From VIB‑to VB‑Group Transition Metal Disulfides:Structure Engineering Modulation for Superior Electromagnetic Wave Absorption

The laminated transition metal disulfides(TMDs),which are well known as typical two-dimensional(2D)semiconductive materials,possess a unique layered structure,leading to their wide-spread applications in various fields,such as catalysis,energy storage,sensing,etc.In recent years,a lot of research work on TMDs based functional materials in the fields of electromagnetic wave absorption(EMA)has been carried out.Therefore,it is of great significance to elaborate the influence of TMDs on EMA in time to speed up the application.In this review,recent advances in the development of electromagnetic wave(EMW)absorbers based on TMDs,ranging from the VIB group to the VB group are summarized.Their compositions,microstructures,electronic properties,and synthesis methods are presented in detail.Particularly,the modulation of structure engineering from the aspects of heterostructures,defects,morphologies and phases are systematically summarized,focusing on optimizing impedance matching and increasing dielectric and magnetic losses in the EMA materials with tunable EMW absorption performance.Milestones as well as the challenges are also identified to guide the design of new TMDs based dielectric EMA materials with high performance.

Impact of Oxygen Vacancy on Band Structure Engineering of n-p Codoped Anatase TiO2

Doping with various impurities is an effective approach to improve the photoelectrochemical properties of TiO2. Here, we explore the effect of oxygen vacancy on geometric and elec- tronic properties of compensated （i.e. V-N and Cr-C） and non-compensated （i.e. V-C and Cr-N） codoped anatase TiO2 by performing extensive density functional theory calculations. Theoretical results show that oxygen vacancy prefers to the neighboring site of metal dopant （i.e. V or Cr atom）. After introduction of oxygen vacancy, the unoccupied impurity bands located within band gap of these codoped TiO2 will be filled with electrons, and the posi- tion of conduction band offset does not change obviously, which result in the reduction of photoinduced carrier recombination and the good performance for hydrogen production via water splitting. Moreover, we find that oxygen vacancy is easily introduced in V-N codoped TiO2 under O-poor condition. These theoretical insights are helpful for designing codoped TiO2 with high photoelectrochemical performance.

Band structure engineering in metal halide perovskite nanostructures for optoelectronic applications

Metal halide perovskite nanostructures have emerged as low-dimensional semiconductors of great significance in many fields such as photovoltaics,photonics,and optoelectronics.Extensive efforts on the controlled synthesis of perovskite nanostructures have been made towards potential device applications.The engineering of their band structures holds great promise in the rational tuning of the electronic and optical properties of perovskite nanostructures,which is one of the keys to achieving efficient and multifunctional optoelectronic devices.In this article,we summarize recent advances in band structure engineering of perovskite nanostructures.A survey of bandgap engineering of nanostructured perovskites is firstly presented from the aspects of dimensionality tailoring,compositional substitution,phase segregation and transition,as well as strain and pressure stimuli.The strategies of electronic doping are then reviewed,including defect-induced self-doping,inorganic or organic molecules-based chemical doping,and modification by metal ions or nanostructures.Based on the bandgap engineering and electronic doping,discussions on engineering energy band alignments in perovskite nanostructures are provided for building high-performance perovskite p-n junctions and heterostructures.At last,we provide our perspectives in engineering band structures of perovskite nanostructures towards future low-energy optoelectronics technologies.

Progress on band structure engineering of twisted bilayer and two-dimensional moiré heterostructures

Artificially constructed van der Waals heterostructures(vdWHs)provide an ideal platform for realizing emerging quantum phenomena in condensed matter physics.Two methods for building vdWHs have been developed:stacking two-dimensional(2D)materials into a bilayer structure with different lattice constants,or with different orientations.The interlayer coupling stemming from commensurate or incommensurate superlattice pattern plays an important role in vdWHs for modulating the band structures and generating new electronic states.In this article,we review a series of novel quantum states discovered in two model vdWH systems—graphene/hexagonal boron nitride(hBN)hetero-bilayer and twisted bilayer graphene(tBLG),and discuss how the electronic structures are modified by such stacking and twisting.We also provide perspectives for future studies on hetero-bilayer materials,from which an expansion of 2D material phase library is expected.

