A thin Si nanowire network anode for high volumetric capacity and long-life lithium-ion batteries

Silicon nanowires(Si NWs)have been widely researched as the best alternative to graphite anodes for the next-generation of high-performance lithium-ion batteries(LIBs)owing to their high capacity and low discharge potential.However,growing binder-free Si NW anodes with adequate mass loading and stable capacity is severely limited by the low surface area of planar current collectors(CCs),and is particularly challenging to achieve on standard pure-Cu substrates due to the ubiquitous formation of Li+inactive silicide phases.Here,the growth of densely-interwoven In-seeded Si NWs is facilitated by a thin-film of copper-silicide(CS)network in situ grown on a Cu-foil,allowing for a thin active NW layer(<10μm thick)and high areal loading(≈1.04 mg/cm^(2))binder-free electrode architecture.The electrode exhibits an average Coulombic efficiency(CE)of>99.6%and stable performance for>900 cycles with≈88.7%capacity retention.More significantly,it delivers a volumetric capacity of≈1086.1 m A h/cm^(3)at 5C.The full-cell versus lithium manganese oxide(LMO)cathode delivers a capacity of≈1177.1 m A h/g at 1C with a stable rate capability.This electrode architecture represents significant advances toward the development of binder-free Si NW electrodes for LIB application.

封闭锻造挤压镁合金同步提高强度和塑性

介绍一种用于AZ31镁合金的新型连续塑性工艺,即闭式锻造挤压。采用光学显微镜、扫描电子显微镜、电子背散射衍射和拉伸和压缩试验研究合金微观结构的演变和强化机制。结果表明,该工艺可以促进动态再结晶,消除粗大的未动态再结晶晶粒区域,有效细化晶粒,并提高合金的强度、塑性和各向异性。晶粒细化主要归功于应力,促进再结晶的形核并细化组织。完全再结晶的超细晶组织同时提高了强度和塑性。经过60 s封闭锻造和连续挤压后,合金表现出较高的力学性能,其拉伸屈服强度、抗拉强度、抗压强度、伸长率和屈服不对称性分别为305 MPa、337 MPa、295 MPa、27%和0.97。

赤泥堆场修复促进土壤发育和植被重建（英文）

赤泥是氧化铝工业生产过程排放的强碱性固体废物,盐碱性强和营养元素匮乏是影响赤泥堆场植物生长的主要限制因素。对赤泥堆场的长期野外研究,分析基质改良对赤泥理化特性和植物多样性的影响,结果表明:施用石膏后,赤泥pH和可交换钠明显降低,黑麦草和红牛轴草发芽指数分别由22%和42%提高到100%;施用堆肥显著提高赤泥碳、氮、磷等养分元素含量;赤泥改良1年后,绒毛草主要元素含量与普通草地植物元素含量相似;基质改良5年后,绒毛草和红牛轴草钠含量显著降低,分别由0.6%和0.58%降低到0.3%和0.1%,赤泥堆场优势物种为菊科、豆科和禾本科植物。研究结果对赤泥土壤化研究及堆场生态修复实践具有重要的参考价值。

Ti−6Al−4V颗粒增强体对Mg−9Al−1Zn合金力学性能的影响

采用粉末冶金法制备Ti−6Al−4V(TC4)颗粒增强Mg−9Al−1Zn(AZ91)镁基复合材料。随着TC4含量的增加,复合材料的屈服强度、极限抗拉强度和伸长率先升高后降低。当TC4颗粒的含量达到10%(质量分数)时,复合材料具有优异的综合力学性能,其屈服强度、抗拉强度和伸长率分别为335 MPa、370 MPa和6.4%。综合力学性能的改善是由于镁基体和TC4颗粒之间具有良好的界面结合,载荷可从镁基体转移到TC4颗粒上,其强化机制主要包括热膨胀系数差异引起的位错强化及细晶强化。

Understanding the low temperature electrochemistry of magnesium-lithium hybrid ion battery in all-phenyl-complex solutions

