High quality ZnS and core/shell CdSe/ZnS nanoparticles from air-stable precursors

We report the synthesis of high quality ZnS nanoparticles using sulfur and zinc acetate as the S and Zn source, respectively. It was found that sulfur and zinc acetate could be easily dissolved in the mixture of trioctylphosphine oxide (TOPO) and hexadecylamine (HDA) at a temperature of about 65°C and ZnS nanoparticles were generated at temperatures above 150°C. These reactive species of sulfur and zinc were also used for an epitaxial growth of ZnS shell around a CdSe core. The formation of ZnS nanoparticles was confirmed by powder X-ray diffraction (XRD). Particle size and size distribution were studied by transmission electron microscopy (TEM). Optical properties were characterized by a combination of UV-vis and photoluminescence (PL) spectroscopy. The PL quantum yield of the CdSe/ZnS nanoparticles reached about 66% compared with the dye, Rhodamine 6G (R6G). The present synthetic strategy is a "greener" and simpler synthetic scheme due to the use of air-stable and environmentally benign reagents of sulfur and zinc acetate instead of air-sensitive ones such as dimethylzinc and bis(trimethylsilyl) sulfide.