Modulating Polyoxovanadate Nanozyme via Interface Engineering for Enhancing Oxidase-Like Activity toward...

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^-, HPO₄^2-, HCO₃^-, NO₃^-, and SO₄^2-). 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.