Synthesis of N,Si co-doped carbon dots to establish a fluorescent sensor for Hg(II) detection with triple signal output.

Mercury is a heavy metal with extreme toxicity. Thus, it is of significance to develop an effective method for mercury ion detection with high performance. In this study, carbon dots doped with nitrogen and silicon (N,Si/CQDs) were successfully prepared from folic acid and N -[3-(trimethoxysily)propyl]-ethylenediamine. The N,Si/CQDs show an obvious cyan fluorescence of 460 nm with the radiation of 350 nm. The existence of mercury ions induces the fluorescence quenching of N,Si/CQDs due to photoinduced electron transfer, which was applied for the sensitive sensing of Hg(II). More importantly, the practical application of the N,Si/CQD probe was confirmed by measurements of Hg(II) in real samples of lake water, sorghum and rice. In addition, the N,Si/CQD nanoprobe was integrated on a sensing strip for specific detection of Hg(II). Quantitative measurement of Hg(II) was realized by the outstanding linearity between the diameter (or fluorescence intensity) of the fluorescence quenching ring and the concentration of mercury ions. The sensor shows potential for rapid detection with a triple signal readout on-site and represents a larger step towards practical applications.