Highly symmetrical CdS tetrahedral nanocrystals prepared by low-temperature chemical vapor deposition using polysulfide as the sulfur source

In this paper, we report a new scheme for chemical vapor deposition (CVD) of CdS nanocrystals, in which polysulfide and cadmium chloride were used as the sulfur and cadmium source, respectively. During the reaction, hydrogen sulfide was generated by controlled hydrolysis of polysulfide and reacted with cadmium chloride to give CdS. Tetrahedral CdS nanocrystals with homogeneous size and nearly perfect T-d point group symmetry were obtained in high yield. The source and deposition temperature were only 540 and 400 degrees C, respectively, which were significantly lower than those in conventional CVD methods. The low deposition temperature was found critical for the formation of the tetrahedral nanostructures. The photoluminescence spectra of the tetrahedral nanocrystals consisted of a sharp band edge emission peak and a broad band related to trapped states.