Asymmetric Oxygen Vacancy-Boosted Peroxidase-Like Activity of Zn-Doped Fe ₃ O ₄ Nanozyme for Colorimetric Detection of Uric Acid

Oxygen vacancy (Ov) can enhance the catalytic activity of a metal oxide nanozyme. However, in pure metal oxide, the highly symmetrical arrangement of cations surrounding the Ov confines electrons within the vacancies, leading to low electron transfer efficiency. In this study, we engineered the asymmetric Ov sites in Fe3O4 nanoparticles by simple Zn doping and nitrogen-atmosphere annealing. The resulting Zn-doped Fe3O4 (Zn–Fe3O4) nanostructured microspheres featuring asymmetric oxygen vacancies (Zn–Ov–Fe) exhibited peroxidase-like activity. The affinity of the Zn–Fe3O4 nanozyme for H2O2 molecules was ca. 30.6-fold that of Fe3O4 nanoparticles. The superior catalytic activity is attributed to the asymmetric Zn–Ov–Fe sites, where the electronegativity difference between Zn and Fe enhances the adsorption and polarization of H2O2, thereby accelerating the cleavage of the HO–OH bond and generating more •OH radicals. Furthermore, by coupling the Zn–Fe3O4 nanozyme with uric acid oxidase, we developed a colorimetric method for uric acid detection. In this work, a high-performance nanozyme was obtained through simple experimental steps using two inexpensive and environmentally friendly metals (Fe and Zn). More importantly, as a proof-of-concept, this work demonstrates that introducing asymmetric oxygen vacancies into metal oxides is an effective strategy for boosting the catalytic activity of nanozymes.