Magnesium-lithium hybrid ion batteries have emerged as a new class of energy storage systems owing to dendrite free cycling of magnesium anode and possibility of practice of numerous conventional lithium cathodes.In present work,we used hybrid ion strategy to analyze the performance of lithium titanate based lithium cathode,magnesium metal anode,and all-phenyl complex(APC)electrolytes at different temperatures(25℃,10℃,0℃,-10℃,and-20℃).The hybrid ion battery exhibited excellent rate performance(228 m Ah g^(-1)/20 m A g^(-1) and 163 mAh g^(-1)/1000 mA g^(-1))with stable voltage plateaus at 0.90 and 0.75 V,which corresponds to specific energy of 178 Wh kg^(-1) at room temperature(25℃).Experimental results revealed that APC-THF solutions have strong potential to suppress the freezing of electrolyte solutions owing to low boiling point of THF.The low temperature electrochemical testing revealed the reversible capacities of 213.4,165.5,143.8,133.2 and 78.56 mAh g^(-1) at 25,10,0,-10,and-20℃,respectively.Furthermore,ex-situ XRD,SEM,and EIS tests were carried out to understand the reaction kinetics of both Mg2+and Li+ions inside the lithium titanate cathode.We hope this work will shed light on low temperature prospective of electrochemical devices for use in cold environments.

Modulating vectored non-covalent interactions for layered assembly with engineerable properties

Vectored non-covalent interactions—mainly hydrogen bonding and aromatic interactions—extensively contribute to(bio)-organic self-assembling processes and significantly impact the physicochemical properties of the associated superstructures.However,vectored non-covalent interaction-driven assembly occursmainly along one-dimensional(1D)or three-dimensional(3D)directions,and a two-dimensional(2D)orientation,especially that of multilayered,graphene-like assembly,has been reported less.In this present research,by introducing amino,hydroxyl,and phenyl moieties to the triazine skeleton,supramolecular layered assembly is achieved by vectored non-covalent interactions.The planar hydrogen bonding network results in high stability,with a thermal sustainability of up to about 330°C and a Young’s modulus of up to about 40 GPa.Upon introducing wrinkles by biased hydrogen bonding or aromatic interactions to disturb the planar organization,the stability attenuates.However,the intertwined aromatic interactions prompt a red edge excitation shift effect inside the assemblies,inducing broad-spectrum fluorescence covering nearly the entire visible light region(400–650 nm).We show that bionic,superhydrophobic,pillar-like arrays with contact angles of up to about 170°can be engineered by aromatic interactions using a physical vapor deposition approach,which cannot be realized through hydrogen bonding.Our findings show the feasibility of 2D assembly with engineerable properties by modulating vectored non-covalent interactions.

Tuning the local coordination environment of silver(Ⅰ) coordination networks with counterions for enhanced electrocatalytic CO_(2) reduction

Very recently, the local coordination environment of active sites has been found to strongly influence their performance in electrocatalytic CO_(2) reduction by tuning the intrinsic kinetics of CO_(2) activation and intermediate stabilization. It is imperative to elucidate the mechanism for such an influence towards the rational design of efficient catalysts;however, the complex interactions between the multiple factors involved in the system make it challenging to establish a clear structure–performance relationship. In this work, we chose ion-intercalated silver(I)-based coordination networks(AgCNs) with a well-defined structure as a model platform, which enables us to understand the regulation mechanism of counterions as the counterions are the only tuning factor involved in such a system. We prepared two isostructural Ag CNs with different intercalation ions or counterions of BF_(4)^(-) and ClO_(4)^(-)(named as AgCNs-BF_(4) and AgCNs-ClO_(4)) and found that the former has a more competitive CO_(2) electroreduction performance than the latter. AgCNs-BF_(4) achieves the highest Faradaic efficiency for CO_(2) to CO of 87.1% at-1.0 V(vs. RHE) with a higher partial current density, while AgCNs-ClO_(4) exhibits only 77.2% at the same applied potential.Spectroscopic characterizations and theoretical calculation reveal that the presence of BF_(4)^(-)is more favorable for stabilizing the COOH^(*) intermediate by weakening hydrogen bonds, which accounts for the superior activity of Ag CNs-BF_(4).

