Glucose-oxidase like catalytic mechanism of noble metal nanozymes

Gold nanoparticles (Au NPs) with enzyme-like activities are useful glucose oxidase mimics, but the insights into the mechanism of this reaction are limited. Here, the authors show that the process of glucose oxidation by Au NPs is analogous to the one catalysed by glucose oxidase, involving dehydrogenation and oxygen reduction to H2O2; and that other noble metal NPs also catalyse glucose dehydrogenation, but oxygen is preferably reduced to water. Au nanoparticles (NPs) have been found to be excellent glucose oxidase mimics, while the catalytic processes have rarely been studied. Here, we reveal that the process of glucose oxidation catalyzed by Au NPs is as the same as that of natural glucose oxidase, namely, a two-step reaction including the dehydrogenation of glucose and the subsequent reduction of O-2 to H2O2 by two electrons. Pt, Pd, Ru, Rh, and Ir NPs can also catalyze the dehydrogenation of glucose, except that O-2 is preferably reduced to H2O. By the electron transfer feature of noble metal NPs, we overcame the limitation that H2O2 must be produced in the traditional two-step glucose assay and realize the rapid colorimetric detections of glucose. Inspired by the electron transport pathway in the catalytic process of natural enzymes, noble metal NPs have also been found to mimic various enzymatic electron transfer reactions including cytochrome c, coenzymes as well as nitrobenzene reductions.