A fluorescent probe based on N-doped carbon dots for highly sensitive detection of Hg2+ in aqueous solutions

A facile and green hydrothermal method was developed for the preparation of highly luminescent nitrogen-doped carbon dots (NCDs) by using anhydrous citric acid and urea as the carbon source and nitrogen source, respectively. The NCDs show good water-solubility and exhibit excitation-independent fluorescence behaviors at excitations of 300-390 nm with a quantum yield of 42.5% at a lambda(em) of 440 nm. Based on the fluorescence quenching strategy, the NCDs were successfully applied to the measurement of Hg2+ in tap and lake water samples with high sensitivity and excellent selectivity. The detection limit was 7.3 nmol L-1 (3 sigma, n = 9), indicating its potential applications for the detection of trace Hg2+ in water samples.