In situ formation of absorbance agents for ascorbic acid detection using SnO2/carbon dots nanozyme with a wide detection range

The strong reducing ability of ascorbic acid (AA) usually resulted in a limited linear detection range. To address the defect, a colorimetric sensor was constructed using an in-situ generated absorbance indicator. The SnO 2 /carbon dots (Sn-CDs) displayed high peroxidase-like (POD) activity, which could oxidize o-phenylenediamine (oPD) to ox-oPD (450 nm), and the absorbance at 450 nm decreased as the concentration of AA increased. The dehydroascorbic acid (DHA) formed by the oxidation of AA further reacted with oPD to produce 3-(1,2-dihydroxyethyl) furo [3,4- b ] quinoxalin-1(3 H )-one (DFQ, at 336 nm absorbance). And the absorbance at 336 nm increased as the concentration of AA increased. Based on the two signals, the DFQ signal offered two broader detection ranges (5.62–131.03 μM and 2.84–28.39 mM) and a lower limit of detection (0.88 μM) than the ox-oPD signal (16.54–51.62 μM, 6.88 μM). And the colorimetric sensor based on 336 nm DFQ signal exhibited a higher anti-interfering ability in complex environments. In the practical samples (Vitamin C tablets, orange, and lemon), the concentrations of AA detected by colorimetric sensor was close to that detected by high-performance liquid chromatography, which indicated that constructed sensor exhibited superior precision and practicality. The study not only presented a valuable tool for the detection of AA, but also offered a novel strategy for highly selective colorimetric sensors.