▎ 摘　　要

Cystenine-functionalized graphene quantum dots (cys-GQDs) were synthesized by a simple and facile method, which involves chemical bond formation between L-cysteine and the graphene quantum dots (GQDs) prepared by the carbonization of citric acid. The obtained cys-GQDs show a strong green fluorescence and a uniform lateral size distribution with high crystallinity. The cys-GQDs are further demonstrated as highly sensitive and selective fluorescence probes for Hg2+. In the Hg2+ detection process, the cys-GQDs shows significant fluorescence quenching through a charge transfer process within the cys-GQDs and Hg2+ complex.