Study On The Regulatory Mechanism Of Metal And Ligand Atom Species On The Peroxidase Activity Of Single-atom Nanozymes

Nanozymes are nanomaterials that have the activity to mimic the catalytic function of natural enzymes and follow the kinetics of enzyme catalysis.To date,at least 1200 different nanomaterials such as metals,metal oxides,carbon,and metal-organic frameworks have been reported worldwide to possess the catalytic functions of more than a dozen biological enzymes such as peroxidase,catalase,oxidase,and superoxide dismutase.Among them,peroxide-like nanozymes are of wide interest for their important applications in biosensing and immunoassays due to their ability to convert the less oxidizing H2O2 to highly oxidizing HO· or monoatomic oxygen,which in turn oxidizes the reducing substrate with significant color change.Single-atom nanozymes,due to their high atom utilization,large surface area,multiple active sites and strong binding to substrates,have become the star material for nanozyme research.The central metal and ligand atom species have significant effects on the catalytic activity of monoatomic nanozymes,and the study of their catalytic molecular mechanisms and structure-activity relationship is of great importance for the rational design of single-atom nanozymes.In practice,the controllability and characterization of metal loading rate,dispersion and ligand environment have been a difficult problem in experimental science.First-principles calculations have a unique advantage in solving the above-mentioned difficulties,which can profoundly portray the dynamic processes of structural and electronic structure of molecules and materials during chemical reactions at the molecular level based on a clear chemical structure,and have become the most effective and irreplaceable theoretical tool for studying the mechanism of chemical reactions by experimental means.In view of this,in this paper,the electronic structure properties of the 3d transition metal carbon-based monoatomic nanozyme M-Nn X(4-n)-C(M = Sc – Zn,X = B,N,P,S)were systematically investigated with the change of metal and ligand atoms as the object of study.We also used the oxidation of 3,3’,5,5’-tetramethylbenzidine(Tetramethylbenzidine,abbreviation TMB),a commonly used chromogenic substrate,by H2O2 as a model reaction to simulate the peroxidase-like activity,and systematically investigated the chemical reaction history at the active center of the above single-atom nanozyme,searched for possible reaction intermediates and transition states,determined the kinetically optimal reaction path and the decisive step energy barrier,and depicted the potential energy surface of the catalytic reaction history.The structure-activity relationship was explored in terms of both metal species and ligand atom species to theoretically predict the single-atom nanozyme with optimal peroxidase activity.The following major research results were achieved:(1)The adsorption energy of OH radical on the single-atom nanozyme,Eads,OH,can be used as a descriptor to predict their catalytic activity,when-6.25 e V < Eads,OH <-2.58 e V,the peroxidase-like activity has higher specificity and while-2.58 e V < Eads,OH<-1.00 e V,the catalase-like activity has higher specificity;(2)Metal and ligand atom species significantly affect the d-band center height of the material,which in turn modulates Eads,OH and affects the peroxidase activity of the nanoparticle enzyme;(3)Fe-N4-C nanomaterials have good peroxidase-like activity and Co-N4-C has good catalase-like activity.The above findings provide the first systematic study of the effects of metal and ligand atom species on the peroxidase activity of single-atom nanozymes.It not only deepens the understanding of the catalytic molecular mechanism of such materials,but also provides theoretical tools for the design and optimization of single-atom nanozymes.