Supercritical fluid-assisted fabrication of C-doped Co3O4 nanoparticles based on polymer-coated metal salt nanoreactors for efficient enzyme-mimicking and glucose sensor properties

Nanomaterials doped with non-metallic C have attracted tremendous attention as potential nano-artificial enzymes due to their ability to change the energy band structure to improve their intrinsic properties. Herein, we report a green, facile, efficient, and fast strategy to access high-performance nanozymes via supercritical CO2 fluid technology-fabricated polymer nanoreactor of poly-(methyl vinyl ether-co-maleic anhydride) (PVM/MA) coated Co(NO3)2 into C-doped Co3O4 (C-Co3O4) nanozyme by a one-step calcination process. Converting PVM/MA to C doping into Co3O4 shortens the entire lattice constant of the crystal structure, and the overall valence band energy level below the Fermi level shifts toward the lower energy direction. The as-prepared C-Co3O4 demonstrated significant peroxidase-like catalytic activity, significantly greater than the undoped Co3O4 nanoparticle nanozyme. The following density functional theory (DFT) calculations revealed that the doped nano-enzyme catalytic site displayed a unique electronic structure, altering the material surface with more electrons to fill the anti-bond of the two molecular orbitals, and significantly improving the peroxidase-like enzyme catalytic and glucose sensor performance. The resultant enzymatic glucose sensing in a linear range of 0.1–0.6 mM with a detection limit of 3.86 µM is in line with standard Michaelis—Menten theory. Collectively, this work demonstrates that converting polymers into nanozymes of C-doped form by supercritical CO2 fluid technology in a step is an effective strategy for constructing high-performance glucose sensor nanozymes. This cost-effective, reliable, and precise system offers the potential for rapid analyte detection, facilitating its application in a variety of fields.