Bifunctional Nitrogen and Fluorine Co-Doped Carbon Dots for Selective Detection of Copper and Sulfide Ions in Real Water Samples

Copper ions (Cu(2+)) and sulfur ions (S(2−)) are important elements widely used in industry. However, these ions have the risk of polluting the water environment. Therefore, rapid and quantitative detection methods for Cu(2+) and S(2−) are urgently required. Using 2,4-difluorobenzoic acid and L-lysine as precursors, nitrogen and fluorine co-doped dots (N, F-CDs) were synthesized in this study via a hydrothermal method. The aqueous N, F-CDs showed excellent stability, exhibited satisfactory selectivity and excellent anti-interference ability for Cu(2+) detection. The N, F-CDs, based on the redox reactions for selective and quantitative detection of Cu(2+), showed a wide linear range (0–200 μM) with a detection limit (215 nM). By forming the N, F-CDs@Cu(2+) sensing platform and based on the high affinity of S(2−) to Cu(2+), the N, F-CDs@Cu(2+) can specifically detect S(2−) over a linear range of 0–200 μM with a detection limit of 347 nM. In addition, these fluorescent probes achieved good results when used for Cu(2+) and S(2−) detection in environmental water samples, implying the good potential for applications.