Zobrazeno 1 - 10 of 137 pro vyhledávání: '"Ehret, E."'
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Synthesis of nanoparticles (NPs) with well controlled characteristics is crucial to better understand the behaviour of the active phase during reaction and to better correlate it with its catalytic performance. Among other self-assembly methods, the di-block copolymer approach is well suited to obtain monodisperse supported NPs which can serve as supported metallic catalysts on both flat (model catalysts) and powder (realistic catalysts) supports. In this approach, an amphiphilic di-block copolymer dissolved in toluene yields a system of inverse micelles of which the core can be charged with metallic precursors to ultimately yield networks with well-controlled characteristics (size, composition, inter-distance). Important questions must be addressed, in particular in the case of bimetallic systems, concerning the formation of unique NPs at the cores from the initially pre-formed bimetallic seeds or the stability of the NPs networks with increasing temperature in presence of reactive gases. We have chosen to work with PS-b-P2VP di-block copolymer micelles that were functionalized with chloro-auric acid and palladium di-acetate precursors. The precursors selectively bind with N-functions in the P2VP cores to form (bi-)metallic seeds within the micelles’ cores as it was previously established in the case of PdAg alloys. We have used an Environmental TEM (Titan ETEM G2, FEI/TFS) operated at 300kV under gas pressures up to 20 mbar to gain insight on their evolution/stability during heating under oxygen and CO (for CO oxidation catalysis). Temperature variation was achieved with a WildFire sample holder with dedicated heating MEMS-microchips (DENS Solutions) capable of reaching temperatures up to 1300°C. Monolayers of controlled AuxPd1-x core-metallized PS-b-P2VP micellar solutions were deposited by spin-coating (2000/4000 rpm) on the microchips. Special care was taken to minimize/prevent any influence of the electron beam on the observed events.The Au-rich system (Au80Pd20) showed that, under oxygen, the (bi-)metallic seeds within the P2VP cores begin to sinter around 350° and unique NPs are eventually formed around 500°C which is consistent with the decomposition temperature range of the PS-b-P2VP copolymer associated with metallic nuclei. Further heating up shows that the NPs network is stable up to 900°C. Approaching the melting temperature of gold (1064°C) the NPs begin to shrink; concomitantly, smaller NPs (that grow even at 1100°C) form around the shrinking NPs. These smaller NPs are formed with Pd atoms from the initial bimetallic NPs.In the case of the Pd-rich system (Au20Pd80), under oxygen, the seeds begin to sinter around 300°C and at 450°C demixing of the NPs is observed leading to Janus NPs (Au-rich/PdO, cf. Figure); the latter are readily reduced and homogeneous NPs reform upon CO exposure (cf. Figure).The stability of the bimetallic NPs seems to be driven by the intrinsic properties of the metals composing them.Thanks are due to the METSA network for supporting this study and to CLYM for the access to the ETEM
Autor: Cadete Santos Aires, F.J., Ehret, E., Vas, J.V., Chatre, C., Landrivon, E., Duchamp, M., Epicier, Thierry
Observation of liquids within a transmission electron microscope (TEM) has long been impossible owing to basic thermodynamic limitations due to the need for a high vacuum, typically 10-5 mbar or better, within the column of the instrument, making it
Externí odkaz: https://explore.openaire.eu/search/publication?articleId=od_______166::45ec86f607549740bb71e2e038036585
https://hal.archives-ouvertes.fr/hal-03681072
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Windowless wet Environmental TEM: a dedicated approach for water condensation / evaporation experiments
Autor: Vas, J., Cadete Santos Aires, F.J., Ehret, E., Landrivon, E., Muller, A., Epicier, Thierry
Efficient closed cells specimen holders for Liquid Cell Transmission Electron Microscopy (TEM) has led to many advances over the last two decades but still suffer limitations due to their sealing membranes which hamper comfortable tomography approach
Externí odkaz: https://explore.openaire.eu/search/publication?articleId=od_______166::1fd8025578dd9a3cdf72499d5f69780a
https://hal.archives-ouvertes.fr/hal-03662983
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Windowless in situ Water Condensation on NaCl nanocubes in Environmental TEM. - VIRTUEL
Autor: Cadete Santos Aires, F.J., Ehret, E., Chatre, C., Massin, L., Roiban, L., Epicier, Thierry
Publikováno v: Microscopy at the Frontiers of Science 2021. 7th Joint Congress of the Portuguese and Spanish Microscopy Societies
