Selective detection of parathion-methyl based on near-infrared CuInS2 quantum dots

A novel and sensitive fluorescence probe based on near-infrared CuInS2 quantum dots (QDs) for parathion-methyl (PM) detection was developed. Water-soluble CuInS2 QDs were directly synthesised in aqueous solution with mercaptopropionic acid as stabilizers. The fluorescence intensity of CuInS2 QDs was quenched in the presence of Pb2+ due to the competitive binding of Pb2+ and mercaptopropionic acid with QDs. PM could be hydrolysed by organophosphorus hydrolase to form di-methylthiophosphoricacid. Subsequently, di-methylthiophosphoricacid moiety with a PS bond could capture Pb2+ on the surface of the CuInS2 QDs, which would lead the fluorescence of the CuInS2 QDs-Pb2+ system recovery. The fluorescence intensity of the CuInS2 QD-Pb2+ system was proportional to the PM concentration in the range of 0.10–38.00 μmol/L, with a detection limit of 0.06 μmol/L. The proposed method had been used for PM detection in environmental and agricultural samples with satisfactory results.