A highly selective and sensitive “on-off-on” fluorescent probe for detecting Hg(II) based on Au/N-doped carbon quantum dots

Herein, a one-step hydrothermal tactics is developed for the preparing gold and nitrogen co-doped carbon quantum dots by using folic acid, glycerol and chloroauric acid as raw materials. The as-prepared Au/N-CQDs with the average size of 4.01 ± 1 nm had both crystalline and amorphous carbon. Au/N-GQDs exhibited the excitation-dependent fluorescence behavior with the maximum excitation and emission at 355 and 450 nm, respectively. Furthermore, Au/N-GQDs were an excellent fluorescent probe for the detection of Hg(II) based on the fluorescence quenching effect, Au/N-CQDs showed high sensitivity for detecting of Hg(II) with a detection limit of 0.118 μM and the linear relationship ranged from 0 to 41.86 μM. The results of the selectivity experiments illustrated that the fluorescent probe was particular for Hg(II) and it was not interfered by high concentrations other metal cations and anions. When EDTA-2Na or I− was added, the fluorescence intensity of Au/N-GQDs containing Hg(II) turned on and increased to 90% of the blank sample. More importantly, the fluorescent probe based on Au/N-CQDs was successfully applied to the detection of Hg(II) in real sample. This work not only provides a novel method for the synthesis of Au/N-CQDs, but also provides a promising sensing platform for monitoring of Hg(II) in the environmental application.