One-Pot Etching Pyrolysis to Defect-Rich Carbon Nanosheets to Construct Multiheteroatom-Coordinated Iron Sites for Efficient Oxygen Reduction.

Constructing multiheteroatom coordination structure in carbonaceous substrates demonstrates an effective method to accelerate the oxygen reduction reaction (ORR) of supported single-atom catalyst. Herein, the novel etching route assisted by potassium thiocyanate (KCNS) is developed to convert metal-organic framework to 2D defect-rich porous N,S-co-doped carbon nanosheets for anchoring atomically dispersed iron sites as the high-performance ORR catalysts (Fe-SACs). The well-designed KCNS-assisted etching route can generate spatial confinement template to direct the carbon nanosheet formation, etching condition to form defect-rich structure, and additional sulfur atoms to coordinate iron species. Spectral and microscopy analysis reveals that the iron element in Fe-SACs is highly isolated on carbon nanosheet and anchored by nitrogen and sulfur atoms in unsymmetrical Fe-S1N3 structure. The optimized Fe-SACs with large specific surface area could show remarkable alkaline ORR performances with a high half-wave potential of 0.920 V versus RHE and excellent durability. The rechargeable zinc-air battery assembled with Fe-SACs air electrodes delivers a large power density of 350 mW cm-2 and a stable voltage platform during charge and discharge over more than 1300 h. This work proposes a novel strategy for the preparation of single-atom catalysts with multiheteroatom coordination structure and highly exposed active sites for efficient ORR.

Tuning Carbon Defect in Copper Single-Atom Catalysts for Efficient Oxygen Reduction.

Defect chemistry in carbon matrix shows great potential for promoting the oxygen reduction reaction (ORR) of metal single-atom catalysts. Herein, a modified pyrolysis strategy is proposed to tune carbon defects in copper single-atom catalysts (Cu-SACs) to fully understand their positive effect on the ORR activity. The optimized Cu-SACs with controllable carbon defect degree and enhanced active specific surface area can exhibit improved ORR activity with a half-wave potential of 0.897 VRHE , ultrahigh limiting current density of 6.5 mA cm-2 , and superior turnover frequency of 2.23 e site-1 s-1 . The assembled Zn-air batteries based on Cu-SACs can also show well-retained reversibility and voltage platform over 1100 h charge/discharge period. Density functional theory calculations reveal that suitable carbon defects can redistribute charge density of Cu-N4 active sites to weaken the O-O bond in adsorbed OOH* intermediate and thus reduce its dissociation energy. This discovery offers a universal strategy for fabricating superior single-atom catalysts with high-efficiency active sites toward energy-directed applications.

Dihydromyricetin attenuates Escherichia coli lipopolysaccharide-induced ileum injury in chickens by inhibiting NLRP3 inflammasome and TLR4/NF-κB signalling pathway.

Lipopolysaccharide (LPS) as a major component of Escherichia coli cell wall can cause inflammation and cell death. Dihydromyricetin (ampelopsin, DHM) is a natural flavonoid compound with anti-inflammatory, anti-oxidant and anti-bacterial effects. The preventive effects of DHM against ileum injury remain unclear. Here, we explored the protective role of DHM against LPS-induced ileum injury in chickens. In this study, DHM significantly attenuated LPS-induced alteration in diamine oxidase, malondialdehyde, reduced glutathione, glutathione peroxidase and superoxide dismutase levels in chicken plasma and ileum. Histology evaluation showed that the structure of blood vessels in ileum was seriously fragmented and presence of necrotic tissue in the lumen in the LPS group. Scanning electron microscopic observation revealed that the surface of the villi was rough and uneven, the structure was chaotic, and the normal finger shape was lost in the LPS group. In contrast, 0.05% and 0.1% DHM treatment partially alleviated the abnormal morphology. Additionally, DHM maintained the barrier function by restoring the protein expression of occludin, claudin-1 and zonula occludens protein-1. DHM inhibited apoptosis through the reduction of the expression of bax and caspase-3 and restored the expression of bcl-2. Importantly, DHM could reduce ileum NLR family pyrin domain-containing 3 (NLRP3), caspase-1, interleukin (IL)-1ß and IL-18 expression to protect tissues from pyroptosis and inhibited toll-like receptor 4 (TLR4)/nuclear factor kappa-B (NF-κB) signalling pathway. In summary, DHM attenuated the ileum mucosal damage, oxidative stress and apoptosis, maintained barrier function, inhibited NLRP3 inflammasome and TLR4/NF-κB signalling pathway activation triggered by Escherichia coli LPS.

