Ratiometric fluorescent probe for ascorbic acid detection based on MnO2 nanosheets, gold nanoclusters and thiamine

In this work, an ascorbic acid (AA) sensing platform by employing MnO2 nanosheets and gold nanocluster (AuNCs) as a ratiometric fluorescent probe has been reported. AuNCs serves as a fluorescence reporter and MnO2 nanosheets play three roles, such as fluorescence quencher, AA recognition unit and artificial enzyme in this sensing system. The fluorescence of AuNCs could efficiently be quenched by MnO2 nanosheets through fluorescence resonance energy transfer (FRET), and MnO2 nanosheets would oxidize non-fluorescent thiamine (vitamin B1, VB1) to blue fluorescent thiochrome (oxVB1) at the same time. However, the introduction of AA could lead to the etching of MnO2 nanosheets and the recovery of the fluorescence of AuNCs. Based on this phenomenon and the redox reaction between MnO2 nanosheets and AA, we have developed a sensitive ratiometric fluorescent method for AA detection. The proposed ratiometric fluorescent probe exhibited a good linearity range of 1.5–100.0 μmol L−1 and a low limit of detection (LOD) of 0.45 μmol L−1.