Yellow fluorescent carbon dots sensitive detection of Hg2+ and its detection mechanism

In this paper, yellow fluorescent carbon dots (Y-CDs) were successfully synthesized by carbonization of o-phe-nylenediamine and p-aminobenzoic acid with hydrogen peroxide. The as-prepared Y-CDs possess excellent photoluminescence, high photostability, good water solubility and are rich in various functional groups on the surface by the analysis of transmission electron microscope, Fourier transform infrared spectrum, X-ray photo-electron spectroscopy, fluorescence spectrophotometer and ultraviolet-visible absorption spectrum. With these superior properties, Y-CDs have been used as sensing probes for the detection of Hg2+ ions and show a high selectivity for Hg2+. There is a good linear relationship between the fluorescence intensity of Y-CDs and the concentration of Hg2+ between 20 mu M and 150 mu M, and the minimum detection limit reach to 0.12 mu M. Furthermore, the detection method was applied to the recovery test of Hg2+ in real water samples and the ideal recovery rate was obtained. Based on above researches, the fluorescent test paper which is convenient to carry is prepared. In order to explore the mechanism of fluorescence quenching, Y-CDs was combined with zeolite imidazole skeleton-8 to synthesize Y-CDs@ZIF-8 composites. After adding Hg2+, the fluorescence of Y-CDs@ZIF-8 was no longer quenched. By analyzing the fluorescence lifetime, UV-vis absorption spectra and Fourier transform infrared spectra of Y-CDs before and after adding Hg2+, the mechanism of fluorescence quenching was finally determined to be static quenching.

Automated summary

In this paper, yellow fluorescent carbon dots (Y-CDs) were successfully synthesized and used as sensing probes for the detection of Hg2+ ions. The Y-CDs exhibited excellent performance with high selectivity and low detection limit. Additionally, a portable fluorescence test paper was prepared based on Y-CDs, and the mechanism of fluorescence quenching was investigated by synthesizing Y-CDs@ZIF-8 composites.