▎ 摘　　要

A facile and environmentally friendly strategy to prepare nitrogen-doped graphene quantum dots (NGQDs) with a high quantum yield of 28.10% was reported. The obtained N-GQDs exhibited strong blue fluorescence emission with the maximum emission and excitation at 450 nm and 355 nm, respectively. Taking advantage of the effective quenching effect of Hg2+ on N-GQDs, such N-GQDs were developed for the efficient and sensitive detection of Hg2+ with a relatively low detection limit of 0.032 mu M. Based on the selective coordination of biothiols and Hg2+, the fluorescence of the N-GQD/Hg system was recovered with the addition of biothiols. This fluorescent "Off-On" process showed a sensitive response to biothiols with a detection limit of 0.036 mu M for cysteine and 0.034 mu M for glutathione. Most importantly, the N-GQD-based fluorescence method was successfully used to monitor Hg2+ in real water samples and biothiols in serum samples.