Preparation of AgInS2 quantum dots and their application for Pb2+ detection based on fluorescence quenching effect

Water soluble AgInS2 quantum dots (AIS QDs) were successfully prepared by an environmentally friendly onepot water phase method using glutathione (GSH) as the stabilizing agent. The crystal structure, morphology, size, chemical states, and optical properties of as-prepared AIS QDs were characterized through X-ray diffraction (XRD), Scanning transmission electron microscopy (STEM), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectrometer (FTIR), Ultraviolet-visible spectrophotometer (UV-vis) and Photoluminescence spectrometer (PL). Factors affecting the fluorescence intensity of AIS QDs including reaction solution pH value, fluorescence test temperature and concentration of AIS QDs were investigated. The fluorescence stability of AIS QDs and the selectivity of AIS QDs toward Pb2+ detection was also evaluated. Under optimized test conditions, three excellent linear relationships ((F-0-F)/F-0 = 27.938C(Pb2+) 0.002 (R = 0.998), (F-0-F)/F-0 = 10.362C(Pb2+) 0.005 (R = 0.997), (F-0 F)/F-0 = (6).554CPb(2+) 0.240 (R = 0.9993) were achieved between the concentration of Pb2+ and the relative fluorescence quenching amount of AIS QDs in the range of 9-96 nM, 48-434 nM and 193-530 nM, respectively. The detection limit was 4 nM and the recovery was in the range of 92.2%-102.6%. Our method had wide detection range, excellent selectivity, high sensitivity and easy operability, and could be applied for the content determination of Pb2+ in water. The possible fluorescence quenching mechanism of AIS QDs by Pb2+ was discussed in detail and the dynamic quenching mechanism of light-induced electron transfer was put forward.