Green synthesis of highly luminescent ZnS:Mn²⁺quantum dots

Wurtzite-type ZnS:Mn²⁺quantum dots (QDs) were successfully prepared by a simple hydrothermal method at 180 °C without any surface-active agent. The XRD and EDAX results showed that Mn²⁺ ions were incorporated into ZnS lattice. The average size of ZnS:Mn²⁺QDs was about 5.43 nm. The maximum concentration of Mn²⁺ions in ZnS QDs was 3.81 %. The yellow-orange emission coming from the ⁴T1–⁶A₁ transition of Mn²⁺ ions was observed in photoluminescence spectra, the peak intensity increased as the Mn²⁺ doped ratio increased, and showed a maximum when the concentration of Mn²⁺ ions kept at 3 %.