Peroxidase-like Activity Of FeVO₄ Nanobelts And Its Analytical Application For Optical Detection Of Hydrogen Peroxide

Natural enzymes are involved in a series of biochemical reactions in the organism. They have high efficiency and specificity and play important roles in the metabolic process of living organisms. But natural enzymes are mainly proteins（a few are RNAs）, which makes them easy to lose their enzymatic activities in extreme environments, leading to limited practical applications. Nanomaterial catalysts have been developed with the development of nanotechnology Peroxidase plays an important role in organisms’ physiological and biochemical reactions. And hydrogen peroxide is an important intermediate in certain analysis and detection. In 2007, researchers discovered Fe3O₄ magnetic nanoparticles possess peroxidase-like enzyme activity for the first time. So far, metal nanomaterials, metal oxide nanomaterials and carbon nanomaterials have been proved to have mimetic enzyme activity. Nanomaterials mimetic enzymes can be used to make up for the deficiencies of natural enzyme in separation, extraction, purification, high cost and low stability. This work developed a novel, accessible and highly sensitive system for visual detection of H₂O₂, making FeVO₄ peroxidase-like enzyme a potential biomimetic catalysts in H₂O₂ detection, biomedical analysis and hydrogen peroxide sewage treatment.The main research work can be summarized as following:1. Preparation of FeVO₄ peroxidase-like enzyme.With NH4VO₃ and Fe（NO₃）3 · 9H₂ O as starting materials, we used hydrothermal synthesis method to synthesize FeVO₄ nanomaterials at pH 1.0, 4.0, 7.0 and 10.0 by adjusting the pH of the rection system. Obtained products were named FeVO₄-1, FeVO₄-4, FeVO₄-7 and FeVO₄-10 respectively, with the number denoting the pH under which the material was prepared.2. Characterization of Fe VO₄ peroxidase-like enzyme.The crystal structure of FeVO₄ nanomaterial was studied via TEM, FESEM, XRD, EDX, XPS and BET. We found FeVO₄ nanomaterials prepared under different pH conditions showed different crystal structures and morphology characteristics. The product（FeVO₄-4） obtained at pH = 4 possessed a belt-like nanostructure with a large BET specific surface area and exhibited the best intrinsic peroxidase-like activity compared to other Fe VO₄ materials.3. Catalytic activity study of FeVO₄ peroxidase-like enzyme.Fe VO₄-4 nanobelts（NBs） could efficiently catalyze the oxidation of 3,3’,5,5’-tetramethylbenzidine（TMB） in the presence of H₂O₂ to generate a blue oxide. And this oxide had characteristic absorption peak at 652 nm. Based on this principle, we compared the peroxidase activity of Fe VO₄ peroxidase-like enzyme prepared under different pH. We found Fe VO₄-4 NBs obtained at pH = 4 had the best crystal structure and a large BET specific surface area and exhibited the best peroxidase activity. We also found the peroxidase-like activity of FeVO₄ can be influenced by the substrate concentration, the external environment factors such as pH and temperature, and the concentration of FeVO₄. The optimum reaction conditions of FeVO₄ peroxidase-like enzyme were determined. Through peroxidase-like enzyme kinetic simulation experiment, we proved FeVO₄ peroxidase-like catalytic reaction conformed to ping-pong mechanism. Results also showed FeVO₄-4 NBs peroxidase-like enzyme had good reusability and long-term stability.4. Applications of Fe VO₄ peroxidase-like enzyme.Based on the highly efficient catalytic activity of FeVO₄-4 NBs, a novel system for optical determination of H₂O₂ was successfully established, and the detection limit of H₂O₂ could reach 0.2 μM. Selective experiments and real samples detection experiments proved the visual inspection system of Fe VO₄-4 NBs-H₂O₂-TMB had broad specificity and applicability.