A fluorescent probe based on S,N- carbon dots – MnO2 nanosheets for determination of quercetin

Ultrathin two dimensional MnO2 nanosheets have several interesting physicochemical properties such as high extinction coefficient, rich redox chemistry, high colloidal stability and good biocompatibility which make them an excellent quencher in fluorescence sensing platform [1,2]. In this study, a turn-on fluorescent probe based on the effect of MnO2 nanosheets on the fluorescence of sulfur and nitrogen co-doped carbon dots (S,N-CDs) is reported for detection of quercetin. The fluorescence of S,N-CDs, a novel classes of highly luminescent nanomaterials, efficiently turns off in the presence of MnO2 nanosheets due to the formation of carbon dots–MnO2 nanocomposite. By adding quercetin to the solution of S,N-CDs–MnO2 nanosheets, the fluorescence of S,N-CDs is partially recovered as a result of its reaction with MnO2 nanosheets. Under the optimum conditions, the recovered fluorescence intensity displays a linear relationship with the concentration of quercetin in the range of 2.5–30 µM with a detection limit of 0.7 µM. The method was applied for analysis of water samples with satisfactory results.