Stabilizing NIR emission of Ag2S quantum dots in water using SnS2 Shell

In this study Ag2S@SnS2 core-shells were synthesized successfully for the first time. Pulsing microwave irradiation was quite an effective technique for the controlled growth of core-shells using a one pot technique. Different parameters were optimized in the synthesis of core-shells and they were verified structurally using X-ray diffraction (XRD), Energy dispersive x-ray spectroscopy (EDX), Transmission electron microscopy (TEM) and Fourier Transform Infrared Spectroscopy (FTIR). Ultraviolet-Visible spectroscopy (UV-Vis) revealed a strong absorption at 805 nm. Photoluminescence spectroscopy (PL) showed that the samples had a considerable emission around 870 nm and it was stable for at least 30 days in water. EDX analysis confirmed the presence of Sn, Ag and S atoms in the samples and their atomic ratio was quite close to their nominal chemical values. XRD analysis showed the formation of Ag2S monoclinic and SnS2 hexagonal phases. TEM images showed clearly formation of core-shells with sizes below 10 nm. FTIR spectroscopy revealed that thioglycolic acid (TGA) is an effective and stable capping agent for the synthesis of Ag2S@SnS2 core-shells using this pulsing technique.