Optical properties of monodisperse spherical aggregates formed by self-assembly of ZnS nanoparticles

ZnS nanoparticles of diameters between 3-4 nm were aggregated to form dense nanospheres of sizes similar to 100 nm by a colloidal precipitation method using PVP as the stabilizing agent. XRD studies showed that the ZnS nanoparticles were of zinc blend (cubic) structure. It was observed that the dense nanospheres had a tendency to form supramolecular nanostructures on a solid substrate upon solvent evaporation. The resulting films had highly ordered structures with the aggregated nanospheres inter-connected to form dendrite like structures and chains of micrometer length scale. Optical absorption spectra of the samples demonstrated the effect of quantum confinement in the ZnS nanocrystals. Photoluminescence measurements showed a sharp UV emission at similar to 370 nm.