Since the ferromagnetic (Fe3O4) nanoparticles were firstly reported to exert enzyme-like activity in 2007, extensive research progress in nanozymes has been made with deep investigation of diverse nanozymes and rapid development of related nanotechnologies. As promising alternatives for natural enzymes, nanozymes have broadened the way toward clinical medicine, food safety, environmental monitoring, and chemical production. The past decade has witnessed the rapid development of metal- and metal oxide-based nanozymes owing to their remarkable physicochemical properties in parallel with low cost, high stability, and easy storage. It is widely known that the deep study of catalytic activities and mechanism sheds significant influence on the applications of nanozymes. This review digs into the characteristics and intrinsic properties of metal- and metal oxide-based nanozymes, especially emphasizing their catalytic mechanism and recent applications in biological analysis, relieving inflammation, antibacterial, and cancer therapy. We also conclude the present challenges and provide insights into the future research of nanozymes constituted of metal and metal oxide nanomaterials.

/pdf/a-review-on-metal-and-metal-oxide-based-nanozymes-properties-42jd6wb2mo.pdf

A Review on Metal- and Metal Oxide-Based Nanozymes: Properties, Mechanisms, and Applications

Nanomaterial-based enzyme-mimetic catalysts (Enz-Cats) have received considerable attention because of their optimized and enhanced catalytic performances and selectivities in diverse physiological environments compared with natural enzymes. Recently, owing to their molecular/atomic-level catalytic centers, high porosity, large surface area, high loading capacity, and homogeneous structure, metal-organic frameworks (MOFs) have emerged as one of the most promising materials in engineering Enz-Cats. Here, the recent advances in the design of MOF-engineered Enz-Cats, including their preparation methods, composite constructions, structural characterizations, and biomedical applications, are highlighted and commented upon. In particular, the performance, selectivities, essential mechanisms, and potential structure-property relations of these MOF-engineered Enz-Cats in accelerating catalytic reactions are discussed. Some potential biomedical applications of these MOF-engineered Enz-Cats are also breifly proposed. These applications include, for example, tumor therapies, bacterial disinfection, tissue regeneration, and biosensors. Finally, the future opportunities and challenges in emerging research frontiers are thoroughly discussed. Thereby, potential pathways and perspectives for designing future state-of-the-art Enz-Cats in biomedical sciences are offered.

Metal–Organic‐Framework‐Engineered Enzyme‐Mimetic Catalysts

Advances in oxidase-mimicking nanozymes: Classification, activity regulation and biomedical applications

Enzyme mimics, especially nanozymes, play a crucial role in replacing natural enzymes for diverse applications related to bioanalysis, therapeutics and other enzyme-like catalysis. Nanozymes are catalytic nanomaterials with enzyme-like properties, which currently face formidable challenges with respect to their intricate structure, properties and mechanism in comparison with enzymes. The latest emergence of single-atom nanozymes (SAzymes) undoubtedly promoted the nanozyme technologies to the atomic level and provided new opportunities to break through their inherent limitations. In this perspective, we discuss key aspects of SAzymes, including the advantages of the single-site structure, and the derived synergetic enhancements of enzyme-like activity, catalytic selectivity and the mechanism, as well as the superiority in biological and catalytic applications, and then highlight challenges that SAzymes face and provide relevant guidelines from our point of view for the rational design and extensive applications of SAzymes, so that SAzyme may achieve its full potential as the next-generation nanozyme.

