Nanozyme-based chemical sensing is a rapidly emerging field of research. Herein, a simple colorimetric assay for the detection of hydrogen peroxide and glucose based on the peroxidase-like activity of V₂O₅ nanozymes has been established. In this assay, the effects of pH, substrate, nanozyme concentrations and buffer solution have been investigated. It was found that compared with 3,3′,5,5′-tetramethylbenzidine (TMB), the enzyme substrate o-phenylenediamine (OPD) seriously interfered with the H₂O₂ detection. Under the optimal reaction conditions, the resulting sensor displayed a good response to H₂O₂ with a linear range of 1 to 500 μM, and a detection limit of 1 μM at a signal-to-noise ratio of 3. A linear correlation was established between absorbance intensity and concentration of glucose from 10 to 2000 μM, with a detection limit of 10 μM. The current work presents a simple, cheap, more convenient, sensitive, and easy handling colorimetric assay.

Nanozyme-based colorimetric sensors have received considerable attention due to their unique properties. The size, shape, and surface chemistry of these nanozymes could dramatically influence their sensing behaviors. Herein, a comparative study of VO₂ nanoparticles with different morphologies (nanofibers, nanosheets, and nanorods) was conducted and applied to the sensitive colorimetric detection of H₂O₂ and glucose. The peroxidase-like activities and mechanisms of VO₂ nanoparticles were analyzed. Among the VO₂ nanoparticles, VO₂ nanofibers exhibited the best peroxidase-like activity. Finally, a comparative quantitative detections of H₂O₂ and glucose were done on fiber, sheet, and rod nanoparticles. Under the optimal reaction conditions, the lower limit of detection (LOD) of the VO₂ nanofibers, nanosheets, and nanorods for H₂O₂ are found to be 0.018, 0.266, and 0.41 mM, respectively. The VO₂ nanofibers, nanosheets, and nanorods show the linear response for H₂O₂ from 0.025–10, 0.488–62.5, and 0.488–15.625 mM, respectively. The lower limit of detection (LOD) of the VO₂ nanofibers, nanosheets, and nanorods for glucose are found to be 0.009, 0.348, and 0.437 mM, respectively. The VO₂ nanofibers, nanosheets, and nanorods show the linear response for glucose from 0.01–10, 0.625–15, and 0.625–10 mM, respectively. The proposed work will contribute to the nanozyme-based colorimetric assay.