss spectroscopy (EELS) [2, 3]. 

In this work, we focus on the low-energy electronic excitations, id est, the plasmon and the d-d excitations on the SrVO3 oxides. The SrVO3 is an attractive earth‐abundant transparent conducting oxide. It is also described as a typical correlated metal where low-energy plasmon fluctuation can also leads to an appreciable renormalization of the low-energy band. Nevertheless, the experimental occurrence of plasmons is poorly reported. The observations of plasmonic type d-d excitations (dipolar contribution, strong surface delocalization in aloof beam) on SrVO3 by EELS are shown in Figure 1. Furthermore, the dispersion curve of the bulk plasmon, as measured for different slabs thicknesses, will be presented and discussed with respect to ab-initio calculation. The Figure 2 shows that the nanostructures based on SrVO3 exhibit the Fabry-Perot type surface plasmon modes. Several surface plasmons modes are visible on “rod-type” geometries, such as half-rod or slit and have been compared to the finite-difference time-domain (FDTD) simulation. We will report energy widths of surface plasmon as low as 50 meV in the sub 0.5eV loss range..It suggests that SrVO3 could be one alternative plasmonic materials due to the high quality factor in the near-infrared range, and thereby providing a reference for searching for better plasmonic materials.

References :

[1] O.L. Krivanek et al., Nature 514 (2014), 209.

[2] A. Gloter et al., Ultramicroscopy 109 (2009), 1333.

[3] V. Mkhitaryan et al., Nano letters 21 (2021), 2444.

Figure 1: (a) Disperson curve and (b) bulk/aloof measurements on SrVO3. (c) Dispersion curve of the plasmon peaks.

Figure 2: The Fabry-Perot type d-d based surface plasmon modes in SrVO3 of (a) half-rod and (c) slit nanostructures. (b) FDTD simulation of (a).


Chia-Ping SU (Orsay)
17:40 - 17:50 Discussion.
17:50 - 18:00 Electron detectors for counted EELS acquisition - Gatan. Ray TWESTEN (Product Manager – Analytical Instruments) (GATAN, Etats-Unis)
18:00 - 18:10 Discussion.
Room 2