Facile synthesis of ZnS–CdIn2S4-alloyed nanocrystals with tunable band gap and its photocatalytic activity

High-quality colloidal ZnS–CdIn2S4 (ZCIS) quaternary alloyed nanocrystals (NCs) have been synthesized via the reaction between acetate salts of the corresponding metals and elemental sulfur in the presence of dodecanethiol in octadecene media at 230 °C. The photoluminescence (PL) emission wavelength can be conveniently tuned from 498 to 635 nm via the variation of stoichiometric ratio of corresponding components. The influence of various experimental variables, such as reaction temperature, amounts of sulfur and dodecanethiol, and Zn:CdIn2 ratio, on the optical properties of the obtained ZCIS NCs have been systematically investigated. The plain ZCIS core NCs did show PL but with quite low quantum yield (QY, typically below 5%). In order to improve the PL QY, ZnS shell was subsequently overcoated around the ZCIS core NCs. With the overgrowth of ZnS shell, the PL QY can be up to 48%. Furthermore, the obtained ZCIS/ZnS NCs show a promising photocatalytic activity in the degradation of rhodamine B.