Mesoscale morphology of airborne core–shell nanoparticle clusters: x-ray laser coherent diffraction imaging

Abstract

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.

Time-resolved x-ray imaging of a laser-induced nanoplasma and its neutral residuals

“…On a long timescale, from 500 ps on, a novel kind of pattern shows up as presented in figure 4(a). These speckle patterns from fragmenting xenon clusters were to our knowledge never detected before from atomic clusters but are mainly known from imaging of colloid systems [28,54,55]. All three patterns exhibit a characteristic speckle distribution with distinct speckle size and intensity.…”

X-ray scattering characterisation of nanoparticles

“…It is possible to measure individual molecules, and by extension, individual nanoparticles. Coherent diffraction imaging has been used to investigate the size distributions of and elemental distributions within Ag nanocubes and Au/Ag nanoboxes 100-200 nm in size, [380] Co@SiO 2 core-shell particles 10-30 nm in size, [381] and ellipsoidal iron oxide particles 50 × 250 nm. [382] Hundreds of individual particles are measured and the images processed through Fourier transformation to reconstruct the original nanoparticle.…”

The 3D-architecture of individual free silver nanoparticles captured by X-ray scattering

“…Third, free particle growth is a statistical process such that a specific combination of shape, orientation and size cannot be repeatedly prepared, excluding tomographic techniques 11 12 that rely on multiple measurements of the same object or of equivalent replicas. Considerable efforts have been devoted to obtaining 3D structure information of nanosystems via diffractive imaging with intense femtosecond pulses from X-ray free-electron lasers (X-FELs) 13 14 15 16 17 18 19 20 21 . In-flight characterization of single nanoparticles by X-ray small-angle scattering has been successfully demonstrated, revealing the effective two-dimensional (2D) projection of the electron density 14 16 20 .…”

“…Considerable efforts have been devoted to obtaining 3D structure information of nanosystems via diffractive imaging with intense femtosecond pulses from X-ray free-electron lasers (X-FELs) 13 14 15 16 17 18 19 20 21 . In-flight characterization of single nanoparticles by X-ray small-angle scattering has been successfully demonstrated, revealing the effective two-dimensional (2D) projection of the electron density 14 16 20 . The 3D reconstruction based on single-shot small-angle X-ray scattering data can only be achieved by exploiting additional symmetry information, as was shown for the case of deposited particles 18 .…”