Light-modulated discrimination of inorganic and organic mercury via quinone nitrogen polarization on carbon dot/gold nanozymes.

Both inorganic and organic mercury species are highly biotoxic. They coexist in the environment and are prone to causing severe cross-interference during detection. Therefore, the rapid identification and precise differentiation of heavy metal forms in complex systems remain key issues that urgently need to be addressed in the field of analysis. Here, Light-responsive intelligent carbon dots-nanozymes (AN-CDs/AuNPs) was designed, which, in combination with photo-controlled regulation and surface-enhanced Raman spectroscopy (SERS), can selectively distinguish between Hg2+ and methylmercury (MeHg+). The experimental studies and theoretical calculations revealed that the quinone-type nitrogen structure in AN-CDs/AuNPs can be polarized by light irradiation, and further interact with Hg2+/MeHg+ to form different morphologies of amalgam. Polarization can further generate hot electrons and enhance peroxidase-like (POD-like) activity, and induce hole accumulation by capturing electrons, thereby achieving the heterolytic cleavage of the O-O bond in H2O2 through a non-radical pathway. The detection limits for MeHg+ and Hg2+ were 0.62 μg L-1 and 4.2 μg L-1, respectively. This work provides a new strategy for regulating the surface structure of nanozymes and selectively detecting inorganic and organometallic species.