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/Cu 2 O was prepared to develop a colorimetric and photoelectrochemical (PEC) dual-sensing mode for broad-range Hg 2+ detection. The AgCuO/Cu 2 O was evidenced with Hg 2+ -enhanced peroxidase activity. In the solution, the appearance of Hg 2+ promotes AgCuO/Cu 2 O 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 Hg 2+ . The linear response range is 1 nmol·l −1 to 10 μ mol·l −1 , and the detection limit is 3.5 nmol·l −1 . On the electrode surface, the emergence of Hg 2+ facilitates AgCuO/Cu 2 O 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 Hg 2+ with a linear response range of 10 pmol·l −1 to 10 μ mol·l −1 and a detection limit of 8.7 pmol·l −1 . The enhancement of the enzyme-mimicking activity of AgCuO/Cu 2 O by Hg 2+ 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 Hg 2+ and ensuring the reliability and accuracy of the results. The work paves the way for sensitive, selective, and accurate determination of Hg 2+ in serum samples.