Anionic Se-Substitution toward High-Performance CuS1- x Sex Nanosheet Cathode for Rechargeable Magnesium Batteries.

Rechargeable magnesium batteries (rMBs) are promising as the most ideal further energy storage systems but lack competent cathode materials due to sluggish redox reaction kinetics. Herein, developed is an anionic Se-substitution strategy to improve the rate capability and the cycling stability of 2D CuS1- x Sex nanosheet cathodes through an efficient microwave-induced heating method. The optimized CuS1- x Sex (X = 0.2) nanosheet cathode can exhibit high reversible capacity of 268.5 mAh g-1 at 20 mA g-1 and good cycling stability (140.4 mAh g-1 at 300 mA g-1 upon 100 cycles). Moreover, the CuS1- x Sex (X = 0.2) nanosheet cathode can deliver remarkable rate capability with a reversible capacity of 119.2 mAh g-1 at 500 mA g-1 , much higher than the 21.7 mAh g-1 of pristine CuS nanosheets. The superior electrochemical performance can be ascribed to the enhanced reaction kinetics, enriched cation storage active sites, and shortened ion diffusion pathway of the CuS1- x Sex nanosheet. Therefore, tuning anionic chemical composition demonstrates an effective strategy to develop novel cathode materials for rMBs.

Scalable 2D Mesoporous Silicon Nanosheets for High-Performance Lithium-Ion Battery Anode.

Constructing unique mesoporous 2D Si nanostructures to shorten the lithium-ion diffusion pathway, facilitate interfacial charge transfer, and enlarge the electrode-electrolyte interface offers exciting opportunities in future high-performance lithium-ion batteries. However, simultaneous realization of 2D and mesoporous structures for Si material is quite difficult due to its non-van der Waals structure. Here, the coexistence of both mesoporous and 2D ultrathin nanosheets in the Si anodes and considerably high surface area (381.6 m2 g-1 ) are successfully achieved by a scalable and cost-efficient method. After being encapsulated with the homogeneous carbon layer, the Si/C nanocomposite anodes achieve outstanding reversible capacity, high cycle stability, and excellent rate capability. In particular, the reversible capacity reaches 1072.2 mA h g-1 at 4 A g-1 even after 500 cycles. The obvious enhancements can be attributed to the synergistic effect between the unique 2D mesoporous nanostructure and carbon capsulation. Furthermore, full-cell evaluations indicate that the unique Si/C nanostructures have a great potential in the next-generation lithium-ion battery. These findings not only greatly improve the electrochemical performances of Si anode, but also shine some light on designing the unique nanomaterials for various energy devices.

Silicon hollow sphere anode with enhanced cycling stability by a template-free method.

Silicon is a promising alternative anode material since it has a ten times higher theoretical specific capacity than that of a traditional graphite anode. However, the poor cycling stability due to the huge volume change of Si during charge/discharge processes has seriously hampered its widespread application. To address this challenge, we design a silicon hollow sphere nanostructure by selective etching and a subsequent magnesiothermic reduction. The Si hollow spheres exhibit enhanced electrochemical properties compared to the commercial Si nanoparticles. The initial discharge and charge capacities of the Si hollow sphere anode are 2215.8 mAh g-1 and 1615.1 mAh g-1 with a high initial coulombic efficiency (72%) at a current density of 200 mA g-1, respectively. In particular, the reversible capacity is 1534.5 mAh g-1 with a remarkable 88% capacity retention against the second cycle after 100 cycles, over four times the theoretical capacity of the traditional graphite electrode. Therefore, our work demonstrates the considerable potential of silicon structures for displacing commercial graphite, and might open up new opportunities to rationally design various nanostructured materials for lithium ion batteries.

