摘要： The nitrogen-sulfur co-doped fluorescent carbon quantum dots (N/S-CQDs) were synthesized from sulfanilic acid. The fluorescence emission was independent of the excitation wavelength. In this experiment, the carbonization degree of the precursors was adjusted by solvent-thermal method to affect the sp2 conjugated dimension of CQDs, thus affecting the fluorescence performance of CQDs. They are well dispersed in water and ethanol, and have high selectivity for Fe3 +. The detection range is 0.025 ～ 0.4 mmol/L, and the detection limit is about 2.549 μmol/L. The CQDs prepared in this experiment emit light indirectly through the surface defect state. When CQDs is illuminated by light, the carriers generated by photons will emit light at a very fast speed due to the surface defect state, so the excited electrons in CQDs can be easily transferred to Fe3 +, making the surface of CQDs more complete, thus leading to the quenching of CQDs fluorescence.