Facile one-step photochemical synthesis of water soluble CdTe(S) nanocrystals with high quantum yields

Abstract

This paper describes a successful synthesis of water soluble CdTe(S) nanocrystals (NCs) with high quantum yields (QYs) via a mild photochemical route in one step with thioglycolic acid as the stabilizer and sulfur source. The precursor solution of mixed cadmium chloride, freshly prepared sodium hydrogen telluride and thioglycolic acid was subjected directly to UV irradiation using a 500 W high-pressure mercury lamp under the protection of N₂. NCs with a small particle size (2.2 nm) and a high photoluminescence quantum yield (up to 80% at room temperature) were formed within 25 min. The NCs were characterized by UV-vis absorption and fluorescence spectroscopy, transmission electron microscopy, powder X-ray diffraction and energy-dispersive X-ray spectroscopy to evaluate their structure, size and composition. The photochemically prepared NCs were compared with CdTe NCs prepared by conventional hydrothermal synthesis and CdTe/CdS core/shell NCs obtained by post-preparative photochemical passivation. The effects of UV irradiation intensity, illumination time, temperature and concentration of Te²⁻ on the optical properties of NCs were studied in detail.