A facile route to aqueous Ag:ZnCdS and Ag:ZnCdSeS quantum dots: Pure emission color tunable over entire visible spectrum

Aqueous Ag:ZnCdS quantum dots (QDs) with pure, color-tunable fluorescence were prepared based on co-nucleation doping strategy by using a highly reactive S powder precursor, which was reduced by NaBH4 at high temperature of 180 °C in a closed hydrothermal autoclave. For a meaningful comparison, thiourea as a relatively low reactive precursor was employed to test the advantages of this highly reactive S powder precursor in synthetic chemistry. The influences of various experimental variables, including the Zn/Cd ratio and Ag-doping concentration, on the optical properties of Ag:ZnCdS QDs were systematically investigated. The color-tunable quarternary Ag:ZnCdSeS QDs were also successfully prepared via the variation of Se/S precursor ratio based on the similar reactivity of the Se and S powder precursors. Further, the highly efficient Ag:ZnCdS/ZnS and Ag:ZnCdSeS/ZnS core/shell QDs were constructed by the deposition of the ZnS shell around the crude Ag:ZnCdS and Ag:ZnCdSeS core QDs. The results indicated that this facile synthetic route would provide a versatile approach for preparation of other aqueous multinary metal chalcogenide QDs.