Sulfur-modified V₂O₅ nanozymes with altered ROS generation characteristics for enhanced glucose colorimetry

Defect and surface-chemistry regulation are widely used strategies to improve the catalytic performance of metal oxide nanozymes and to modulate reactive oxygen species (ROS) generation. However, in V₂O₅-based nanozymes, the relationship among sulfur-related structural modification, surface oxygen environment, and ROS generation behavior remains insufficiently clarified. Herein, sulfur-modified V₂O₅ (S-V₂O₅) nanozymes were prepared through a precursor-transformation route involving sulfurization and subsequent air-oxidation reconstruction. The resulting S-V₂O₅ retained the main V₂O₅ crystalline framework, while showing local structural perturbation, altered surface oxygen environment, increased defect-associated features, and a higher contribution of reduced V-related species. These changes were accompanied by enhanced peroxidase-like (POD-like) activity, stronger apparent substrate affinity, and good cycling stability. Radical scavenging and electron paramagnetic resonance (EPR) spin-trapping results indicated altered ROS generation characteristics under the tested TMB-H₂O₂ reaction conditions, with a more pronounced superoxide-related signal in S-V₂O₅ compared with pristine V₂O₅. However, multiple ROS-related pathways may coexist, and these results should not be interpreted as definitive proof of an exclusive ROS pathway switch. As a proof-of-concept application, a glucose oxidase (GOx)/S-V₂O₅ cascade system enabled sensitive and selective glucose colorimetric detection. This work suggests that sulfurization-oxidation reconstruction can modulate the local structure and surface chemical environment of V-based oxide nanozymes, thereby improving POD-like catalytic output and colorimetric sensing performance.