▎ 摘　　要

Detection of metal ions in living cells is significant in environmental monitoring and health risk assessment. This paper reports a simple and facile method for the detection of Hg2+ ions in Hela cells through fluorescence imaging, which was based on the fluorescence quenching in thymine-rich DNA modified graphene quantum dots (DNA-GQDs) in the presence of Hg2+. The decrease in the fluorescence intensity was attributed to the electron transfer of DNA-GQDs due to Hg2+ bound to the thymine bases of the DNA, resulting in a T-T mismatch hairpin structure. The method shows high selectivity and sensitivity. This present sensing platform will have broad applications in biological imaging and environmental monitoring.