Structure engineering of cathode host materials for Li-S batteries

Although lithium-sulfur batteries are one of the favorable candidates for next-generation energy storage devices,a few key challenges that have not been addressed have limited its commercialization.These challenges include lithium dendrite growth in the anode side,volume change of the active material,poor electrical conductivity,dissolution and migration of poly sulfides,and slow rate of solid-state reactions in the cathode side.Since the electrochemical performance of lithium-sulfur batteries is greatly affected by the design of the cathode host material,it has also been widely discussed in addressing the abovementioned issues.In this paper,three design ideas of cathode host materials in terms of microstructure,crystal structure and electronic structure are introduced and summarized.Crucially,the current progress of these three structural design strategies and their effects on the electrochemical performance of lithium-sulfur batteries are discussed in detail.Finally,future directions in the structural design of cathode materials for lithium-sulfur batteries are discussed and further perspectives are provided.

Surface and structure engineering of MXenes for rechargeable batteries beyond lithium

With the rapid growth in renewable energy,researchers worldwide are trying to expand energy storage technologies.The development of beyond-lithium battery technologies has accelerated in recent years,amid concerns regarding the sustainability of battery materials.However,the absence of suitable high-performance materials has hampered the development of the next-generation battery systems.MXenes,a family of 2D transition metal carbides and/or nitrides,have drawn significant attention recently for electrochemical energy storage,owing to their unique physical and chemical properties.The extraordinary electronic conductivity,compositional diversity,expandable crystal structure,superior hydrophilicity,and rich surface chemistries make MXenes promising materials for electrode and other components in rechargeable batteries.This report especially focuses on the recent MXene applications as novel electrode materials and functional separator modifiers in rechargeable batteries beyond lithium.In particular,we highlight the recent advances of surface and structure engineering strategies for improving the electrochemical performance of the MXene-based materials,including surface termination modifications,heteroatom doping strategies,surface coating,interlayer space changes,nanostructure engineering,and heterostructures and secondary materials engineering.Finally,perspectives for building future sustainable rechargeable batteries with MXenes and MXene-based composite materials are presented based upon material design and a fundamental understanding of the reaction mechanisms.

Structure Engineering of Layered Double Hydroxides(LDHs)for Heterogeneous Catalysis

Layered double hydroxide(LDH)is regarded as an advanced platform material in catalysis and attracts vast attrition recently.As a kind of two-dimensional layered material,it exhibits great advantages including cation-tunability in layer,lattice limitation,topological transformation,ion exchange and intercalation characteristics.It also can be used as building blocks for composite catalytic materials.Over 100 years,a large number of works have been accomplished and researchers made great progress on investigating the LDH-based catalytic materials.In this review,we summarize representative achievements and significant progress in recent years,which mainly include constructing high entropy catalytic material,high dispersion/stability and interfacial supported catalytic material,composite catalytic materials and nano-reactor based on LDH.Furthermore,through collecting the excellent works,we conclude the future development potential of LDH and provide a perspective.

Multi-scale structure engineering of covalent organic framework for electrochemical charge storage

Covalent organic frameworks(COFs),which are constructed by linking organic building blocks via dynamic covalent bonds,are newly emerged and burgeoning crystalline porous copolymers with features including programmable topological architecture,pre-designable periodic skeleton,well-defined micro-/meso-pore,large specific surface area,and customizable electroactive functionality.Those benefits make COFs as promising candidates for advanced electrochemical energy storage.Especially,for now,structure engineering of COFs from multiscale aspects has been conducted to enable optimal overall electrochemical performance in terms of structure durability,electrical conductivity,redox activity,and charge storage.In this review,we give a fundamental and insightful study on the correlations between multi-scale structure engineering and eventual electrochemical properties of COFs,started with introducing their basic chemistries and charge storage principles.The careful discussion on the significant achievements in structure engineering of COFs from linkages,redox sites,polygon skeleton,crystal nanostructures,and composite microstructures,and further their effects on the electrochemical behavior of COFs are presented.Finally,the timely cutting-edge perspectives and in-depth insights into COFbased electrodematerials to rationally screen their electrochemical behaviors for addressing future challenges and implementing electrochemical energy storage applications are proposed.

