A switchable sensor based on N and S co-doped carbon dots (N,S-CDs) was developed to determine ascorbic acid (AA) content in common fruits via fluorescence quenching of N,S-CDs by Fe³⁺ (off) and recovery by AA (on). TEM showed that the particle size was 2.35–7.95 nm with an average diameter of 5.12 nm. XPS and FTIR confirmed the presence of –OH, –COOH and –NH₂ on N,S-CDs surface. UV–vis and FTIR revealed that the coordination of –COOH and –NH₂ on N,S-CDs surface with Fe³⁺ accounted for FL quenching, and the release of –NH₂ from coordination complexes due to the reduction of Fe³⁺ by AA led to partly FL recovery. The sensor allowed detecting AA in the linear range of 10–200 μmol/L with a LOD of 4.69 μmol/L. AA contents in common fruits detected by the sensor were in good agreement with the reference method (P > 0.05), indicating a practical fluorescent sensor for AA detection in common fruits.

开发了一种基于N和S共掺杂碳点（N，S-CDs）的可转换传感器，以通过Fe ³⁺（off）和N（S）的荧光猝灭N，S-CDs来测定普通水果中的抗坏血酸（AA）含量。通过AA恢复（上）。TEM显示，粒径为2.35–7.95 nm，平均直径为5.12 nm。XPS和FTIR证实N，S-CDs表面存在–OH，–COOH和–NH ₂。UV-vis和FTIR结果表明，N，S-CDs表面的–COOH和–NH ₂与Fe ^3+的配位是FL猝灭的原因，并且由于Fe ³⁺的还原，从配位化合物中释放出–NH ₂。AA导致部分FL恢复。传感器允许检测线性范围为10–200μmol/ L的AA，LOD为4.69μmol/ L。传感器检测到的普通水果中AA的含量与参考方法相吻合（P> 0.05），说明一种实用的荧光传感器可用于普通水果中AA的检测。