Tumor-Targeted Multimodal Optical Imaging with Versatile Cadmium-Free Quantum Dots.

The rapid development of fluorescence imaging technologies requires concurrent improvements in the performance of fluorescent probes. Quantum dots have been extensively used as an imaging probe in various research areas because of their inherent advantages based on unique optical and electronic properties. However, their clinical translation has been limited by the potential toxicity especially from cadmium. Here, a versatile bioimaging probe is developed by using highly luminescent cadmium-free CuInSe2/ZnS core/shell quantum dots conjugated with CGKRK (Cys-Gly-Lys-Arg-Lys) tumor-targeting peptides. This probe exhibits excellent photostability, reasonably long circulation time, minimal toxicity, and strong tumor-specific homing property. The most important feature of this probe is that it shows distinctive versatility in tumor-targeted multimodal imaging including near-infrared, time-gated, and two-photon imaging in different tumor models. In a glioblastoma mouse model, the targeted probe clearly denotes tumor boundaries and positively labels a population of diffusely infiltrating tumor cells, suggesting its utility in precise tumor detection during surgery. This work lays a foundation for potential clinical translation of the probe.

Hierarchical mesoporous NiCo2O4 hollow nanocubes for supercapacitors.

In the present work, mesoporous NiCo2O4 hollow nanocubes are synthesized using a "coordinating etching & precipitating" (CEP) route. The hollow nanocubes are characterized using SEM, TEM, XRD, XPS and BET methods. The hollow nanocubes have a uniform morphology of 300-500 nm, a high surface area of 134.52 m(2) g(-1) and a mesoporous structure of 2.4-6 nm. These mesoporous NiCo2O4 hollow nanocubes exhibit the specific capacitance of 795.6 F g(-1) at a constant discharge current density of 1 A g(-1). The high specific capacitance and the stability of the NiCo2O4 hollow nanocube electrode are attributed to its large specific surface area and mesoporous structure. The specific capacity retention is 97.5% at a current density of 1 A g(-1) and 96.1% at a current density of 2 A g(-1) over 2000 charge-discharge cycles. The high specific capacitance and excellent cyclic stability indicate that NiCo2O4 hollow nanocubes are excellent supercapacitor electrode materials.

Bamboo-Like Nitrogen-Doped Carbon Nanotubes with Co Nanoparticles Encapsulated at the Tips: Uniform and Large-Scale Synthesis and High-Performance Electrocatalysts for Oxygen Reduction.

In recent years, various non-precious metal electrocatalysts for the oxygen reduction reaction (ORR) have been extensively investigated. The development of an efficient and simple method to synthesize non-precious metal catalysts with ORR activity superior to that of Pt is extremely significant for large-scale applications of fuel cells. Here, we develop a facile, low-cost, and large-scale synthesis method for uniform nitrogen-doped (N-doped) bamboo-like CNTs (NBCNT) with Co nanoparticles encapsulated at the tips by annealing a mixture of cobalt acetate and melamine. The uniform NBCNT shows better ORR catalytic activity and higher stability in alkaline solutions as compared with commercial Pt/C and comparable catalytic activity to Pt/C in acidic media. NBCNTs exhibit outstanding ORR catalytic activity due to high defect density, uniform bamboo-like structure, and the synergistic effect between the Co nanoparticles and protective graphitic layers. This facile method to synthesize catalysts, which is amenable to the large-scale commercialization of fuel cells, will open a new avenue for the development of low-cost and high-performance ORR catalysts to replace Pt-based catalysts for applications in energy conversion.

Silk-regulated hierarchical hollow magnetite/carbon nanocomposite spheroids for lithium-ion battery anodes.

Hierarchical olive-like structured carbon-Fe3O4 nanocomposite particles composed of a hollow interior and a carbon coated surface are prepared by a facile, silk protein-assisted hydrothermal method. Silk nanofibers as templates and carbon precursors first regulate the formation of hollow Fe2O3 microspheres and then they are converted into carbon by a reduction process into Fe3O4. This process significantly simplifies the fabrication and carbon coating processes to form complex hollow structures. When tested as anode materials for lithium-ion batteries, these hollow carbon-coated particles exhibit high capacity (900 mAh g(-1)), excellent cycle stability (180 cycles) and rate performance due to their unique hierarchical hollow structure and carbon coating.

