Controlled synthesis and structural evolutions of ZnS nanodots and nanorods using identical raw material solution

Abstract

We controlled-synthesized ZnS nanodots and nanorods from identical raw materials. Thermal decomposition of an amine complex in an organic solvent was applied as the synthesis method. ZnS nanodots and nanorods were controlled-synthesized by simply changing the heating rate. We analyzed the temporal evolution of products from the early stages using HR-TEM and XRD in detail. At a higher heating rate, the particle shape was spherical and the crystalline phase was zinc blende. At the lower heating rate, nanorods were formed and the length was increased concomitantly with decrease in the heating rate. The nanorods had a wurtzite structure below 175 °C, and consequently transformed to zinc blende phase during a temperature rise to 200 °C. This is opposite to the thermodynamic transformation of the bulk material. This particle shape and crystalline phase would be influenced by the adsorption property of amine ligands incorporating changes in the particle surface structure. Additionally, the synthesized ZnS nanodots and nanorods exhibited predominantly band-edge emission in fluorescence spectra. The fluorescence emission peak was narrow, with its position dependent on the particle shape and size.