Effects of synthesis temperature on particle size/shape and photoluminescence characteristics of ZnS:Cu nanocrystals

Abstract

ZnS:Cu nanocrystals are prepared by solution synthesis technique, and the optimum range of synthesis temperature and the particle size/shape for the high photoluminescence (PL) properties of ZnS:Cu nanocrystals are investigated in this study. With an increase of synthesis temperature, the crystal structure is not changed. However, the particle size increases slightly. PL intensity is maximum for the sample prepared at 85 °C for the temperature range used in this study (70–95 °C). This is the first observation for the ZnS:Cu nanocrystals prepared by solution synthesis technique. The X-ray photoelectron spectroscopy (Cu2p 3/2), performed to explain this phenomenon, demonstrates that with lower synthesis temperature (<85 °C), Cu acts as the normal accepter dopant, leading to the high PL intensity. With higher temperature (>90 °C), however, Cu is transformed into CuO, and CuO acts as the nonradiative recombination center, resulting in the substantial decrease of PL intensity observed in this study.