A novel and facile ultraviolet-induced photo-reduction for preparing oxidase-like AuNCs@H2N-ZIF-8 composites in alcohol-water solutions

Abstract

The composites of H₂N-ZIF-8 supported gold nanoclusters (AuNCs@H₂N-ZIF-8) were prepared by UV-induced photochemical reduction method in the methanol–water solution. The photochemical reaction was attributed to the generation of free radical as.

CH₂·–OH, which reduced Au(III) to Au(0) and produced monodisperse AuNCs (<2.5 nm) in the mesoporous of H₂N-ZIF-8. The generated AuNCs@H₂N-ZIF-8 show oxidase-like properties to catalyze the oxidation of TMB, ABTS and OPD under mild conditions. Besides, the mechanism study by EPR shows that the composites can promote oxygen to generate singlet oxygen (¹O₂) and superoxide radicals (${\text{·O}}_{\text{2}}^{\text{-}}$), endowing it excellent catalytic activity of oxidation. Further studies revealed that the large number of exposed small AuNCs in the mesoporous pores of H₂N-ZIF-8 and the highly active 211 crystalline facets formed at the edges contribute to the ROS generation intrinsically. Therefore, the present study demonstrates the significance of photochemical reduction method to prepare highly efficient oxidase-like materials, opening up a new avenue to construct noble metal materials as ultra-small nanozyme.