An enzyme-free fluorescent probe based on carbon dots – MnO2 nanosheets for determination of uric acid

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 uric acid. MnO2 nanosheets have several interesting physicochemical properties such as high extinction coefficient and rich redox chemistry, which make them an excellent sensing platform. The fluorescence of S,N-CDs efficiently turns off in the presence of MnO2 nanosheets due to the inner filter effect as well as other quenching mechanisms. By adding uric acid 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 uric acid in the range of 2.5–30 μM with a detection limit of 0.8 μM. The method was applied for analysis of biological samples with satisfactory results.