A bifunctional nanozyme with dual oxidase- and catalase-mimicking activities for catalytic oxidation cycling of its target substrate

Abstract

We report the new concept of a bifunctional nanozyme that participates in oxidase- and catalase-mimicking activities, where the catalytic product H₂O₂, via its oxidase-mimicking O₂-consuming activity, can be converted to O₂ again via its own catalase-mimicking activity, thus allowing catalytic oxidation cycling of its target substrate. The bifunctional nanozyme was synthesized by pyrolyzing iron-doped ZIF-8 as a precursor at 900 °C in a N₂ atmosphere. Pyrolysis produced a composite material of Fe and Zn nanoparticles dispersed in a N- and O-co-doped carbon matrix (Fe–Zn@NOC), where the partial evaporation of zinc enabled the formation of well-dispersed Fe nanoparticles. Fe–Zn@NOC displayed potent ascorbate oxidase-mimicking and catalase-mimicking activities, while the control Zn@NOC exhibited none of them, demonstrating that Fe-doping was paramount for the dual nanozymatic activities of Fe–Zn@NOC, and Fe nanoparticles thereby played key roles for the two active centers. Under the catalysis of Fe–Zn@NOC, the catalytic product H₂O₂ from the oxidation of ascorbic acid, consuming O₂, was decomposed into O₂ and H₂O via its own catalase-mimicking activity, allowing catalytic oxidation cycling of ascorbic acid. This work may open new approaches for developing bifunctional nanozymes with oxidase- and catalase-mimicking activities for potential applications in areas such as biocatalysis, sensing, and energy conversion.