Development and characterization of 3D-printed electroconductive pHEMA-co-MAA NP-laden hydrogels for tissue engineering

Tissue engineering(TE)continues to be widely explored as a potential solution to meet critical clinical needs for diseased tissue replacement and tissue regeneration.In this study,we developed a poly(2-hydroxyethyl methacrylate-co-methacrylic acid)(pHEMA-co-MAA)based hydrogel loaded with newly synthesized conductive poly(3,4-ethylene-dioxythiophene)(PEDOT)and polypyrrole(PPy)nanoparticles(NPs),and subsequently processed these hydrogels into tissue engineered constructs via three-dimensional(3D)printing.The presence of the NPs was critical as they altered the rheological properties during printing.However,all samples exhibited suitable shear thinning properties,allowing for the development of an optimized processing window for 3D printing.Samples were 3D printed into pre-determined disk-shaped configurations of 2 and 10 mm in height and diameter,respectively.We observed that the NPs disrupted the gel crosslinking efficiencies,leading to shorter degradation times and compressive mechanical properties ranging between 450 and 550 kPa.The conductivity of the printed hydrogels increased along with the NP concentration to(5.10±0.37)×10^(−7)S/cm.In vitro studies with cortical astrocyte cell cultures demonstrated that exposure to the pHEMA-co-MAA NP hydrogels yielded high cellular viability and proliferation rates.Finally,hydrogel antimicrobial studies with staphylococcus epidermidis bacteria revealed that the developed hydrogels affected bacterial growth.Taken together,these materials show promise for various TE strategies.

Hyaluronic acid association with bacterial,fungal and viral infections:Can hyaluronic acid be used as an antimicrobial polymer for biomedical and pharmaceutical applications?

The relationships between hyaluronic acid(HA)and pathological microorganisms incite new understandings on microbial infection,tissue penetration,disease progression and lastly,potential treatments.These understandings are important for the advancement of next generation antimicrobial therapeutical strategies for the control of healthcare-associated infections.Herein,this review will focus on the interplay between HA,bacteria,fungi,and viruses.This review will also comprehensively detail and discuss the antimicrobial activity displayed by various HA molecular weights for a variety of biomedical and pharmaceutical applications,including microbiology,pharmaceutics,and tissue engineering.

Ferroelectricity in biological building blocks:Slipping on a banana peel?

Ferroelectricity in biological system has been anticipated both theoretically and experimentally over the past few decades.Claims of ferroelectricity in biological systems have given rise to confusion and methodological controversy.Over the years,a“loop”of induced polarization in response to a varying applied electrical field and a consequent polarization reversal has prompted many researchers to claim ferroelectricity in biological structures and their building blocks.Other observers were skeptical about the methodology adopted in generating the data and questioned the validity of the claimed ferroelectricity as such,“loop”can also be obtained from linear capacitors.In a paper with somewhat tongue-in-cheek title,Jim Scott showed that ordinary banana peels could exhibit closed loops of electrical charge which closely resemble and thus could be misinterpreted as ferroelectric hysteresis loops in barium sodium niobate,BNN paraphrasing it as“banana”.In this paper,we critically review ferroelectricity in biological system and argue that knowing the molecular and crystalline structure of biological building blocks and experimenting on such building blocks may be the way forward in revealing the“true”nature of ferroelectricity in biological systems.

The role of externally-modulated electrostatic interactions in amplifying charge transport across lysine-doped peptide junctions

