The advent of the new 4^th generation x-ray light sources represents an unprecedented opportunity to conduct in situ and operando studies on the structure of nanoparticles in reactive liquid or gas environments. Here, we will illustrate how Bragg coherent x-ray imaging ^[1] allows to image in three dimensions (3D) and at the nanoscale the strain and defect dynamics inside nanoparticles as well as their refaceting during catalytic reactions ^[2–6]. This imaging technique can be coupled with molecular statics simulations to investigate the 3D strain and stress fields in nanoparticles. We will also discuss the possibility to measure particles as small as 20 nm ^[7] and to enable high-resolution and high-energy imaging with Bragg coherent x-ray diffraction at 4th generation x-ray light sources. Finally, we will highlight the potential of machine learning to predict characteristic structural features in nanocrystals just from their 3D Bragg coherent diffraction patterns ^[8].


Citations:
[1] I. Robinson and R. Harder, Coherent X-Ray Diffraction Imaging of Strain at the Nanoscale, Nat. Mater. 8, 291 (2009).
[2] S. Fernández et al., In Situ Structural Evolution of Single Particle Model Catalysts under Ambient Pressure Reaction Conditions, Nanoscale 11, 331 (2018).
[3] M.-I. Richard et al., Crystallographic Orientation of Facets and Planar Defects in Functional Nanostructures Elucidated by Nano-Focused Coherent Diffractive X-Ray Imaging, Nanoscale 10, 4833 (2018).
[4] J. Carnis, L. Gao, S. Fernández, G. Chahine, T. U. Schülli, S. Labat, E. J. M. Hensen, O. Thomas, J. P. Hofmann, and M.-I. Richard, Facet-Dependent Strain Determination in Electrochemically Synthetized Platinum Model Catalytic Nanoparticles, Small Weinh. Bergstr. Ger. e2007702 (2021).
[5] J. Carnis et al., Twin Boundary Migration in an Individual Platinum Nanocrystal during Catalytic CO Oxidation, Nat. Commun. 12, 5385 (2021).
[6] M. Dupraz et al., Imaging the Facet Surface Strain State of Supported Multi-Faceted Pt Nanoparticles during Reaction, Nat. Commun. 13, 1 (2022).
[7] M.-I. Richard et al., Bragg Coherent Diffraction Imaging of Single 20 nm Pt Particles at the ID01-EBS Beamline of ESRF, J. Appl. Crystallogr. 55, 621 (2022).
[8] B. Lim et al., A Convolutional Neural Network for Defect Classification in Bragg Coherent X-Ray Diffraction, Npj Comput. Mater. 7, 1 (2021).