Microscopy at the Frontiers of Science 2021. 7th Joint Congress of the Portuguese and Spanish Microscopy Societies, Sep 2021, Braga, Portugal
SSCI-VIDE+ATARI:MEME+FCA:EEH:CLH:LMA:TEP; International audience; Observing liquids in a Transmission Electron Microscope (TEM) has long been impossible owing to basic thermodynamic limitations due to the need for a high vacuum, typically 10-5 mbar o
Externí odkaz: https://explore.openaire.eu/search/publication?articleId=dedup_wf_001::fbea180af36abdc31f779d787cefbd3c
https://hal.archives-ouvertes.fr/hal-03367024
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Model catalysts synthesized by the di-block copolymer inverse micelle method: insights on nanoparticle formation and network stability within the environmental TEM. - VIRTUAL
Autor: Cadete Santos Aires, F. J., Ehret, E., Bruno Domenichini, Burel, L., Thierry Epicier
Publikováno v: Scientific School for Young Scientists “New catalysts and catalytic processes to solve the challenges of environmentally responsible and resource-saving energy production”
Scientific School for Young Scientists “New catalysts and catalytic processes to solve the challenges of environmentally responsible and resource-saving energy production”, Sep 2021, Tomsk, Russia
HAL
MICROSCOPIE+MEME+FCA:EEH:LBU:TEP; International audience; The di-block copolymer inverse micelle method, where an amphiphilic di-block copolymer dissolved in toluene creates a system of inverse micelles, is a rather simple method to obtain well contr
Externí odkaz: https://explore.openaire.eu/search/publication?articleId=dedup_wf_001::bd1a7e722a2529226005d07d606e4abb
https://hal.archives-ouvertes.fr/hal-03367029
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Formation of Bimetallic Nanoparticle Arrays and Evidence for their Stability at High Temperature under Gas Pressure in the Environmental TEM - VIRTUAL
Autor: Ehret, E., Aires, Francisco Jose Cadete Santos, Domenichini, Bruno, Burel, Laurence, Epicier, Thierry
Publikováno v: 5th International Conference on In-Situ and Correlative Electron Microscopy – CISCEM 2021
5th International Conference on In-Situ and Correlative Electron Microscopy – CISCEM 2021, Sep 2021, Paris, France
MICROSCOPIE+MEME+EEH:FCA:LBU:TEP; International audience; Supported catalysts are generally composed of, at least, one nanometric active phase deposited and/or synthesized at the surface of a convenient nanometer/micrometer powder support. As such th
Externí odkaz: https://explore.openaire.eu/search/publication?articleId=dedup_wf_001::7564e9240d77605f79a405d4c7f90e92
https://hal.archives-ouvertes.fr/hal-03367031
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Arrays of bimetallic nanoparticles obtained by the block copolymer inverse micelle method
Autor: Ehret, E., Thierry Epicier, Beyou, E., Bruno Domenichini, Mamontov, G. V., Bugrova, T. A., Aouine, M., Burel, L., Cadete Santos Aires, F. J.
Publikováno v: XVIII International Conference of Students and Young Scientists "Prospects of Fundamental Sciences Development"
XVIII International Conference of Students and Young Scientists "Prospects of Fundamental Sciences Development", Apr 2021, Tomsk, Russia
HAL
MICROSCOPIE+MEME+EEH:TEP:MAO:LBU:FCA; International audience; We used self-assembled block copolymer templates to generate arrays of bimetallic nanoparticles. In this approach, a block copolymer consisting of hydrophilic and hydrophobic blocks is dis
Externí odkaz: https://explore.openaire.eu/search/publication?articleId=dedup_wf_001::53e097aa88067cd2aba95267ab1d0c8c
https://hal.archives-ouvertes.fr/hal-03227242
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Self-Organized Bimetallic Catalysts Obtained from Di-Block Copolymer Micellar Solutions: Nanoparticle Formation and Network Stability at High Temperature under Gas Pressure within the Environmental TEM
Autor: Ehret, E., Cadete Santos Aires, F. J., Bruno Domenichini, Burel, L., Thierry Epicier
Publikováno v: Microscopy at the Frontiers of Science 2021. 7th Joint Congress of the Portuguese and Spanish Microscopy Societies
Microscopy at the Frontiers of Science 2021. 7th Joint Congress of the Portuguese and Spanish Microscopy Societies, Sep 2021, Braga, Portugal
HAL
MICROSCOPIE+MEME+EEH:FCA:LBU:TEP; International audience; Systems of self-organized nanoparticles (NPs) are useful in many domains such as, for instance, optics, nanostructure growth and, the domain of most interest in our case, catalysis. It is inde
Externí odkaz: https://explore.openaire.eu/search/publication?articleId=dedup_wf_001::648b706a0ece80bc4a49fed20290b790
https://hal.science/hal-03367026
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