Tuning electronic structure of RuO_(2)by single atom Zn and oxygen vacancies to boost oxygen evolution reaction in acidic medium

The poor stability of RuO_(2)electrocatalysts has been the primary obstacles for their practical application in polymer electrolyte membrane electrolyzers.To dramatically enhance the durability of RuO_(2)to construct activity-stability trade-off model is full of significance but challenging.Herein,a single atom Zn stabilized RuO_(2)with enriched oxygen vacancies(SA Zn-RuO_(2))is developed as a promising alternative to iridium oxide for acidic oxygen evolution reaction(OER).Compared with commercial RuO_(2),the enhanced Ru–O bond strength of SA Zn-RuO_(2)by forming Zn-O-Ru local structure motif is favorable to stabilize surface Ru,while the electrons transferred from Zn single atoms to adjacent Ru atoms protects the Ru active sites from overoxidation.Simultaneously,the optimized surrounding electronic structure of Ru sites in SA ZnRuO_(2)decreases the adsorption energies of OER intermediates to reduce the reaction barrier.As a result,the representative SA Zn-RuO_(2)exhibits a low overpotential of 210 mV to achieve 10 mA cm^(-2)and a greatly enhanced durability than commercial RuO_(2).This work provides a promising dual-engineering strategy by coupling single atom doping and vacancy for the tradeoff of high activity and catalytic stability toward acidic OER.

Band structures of strained kagome lattices

Materials with kagome lattices have attracted significant research attention due to their nontrivial features in energy bands.We theoretically investigate the evolution of electronic band structures of kagome lattices in response to uniaxial strain using both a tight-binding model and an antidot model based on a periodic muffin-tin potential.It is found that the Dirac points move with applied strain.Furthermore,the flat band of unstrained kagome lattices is found to develop into a highly anisotropic shape under a stretching strain along y direction,forming a partially flat band with a region dispersionless along ky direction while dispersive along kx direction.Our results shed light on the possibility of engineering the electronic band structures of kagome materials by mechanical strain.

Hybrid 1D/2D heterostructure with electronic structure engineering toward high-sensitivity and polarization-dependent photodetector

The widespread application of photodetectors has triggered an urgent need for high-sensitivity and polarization-dependent photodetection.In this field,the two-dimensional(2D)tungsten disulfide(WS_(2))exhibits intriguing optical and electronic properties,making it an attractive photosensitive material for optoelectronic applications.However,the lack of an effective built-in electric field and photoconductive gain mechanism in 2D WS_(2)impedes its application in high-performance photodetectors.Herein,we propose a hybrid heterostructure photodetector that contains 1D Te and 2D WS_(2).In this device,1D Te induces in-plane strain in 2D WS_(2),which regulates the electronic structures of local WS_(2)and gives rise to type-Ⅱ band alignment in the horizontal direction.Moreover,the vertical heterojunction built of 2D WS_(2)and 1D Te introduces a high photoconductive gain.Benefiting from these two effects,the transfer of photogenerated carriers is optimized,and the proposed photodetector exhibits high sensitivity(photoresponsivity of ~27.7 A W^(-1),detectivity of 9.5×10^(12)Jones,and short rise/decay time of 19.3/17.6 ms).In addition,anisotropic photodetection characteristics with a dichroic ratio up to 2.1 are achieved.This hybrid 1D/2D heterostructure overcomes the inherent limitations of each material and realizes novel properties,opening up a new avenue towards constructing multifunctional optoelectronic devices.

Local structure engineering for active sites in fuel cell electrocatalysts

In this review,we surveyed the significance of local structure engineering on electrocatalysts and electrodes for the performance of oxygen reduction reaction(ORR)in proton exchange membrane fuel cells(PEMFCs).Both on precious metal catalysts(PMC)and non-precious metal catalysts(NPMC),the main methods to modulate local structure of active sites have been summarized.By change of atomic coordination,modulation of bonding distortion and synergy effect from hierarchical structure,local structure engineering has influence on the intrinsic activity and stability of electrocatalysts.Moreover,we emphasized the intimate correlation between lyophobicity of electrocatalysts and membrane electrodes by local structure engineering.Our review aimed to inspire the exploration of advanced electrocatalysts and mechanism study for PEMFCs based on local structure engineering.

