Low-temperature solid-state synthesis and optical properties of CdS–ZnS and ZnS–CdS alloy nanoparticles

A simple low-temperature solid-state synthetic method was employed to obtain ZnS–CdS and CdS–ZnS alloy nanoparticles. The effects of reaction sequence, reactant molar ratios, and synthesis temperature on the products were investigated. The crystal structure and morphology of the products were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), and fourier transform infrared (FT-IR) spectroscopy. The results show that the products are alloy nanoparticles with a cubic phase structure. The formation mechanism of the alloy nanoparticles is briefly discussed. Sufficient grinding and crystalline water may be essential to form alloy nanoparticles. Ultraviolet–visible (UV–vis) spectra show that the edge absorptions of the CdS–ZnS and ZnS–CdS nanoparticles were located between those of ZnS and CdS bulks, and the absorbance at the peak maximum was practically dependent on reaction temperature, reaction sequence, and molar ratio. Extrinsic deep-level emission resulted in strong peaks in the photoluminescence (PL) spectra. The position and intensity of the emission peaks varied with the conditions during synthesis.

► Using a simple low-temperature solid-state synthetic method, ZnS–CdS and CdS–ZnS alloy nanoparticles were obtained, respectively.
► The size of the nanoparticles increased with increasing reaction temperature, and reaction sequence had no effect on the size of the nanoparticles under the same temperature.
► The particle diameters of the CdS–ZnS products decreased gradually with increasing Cd2+/Zn2+ molar ratio, whereas those of the ZnS–CdS products increased gradually with increasing Zn2+/Cd2+ molar ratio.
► The study shows that sufficient grinding and crystalline water may be a key in forming the alloy nanoparticles.
► Optical properties of the products depend on reaction temperature, reactant addition sequence, and reactant molar ratio.