An Off-Off fluorescence sensor based on ZnS quantum dots for detection of glutathione

Quantum dots (QDs) are excellent fluorescent indicators for chemical and biological analysis. In this paper, an Off-Off fluorescence sensor based on ZnS quantum dots was designed. It was found that Co2+ can quench the fluorescence of ZnS QDs, moreover glutathione (GSH) can further quench the fluorescence. Therefore, this method can be used for indirect detection of GSH. However, if change Co2+ into other metal ions, the system cannot be used to detect GSH indirectly. For direct detection GSH, that is adding GSH without Co2+, the fluorescence intensity changes little, while only amino acid or monosaccharide has no effect. When indirect detection of GSH based on this Off-Off fluorescent probe, the fluorescence quenching was linearly related to the concentration range of 1–300 μM GSH, and the detection limit could reach 0.48 μM, which can rival most Off-On and On-Off fluorescent probe. The relative standard deviation for parallel measurement of 300 μmol·L-1 GSH solution (for n = 10) was 1.43 %.