In situ formed Bi/BiOBrxI1-x heterojunction of hierarchical microspheres for efficient visible-light photocatalytic activity.

Bi nanoparticles deposited in situ in BiOBrxI1-x hierarchical microspheres (Bi/BiOBrxI1-x heterojunction) were synthesized by a facile one-step solvothermal method. The as-prepared samples were characterized via XRD, SEM, TEM, XPS, UV-vis absorption spectroscopy and N2 adsorption-desorption. The hierarchical microspheres were composed of numerous nanosheets aggregated together compactly to form a spherical geometry. Results indicated that Bi nanoparticles were generated on the surface of BiOBrxI1-x microspheres via the in situ reduction of Bi(3+) by ethylene glycol. BiOBrxI1-x microspheres with deposited Bi nanoparticles were employed for the degradation of RhB under visible-light irradiation and the samples exhibited exceptionally enhanced photocatalytic activity. This immense enhancement in photocatalytic activity was attributed to the contribution of Bi nanoparticles to the efficient separation of electron-hole pairs and prolongation of the lifetime of charge carriers. The behavior of Bi nanoparticles as a cocatalyst for enhancing photocatalytic activity is similar to that of noble metals in photocatalysis. The as-prepared Bi/BiOBr0.266I0.734 sample exhibited highest photocatalytic activity, which exceeded those of other types of visible-light photocatalysts such as N-TiO2, Eu(3+)-BiOI, BiOBr, BiOBr0.2I0.8/graphene and even Ag/AgBr/BiOBr. The Bi/BiOBr0.266I0.734 sample displayed high photochemical stability under repeated visible-light irradiation, which is especially important for its practical application. The active species produced from Bi/BiOBrxI1-x under visible light were hydroxyl radicals. Bi/BiOBrxI1-x could generate more hydroxyl radicals due to the Bi nanoparticles, contributing to the enhance oxidation ability. This study demonstrated the high feasibility of utilizing low-cost Bi nanoparticles as a substitute for noble metals to enhance visible-light photocatalysis.

The superelastic mechanism of Si3N4 microsprings using micro-Raman spectroscopy.

Silicon nitride microsprings with superelasticity are characterized using SEM, XRD, TEM and micro-Raman methods. The internal structure and the superelastic mechanism of silicon nitride microsprings are proposed through analyzing the variation of Raman peaks upon stretching gradually. During the stretching process, since all the vibrations are internal vibrations within the primitive unit cell, the basic structure has no changes and the residual stress never concentrates. The special structure of the fine grains and no sharp grain boundaries make the silicon nitride microsprings possess such good superelastic properties.

Different Dual-Task Paradigm Reduce Postural Control Ability and Dynamic Stability of Healthy Young Adults during Stair Descent.

Objective: This study aimed to compare the impacts of different dual-task paradigms on the postural control ability and dynamic stability of the youth during stair descent. Method: Twenty young adults without regular exercise habits were randomly recruited to perform stair descent tasks with three different paradigms: single-task, cognitive dual-task, and manual dual-task. Kinematic and dynamic data were collected using an 8 Vicon motion analysis system and a Kistler force plate to evaluate postural control ability and dynamic stability during stair descent. Results: The variation trends of lower limb joint moment were similar under the three task models. Compared with a single-task, both dual-task paradigms significantly reduced the mechanical parameters and dynamic stability during stair descent. Conclusion: The dual-task paradigm increases the risk of stair-related falls. Both cognitive and manual tasks have similar impacts on postural control ability and dynamic stability during stair walking. It is recommended that people avoid performing dual tasks during stair descent.

Sustainable Cathodic Performances of VS4 in Rechargeable Magnesium Batteries by Cobalt Substitution.

