Construction of S, O-Doped g-CN QDs Encapsulated in Eu-MOF with Dual-Emission for Ratiometric Fluorescence Detection of Hg²⁺.

Mercury ions (Hg) are categorized as environmental pollutants, which distributed in water, soil, and food systems due to environmental contamination. Hence, designing a sensitive assay for the convenient determination of Hg is of great importance. Herein, S and O-doped graphite phase nitrogenized carbon quantum dots (S, O-CNQDs) was encapsulated within a europium -based metal-organic framework (Eu-MOF) to construct a novel ratiometric fluorescent nanoprobe for the quantitative detection of Hg. The native emission of S, O-CNQDs at 445 nm is used as a response signal, while Eu-MOF with fluorescence offers a reference signal at 619 nm. Hg exhibits high affinity for the surface functional groups of S/O-CN QDs, forming non-fluorescent chelation complexes that induce static quenching. This results in significant attenuation of the fluorescence intensity at 445 nm, while the emission at 619 nm remains invariant. A ratiometric fluorescence sensing platform was established based on the intensity ratio (F/F) for the selective detection of Hg. The linear range of S, O-CNQDs/Eu-MOF of Hg was 0.25-35 µM and with a detection limit of 4.3 nM. The satisfying results demonstrate the effectiveness of the developed S, O-CNQDs/Eu-MOF-based fluorescence probe for Hg detection, highlighting its promising potential for environmental monitoring applications.