Some Problems in Nonlinear Dynamic Instability and Bifurcation Theory for Engineering Structures

In civil engineering, the nonlinear dynamic instability of structures occurs at a bifurcation point or a limit point. The instability at a bifurcation point can be analyzed with the theory of nonlinear dynamics, and that at a limit point can be discussed with the theory of elastoplasticity. In this paper, the nonlinear dynamic instability of structures was treated with mathematical and mechanical theories. The research methods for the problems of structural nonlinear dynamic stability were discussed first, and then the criterion of stability or instability of structures, the method to obtain the bifurcation point and the limit point, and the formulae of the directions of the branch solutions at a bifurcation point were elucidated. These methods can be applied to the problems of nonlinear dynamic instability of structures such as reticulated shells, space grid structures, and so on. Key words nonlinear dynamic instability - engineering structures - non-stationary nonlinear system - bifurcation point - instability at a bifurcation point - limit point MSC 2000 74K25 Project supported by the Science Foundation of Shanghai Municipal Commission of Education (Grant No. 02AK04), the Science Foundation of Shanghai Municipal Commission of Science and Technology (Grant No. 02ZA14034)

Application of 2-D and 3-D Geo-electrical Resistivity Tomography and Geotechnical Soil Evaluation for Engineering Site Investigation:A Case Study of Okerenkoko Primary School,Warri-Southwest,Delta State,Nigeria

In the design of building structures,joint efforts must be decided to resolve the depth of competent layers across the intended site to safeguard the durability of civil engineering structures and to avert the disastrous consequences of structural failure and collapse.In this study,an integrated methodology that employed DC resistivity tomography involving 2-D and 3-D techniques and geotechnical-soil analysis was used to evaluate subsoil conditions for engineering site investigation at Okerenkoko primary school,in the Warri-southwest area of Delta State,to adduce the phenomena responsible for the visible cracks/structural failure observed in the buildings.The results obtained brought to light the geological structure beneath the subsurface,which consists of four geoelectric layers identified as topsoil,dry/lithified upper sandy layer,wet sand(water-saturated)and peat/clay/sandy clayey soil(highly water-saturated).The deeply-seated peat/clay materials(ρ≤20Ωm)were delineated in the study area to the depths of 17.1 m and 19.8 m from 2-D and 3-D tomography respectively.3-D images presented as horizontal depth slices revealed the dominance of very low resistivity materials i.e.peat/clay/sandy clay within the fourth,fifth and sixth layers at depths ranging from 8.68-12.5 m,12.5-16.9 m and 16.9-21.9 m respectively.The dominance of mechanically unstable peat/clay/sandy clay layers beneath the subsurface,which are highly mobile in response to volumetric changes,is responsible for the noticeable cracks/failure detected on structures within the study site.These observations were validated by a geotechnical test of soil samples in the study area.Atterberg’s limits of the samples revealed plasticity indices of zero.Thus,the soil samples within the depth analyzed were representatives of sandy soil that does not possess any plasticity.The methods justifiably provided relevant information on the subsurface geology beneath the study site and should be appropriated as major tools for engineering site assessment/geotechnical projects.

Tailoring the Meso-Structure of Gold Nanoparticles in Keratin-Based Activated Carbon Toward High-Performance Flexible Sensor

Flexible biosensors with high accuracy and reliable operation in detecting pH and uric acid levels in body fluids are fabricated using well-engineered metaldoped porous carbon as electrode material.The gold nanoparticles@N-doped carbon in situ are prepared using wool keratin as both a novel carbon precursor and a stabilizer.The conducting electrode material is fabricated at 500℃ under customized parameters,which mimics A-B type(two different repeating units) polymeric material and displays excellent deprotonation performance(pH sensitivity).The obtained pH sensor exhibits high pH sensitivity of 57 mV/pH unit and insignificant relative standard deviation of 0.088%.Conversely,the composite carbon material with sp^2 structure prepared at 700℃ is doped with nitrogen and gold nanoparticles,which exhibits good conductivity and electrocatalytic activity for uric acid oxidation.The uric acid sensor has linear response over a range of 1-150 μM and a limit of detection 0.1 μM.These results will provide new avenues where biological material will be the best start,which can be useful to target contradictory applications through molecular engineering at mesoscale.

