One-pot synthesis of N, S co-doped photoluminescent carbon quantum dots for Hg²⁺ ion detection

N and S co-doped carbon quantum dots (N, S-CQDs) with a high fluorescence quantum yield (12.6%) were synthesized by a one-pot hydrothermal method. Results indicate that the N, S-CQDs have a small particle size and an amorphous structure, exhibiting unique surface states and excitation wavelength-independent fluorescent properties. Co-doping of N and S increases the electron-transfer rate and improves the coordination interaction between the N, S-CQDs and Hg²⁺ ions. The N, S-CQDs show a high sensitivity and selectivity in detecting Hg²⁺ ions even for a lake water sample. They are promising fluorescence probes for environmental monitoring.