AgCuO/Cu2O Nanozyme-Based Colorimetric and Photoelectrochemical Dual-Models Strategy for Sensing Hg2+ in Serum

A stable and highly visible-light responsive semiconductor material of AgCuO/Cu2O was prepared to develop a colorimetric and photoelectrochemical (PEC) dual-sensing mode for broad-range Hg2+ detection. The AgCuO/Cu2O was evidenced with Hg2+-enhanced peroxidase activity. In the solution, the appearance of Hg2+ promotes AgCuO/Cu2O to catalyze more 3, 3′, 5, 5′-tetramethylbenzidine (TMB) oxidization, deepening the color of the TMB solution and increasing the light absorption, thus realizing the colorimetric detection of Hg2+. The linear response range is 1 nmol·L-1 to 10 μmol·L-1, and the detection limit is 3.5 nmol·L-1. On the electrode surface, the emergence of Hg2+ facilitates AgCuO/Cu2O to convert more 4-chloro-1-naphthol (4-CN) into insoluble precipitates benzo-4-chlorohexadienone (4-CD), depressing the PEC signal and realizing the PEC detection of Hg2+ with a linear response range of 10 pmol·L-1 to 10 μmol·L-1 and a detection limit of 8.7 pmol·L-1. The enhancement of the enzyme-mimicking activity of AgCuO/Cu2O by Hg2+ is closely related to the in-situ formation of the Ag-Hg amalgam. The colorimetric and the PEC sensing modal complement each other, significantly broadening the detection range of Hg2+ and ensuring the reliability and accuracy of the results. The work paves the way for sensitive, selective, and accurate determination of Hg2+ in serum samples.