Selection of single-shot diffraction patterns from clusters of Co@SiO2 NPs taken at 1200 and 777 eV photon energies, respectively
Figure 1. Selection of single-shot diffraction patterns from clusters of Co@SiO2 NPs taken at 1200 and 777 eV photon energies, respectively. Each image shows a border between the brighter inner circle and the darker surrounding area, due to the form factor of the 30 nm diameter single NPs. (a), (b) Large clusters, (c), (d) medium-sized clusters, and (e), (f) small clusters. Qualitative variations between patterns are due to variations in size poly-dispersity, the number and arrangement of NPs within the cluster.
Unraveling the complex morphology of functional materials like core–shell nanoparticles and its evolution in different environments is still a challenge. Only recently has the single-particle coherent diffraction imaging (CDI), enabled by the ultrabright femtosecond free-electron laser pulses, provided breakthroughs in understanding mesoscopic morphology of nanoparticulate matter. Here, we report the first CDI results for Co@SiO2 core–shell nanoparticles randomly clustered in large airborne aggregates, obtained using the x-ray free-electron laser at the Linac Coherent Light Source. Our experimental results compare favourably with simulated diffraction patterns for clustered Co@SiO2 nanoparticles with ~10 nm core diameter and ~30 nm shell outer diameter, which confirms the ability to resolve the mesoscale morphology of complex metastable structures. The findings in this first morphological study of core–shell nanomaterials are a solid base for future time-resolved studies of dynamic phenomena in complex nanoparticulate matter using x-ray lasers.