/pdf/atomic-engineering-of-single-atom-nanozymes-for-enzyme-like-127h1e0woa.pdf

Atomic engineering of single-atom nanozymes for enzyme-like catalysis

Development of highly sensitive biosensors has received ever-increasing attention over the years. Due to the unique physicochemical properties, the functional nanomaterial-enabled signal amplification strategy has made some great breakthroughs in biosensing. However, the sensitivity and selectivity still need further improvement. Single-atom catalysts (SACs) containing atomically dispersed metal active sites demonstrate distinctive advantages in catalytic activity and selectivity for various catalytic reactions. As a consequence, the SAC-enabled signal amplification strategy holds great promise in biosensors, demonstrating satisfactory sensitivity and selectivity with the assistance of tunable metal–support interactions, coordination environments and geometric/electronic structures of active sites. In this tutorial review, we briefly discuss the structural advantages of SACs. Then, the catalytic mechanism at the atomic scale and signal amplification effects of SACs in the colorimetric, electrochemical, chemiluminescence, electrochemiluminescence, and photoelectrochemical biosensing applications are highlighted in detail. Finally, opportunities and challenges to be faced in the future development of the SAC-enabled signal amplification strategy for biosensing are discussed and outlooked.

Single-atom catalysts boost signal amplification for biosensing.

Nanozymes become currently a frontier of chemical research. However, exploiting a novel nanozyme with high activity, good stability and reproducibility is challenging. Here, size-controllable Fe-N/C nanozymes containing exclusive single Fe atoms coordinated Fe-Nx sites were succesfully prepared through a facile pyrolysis of size controllable Fe-Zn ZIFs precursors. The Fe-N/C nanozymes exhibit exceptional high oxidase-mimicking activity able to catalyze oxidation of colorless 3,3′,5,5′-tetramethylbenzidine (TMB) by dissolved oxygen to generate blue product. Their catalytic activities can be regulated by modulating the molar ratios of methanol to metal salts (e.g., Fe and Zn) through which the size controllable Fe-Zn ZIFs precursors are obtained. Upon introduction of ascorbic acid (AA) into Fe-N/C/TMB system, complete inhibition of TMB oxidation was observed, resulting in significant decline in absorbance with a clear color change. In the presence of alkaline phosphatase (ALP), ascorbic acid 2-phosphate (AAP) is hydrolyzed to produce AA. When coupled with AAP, a novel colorimetric biosensor platform was fabricated for ALP activity screening in the range of 0.05 U/L-100 U/L (four orders of magnitude) with an ultra-low limit of detection of 0.02 U/L. The work provides a promising strategy to rationally design the transition metal-N/C single-atom nanozyme with high oxidase-like activity.

Size-controllable Fe-N/C single-atom nanozyme with exceptional oxidase-like activity for sensitive detection of alkaline phosphatase

Atomically dispersed Fe/Bi dual active sites single-atom nanozymes for cascade catalysis and peroxymonosulfate activation to degrade dyes.

Hierarchical Bi0.5Fe0.5VO4/honeycomb ceramic plate synergize plasma induce multi-catalysis by constructing a plasma-catalyst system for organic pollutant degradation

Graphitic carbon nitride decorated with appropriate co-catalysts has attracted widespread attention owing to its excellent photocatalytic H2 evolution activity. Herein, monodisperse Pt nanoparticles are synthesized by a facile method and anchored on graphitic carbon nitride (PCN) via self-assembly route. Among the different Pt content, the 3 % Pt-loaded PCN (Pt/PCN3) hybrid reveals highest photocatalytic activity for water splitting with the H2 evolution rate of 2.02 mmol g−1 h−1, about 4 times higher than that of Pt-PCN by traditional photo-deposition way. This work provides a new strategy for constructing high-performance Pt-based co-catalysts on PCN to boost its photocatalytic activity. 

Yuan Liu

Papers

Size-controllable Fe-N/C single-atom nanozyme with exceptional oxidase-like activity for sensitive detection of alkaline phosphatase

Atomically dispersed Fe/Bi dual active sites single-atom nanozymes for cascade catalysis and peroxymonosulfate activation to degrade dyes.

Hierarchical Bi0.5Fe0.5VO4/honeycomb ceramic plate synergize plasma induce multi-catalysis by constructing a plasma-catalyst system for organic pollutant degradation

Facile Synthesis of Monodisperse Pt Nanoparticles on Graphitic Carbon Nitride for High‐Performance Photocatalytic H 2 evolution