Size and distribution: a comparison of XRD, SAXS and SANS study of II-VI semiconductor nanocrystals

The uniqueness of size dependent functional properties of II-VI semiconductor nanocrystals have led to the development of various techniques for determination of shape, size and distributions, although the accurate measurements of the particle sizes has always been a fundamental task in nanoscience and even become more crucial with the discovery of quantum confinement effect. A comparison of the well established techniques X-ray diffraction (XRD), small angle X-ray scattering (SAXS) and small angle neutron scattering (SANS) with an emphasis on size and distribution of the prepared samples are reported in order to elaborate more precise techniques for the analysis of particles sizes. Modified Scherrer formula for spherical particles has been used to calculate the particle sizes from XRD spectra. Analysis of SAXS data has been reported using Guinier model. Small angle neutron scattering measurements has been performed for ZnO nanocrystals and the scattering data obtained is simulated for polydisperse sphere. The bare ZnO, ZnS and CdS and doped with Mn2+ systems are taken within the framework of our discussion. These materials were synthesized by chemical precipitation route and found to have size distribution from 2 to 6 nm for spherical particles. Sizes determined from various techniques are in good agreement with each other however small angle scattering technique is more reliable than XRD to determine the sizes of the nanoparticles.