Structure determination of very small (1–5 nm) nano-particles

The investigation of nanoparticles and quantum dots is of great interest, and the understanding of their optical, electronic and structural properties could be significantly improved if better structural information was available. In this paper a review is given on the latest improvements in a novel fit approach for powder X-ray diffraction data obtained from nanoparticles with diameters below 5 nm. The procedure is based on modelling on an atomic level and yields precise information on size, shape, structure (including impurities and stacking faults) stress, relaxation effects, etc. By implementing an ensemble averaging, we could consider distributions of the basic parameters (e.g., size distribution) and, therefore, a more realistic fit of the diffraction data is enabled. Different refinements of CdS, ZnS and ZnO particles are presented and demonstrate the superiority of the new approach compared to simpler models.