One-step fabrication of high quantum yield sulfur- and nitrogen-doped carbon dots for sensitive and selective detection of Cr(VI)

In this work, we have developed a green, simple, and low-cost hydrothermal method using wool and pig hair as the precursor to fabricate sulfur- and nitrogen-doped carbon dots (CDs). The precursors are natural and nontoxic raw materials, and the one-step strategy requires no organic solvents. The as-prepared carbon dots exhibit good water dispersibility, strong fluorescence emission with a relatively high quantum yield of 25.6% (contributed by the doped N and S elements), excellent pH stabilities and high ionic strength tolerance. More importantly, the fluorescence intensity of the CDs could be significantly and selectively quenched in the presence of Cr(VI) due to the oxidation-reduction reaction between Cr(VI) and the oxygen-containing groups and S-related species on the surface of CDs. Accordingly, the CDs are employed as a fluorescent probe for the detection of Cr(VI) ions in water. This CDs sensor exhibits high sensitivity to Cr(VI) with a limit of detection of 16.8 nM in a wide range of 50 nM to 100 mM. Furthermore, the sensor is successfully applied in the detection of Cr(VI) in real water samples.