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

Abstract

We report a new concept of a bifunctional nanozyme that holds both the oxidase-and catalase mimicking activities, where the catalytic product H2O2 via its oxidase-mimicking activity consuming O2 can be converted to O2 again via its own catalase-mimicking activity, allowing catalytic oxidation cycling of its target substrate. The bifunctional nanozyme was synthesized by pyrolyzing iron-doped ZIF-8 as a precursor at 900oC in a N2 atmosphere. It was the pyrolysis process that produced a composite material of Fe and Zn nanoparticles dispersed in N and O co-doped carbon matrix (Fe-Zn@NOC), where the partial evaporation of zinc allowed well-dispersed Fe nanoparticles. Fe-Zn@NOC displayed both 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 the key roles for both 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 up new approaches for developing bifunctional nanozymes with both oxidase- and catalase-mimicking activities for potential applications in the areas, such as biocatalysis, sensing and energy conversion.