Silver nanoparticles deposited carbon microspheres nanozyme with enhanced peroxidase-like catalysis for colorimetric detection of Hg in seafood.

Novel methods for high-performance detection of Hg in seafood are critical for ensuring food safety and human health. Herein, Ag nanoparticles (Ag NPs) were successfully deposited on carbon microspheres (CMs) to form Ag NPs-CMs nanocomplex. The proposed Ag NPs-CMs could oxidize colorless 3,3',5,5'-tetramethylbenzidine (TMB) to blue oxidation state TMB (oxTMB) in the presence of hydrogen peroxide (HO) and had a significant UV-vis absorption peak at 652 nm. The excellent peroxidase-like activity was attributed to the increased electrostatic attraction of CMs and the catalytic synergistic effect. After adding Hg, the catalytic activity of Ag NPs-CMs was specifically enhanced and the Michaelis-Menten constant (K) decreased from 0.067 to 0.052 mmol/L due to the formation of Ag-Hg amalgam which produced more superoxide anions (O) and hydroxyl radicals (•OH). The linear response ranges for Hg were 2~833 nmol/L and 2.5~40 μmol/L, with the low detection limit of 1.10 nmol/L. This method was applied to detect Hg in seafood with satisfactory recoveries of 95.65~106.56%. A hydrogel kit was designed for portable detection of Hg, and the response range was 0.5~5 μmol/L. This work provides a reliable method for visual Hg detection in seafood as well as a feasible strategy for the design of high-performance nanozymes.