Heterogeneous catalysis of nanomaterials has emerged as an efficient way to speed up the catalytic process due to the higher surface area of nanoparticles compared to their bulk counterparts. A challenging issue is the development of heterogeneous catalysis with a high selectivity close to 100% as well as understanding the durability issues of catalysts. To tackle these problems, the CHARLINE young-scientist project proposes to develop new faster characterization systems and state-of-the-art in situ monitoring to optimize catalyst and reactor operations simultaneously. The ambition of the project is to study in situ and operando the structural evolution of catalytic nanoparticles in various gaseous and liquid environments during reaction by using the unique capabilities of coherent X-ray diffraction Bragg imaging (CDI). Recently, we have successfully performed first proof-of-concept experiments using Pt nanocrystals to show the feasility of the Bragg CDI approach under atmospheric air and gas conditions. As dedicated instruments have just reached user operation, it is only now that this new imaging technique can be applied during chemical reaction. Operando X-ray catalysis has often been carried out under idealized conditions and averaging information from macroscopic “facets”. This approach suffers from the lack of transferability to nanocrystalline systems, where the facets are assumed to change during each state of the reaction leading eventually to the much higher catalytic activity of nanocrystals. In situ and operando CDI is thus of highest priority and extremely timely as the technique can probe structural changes in individual nanocrystals and under conditions where up to now, no other technique could probe the relevant structural parameters. The project will shed light on most relevant industrial processes and will open new horizons in the field of heterogeneous catalysis by probing the structure of nanocatalysts using the unique capabilities of in situ and operando Bragg CDI. Ex situ local characterization tools, like atom probe tomography and transmission electron microscopy, will also be employed as complements to spatially resolve strain, segregation and/or composition at the atomic scale.

Heterogeneous catalysis of nanoparticles has recently emerged as highly promising way to speed up catalytic processes due to their far higher surface area compared to bulk materials. But they face significant challenges in achieving high catalytic activity and sufficient durability. A key problem has been that all existing approaches to the characterization of atomic scale phenomena in these materials either lack structural specificity or can be employed under highly unrealistic catalytic environments. As an example, operando x-ray catalysis has often been carried out under idealized conditions and averaging information from macroscopic facets. This approach suffers from the lack of transferability to nanocrystalline systems. To tackle this problem, I am developing new state-of-the-art in situ techniques based on coherent x-ray scattering and complementary chemical characterization, with which I will optimize catalyst and reactor operations simultaneously. This is the ambition of the CHARLINE project to study in situ and operando the structural evolution of catalytic nanoparticles in realistic conditions during reaction by using the unique capabilities of coherent diffraction Bragg imaging (CDI). My proposed work builds on my recent exciting proof-of-concept experiments using Pt nanocrystals that demonstrate the sensitivity and spatial resolution of CDI under liquid conditions. As dedicated instruments for CDI have just reached user operation, it is only now that this new imaging technique can be applied during reaction and can probe structural changes of individual nanocrystals under conditions where up to now, no other techniques could probe the relevant parameters. My project will shed light into most relevant unsolved issues (durability, activity…) that limit the efficiency of today’s industrial processes and will open new horizons with outstanding impact in catalytic research.

Enantiomers physical separation starting from a racemic mixture remains a major challenge in modern chemistry from an academic as well as industrial point of view, given the few existing solutions. Indeed, these solutions are composed of either a separation based on physical principles, or indirectly by enantioselective or diastereoselective reactions requiring additional separation and transformation steps. The CoMuCat project aims to bring an alternative answer to this problem combining the enantioselective multicatalysis with a physical separation using modified membranes. In the envisioned scenarios, several catalyzed reactions are done in compartmentalized reactors separated by a membrane able to allow a selective diffusion of chemical species based on their polarity. A first task is dedicated to the modulation of the membrane permeability by surface and/or core modifications. A second task aims to elaborate new compartmentalized multicatalytic systems leading to the physical separation of enantiomers starting from a racemic mixture using membranes elaborated in the first task. Two processes are envisioned to reach this goal. The first allows the compartmentalized production of enantiomers, while the second aims to separate enantiomers from racemic substrates. Each of these processes leads to enantioenriched mixtures isolated in the dedicated compartments.

Within the frame of the nanostructures surface functionalization, this project aims to generate, to manipulate, and to detect magnetic states localized at the surface of semiconducting and polar zinc oxide nanoparticles (NPs), by electron paramagnetic resonance (EPR). The monitoring of such surface spin states in stable, robust and safe NPs allows for the realization of optically-controlled spin switch, paving the way to future information storage and processing nanotechnologies. After the recent demonstration of the possibility to generate these surface spin state by visible light irradiation (violet laser, 405 nm) in ZnO NPs, we now want to precise the conditions for the generation and the extinction of these excited states by different optical wavelength, but also to study the growth-parameters influence, that of the post-growth gaseous environment, and that of NPs size and morphology.The basic properties study of these excited magnetic states is done by continuous wave EPR (X band) at liquid nitrogen temperature and with optical excitation. The dynamical properties of the spin-spin and spin-lattice interactions are probed by pulse-EPR measurements, preformed on the excited states. Besides, we plan to modulate the statical and dynamical features of the excited magnetic states by applying static and alternative (up to radiofrequency) electric field onto layers of ZnO NPs. These surface spin-states arise from the dissociation of some photo-generated electron-hole pairs (excitons), and are directly related to the greatness of the surface-to-volume ratio, and to the chemical and physical passivation of the polar interfaces between polar NPs and environment. The exacte nature of these spin states is in all probability a complexe of intrinsic and extrinsic point defects, namely some hydrogen ions bound to a zinc vacancy. The appropriate spin Hamiltonian implies a hyperfine interaction between an electronic spin 1/2 and three equivalent protons.

In the LEGO project, we propose a new approach to realize the fabrication of 2D and 3D metal oxide structures, from solutions, using direct laser writing, layer by layer, without thermal post-processing, the layers being deposited by dip-coating. We aim at multi-scale structural control and hierarchical functionalities, with control and versatility of material structure (dense or mesoporous structures of metal oxides TiO2, ZrO2, HfO2, ZnO). Directed self-assembly (DSA) will be introduced to prepare 2D nanoporous thin films with controlled long-range organization. By extension in 3D, 3D hierarchical nanoporous structures will be obtained, with each layer serving as a guide for the next. The final 3D material can thus be built as a LEGO by precise positioning of each layer.