MnO2 nanosheet-assisted ratiometric fluorescent sensor for ascorbic acid based on Pyronin Y and thiamine

• A facile MnO 2 nanosheet-assisted ratiometric fluorescent sensor for sensitive and selective detection of ascorbic acid was developed. • MnO 2 nanosheet could not only greatly quench the fluorescence of Pyronin Y by inner filter effect，but also oxidize non-fluorescent VB 1 to blue fluorescent oxVB 1 by oxidase-mimicking activity simultaneously. • This method displayed a good assay performance in orange juice and human serum. Ascorbic acid (AA) which can be supplemented by exogenous sources such as food and beverage, plays an important role in human health. Abnormal level of AA in human body usually leads to various diseases. A facile MnO 2 nanosheet-assisted ratiometric fluorescent sensor for AA was constructed in this work. MnO 2 nanosheet (MnO 2 NS) could not only greatly quench the fluorescence of Pyronin Y (PY) by inner filter effect (IFE) but also oxidize non-fluorescent thiamine (vitamin B 1 , VB 1 ) to blue fluorescent thiochrome (oxVB 1 ) by taking advantage of the oxidase-mimicking activity simultaneously. However, MnO 2 NS could be reduced to Mn 2+ in the presence of AA, inhibiting the IFE and oxidase-mimicking activity. According to this principle, the fluorescence intensity of oxVB 1 decreasing at 440 nm and the fluorescence of PY recovering at 560 nm. Under optimal conditions, the MnO 2 NS-PY-VB 1 system showed a wide linear range towards AA in the range of 0.25–110 µM with a low detection limit reaching 0.1 µM. Furthermore, it was also applied for sensitive detection of AA in orange juice and human serum.