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

Abstract

The diversity of nanoparticle shapes generated by condensation from gaseous matter reflects the fundamental competition between thermodynamic equilibration and the persistence of metastable configurations during growth. In the kinetically limited regime, intermediate geometries that are favoured only in early formation stages can be imprinted in the finally observed ensemble of differently structured specimens. Here we demonstrate that single-shot wide-angle scattering of femtosecond soft X-ray free-electron laser pulses allows three-dimensional characterization of the resulting metastable nanoparticle structures. For individual free silver particles, which can be considered frozen in space for the duration of photon exposure, both shape and orientation are uncovered from measured scattering images. We identify regular shapes, including species with fivefold symmetry and surprisingly large aspect ratio up to particle radii of the order of 100 nm. Our approach includes scattering effects beyond Born’s approximation and is remarkably efficient—opening up new routes in ultrafast nanophysics and free-electron laser science.

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

“…The new imaging method of femtosecond coherent diffraction imaging emerged [21,22]. For the first time it has become possible to image isolated, non-crystalline, finite targets in flight [23][24][25], allowing to investigate nanoparticle geometries [26,27] and in particular ultrafast structural changes with high spatial and temporal resolution [25,28]. Coherent diffractive imaging on single clusters has opened new avenues, especially for intense laser matter studies, because the elastic light scattering directly maps the electronic structure of the sample, i.e.…”

Shapes of rotating superfluid helium nanodroplets

“…This long wavelength regime is not available at LCLS, but is common at the FLASH and FERMI free electron lasers [37][38]. A recent XFEL based wide angle x-ray scattering study of Ag nano-particles enabled the reconstruction of their three-dimensional shapes [36]. Very recently, wide angle scattering from He droplets in the XUV regime has been studied [39].…”

Effect of substrate interface on the magnetism of supported iron nanoparticles

“…The interface energy depends on both the free surface energy of the particles and of the substrate. Metastable structures or defects may result from the particle growth or from the impact on the substrate [46,47]. In the first scenario, a defect present in the nanoparticle would remain when landing on the relatively inert SiO x surface, with its relatively low surface energy of ∼0.2-0.3 J/m 2 [48], but would be increasingly more likely to be removed when deposited onto substrates with higher surface energies.…”