Synthesis of novel Zn-In-S/ZnS core/shell quantum dots: Temporal evolution and functionalization

Ternary quantum dots (QDs) have been developed as a safer alternative to conventional cadmium containing binary QDs due to their low toxicity. However, the reports on ternary QDs are majorly based on I–III–VI QDs such as CuInS and AgInS QDs. II–III–VI​ QDs such as ZnInS (ZIS) QDs have been given less attention due to their inherent lamellar structure that causes synthetic difficulties in obtaining the zero-dimensional (0D)structure. In this work, we, report an aqueous synthesis of thioglycolic acid and gelatin capped novel ZIS/ZnS core/shell QDs. The results revealed that the as-synthesized ZIS/ZnS QDs were well dispersed with an average particle size of 7.0 ± 2.0 nm and emitting in the green region. The synthetic condition for the ZnS shell was optimized by changing the concentration of the shell precursors which resulted in improved photoluminescence quantum yield (PLQY). Contrary to the blue-shifted emission usually experienced during the shell growth in I–III–VI ternary QDs, ZIS/ZnS displayed slight red shift compared to core ZIS QDs in the optical spectra. In addition, functionalization of the ZIS/ZnS QDs with amino acids (L-arginine and L-cysteine) enhanced the luminescence and offers new possibilities for its use in diverse applications.