Strong NIR luminescent Ag2S@ZnS core-shells synthesized by a novel one pot pulsed microwave irradiation

Synthesis of Ag2S quantum dots (QDs) in water with increasing both Near Infrared (NIR) emission and nontoxicity of Ag2S quantum dots (QDs) have been a great challenge in nano-biotechnology. To reconcile these issues synthesis of Ag2S@ZnS in water with high quantum yield has been a great challenge. In this report, we have synthesized high quality and ultrafine Ag2S@ZnS core-shells in water with a fast and facile microwave irradiation technique. Thioglycolic acid (TGA) was employed as capping agent for the synthesis of Ag2S@ZnS in water for the first time. The prepared core-shells were optimized based on different experimental parameters and verified using UV-vis and PL spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy and transmission electron microscopy. It was found that the core-shells show a strong absorption at 805 nm and emission located at 857 nm with a narrow width of 60 nm. The quantum yield of prepared core-shells was found to be 5.3% which is the highest value reported yet.