Graphene oxide-assisted synthesis of N, S Co-doped carbon quantum dots for fluorescence detection of multiple heavy metal ions

Detection of heavy metal ions (HMIs) in water is an important topic in the field of analytical chemistry and environmental science. Fluorescence spectroscopy is one of the most promising strategies due to its simple instrument, low investment, rapid and convenient operation. However, current fluorescence probes for detecting HMIs are typically selective for certain ions. Herein we reported the development of a novel strategy that determined the total content of HMIs in water by fluorescence spectroscopy. A novel fluorescent nitrogen, sulfur co-doped carbon quantum dots (N, S-CQDs) was prepared via graphene oxide-assisted synthesis method. The results showed that, with the fluorescence quenching strategy, N, S-CQDs exhibited a wide linear response to a series of water-soluble metal ions. The fluorescence of N, S-CQDs is stable in a wide range of pH 4-11. The detection mechanism was proved that the integration, caused by coordination interaction between S element in N, S-CQDs and the d-orbital of associated metal ions, was the main reason for fluorescence quenching. In practice, the N, S-CQDs were applied to determine total content of HMIs in water successfully. Interestingly, further experiment proved that the N, S-CQDs could effectively remove HMIs in water after centrifuging and filtering thoroughly. It was shown that the fluorescence of N, S-CQDs was obviously quenched by the multiple-ions-involved water and scavenging effect of N, S-CQDs on HMIs with centrifugal in which the concentration of individuals meets the Chinese National Standard. This indicates that the N, S-CQDs are of a wide application prospect in water quality analysis.