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.

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