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 Ag2S quantum dots (QDs) are excellent fluorescent nanoprobes for bioassays with low toxicity. A novel fluorescent sensing platform which employing NIR fluorescent Ag2S QDs and MnO2 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 Ag2S QDs with the emission of 845 nm. Then the NIR fluorescent nanoprobe of Ag2S QDs-MnO2 nanosheets is obtained by adsorbing Ag2S QDs onto the surface of MnO2 nanosheets which have atomically thick two-dimensional structure and high specific surface area. And the NIR fluorescence of Ag2S QDs is quenched by the MnO2 nanosheets. The presence of GSH could reduce MnO2 to Mn2+ that results in the restoration of NIR fluorescence for Ag2S 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 Ag2S 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.