Theoretical Study On The Mechanisms Of Oxidoreductase Mimicing Activities Of Single Atom Fe-N_x-C(x=1-4) Catalytic Site

Nanozymes are the nanomaterials with enzyme mimicking activities.Thanks to their low costs and high stabilities,they are considered as the next generation of enzyme mimics.Single-atom catalysts?SACs?is catalysts that contains isolated metal atoms singly dispersed on supports.The active center of the SAC is a single atom,which has high activity,selectivity and stability compared to the conventional nanocatalysts.Single-atom catalysts with natural enzyme mimicking activities are single-atom nanoenzymes?SANs?.Although there have been many reports on the synthesis and application of SANs,the precise structural characterization of the active centers and the catalytic mechanisms at atomic level are still less reported,which hinders the establishment of the structure-activity relationship and makes it difficult to realize the rational design of SANs.Fe-N-C is a representative kind of SACs where the Fe atom are dispersed on the N-doped carbon nanomaterials.A number of experimental studies have shown that Fe-N-C have four types of oxidordeuctase mimicing activities,namely,oxidase-,peroxidase-,catalase-and superoxide dismutase-mimicing activities.In this paper,the possible molecular mechanisms responsible for the above four types of oxidordeuctase-mimicing activities are explored using density functional theory?DFT?.The results can provide new ideas for the rational design,optimization and screening of Fe-N-C nanoenzymes.The main results of this paper include the following three parts.?1?The geometric and electronic structures for the cluster and periodic structure models for Fe-N_x-C?x=1–4?are investigated.The result show that Fe-N_x-C have almost the same kinetic stability as the naturally occurring iron porphyrins with similar structures.?2?The mechanisms for the four types of oxidordeuctase-mimicing activites of Fe-N₄-C are investigated and the results indicated that Fe-N₄-C had catalase-mimicing,peroxidase-mimicing and superoxide dismutase-mimicing activities.?3?Based on the results of Fe-N₄-C,the corresponding mechanisms for Fe-N_1-3-C are also explored.The results indicated that the SANs which had peroxidase-mimicing activiry is Fe-N₁-C,those have superoxide dismutase-mimicing activity is Fe-N_1-3-C.Fe-N_1-3-C have no catalase-mimicing and oxidordeuctase-mimicing activites.