Quantitative analysis of gold nanoparticles from synchrotron data by means of least-squares techniques

摘要

Powder samples of thiol-capped gold nanoparticles in the size range of 2-4 nm were quantitatively characterized by means of synchrotron X-ray diffraction data, with respect to their structure, size and strain distributions. A novel Rietveld-like approach was applied, refining domain size distribution, strain-size dependence and structure type concentrations. Three structure types (cuboctahedron, icosahedron, decahedron) were considered in this analysis and a detail study of the strain content was performed by comparing different models. The results showed a strong influence of the strain model and a careful analysis is presented. Final domain size and strain distributions agree well with the existence of both single-domain and imperfectly formed or multi-domain nanoparticles, but the final strain profiles seem to be mostly related to the different degree of structural perfection at different sizes as a result of the synthesis process. The present work represents an important step towards the development of robust methods to determine strain profiles in nanosystems, aiming to fulfill the description of these important but complex systems.