N, P Co-Doped Carbon Dots as Multifunctional Fluorescence Nano-Sensor for Sensitive and Selective Detection of Cr(VI) and Ascorbic Acid

It is particularly important to monitor Cr(VI) for its high toxicity. In this paper, a novel, simple, low-cost and “on-off-on” fluorescence sensor of carbon dots doped with nitrogen and phosphorus (N, P-CDs) was developed via one-step hydrothermal method for highly sensitive and good selective detection of Cr(VI) and ascorbic acid (AA). The prepared N, P-CDs exhibited the ability for detection of Cr(VI) based on the inner filter effect (IFE) and static quenching. Under optimized conditions, the fluorescence quenching efficiency of N, P-CDs showed a good linear correlation with Cr(VI) concentration ranged from 0.68 to 87.38 μmol/L (R2 = 0.9946). The limit of detection (LOD) was 0.18 μmol/L, which was acceptable compared with the maximum Cr(VI) concentration of 0.96 μmol/L in drinking water prescribed by WHO. In addition, the N, P-CDs/Cr(VI) hybrid were also used as “turn–on” fluorescent transducers for detecting AA with a wide linear region ranged from 0.02 to 933.33 μmol/L (R2 = 0.9972). Furthermore, the N, P-CDs fluorescence sensor had admissible applicability for Cr(VI) and AA detection in actual water samples with acceptable recovery rate, indicating that the fluorescence sensor had great application potential in environmental monitoring and food field.