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Protein‐protected metal nanoclusters (MNCs), typically consisting of several to a hundred metal atoms with a protein outer layer used for protecting clusters from aggregation, are excellent fluorescent labels for biomedical applications due to their extraordinary photoluminescence, facile synthesis and good biocompatibility. Interestingly, many protein‐protected MNCs have also been reported to exhibit intrinsic enzyme‐like activities, namely peroxidase, oxidase and catalase activities, and are consequently used for biological analysis and environmental treatment. These findings have extended the horizon of protein‐protected MNCs' properties as well as their application in various fields. Furthermore, in the field of nanozymes, protein‐protected MNCs have emerged as an outstanding new addition. Due to their ultra‐small size (<2 nm), they usually have higher catalytic activity, more suitable size for in vivo application, better biocompatibility and photoluminescence in comparison with large size nanozymes. In this review, we will systematically introduce the significant advances in this field and critically discuss the challenges that lie ahead. Ultra‐small nanozymes based on protein‐protected MNCs are on the verge of attracting great interest across various disciplines and will stimulate research in the fields of nanotechnology and biology. This article is characterized under:Therapeutic Approaches and Drug Discovery > Emerging TechnologiesBiology‐Inspired Nanomaterials > Protein and Virus‐Based Structures [ABSTRACT FROM AUTHOR]

The Fe3O4 nanozyme was the first reported nanoparticle with intrinsic peroxidase-like activity and has been widely used in biomedicine. To optimize its catalytic activity, we introduced histidine residues onto the Fe3O4 nanoparticle surface in order to mimic the enzymatic microenvironment of natural peroxidase enzymes. Our results show that modification with a single amino acid could more than ten-fold improve the apparent affinity (KM) of the Fe3O4 nanozyme for the substrate H2O2 and enhanced its catalytic efficiency (kcat/KM) up to twenty fold. Thus we not only optimized the activity of the Fe3O4 nanozyme, but also provide a new rationale for improving the efficiency of nanomaterial-based catalysts by utilizing strategies observed in nature. [ABSTRACT FROM AUTHOR]

Highly C-axis oriented ZnO thin film was manufactured by radio-frequency magnetron sputtering technique on Si (111) substrate. The main objective was to study the influence of rapid thermal annealing (RTA) temperature on the structure and interfacial characteristic of ZnO thin films. X-ray diffraction results showed that the ZnO thin films annealed at 600 °C by RTA technique had a perfect C-axis preferred orientation compared to the other ZnO thin films, and the full width at half maximum of ZnO (002) rocking curve measurements indicted that the RTA-annealed ZnO thin films possessed better crystal structure. Atom force microscopy displayed that the grain size of RTA-annealed ZnO thin films was fine and uniform compared with the as-deposited ZnO thin films, although the grains grew in RTA process and the root meant square roughness was smaller than that of as-deposited films. High-resolution transmission electron microscopy showed that there was an obvious amorphous layer between ZnO thin films and Si substrate, but the RTA-annealed ZnO thin films exhibited larger and denser columnar structure and a preferred orientation with highly c axis perpendicular to the amorphous layer. Copyright © 2012 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

In this study, ZnO/PZT films have been continuously deposited on SiO/Si substrate using radio frequency reactive magnetron sputtering method. The influence of PZT film thickness on the crystallization, surface microstructure and electrical properties of ZnO films were investigated. The X-ray diffraction results showed that the ZnO/PZT-330-nm-thick films had a perfect c-axis preferred orientation and better crystal structure compared to other samples. Simultaneously, the stress in the films has been shown to change from compressive to tensile with the increase of PZT film thickness. Atomic force microscopy displayed that the microstructures of the ZnO/PZT films with little thickness were loosened, and the grains presented a lamellar structure. However, the ZnO films showed a dense, uniform and crack-free uniform microstructure as increasing the PZT film thickness. The relative dielectric constant and dielectric loss of the ZnO/PZT-330-nm-thick films were approximately 21.7 and 0.52 %, respectively. The leakage current density of the ZnO/PZT films first decreased and then increased with increasing PZT film thickness. The ZnO/PZT-330-nm-thick films had a lowest leakage current density of approximately 10 Acm at −5 V, which showed excellent insulating characteristic. [ABSTRACT FROM AUTHOR]

Protein-protected metal nanoclusters (MNCs), typically consisting of several to a hundred metal atoms with a protein outer layer used for protecting clusters from aggregation, are excellent fluorescent labels for biomedical applications due to their extraordinary photoluminescence, facile synthesis and good biocompatibility. Interestingly, many protein-protected MNCs have also been reported to exhibit intrinsic enzyme-like activities, namely peroxidase, oxidase and catalase activities, and are consequently used for biological analysis and environmental treatment. These findings have extended the horizon of protein-protected MNCs' properties as well as their application in various fields. Furthermore, in the field of nanozymes, protein-protected MNCs have emerged as an outstanding new addition. Due to their ultra-small size (<2 nm), they usually have higher catalytic activity, more suitable size for in vivo application, better biocompatibility and photoluminescence in comparison with large size nanozymes. In this review, we will systematically introduce the significant advances in this field and critically discuss the challenges that lie ahead. Ultra-small nanozymes based on protein-protected MNCs are on the verge of attracting great interest across various disciplines and will stimulate research in the fields of nanotechnology and biology. This article is characterized under: Therapeutic Approaches and Drug Discovery > Emerging Technologies Biology-Inspired Nanomaterials > Protein and Virus-Based Structures., (© 2019 Wiley Periodicals, Inc.)

Single-atom catalysts (SACs), as homogeneous catalysts, have been widely explored for chemical catalysis. However, few studies focus on the applications of SACs in enzymatic catalysis. Herein, we report that a zinc-based zeolitic-imidazolate-framework (ZIF-8)-derived carbon nanomaterial containing atomically dispersed zinc atoms can serve as a highly efficient single-atom peroxidase mimic. To reveal its structure-activity relationship, the structural evolution of the single-atom nanozyme (SAzyme) was systematically investigated. Furthermore, the coordinatively unsaturated active zinc sites and catalytic mechanism of the SAzyme are disclosed using density functional theory (DFT) calculations. The SAzyme, with high therapeutic effect and biosafety, shows great promises for wound antibacterial applications., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The Fe 3 O 4 nanozyme was the first reported nanoparticle with intrinsic peroxidase-like activity and has been widely used in biomedicine. To optimize its catalytic activity, we introduced histidine residues onto the Fe 3 O 4 nanoparticle surface in order to mimic the enzymatic microenvironment of natural peroxidase enzymes. Our results show that modification with a single amino acid could more than ten-fold improve the apparent affinity (K M ) of the Fe 3 O 4 nanozyme for the substrate H 2 O 2 and enhanced its catalytic efficiency (k cat /K M ) up to twenty fold. Thus we not only optimized the activity of the Fe 3 O 4 nanozyme, but also provide a new rationale for improving the efficiency of nanomaterial-based catalysts by utilizing strategies observed in nature.