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

Nitrite (NO 2 – ) 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 CoV 2 O 6 /V 2 O 5 hollow cubic nanozyme with boosted oxidase-like (OXD-like) activity via n – n heterojunction engineering for rapid detection of NO 2 – . 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 CoV 2 O 6 . Based on the color change of 3,3′,5,5′-tetramethylbenzidine (TMB) oxidation system triggered by NO 2 – diazotization, we established a colorimetric NO 2 – 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 +, Al 3+, NH 4 +, Ca 2+, Li +, Mg 2+, Cl –, H 2 PO 2 –, HPO 4 2–, HCO 3 –, NO 3 –, and SO 4 2– ). Furthermore, the method demonstrates good reproducibility (RSD