Bridging the Gap between Natural Enzyme and Artificial Nanozyme: A Thorough Structure-Activity Study of Well-Defined Single Atom Catalysts in Glucose Detection

Description

Diabetes is presently estimated to affect more than 400 million people and is the 5th cause of death throughout the world. The development of device for glucose detection is thus urgently required not only as portable glucose monitor but also for lab research. Unfortunately, the price of both portable monitor and lab research kit for glucose detection are not widely affordable due to the high cost of the natural enzymes “glucose oxidase” and “horseradish peroxidase (HRP)” used in the devices. Recently, Ru nanoparticles (NPs) have shown a potential as HRP mimetics, although this artificial enzyme has a lower cost, higher stability and recyclability but the efficiency is not high on a per metal atom basis, because only the exposed metal atoms are involved. More recently, single atom catalysts (SACs) characterized by maximum utilization per metal atom (or activity site) has provided great opportunities to mimic metalloproteases, and demonstrate great potentials for understanding structure-activity relationship such as how the local environments/chemical states affect adsorption/activation energy of reactants and hence bridge the gap between natural enzymes and their artificial mimetics. To achieve this, active sites engineering for single chemical state (cf. multiple for NPs and most SACs) and helps from advanced surface techniques for characterization is thus required and indispensable.This proposal aims to establish a specific guideline for the design of single atom nanozymes with uniform active sites for an in-depth understanding of their interaction with reactant molecules. Our preliminary discovery reveals that the surface atomic arrangement of MgO(111) support can orderly accommodate Ru single atoms (SAs) at a high concentration, which is in stark contrast to the randomly-dispersed SAs of SACs currently being reported. Most importantly, the high uniformity of Ru chemical state and corresponding concentration on MgO(111) revealed by probe-assisted nuclear magnetic resonance (NMR) allow us to unbiasedly investigate the structure-activity relationships for the first time. More comprehensive experiments and characterizations such as probe-assisted/operando X-ray absorption spectroscopy (XAS) and ⁹⁹Ru NMR will be carried out to reveal the adsorption/activation structure of H₂O₂ on Ru/MgO(111) surface. We believe the thorough investigation of interplay between H₂O₂ and Ru/MgO(111) is the key to achieve high activity and the subsequent coupling with glucose oxidase (as HRP mimetics) in glucose detection. The success of this proposal is expected to give insights to resolve the current confusions on the structure-activity of single atom nanozymes and to establish guidelines for their rational design.