Coherent X-ray diffraction to look at stress in nano particles

A research team led by Professor I. Robinson (London Centre for Nanotechnology, University College London) recently analyzed how gold nanocrystal changes after the adsorption of organic molecules because of the strain field. So far, it has been difficult to observe such influence of adsorbed molecules on the particle structure. The team employed the coherent X-ray diffraction method, which is extremely sensitive to displacement of atoms, and therefore to adsorption-induced near-surface stress in a single nanocrystal. It was discovered that the stress generated by thiol adsorption on gold has a fundamentally different nature in the curved, nominally spherical, regions of the crystal surface than in its flat facets. The magnitude of surface stress was also quantitatively analyzed and discussed. The experiments were done with coherent X-rays of 8.92 keV from the 34-ID-C beamline of the Advanced Photon Source (APS), Argonne, USA. For more information, see the paper, "Differential stress induced by thiol adsorption on facetted nanocrystals", M. Watari et al., Nature Materials 10, 862 (2011).