Zn/Cd ratio-dependent synthetic conditions in ternary ZnCdS quantum dots

Highlights: • The optimal reaction conditions for different ZnCdS QDs were different. • The water-soluble ZnCdS QDs were synthesized by aqueous synthesis method. • The band gap engineering was accomplished readily via tuning the Zn/Cd molar ratios. • The as-prepared ternary ZnCdS QDs had high photostability. • The as-prepared alloyed QDs showed potential biological applications. In our study, the synthesis conditions of ternary alloyed ZnCdS quantum dots (QDs) with different Zn/Cd molar ratios were investigated. Our results indicated that the optimal reaction conditions of ZnCdS QDs with various molar ratios were different. The ternary ZnCdS QDs were synthesized by a rather simple, facile, low-cost and effective aqueous synthesis method using air-stable compounds. UV–visible (UV–Vis) absorbance and photoluminescence (PL) emission spectra of the ZnCdS QDs showed a blue shift with the decrease of Cd, indicating the formation of alloyed QDs. The optimal reaction conditions, such as refluxing time and S/(Zn+Cd) molar ratios were different for ZnCdS QDs with different Zn/Cd ratios. The cause of the difference was attributed to the different properties of metal ions. In addition, the investigation on the photostability showed that the as-prepared ternary alloyed QDs had strong light resistance. Therefore, the ternary alloyed QDs with outstanding optical properties and high photostability showed potential biological applications and the results also offered new insights for the synthesis of ZnCdS QDs.