Synthesis, structural and fluorescence optimization of ternary Cu–In–S quantum dots passivated with ZnS

Ternary I-III-VI quantum dots (QDs) have become attractive fluorescent materials due to their low toxicity compared to conventional binary II-VI based QDs. However, these QDs have been majorly synthesized in an organic medium under harsh conditions which is not eco-friendly. Herein, we report aqueous synthesis of glutathione (GSH) capped Cu–In–S based QDs using reflux approach at 95 °C and investigated the effect of synthetic parameters such as Cu:In precursor ratio, pH and the amount of GSH on the core QDs. The as-synthesized material was characterized using Ultraviolet–Visible (UV–vis) absorption, Photoluminescence (PL), Fourier Transform Infrared spectroscopy (FT-IR), X-ray diffraction (XRD) and transmission electron microscopy (TEM) techniques. Passivation of the core QDs with ZnS increased its photoluminescence with a blue shifted absorption and emission wavelength. Structural investigation of the QDs by using TEM, XRD and EDS techniques indicated the possible formation of Cu–In–Zn–S/ZnS “alloy-core/shell” structure due to the diffusion of Zn from ZnS shell into Cu–In–S crystal lattice and its occupation at vacant sites.