Mechanism and optimization of a Hg²⁺-triggered nanozyme based on chitosan-carbon quantum dots-tellurium nanoparticles

Herein, a CS-CQDs-TeNPs-based colorimetric sensor was developed for the highly sensitive detection and simultaneous harmless conversion of Hg²⁺. In the presence of Hg²⁺, the oxidase-like activity of CS-CQDs-TeNPs was specifically triggered, and its catalytic kinetics followed the ping-pong mechanism. Under conditions of pH 4.0 and 30 °C, the colorimetric sensor constructed from 38.6 μg/mL CS-CQDs-TeNPs and 1.040 mmol/L TMB exhibited optimal activity, demonstrating a V_max of 83 (10^-8·M·s^-1) and a K_m of 13 mmol/L. Mechanistic studies indicated that Hg²⁺ reacted with CS-CQDs-TeNPs to form HgTe in situ. The generated HgTe catalyzed the generation of reactive oxygen species from O₂. These reactive oxygen species, in combination with the surface oxygen vacancies of the CS-CQDs-TeNPs, synergistically oxidized TMB, thus resulting in a colorimetric response. The CS-CQDs-TeNPs-based colorimetric sensor exhibited excellent selectivity, anti-interference capability, and considerable detection potential, while converting Hg²⁺ into low-toxicity HgTe during detection, thus realizing the integration of detection and remediation. This study provides a novel strategy for designing environmentally responsive nanozymes and remediating Hg²⁺ pollution.