Modulating Polyoxovanadate Nanozyme via Interface Engineering for Enhancing Oxidase-Like Activity toward Point-Of-Care Nitrite Detection

Nitrite (NO2–) poses severe threats to human health and ecosystems, yet existing nanozyme-based detection methods suffer from insufficient catalytic activity, limiting point-of-care (POC) applications. In order to solve this problem, we synthesized a CoV2O6/V2O5 hollow cubic nanozyme with boosted oxidase-like (OXD-like) activity via n–n heterojunction engineering for rapid detection of NO2–. Density functional theory (DFT) calculations confirm that the heterojunction modulates the d-band center of active sites and oxygen adsorption behavior, delivering 11.4-fold higher activity than pristine CoV2O6. Based on the color change of 3,3′,5,5′-tetramethylbenzidine (TMB) oxidation system triggered by NO2– diazotization, we established a colorimetric NO2– detection platform with a linear range of 10–100 μM and a limit of detection of 0.43 μM. Qualitative testing verified its excellent selectivity toward more than 10 common interfering ions (K+, Al3+, NH4+, Ca2+, Li+, Mg2+, Cl–, H2PO2–, HPO42–, HCO3–, NO3–, and SO42–). Furthermore, the method demonstrates good reproducibility (RSD <7.7%) and satisfactory recovery rates (99.23%–112.93%) when applied to real food and water samples.