Co3O4-reduced graphene oxide nanocomposite as an effective peroxidase mimetic and its application in visual biosensing of glucose.

The well-dispersed Co3O4 nanoparticles on reduced graphene oxide (rGO) surfaces were successfully prepared by in situ controlled nucleation of Co3O4 NPs on GO sheets and subsequent in situ reduction of GO by low temperature hydrothermal reaction in ethanol media. The as-prepared Co3O4/rGO nanocomposites were characterized by transmission electron microscopy (TEM), scanning electron microscope (SEM), thermogravimetry (TG), X-ray diffraction (XRD) and FT-IR spectra. It was found that the Co3O4 NPs were successfully decorated and well dispersed on the surface of rGO sheet without agglomeration. We discovered that the Co3O4/rGO nanocomposites possess intrinsic peroxidase-like activity and catalase-like activity, and could catalytically oxidize 3,3',5,5'-tetramethylbenzidine (TMB) by hydrogen peroxide (H2O2) to produce a intensified colour reaction. Results of electron spin resonance (ESR) experiments demonstrated that the Co3O4/rGO nanocomposites showed catalytic ability to H2O2 decomposition into OH radicals. On this basis, a simple and selective method for glucose detection was developed by coupling the oxidation of glucose catalyzed by glucose oxidase (GOx). As low as 1×10(-6) mol L(-1) glucose could be detected with a linear range from 1×10(-6) to 1×10(-4) mol L(-1). The visual detection of glucose can be realized easily through the observable color change from colorless to blue by the naked eyes without any instrumentation or complicated design. Our research results also suggest a simple route for the facile preparation of a highly active nanoparticles-based enzyme mimetics on proper supporting materials.