Many evolved biomolecular functions such as ion pumping or redox catalysis rely on controlled charge transport through the polypeptide matrix, which can be regulated by shifts in molecular protonation states and dependent supramolecular packing modes in response to environmental cues. However, the exact roles of such dynamic, non-covalent interactions in peptide charge transport have remained elusive. To tackle this challenge, here we report the modulation of charge transport in a series of lysine(Lys)-substituted hepta-glycine(Gly) peptide self-assembled monolayers(SAMs) on template-striped gold(Au^(TS)) bottom electrodes with eutectic gallium-indium(EGaIn) liquid metal top electrodes. We demonstrate systematic modulation of hydrogen bonding and more general electrostatic interactions by shifting the position of the charged Lys-residue and creating different protonation patterns by changing the environmental pH in the Au^(TS)/peptide//Ga Ox/EGa In junctions. The effective modulation is evidenced by current density-voltage(J-V) measurements combined with SAM characterization using ultraviolet photoelectron spectroscopy(UPS) and angle-resolved X-ray photoelectron spectroscopy(ARXPS), polarization modulation-infrared reflection-absorption spectroscopy(PM-IRRAS), and molecular dynamics(MD) simulations. Decreasing the hydrogen bonding inside the peptide SAMs and increasing the electrostatic interactions by environmental counterions amplifies the charge transport differently with Lys-position, which means that the sensitive electrical response of peptide SAMs can be tuned by the peptide sequence. Our results provide insights into the relationship between molecular design and in situ modulation of charge transport properties for the development of bionanoelectronics.

基于半导体纳米材料的偏振光发射:从材料到发光二极管

由于偏光片、彩色滤光片和液晶层等结构的损耗,基于背光源技术的液晶显示器的整体效率不足5%.自发射发光二极管(LED)不但具有巨大的市场潜力,而且能够满足未来显示的需求,迎来了巨大的发展机遇.更重要的是,由于避免了偏光片造成的光损失,偏振LED可以提高背景光利用效率.因此,亟需寻找有效的方法组装高质量的各向异性纳米材料薄膜,从而制备出具有高偏振度和高外量子效率的偏振LED.本文介绍了一些半导体纳米材料的光电特性及其在偏振LED中的潜在应用.综述了在偏振光发射领域从材料到薄膜,再到LED的研究进展;总结和比较了构建偏振光发射薄膜和LED的不同组装策略;最后,讨论了当前面临的挑战,并对偏振LED的潜在商业应用价值进行了展望.我们希望这篇综述能够对偏振LED当前研究进展进行有价值的总结,并对其未来发展激发一些新的、切实可行的想法.

Robust ultra-microporous metal-organic frameworks for highly efficient natural gas purification

The development of highly efficient separation technology for the purification of natural gas by removing ethane(C_(2)H_(6))and propane(C_(3)H_(8))is a crucial but challenging task to their efficient utilization in the chemical industry and social life.Here,we report three isomorphic ultra-microporous metal-organic frameworks(MOFs),M-pyz(M=Fe,Co,and Ni,and pyz=pyrazine)referred to as Fe-pyz,Co-pyz,and Ni-pyz,respectively,which possess high density of open metal sites and suitable pore structure.Compared with the benchmark materials reported,M-pyz not only has high adsorption capacities of C_(2)H_(6)and C_(3)H_(8)at low pressure(up to 51.6 and 63.7 cm^(3)·cm^(−3)),but also exhibits excellent C_(3)H_(8)/CH_(4)and C_(2)H_(6)/CH_(4)ideal adsorption solution theory(IAST)selectivities,111 and 25,respectively.Theoretical calculations demonstrated that the materials’separation performance was driven by multiple intermolecular interactions(hydrogen bonding interactions and van der Waals effect)between gas molecules(C_(2)H_(6)and C_(3)H_(8))and the M-pyz binding sites.And,dynamic breakthrough experiments verified the superior reusability and practical separation feasibility for the ternary CH_(4)/C_(2)H_(6)/C_(3)H_(8)mixtures.Furthermore,M-pyz can be synthesized rapidly and on a large scale at room temperature.This work presents a series of promising MOFs adsorbents to efficiently purify natural gas and promotes the industrial development process of MOFs materials.