Vanadium tetrasulfide (VS4) is one of the most promising cathodic materials for rechargeable magnesium battery systems (RMBSs). Elemental substitution to expand layers, creation of sulfur vacancies, and reduction of particle sizes of VS4 are undoubtedly effective strategies to enhance cathodic performances. Experimental and DFT analysis revealed that valence states of vanadium and cobalt have been elevated from V2+ to V3+ and Co2+ to Co3+ in VS4 and that the Co-S bond length shortened due to cobalt substitution, which resulted in enhanced overall internal polarization in the layered atomic structure of VS4 by increasing cobalt concentrations. This phenomenon of charge accumulation contributes toward regulated magnesiation and accommodated volume expansion while cycling, resulting in the enormous structural stability of VS4 and sustainable battery performance during a long and stable cycling at a cost of 20% capacity diminution as compared to pristine VS4 in RMBS. Hence, 9% CoVS4 demonstrated a capacity of 158 mAh g-1 at a current density of 500 mA g-1 with approximately 98% capacity retention after 1000 cycles. Sustainable cathodic performance is the most desirous feature for commercialization. This work provides insight realization regarding structural limitations and opportunities of VS4 for sustainable cathodic performances in RMBS with non-nucleophilic 0.25 mol/L (R-PhOMgCI)2-A1Cl3/THF (PMC) electrolyte and has laid a theoretical plus experimental foundation for future developments.

Effect of Ni charge states on structural, electronic, magnetic, and optical properties of InN.

The first-principles study of Ni-doped InN has been carried out to explore the doping effect of various charge states of Ni on the structural, electronic, magnetic, and optical properties of InN using generalized gradient approximation. Structural properties like lattice parameters, aspect ratios, bond lengths, and formation energies of (In, Ni) N are used to determine the stability of each doped system. The formation energies of (In, Ni)N systems decrease with the increase in charge state of nickel, while the bond lengths show an opposite trend. The DOS diagram shows that the introduction of Ni-d states within the bang gap region reduces the band gap for Ni(1+)- and Ni(2+)-doped InN, while the isolated states are generated in the case of Ni(3+)- and Ni(4+)-doped systems. The Ni(1+)-, Ni(3+)-, and Ni(4+)-doped InN systems are ferromagnetic in nature, whereas the (In, Ni(2+))N depicts spin-glass-like behavior. The best possible magnetization is obtained for (In, Ni(4+))N with a total magnet moment of 2.42 µB per supercell. Because of the presence of nickel impurities, the optical properties of InN have been significantly improved. The pure and Ni(3+)- and Ni(4+)-doped InN systems show nearly the same values of absorption edges (∼0.56 eV), in contrast with the Ni(1+)- and Ni(2+)-doped systems, where these values are 0.37 and 0.51 eV, respectively. The shift in absorption edges of Ni(1+)- and Ni(2+)-doped InN to lower energies and increase in the intensity of absorption and broadening of absorption peaks can be attributed to the pronounced band-gap reduction for these systems. A negligible shift of absorption edges in the case of Ni(3+)- and Ni(4+)- doped InN is the characteristic of isolated charge states introduced around the Fermi level, which inhibit the band gap reduction, and hence the optical properties are not improved as expected. This study demonstrates an important fact that for best possible optical device applications Ni(1+)-doped InN system is excellent, while for better magnetic properties the (In, Ni(4+))N is more suitable.

[Study of the preparation of silk fibroin gel and its morphology as drug release matrix in vitro and in vivo].

Silk fibroin (SF)/sodium alginate (SA) hydrogels can be used as drug injection materials. Homogenate was prepared by centrifugation of the pig myocardial extracellular matrix (PMM) and its modification of SF gel material. This paper observes and compares the different components SF, SF/SA, SF/SA/PMM to illustrate the SF/SA/PMM ternary material as a drug delivery composition material. This ternary material can shorten the gel time, and can make the gel form to be maintained better. Meanwhile, it makes the internal structure of the gel looser so that the hole wall becomes thinner and more conducive to the drug release. In addition, it has good biocompatibility proved by pathological analysis, and is able to enhance the mesenchymal stem cells growth activity, which has great significance in carrying out drug control release.

