A facile synthetic approach for SiO2@Co3O4 core–shell nanorattles with enhanced peroxidase-like activity

Abstract

SiO₂@Co₃O₄ core–shell nanorattles with different Co₃O₄ shell thicknesses have been successfully synthesized by the calcination of SiO₂@α-Co(OH)₂ at 500 °C. The synthetic approach is facile, economical, and requires no surface modification. The synthesized materials were thoroughly characterized using powder X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), thermal gravimetric analysis (TGA), Brunauer–Emmett–Teller (BET) analysis, field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), and diffuse reflectance spectroscopy (DRS). SEM analysis indicates a hierarchical core–shell morphology for SiO₂@Co₃O₄ and the TEM results indicate the core–shell nanorattle morphology. Diffuse reflectance spectroscopy studies indicate that the SiO₂@Co₃O₄ core–shell nanorattles show two absorption bands in the range 420–450 nm and 700–750 nm related to ligand to metal charge transfer transitions (O²⁻ → Co²⁺ and O²⁻ → Co³⁺). The SiO₂@Co₃O₄ core–shell nanorattles act as an artificial peroxidase enzyme mimic with enhanced intrinsic peroxidase-like activity compared to pure Co₃O₄ nanoparticles and horseradish peroxidase (HRP), a natural enzyme. The SiO₂@Co₃O₄ core–shell nanorattles show higher k_cat and k_cat/K_m values compared to pure Co₃O₄ and HRP indicating their applicability as an artificial enzyme mimic in biomedicine and bio-sensing.