Enhanced Oxidase‐Like Activity of Ag‐Decorated V ₂ O ₅ Hollow Microspheres for the Colorimetric Detection of Mercury (II) Ions

ABSTRACT In this work, we report the synthesis of a novel Ag‐decorated V 2 O 5 nanozyme with intrinsic oxidase‐like activity for the colorimetric detection of Hg 2+ ions. The Ag/V 2 O 5 hollow microspheres were synthesized via a simple hydrothermal method followed by Ag nanoparticle decoration and thoroughly characterized by XRD, XPS, SEM, TEM, HRTEM, and EDX. The resulting nanozyme exhibited excellent oxidase‐like catalytic activity, which was further enhanced upon interaction with Hg 2+ , enabling the oxidation of TMB (3,3′,5,5′‐tetramethylbenzidine) without the need for H 2 O 2 . Under optimized conditions, the proposed sensor showed a linear response to Hg 2+ concentrations in the range of 1.25–8.0 μM with a low detection limit of 0.39 μM. Mechanistic studies revealed that reactive oxygen species (superoxide radicals and singlet oxygen) played a dominant role in the oxidation process. The sensor exhibited remarkable selectivity toward Hg 2+ over other common metal ions, along with outstanding stability. These results suggest that Ag/V 2 O 5 nanozymes offer a robust nanozyme platform for the development of simple, sensitive, and stable colorimetric biosensors for the detection of toxic heavy metals in environmental and biological samples.