Fabrication of shish-kebab structure of MnO₂@Co₃O₄ with remarkably enhanced oxidase-mimicking activity for the detection of l-cysteine

Metal-organic framework (MOF)-derived hollow Co3O4 has attracted considerable attention owing to its porosity, high dispersion and large specific surface area. To further improve its activity, well-dispersed Co3O4-decorated MnO2 was successfully fabricated using MnO2@ZIF-67 as the precursor. Initially, MnO2 nanowires were prepared, which acted as a structure-directing support for the growth of ZIF-67. Polyvinylpyrrolidone (PVP) was exploited as a surface stabilizer, growth modifier and dispersant. After calcination, the one-dimensional shish-kebab MnO2@Co3O4 composite was obtained. Subsequently, its oxidase-mimicking performance was validated using 3,3 ',5,5 '-tetramethylbenzidine (TMB) as the substrate. This composite possessed abundant active sites, continuously ordered hetero-interface, and increased diffusion pathway, and thereby high oxidase-mimicking activity, which was 2 times higher than that of MnO2 and 14.6 times higher than that of Co3O4. The mechanism studies revealed that MnO2@Co3O4 enhanced the O-2 adsorption ability and facilitated the production of O-2(center dot)- radicals, resulting in improved activity. Considering the selective inhibition of L-cysteine, a sensitive and selective assay for the detection of L-cysteine was established. This work presents an effective strategy for designing new types of hybrid materials with potential prospect in the fields of bioanalysis, catalysis, and environmental monitoring.