Band gap modulation of nanostructured WO_(3) nanoplate film by Ti doping for enhanced photoelectrochemical performance

Despite being a promising photoanode material for water splitting,WO_(3) has low conductivity,high onset potential,and sluggish water oxidation kinetics.In this study,we designed Ti-doped WO_(3) nanoplate arrays on fluoride-doped tin oxide by a seed-free hydrothermal method,and the effects of doping on the photoelectrochemical performance were investigated.The optimal Ti-doped WO_(3) electrode achieved a photocurrent density of 0.53 mA/cm^(2) at 0.6 V(vs Ag/AgCl),110%higher than that of pure WO_(3) nanoplate arrays.Moreover,a significant cathodic shift in the onset potential was observed after doping.X-ray photoelectron spectroscopy valence band and ultraviolet–visible spectra revealed that the band positions of Ti-doped WO_(3) photoanodes moved upward,yielding a lower onset potential.Furthermore,electrochemical impedance spectroscopy measurements revealed that the conductivities of the WO_(3) photoanodes improved after doping,because of the rapid separation of photo-generated charge carriers.Thus,we report a new design route toward efficient and low-cost photoanodes for photoelectrochemical applications.

Experimental and computational optimization of Prussian blue analogues as high-performance cathodes for sodium-ion batteries:A review

In this review,we discuss the electrochemical properties of Prussian blue(PB)for Na^(+)storage by combining structural engineering and electrolyte modifications.We integrated experimental data and density functional theory(DFT)in sodium-ion battery(SIB)research to refine the atomic arrangements and crystal lattices and introduce substitutions and dopants.These changes affect the lattice stability,intercalation,electronic and ionic conductivities,and electrochemical performance.We unraveled the intricate structure-electrochemical behavior relationship by combining experimental data with computational models,including first-principles calculations.This holistic approach identified techniques for optimizing PB and Prussian blue analog(PBA)structu ral properties for SIBs.We also discuss the tuning of electrolytes by systematically adjusting their composition,concentration,and additives using a combination of molecular dynamics(MD)simulations and DFT computations.Our review offers a comprehensive assessment of strategies for enhancing the electrochemical properties of PB and PBAs through structural engineering and electrolyte modifications,combining experimental insights with advanced computational simulations,and paving the way for next-generation energy storage systems.

Dynamic response of mountain tunnel,bridge,and embankment along the Sichuan-Tibet transportation corridor to active fault based on model tests

The Sichuan-Tibet transportation corridor is prone to numerous active faults and frequent strong earthquakes.While extensive studies have individually explored the effect of active faults and strong earthquakes on different engineering structures,their combined effect remains unclear.This research employed multiple physical model tests to investigate the dynamic response of various engineering structures,including tunnels,bridges,and embankments,under the simultaneous influence of cumulative earthquakes and stick-slip misalignment of an active fault.The prototype selected for this study was the Kanding No.2 tunnel,which crosses the Yunongxi fault zone within the Sichuan-Tibet transportation corridor.The results demonstrated that the tunnel,bridge,and embankment exhibited amplification in response to the input seismic wave,with the amplification effect gradually decreasing as the input peak ground acceleration(PGA)increased.The PGAs of different engineering structures were weakened by the fault rupture zone.Nevertheless,the misalignment of the active fault may decrease the overall stiffness of the engineering structure,leading to more severe damage,with a small contribution from seismic vibration.Additionally,the seismic vibration effect might be enlarged with the height of the engineering structure,and the tunnel is supposed to have a smaller PGA and lower dynamic earth pressure compared to bridges and embankments in strong earthquake zones crossing active faults.The findings contribute valuable insights for evaluating the dynamic response of various engineering structures crossing an active fault and provide an experimental reference for secure engineering design in the challenging conditions of the Sichuan-Tibet transportation corridor.

Unleashing the Potential of Unidirectional Mechanical Materials: Breakthroughs and Promising Applications

The emergence of mechanically one-way materials presents an exciting opportunity for materials science and engineering. These substances exhibit unique nonreciprocal mechanical responses, enabling them to selectively channel mechanical energy and facilitate directed sound propagation, controlled mass transport, and concentration of mechanical energy amidst random motion. This article explores the fundamentals of mechanically one-way materials, their potential applications across various industries, and the economic and environmental considerations related to their production and use.

Analysis of Bridge-Bearing Capacity Detection and Evaluation Technology

A bridge project is taken as an example to analyze the application of bearing capacity detection and evaluation.This article provides a basic overview of the project,the application of bearing capacity detection technology,and the bearing capacity assessment analysis.It is hoped that this analysis can provide a scientific reference for the load-bearing capacity detection and evaluation work in bridge engineering projects,thereby achieving a scientific assessment of the overall load-bearing capacity of the bridge engineering structure.