One-step pyrolysis synthesis of ternary (P,S,N)-doped graphene as an efficient metal-free electrocatalyst for the oxygen reduction reaction.

Graphene-based materials have been regarded recently as a promising substance for electrochemical energy conversion and storage devices owing to their unique structure and extraordinary properties. Herein, an enormously facile one-step pyrolysis approach is reported for the fabrication of ternary (P,S,N)-doped graphene, which is further investigated as an efficient metal-free electrocatalyst for the oxygen reduction reaction (ORR). Furthermore, optimized ternary-doped graphene can deliver excellent ORR catalytic activity that favors the four-electron ORR process and outstanding long-term durability (90.54% current retention after 20000 s which is far superior to that of commercial Pt/C) owing to the preferable synergetic coupling effect between P, S and N. Density functional theory (DFT) calculations were performed to reveal the synergetic coupling effect between doping elements in the ORR process. This work provides an extremely simple one-step pyrolysis method for the synthesis of P,S,N-doped graphene for electrochemical energy conversion and storage devices.

Transformation mechanism of high-valence metal sites for the optimization of Co- and Ni-based OER catalysts in an alkaline environment: recent progress and perspectives.

As an important semi-reaction process in electrocatalysis, oxygen evolution reaction (OER) is closely associated with electrochemical hydrogen production, CO2 electroreduction, electrochemical ammonia synthesis and other reactions, which provide electrons and protons for the related applications. Considering their fundamental mechanism, metastable high-valence metal sites have been identified as real, efficient OER catalytic sites from the recent observation by in situ characterization technology. Herein, we review the transformation mechanism of high-valence metal sites in the OER process, particularly transition metal materials (Co- and Ni-based). In particular, research progress in the transformation process and role of high-valence metal sites to optimize OER performance is summarized. The key challenges and prospects of the design of high-efficiency OER catalysts based on the above-mentioned mechanism and some new in situ characterizations are also discussed.

The Lower Limb Stiffness, Moments, and Work Mode During Stair Descent Among the Older Adults.

OBJECTIVE: Lower limb stiffness strategies and work mode changes between young and older adults during stair descent are unclear. This study investigated the effect of aging on the lower limb stiffness, moments, and joint work mode during stair descent. DESIGN: Twenty young adults and 20 older adults were recruited from the local community for stair descent test. Kinematics and kinetics data were collected by Vicon system and Kistler force plate. The lower limb stiffness, moments, and work mode were calculated and assess between groups. RESULTS: No significant differences in gait parameters were detected between groups. Compared with young adults, older adults have decreased leg stiffness, knee and ankle stiffness, increased peak hip extension moment, hip stiffness, and ankle work contribution. CONCLUSIONS: The older adults actively reduce the lower limb stiffness to reduce the risk of injury during stair descent. The hip joint strategy reduces the risk of forwarding falls and ankle joint compensation work mode to make up for the lack of knee extension strength. This provides a reference for the focus of exercise intervention and rehabilitation strategies for older adults.

A semiconductor-electrocatalyst nano interface constructed for successive photoelectrochemical water oxidation.

Photoelectrochemical water splitting has long been considered an ideal approach to producing green hydrogen by utilizing solar energy. However, the limited photocurrents and large overpotentials of the anodes seriously impede large-scale application of this technology. Here, we use an interfacial engineering strategy to construct a nanostructural photoelectrochemical catalyst by incorporating a semiconductor CdS/CdSe-MoS2 and NiFe layered double hydroxide for the oxygen evolution reaction. Impressively, the as-prepared photoelectrode requires an low potential of 1.001 V vs. reversible hydrogen electrode for a photocurrent density of 10 mA cm-2, and this is 228 mV lower than the theoretical water splitting potential (1.229 vs. reversible hydrogen electrode). Additionally, the generated current density (15 mA cm-2) of the photoelectrode at a given overpotential of 0.2 V remains at 95% after long-term testing (100 h). Operando X-ray absorption spectroscopy revealed that the formation of highly oxidized Ni species under illumination provides large photocurrent gains. This finding opens an avenue for designing high-efficiency photoelectrochemical catalysts for successive water splitting.