Ordered mesoporous CoO/CeO2 heterostructures with highly crystallized walls and enhanced peroxidase-like bioactivity

Abstract

With increasing requirements of replacing the high-cost and unstable natural enzymes, the rational design of highly efficient inorganic mimetic enzymes (nanozymes), as one of the most important bioactive materials, has attracted more and more attention in recent years. In our work, using the solvent evaporation induced co-assembly strategy with high-molecular weight poly(ethylene oxide)-block-polystyrene (PEO-b-PS) diblock copolymer as the template and two metal salts as the co-precursors in one-pot system, we synthesized ordered mesoporous heteroatom-doped CeO2 with high surface area, bimodal pore sizes and highly crystallized walls. The composite materials were then constructed as the mimetic enzymes to investigate their peroxidase-like catalytic performance and detect H2O2 and glucose as bioactive materials in diverse systems including complex biological samples. It was demonstrated that mesoporous 5%CoO/CeO2 catalyst was the best peroxidase mimic, following the typical Michaelis–Menten kinetics and exhibiting the excellent peroxidase-like catalytic performance toward 3,3′,5,5′-tetramethylbenzidine (TMB) with comparable Km and Vm values to horseradish peroxidase (HRP) enzyme. A highly sensitive and selective colorimetric assay was developed to detect H2O2 and glucose with detection limits of 0.88 and 19.6μM, respectively. The promising catalytic behavior of mesoporous 5%CoO/CeO2 as the peroxidase-like bioactive catalyst could be ascribed to its interconnected large mesopores, rich exposed surface defects and oxygen vacancies introduced by the heterojunction interface of ultrasmall CeO2 and CoO nanocrystals within pore walls.