A "switch-on" fluorescence assay based on silicon quantum dots for determination of ascorbic acid

Water dispersible silicon quantum dots (SiQDs) showing blue fluorescence were synthesized with 3-aminopropyltriethoxysilane (APTES) as silicon source. Based on the synthesized SiQDs as the photoluminescence unit, MnO₂ nanosheets (NS) as the quencher, a "switch-on" fluorescence assay for the determination of ascorbic acid (AA) was designed. The fluorescence of SiQDs can be effectively quenched by MnO₂ NS because of the internal filtration effect. In the presence of AA, MnO₂ is reduced to Mn²⁺, so that the fluorescence of SiQDs is partially recovered. The recovered fluorescence intensity was related to the concentration of AA. Under the optimal experimental conditions, the linear response range of the assay to AA is 1-80 µM, and the detection limit is 0.48 µM. The method for the determination of AA has the advantages of simple, low cost, good selectivity and sensitivity. The assay has been successfully applied to the quantification of AA in beverage (mizone) samples, which proves the practicability of the assay.