Graphene oxide-based hydrogels as a nanocarrier for anticancer drug delivery

Graphene oxide (GO) possesses excellent mechanical strength,biocompatibility,colloidal stability,large surface area and high adsorption capability.It has driven to cancer nanotechnology to defeat cancer therapy obstacles,via integration into three-dimensional (3D) hydrogel network with biocompatible polymers as nanocomposites carrier,and controllable release of anticancer drugs.Specifically,the surface of GO affords π-π stacking and hydrophilic interactions with anticancer drugs.Additionally,modification of GO with various polymers such as natural and synthetic polymers enhances its biodegradability,drug loading,and target delivery.In this review,GO based hydrogels research accomplishments are reviewed on the aspects of crosslinking strategies,preparation methods,the model drug,polymer conjugation and modification with targeting ligands.Moreover,swelling kinetics,drug release profile and biological activity in vivo and in vitro are discussed.The biocompatibility of GO based hydrogels is also discussed from the perspective of its nano-bio interfaces.Apart from that,the clinical potential of GO based hydrogels and its major challenges are addressed in detail.Finally,this review concludes with a summary and invigorating future perspectives of GO based hydrogels for anticancer drug delivery.It is anticipated that this review can stimulate a new research gateway to facilitate the development of anticancer drug delivery by harnessing the unique properties of GO based hydrogels,such as large surface area,chemical purity,high loading capacity of drug,chemical stability,and the nature of lipophilic for cell membrane penetration.

Direct visualization of phase-matched efficient second harmonic and broadband sum frequency generation in hybrid plasmonic nanostructures

Second harmonic generation and sum frequency generation(SHG and SFG)provide effective means to realize coherent light at desired frequencies when lasing is not easily achievable.They have found applications from sensing to quantum optics and are of particular interest for integrated photonics at communication wavelengths.Decreasing the footprints of nonlinear components while maintaining their high up-conversion efficiency remains a challenge in the miniaturization of integrated photonics.Here we explore lithographically defined AlGaInP nano(micro)structures/Al_(2)O_(3)/Ag as a versatile platform to achieve efficient SHG/SFG in both waveguide and resonant cavity configurations in both narrow-and broadband infrared(IR)wavelength regimes(1300-1600 nm).The effective excitation of highly confined hybrid plasmonic modes at fundamental wavelengths allows efficient SHG/SFG to be achieved in a waveguide of a cross-section of 113 nm×250 nm,with a mode area on the deep subwavelength scale(λ2/135)at fundamental wavelengths.Remarkably,we demonstrate direct visualization of SHG/SFG phase-matching evolution in the waveguides.This together with mode analysis highlights the origin of the improved SHG/SFG efficiency.We also demonstrate strongly enhanced SFG with a broadband IR source by exploiting multiple coherent SFG processes on 1μm diameter AlGaInP disks/Al_(2)O_(3)/Ag with a conversion efficiency of 14.8%MW^(−1) which is five times the SHG value using the narrowband IR source.In both configurations,the hybrid plasmonic structures exhibit>1000 enhancement in the nonlinear conversion efficiency compared to their photonic counterparts.Our results manifest the potential of developing such nanoscale hybrid plasmonic devices for state-of-the-art on-chip nonlinear optics applications.

Localization-limited exciton oscillator strength in colloidal CdSe nanoplatelets revealed by the optically induced stark effect

2D materials are considered for applications that require strong light-matter interaction because of the apparently giant oscillator strength of the exciton transitions in the absorbance spectrum.Nevertheless,the effective oscillator strengths of these transitions have bee n scarcely reported,nor is there a con sistent interpretati on of the obtained values.Here,we analyse the transition dipole moment and the ensuing oscillator strength of the exciton transition in 2D CdSe nanoplatelets by means of the optically induced Stark effect(OSE).Intriguingly,we find that the exciton absorption line reacts to a high intensity optical field as a transition with an oscillator strength FStark that is 50 times smaller than expected based on the linear absorption coefficient.We propose that the pronounced exciton absorption line should be seen as the sum of multiple,low oscillator strength transitions,rather than a single high oscillator strength one,a feat we assign to strong exciton center-of-mass localization.Within the quantum mechanical description of excitons,this 50-fold difference between both oscillator strengths corresponds to the ratio between the cohere nee area of the exciton's center of mass and the total area,which yields a coherence area of a mere 6.1 nm2.Since we find that the coherence area in creases with reducing temperature,we conclude that thermal effects,related to lattice vibrations,contribute to exciton localization.In further support of this localization model,we show that FStark is in dependent of the n anoplatelet area,correctly predicts the radiative lifetime,and lines up for strongly confined quantum dot systems.

