Single-atom nanozymes

Abstract

Conventional nanozyme technologies face formidable challenges of intricate size-, composition-, and facet-dependent catalysis and inherently low active site density. We discovered a new class of single-atom nanozymes with atomically dispersed enzyme-like active sites in nanomaterials, which significantly enhanced catalytic performance, and uncovered the underlying mechanism. With oxidase catalysis as a model reaction, experimental studies and theoretical calculations revealed that single-atom nanozymes with carbon nanoframe–confined FeN5 active centers (FeN5 SA/CNF) catalytically behaved like the axial ligand–coordinated heme of cytochrome P450. The definite active moieties and crucial synergistic effects endow FeN5 SA/CNF with a clear electron push-effect mechanism, as well as the highest oxidase-like activity among other nanozymes (the rate constant is 70 times higher than that of commercial Pt/C) and versatile antibacterial applications. These suggest that the single-atom nanozymes have great potential to become the next-generation nanozymes.

Single‐Atom Catalysts in Catalytic Biomedicine

“…Furthermore, rare predictions from theoretical calculations have succeeded in guiding the in vitro and in vivo experiments. More importantly, the in vitro and in vivo catalytic performance of SACs is determined by the intrinsic features (e.g., size, morphology, composition) and the extrinsic factors (e.g., pH, temperature, interaction with biomacromolecules, reaction medium), it is difficult to establish in vivo catalytic mechanism of SACs due to the complicated relationship between the catalytic activity of SACs and their surrounding environment. Therefore, exploring new and efficient in situ characterization techniques and computational modeling approaches are highly urgent to identify the reaction intermediates and thus comprehend probable catalytic kinetics and mechanism of SACs in the catalytic processes for biomedical use. (3)Developing advanced characterization techniques for monitoring in vitro and in vivo catalytic processes.…”

“…The low‐density active sites and non‐homogeneous elemental distribution are the two main facing challenges of conventional nanozymes. Recently, highly active SACs of carbon nanoframes‐supported single Fe atoms (FeN 5 SA/CNF) with oxidase‐mimicking activity were synthesized by pyrolyzing iron phthalocyanine‐encapsualted MOF frameworks (FePc@Zn‐MOF) at 900 °C for biosensing ascorbic acid (AA) ( Figure a) . The successful formation of atomically dispersed single Fe atoms and existence of Fe–N 5 moieties on carbon nanoframes were confirmed by STEM, EELS, XAFS, and XANES.…”

“…g) Free‐energy diagram for oxidase‐mimicking reaction on various SACs with TMB as reductant under acidic conditions. a–g) Reproduced with permission . Copyright 2019, the American Association for the Advancement of Science.…”

“…In addition, DFT calculations were conducted to shed light on the catalytic mechanism of the augmented oxidase‐mimicking activity of FeN 5 SA/CNF . For the catalyst FeN 5 , the high absorption energy of O 2 (G*O 2 ) weakened OO bond and subsequently resulted in distinct elongation of OO bond, which was attributed to the occupation of antibonding orbital of O 2 via the electron push effect of axial‐coordinated N in FeN 5 .…”

“…Accordingly, the AA detection bioassay was performed based on reduction effect of AA. The absorbance of oxidized TMB exhibited significant linear relationship with the AA concentration ranging from 0.1 to 1.0 m , and the limit of detection (LOD) was determined to be 0.07 µ m …”