Nanozymesbased tumor catalytic therapy, in which nanozymes specifically trigger enzymatic activity within the tumor sites to produce toxic reactive oxygen species (ROS) for tumor cells killing, represents an emerging antitumor modality. [3] In recent years, various nanozymes such as metal oxides, noble metals, metal-organic frameworks, and single-atom nanozymes (SAzymes) are explored as diverse enzyme mimics for tumor therapy. [1a,4] Among them, SAzymes are very promising antitumor agents due to their tunable electronic and geometric structures, maximum atomic utilization efficiency, and excellent catalytic activities. [5] The greatest advantage of SAzymes is that their active sites can be directly designed similar to those of natural enzymes, [6] thus allowing SAzymes to exhibit the catalytic behaviors closer to those of natural enzymes, as well as helping to unravel the action mechanisms of nanozymes involved in tumor catalytic therapy. Despite some breakthroughs in this field, it remains a great challenge to precisely optimize the local coordination structures of SAzymes for more efficient enzyme-like catalysis and tumor therapeutic outcome.In many biological application scenarios, the structure and function of enzymes provide important guidance for the rational design of nanozymes. Horseradish peroxidase (HRP), Single-atom nanozymes (SAzymes) represent a new research frontier in the biomedical fields. The rational design and controllable synthesis of SAzymes with well-defined electronic and geometric structures are essential for maximizing their enzyme-like catalytic activity and therapeutic efficacy but remain challenging. Here, a melamine-mediated pyrolysis activation strategy is reported for the controllable fabrication of iron-based SAzyme containing five-coordinated structure (FeN 5 ), identified by transmission electron microscopy imaging and X-ray absorption fine structure analyses. The FeN 5 SAzyme exhibits superior peroxidase-like activity owing to the optimized coordination structure, and the corresponding catalytic efficiency of Fe-species in the FeN 5 SAzyme is 7.64 and 3.45 × 10 5 times higher than those in traditional FeN 4 SAzyme and Fe 3 O 4 nanozyme, respectively, demonstrated by steadystate kinetic assay. In addition, the catalytic mechanism is jointly disclosed by experimental results and density functional theory studies. The as-synthesized FeN 5 SAzyme demonstrates significantly enhanced antitumor effect in vitro and in vivo due to the excellent peroxidase-like activity under tumor microenvironment.

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In this article, the multicomponent copolymers were prepared by the copolymerization of two hydrophobic silicon-containing monomers bis(trimethylsilyloxy) methylsilylpropyl glycerol methacrylate (SiMA) and tris(trimethylsiloxy)-3-methacryloxypropylsilane (TRIS) with three hydrophilic monomers 2-hydroxyethyl methacrylate, N-vinylpyrrolidone, and N,N-dimethyl acrylamide. The copolymers were hydrated to form transparent silicone hydrogels. The oxygen permeability coefficients (Dk) of hydrogels were measured, and their relationships with the equilibrium water contents (EWC) and the types and contents of silicon containing monomers as well as the phase separation structures of silicone hydrogels were analyzed in detail. The results showed that the EWC decreased as the increase of SiMA content. The relationship between Dk and SiMA content, as well as that between Dk and EWC, showed inverted bell curve distributions, which meant two main factors, i.e., silicon-oxygen bond in silicone and water in hydrogel, contributed to oxygen permeation and followed a mutual inhibition competition mechanism. The internal morphologies of the hydrogels were observed by transmission electron microscope, and the results showed that the hydrogels presented two different phase separation structures depending on the types of the silicon-containing monomers. The silicone phase in SiMA containing hydrogel presented to be a granular texture, while the silicone phase in TRIS containing hydrogel formed a fibrous texture which resulted in a higher Dk value. These results could help to design a silicone hydrogel with better properties and wider application.

Zn-ion hybrid supercapacitors (ZHSCs) emerge as promising equipment for energy storage applications due to their eco-efficiency, abundant natural resource, and high safety. However, the development of ZHSCs remains at the...

The regulation of electron distribution of single-atomic metal sites by atomic clusters is an effective strategy to boost their intrinsic activity of oxygen reduction reaction (ORR). Herein we report the construction of single-atomic Mn sites decorated with atomic clusters by an innovative combination of post-adsorption and secondary pyrolysis. The X-ray absorption spectroscopy confirms the formation of Mn sites via Mn-N 4 coordination bonding to FeMn atomic clusters (FeMn ac /Mn-N 4 C), which has been demonstrated theoretically to be conducive to the adsorption of molecular O 2 and the break of OÀ O bond during the ORR process. Benefiting from the structural features above, the FeMn ac /Mn-N 4 C catalyst exhibits excellent ORR activity with half-wave potential of 0.79 V in 0.5 M H 2 SO 4 and 0.90 V in 0.1 M KOH as well as preeminent Zn-air battery performance. Such synthetic strategy may open up a route to construct highly active catalysts with tunable atomic structures for diverse applications.

Sn-based perovskites are the most promising alternative materials for Pb-based perovskites to address the toxicity problem of lead. However, the development of Sn II -based perovskites has been hindered by their extreme instability. Here, we synthesized efficient and stable lead-free Cs 4 SnBr 6 perovskite by using SnF 2 as tin source instead of easily oxidized SnBr 2 . The SnF 2 configures a fluorine-rich environment, which can not only suppress the oxidation of Sn 2 + in the synthesis, but also construct chemically stable SnÀ F coordination to hinder the electron transfer from Sn 2 + to oxygen within the long-term operation process. The SnF 2 -derived Cs 4 SnBr 6 perovskite shows a high photoluminescence quantum yield of 62.8 %, and excellent stability against oxygen, moisture, and light radiation for 1200 h, representing one of the most stable lead-free perovskites. The results pave a new pathway to enhance the optical properties and stability of lead-free perovskite for high-performance light emitters.

Perovskite light-emitting didoes (PeLEDs) have shown considerable potential in solution-processable display applications. However, the performance of blue PeLEDs in terms of efficiency and stability hinders their practicality on account of severe trap-mediated nonradiative recombination losses and halide phase segregation. To ameliorate these issues, mixed-halide sky-blue perovskite materials are strategically modulated through crystal defect passivation with a trifurcate isocyanate oligomer, which leads to the synergistical suppression of charge trap density and halide ion migration. The proposed approach enables the performance improvement for sky-blue PeLEDs, exhibiting a peak external quantum efficiency of 14.82% and spectrally stable emission at 487 nm. In addition, prolonged operational lifetime and enhanced capability of moisture resistance are achieved simultaneously, approaching a half-lifetime of ≈2900 s at an initial brightness of 178 cd m -2 .

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