Fluorescent nanoswitch based on redox-controlled reversible sulfhydryl functionalized carbon dots for highly sensitive detection of ochratoxin A

In this work, sulfhydryl functionalized carbon dots (SH-CDs) were synthesized for the first time by a two-step hydrothermal method. The sulfhydryl group in SH-CDs can be converted efficiently and reversibly in a few minutes under redox conditions. On this basis, ochratoxin A (OTA) induced hybrid chain reaction amplification and alkaline phosphatase enzymatic hydrolysis to produce ascorbic acid (AA). AA reduced the aggregated SH-CDs, thereby realizing the dual-mode rapid quantitative analysis of the OTA concentration by measuring the changes in the fluorescence intensity and absorbance of the SH-CDs solution. The proposed sensor has a good linear relationship with the OTA concentration in the range of 2.0–5.0 nM, and the lowest detection limit is 2.0 nM. Additionally, the visual color change of the solution can improve the simplicity and accuracy of semi-quantitative detection of OTA with the naked eye. In short, this method has the advantages of rapidity, sensitivity, reversibility and visualization.