A near−infrared fluorescent sensor based on the architecture of low−toxic Ag2S quantum dot and MnO2 nanosheet for sensing glutathione in human serum sample

Near−infrared (NIR) emitting Ag 2 S quantum dots (QDs) are excellent fluorescent nanoprobes for bioassays with low toxicity. A novel fluorescent sensing platform which employing NIR fluorescent Ag 2 S QDs and MnO 2 2D nanosheets as NIR emitters and quenchers is designed for rapid and selective determination of glutathione (GSH). A facile and efficient approach was demonstrated for the synthesis of NIR fluorescent Ag 2 S QDs with the emission of 845 nm. Then the NIR fluorescent nanoprobe of Ag 2 S QDs−MnO 2 nanosheets is obtained by adsorbing Ag 2 S QDs onto the surface of MnO 2 nanosheets which have atomically thick two−dimensional structure and high specific surface area. And the NIR fluorescence of Ag 2 S QDs is quenched by the MnO 2 nanosheets. The presence of GSH could reduce MnO 2 to Mn 2+ that results in the restoration of NIR fluorescence for Ag 2 S QDs. The NIR fluorescent nanoprobe could be used for highly selective detection of GSH. Also a low detection limit of 60 μmol/L was obtained. Because NIR fluorescence of the Ag 2 S QDs can efficiently reduce the interferences from background scattering and autofluorescence. The NIR fluorescent nanoprobe was directly applied to monitor the GSH level in human serum sample with high accuracy and precision.