Sensitive colorimetric glucose sensor by iron-based nanozymes with controllable Fe valence

Abstract

The proportion of Fe²⁺ and Fe³⁺ in Fe-based nanozymes is a key point in determining their catalytic activity. However, it is hard to adjust the Fe²⁺/Fe³⁺ ratio in nanozyme systems to achieve the best catalytic performance. In this work, we successfully regulate Fe²⁺/Fe³⁺ ratios in a wide range of 0.81–1.45 based on a novel porous platform of Fe doped silica hollow spheres. The homogeneous distribution and stable fixation of Fe components in Fe doped silica hollow spheres facilitate the valence regulation of Fe in the reduction heating in H₂/Ar. When the Fe doped spheres (FeO_x@SHSs) were used as nanozymes, different Fe²⁺/Fe³⁺ ratios have shown to influence the peroxidase-like catalytic activity greatly. The highest activity at the ratio of 1.41 should be due to the combined effects of the accelerated reaction rate by Fe²⁺ and the enhanced catalytic cycle efficiency by Fe³⁺. The FeO_x@SHSs-based nanozyme is further applied to construct a facile colorimetric biosensing system, which exhibited extremely sensitive determination of glucose. This work presents an effective platform for controlling Fe valences and optimizing the peroxidase-like activity for catalytic processes or sensing systems.