Ionic Liquid-Functionalized Ag-Doped CuO/Activated Carbon Nanozyme for Sensitive and Selective Colorimetric Detection of Hydrogen Peroxide

Hydrogen peroxide (H2O2) is both a chemically reactive oxidant and an important analytical target in food-quality monitoring, where its reliable quantification is mostly challenged by its low abundance and the complexity of food matrices. Herein, we establish an interfacial nanozyme strategy based on ionic liquid-functionalized Ag-doped CuO/C (Ag-doped CuO/C/IL) to amplify the colorimetric response to trace H2O2 through synergistic regulation of surface chemistry and catalytic reactivity. The engineered heterointerface integrates Ag-induced electronic modulation, CuO/C interfacial coupling, and ionic liquid-mediated surface functionalization, creating abundant accessible catalytic sites and facilitating H2O2 adsorption and subsequent interfacial electron-transfer reactions. Consequently, Ag-doped CuO/C/IL efficiently promotes the peroxidase-like oxidation of 3,3′,5,5′-tetramethylbenzidine, producing a pronounced blue-green signal with a characteristic absorption maximum at 652 nm. The resulting platform affords a broad linear response from 0.01 to 200 μM H2O2, an ultralow detection limit of 4 nM, and a correlation coefficient of 0.9989, while maintaining high selectivity, repeatability, and stability. Notably, the nanozyme enables reliable H2O2 determination in milk and yogurt, demonstrating its ability to operate in chemically complex food matrices. These findings establish that deliberate control of nanozyme interfacial structure can translate molecular-level catalytic interactions into amplified optical signals, providing a generalizable framework for sensitive H2O2 analysis and a practical route toward rapid food-safety monitoring.