Engineering a hierarchically micro-/nanostructured Si@Au-based artificial enzyme with improved accessibility of active sites for enhanced catalysis

Abstract

The active site accessibility and high loading of gold nanoparticles (AuNPs) are key factors affecting the catalytic activity of supported AuNP-based catalysts. However, the preparation of supported AuNP-based catalysts with highly accessible active sites still remains a challenge. Herein, sphere-on-sphere (SoS) silica microspheres with a hierarchical structure, good dispersion and high surface density of thiol groups (10 SH nm⁻²) are prepared and used as a platform for the growth of high-density AuNPs. The obtained hierarchical Si@Au micro-/nanostructure consisting of 0.55 μm SoS silica microspheres and 7.3 nm AuNPs (SoS-0.55@Au-7.3) is found to show excellent peroxidase-mimicking activity (K_m = 0.033 mM and V_max = 34.6 × 10⁻⁸ M s⁻¹) with merits of high stability and good reusability. Furthermore, the as-obtained SoS-0.55@Au-7.3-based system can sensitively detect hydrogen peroxide (H₂O₂) with a low detection limit of 1.6 μM and a wide linear range from 2.5 μM to 1.0 mM. The high catalytic activity, excellent stability and good reusability of SoS-0.55@Au-7.3 imply its great prospects in biosensing and biomedical analysis.