Thermally rearranged covalent organic framework with flame-retardancy as a high safety Li-ion solid electrolyte

Solid polymer electrolytes have demonstrated high promise to solve the safety problems caused by conventional liquid electrolytes in lithium ion batteries.However,the inherent flammability of most polymer electrolyte materials remains unresolved,hence hindering their further industrial application.Addressing this challenge,we designed and constructed a thermal-responsive imide-linked covalent organic framework(COF)bearing ortho-positioned hydroxy groups as precursors,which can conduct a thermal rearrangement to transform into a highly crystalline and robust benzoxazole-linked COF upon heating.Benefiting from the release of carbon dioxide through thermal rearrangement reaction,this COF platform exhibited excellent flame retardant properties.By contrast,classic COFs(e.g.,boronate ester,imine,olefin,imide linked)were all flammable.Moreover,incorpo-rating polyethylene glycol and Li salt into the COF channels can produce solid polymer electrolytes with outstanding flame retardancy,high ionic conductivity(6.42×10^(-4) S cm^(-1))and a high lithium-ion transference number of 0.95.This thermal rearrangement strategy not only opens a new route for the fabrication of ultrastable COFs,but also provides promising perspectives to designing flame-retardant materials for energy-related applications.

Crystal engineering of porous coordination networks for C3 hydrocarbon separation

C3 hydrocarbons(HCs),especially propylene and propane,are high‐volume products of the chemical industry as they are utilized for the production of fuels,polymers,and chemical commodities.Demand for C3 HCs as chemical building blocks is increasing but obtaining them in sufficient purity(>99.95%)for polymer and chemical processes requires economically and energetically costly methods such as cryogenic distillation.Adsorptive separations using porous coordination networks(PCNs)could offer an energy‐efficient alternative to current technolo-gies for C3 HC purification because of the lower energy footprint of sorbent separations for recycling versus alternatives such as distillation,solvent extraction,and chemical transformation.In this review,we address how the structural modularity of porous PCNs makes them amenable to crystal engineering that in turn enables control over pore size,shape,and chemistry.We detail how control over pore structure has enabled PCN sorbents to offer benchmark performance for C3 separations thanks to several distinct mechanisms,each of which is highlighted.We also discuss the major challenges and opportunities that remain to be addressed before the commercial development of PCNs as advanced sorbents for C3 separation becomes viable.

Getting the Lead Out:Biomolecular Crystals as Low-Cost,High-Performance Piezoelectric Components

INTRODUCTION There are billions of piezoelectric sensors globally in our vehicles,consumer electronics,medical devices,advanced scientific equipment,fuel gauges,and structural health monitoring units.The vast majority of these sensors contain the perovskite lead zirconium titanate(PZT).It is estimated that there is 100 g of PZT distributed across a variety of integrated sensors in every one of the 1.4 billion cars on our roads.PZT requires toxic lead oxide(PbO)during its synthesis and leaches lead into water supplies at end-of-life disposal.Lead-free alternatives are a large field of research,yet the most-touted candidates,which are also ceramic materials containing elements such as niobium,bismuth,and barium,are even more damaging to the environment(Figure 1).

Ultrathin oxide controlled photocurrent generation through a metal–insulator–semiconductor heterojunction

Recent advances in nanoscale lasers,amplifiers,and nonlinear optical converters have demonstrated the unprecedented potential of metal–insulator–semiconductor(MIS)structures as a versatile platform to realize integrated photonics at the nanoscale.While the electric field enhancement and confinement have been discussed intensively in MIS based plasmonic structures,little is known about the carrier redistribution across the heterojunction and photocurrent transport through the oxide.Herein,we investigate the photo-generated charge transport through a single Cd Se microbelt-Al_(2)O_(3)-Ag heterojunction with oxide thickness varying from 3 nm to 5 nm.Combining photocurrent measurements with finite element simulations on electron(hole)redistribution across the heterojunction,we are able to explain the loss compensation observed in hybrid plasmonic waveguides at substantially reduced pump intensity based on MIS geometry compared to its photonic counterpart.We also demonstrate that the MIS configuration offers a low-dark-current photodetection scheme,which can be further exploited for photodetection applications.