Integration of 2D layered CdS/WO_(3) S-scheme heterojunctions and metallic Ti_(3)C_(2) MXene-based Ohmic junctions for effective photocatalytic H_(2) generation

The rapid recombination of photo-generated electron-hole pairs,insufficient active sites,and strong photocorrosion have considerably restricted the practical application of Cd S in photocatalytic fields.Herein,we designed and constructed a 2D/2D/2D layered heterojunction photocatalyst with cascaded 2D coupling interfaces.Experiments using electron spin resonance spectroscopy,ultraviolet photoelectron spectroscopy,and in-situ irradiation X-ray photoelectron spectroscopy were conducted to confirm the 2D layered CdS/WO_(3) step-scheme(S-scheme)heterojunctions and CdS/MX ohmic junctions.Impressively,it was found that the strong interfacial electric fields in the S-scheme heterojunction photocatalysts could effectively promote spatially directional charge separation and transport between CdS and WO_(3) nanosheets.In addition,2D Ti_(3)C_(2) MXene nanosheets with a smaller work function and excellent metal conductivity when used as a co-catalyst could build ohmic junctions with Cd S nanosheets,thus providing a greater number of electron transfer pathways and hydrogen evolution sites.Results showed that the highest visible-light hydrogen evolution rate of the optimized MX-Cd S/WO_(3) layered multi-heterostructures could reach as high as 27.5 mmol/g/h,which was 11.0 times higher than that of pure CdS nanosheets.Notably,the apparent quantum efficiency reached 12.0% at 450 nm.It is hoped that this study offers a reliable approach for developing multifunctional photocatalysts by integrating S-scheme and ohmic-junction built-in electric fields and rationally designing a 2D/2D interface for efficient light-to-hydrogen fuel production.

Hydrothermal Synthesis and Crystal Structure of a New 2D Layered Cadmium(II) Coordination Polymer:[Cd(bimc)_2]_n(bimc=1H-Benzimidazole-5-carboxylate)

A new coordination polymer [Cd（bimc）2]n was obtained by the reaction of Hbimc with Cd（NO3） 2·4H2O in NaOH solution, and characterized by elemental analysis, IR and singlecrystal X-ray diffraction. The crystal belongs to orthorhombic, space group Pbcn with a = 12.533（4）, b = 15.705（5）, c = 15.200（5） A, V= 2991.8（15） A^3, Mr = 434.68, Z = 8, Dc = 1.930 g/cm^3, F（000） = 1712,μ（MoKa） = 1.492 mm^-1, the final R = 0.0410 and wR = 0.0804 for 1661 observed reflections （I 〉 2σ（I））. The Cd atom exhibits a distorted six-coordinate CdNzOa octahedral coordination geometry. The complex molecules are linked by both μ2-（η2-O, O^-）, NI and μ2-（η2-O, O^-）, N3 coordination modes of ligands to form cross-like wave （4, 4） layer structures which are further stacked through interlayer hydrogen bonds and π-π stacking interactions in an offset fashion to form a 3D supramolecular structure.

A 2D Layered Thiostannate: Synthesis and Crystal Structure of [tmdpH_2]Sn_3S_7

A new thiostannate,[tmdpH2]Sn3S7 1（tmdp = 4,4＇-trimethylenedipiperidine）,has been synthesized under solvothermal conditions and characterized by elemental analysis,IR spectroscopy,and single-crystal X-ray diffraction analysis.In 1,the Sn3S4 secondary incomplete cubane-like building units are bridged by μ2-S atoms to form Sn12S12 rings which are then joined parallelly to the [001] plane,giving the final 2D（Sn3S7^2-）n layer of（6,3） network.The layers are stacked along the c axis so that 24-membered ring channels are generated,in which the organic cations are accommodated.The compound crystallizes in monoclinic,space group C2/c,with a=23.052（3）,b=13.4039（12）,c=18.412（2）A,β=120.112（4）°,V=4921.3（9）A^3,C13H28N2S7Sn3,Mr=792.86,Z=8,Dc=2.140 g/cm^3,F（000）=3056,μ=3.619 mm^-1,the final R=0.0488 and wR=0.1125 for 4607 observed reflections with I〉2σ（I）.

Weak Interactions and 2D Layer Structure of a New Ion-pair Complex Bis(1-benzyl-4-methylquinolinium)-bis(maleonitriledithiolato)nickel(Ⅱ)

A new ion-pair complex, [BzMeQ1]2[Ni（nmt）2]1（[BzMeQ1]^＋ = 1-benzyl-4-ntethylquino- linium, mnta- -- maleonitriledithiolate） has been synthesized and structurally characterized by IR, ESI-MS and X-ray diffraction methods. Complex 1 is of triclinic, space group PI, with a = 9.079（2）, b = 10.154（2）, c = 11.243（2）A, α= 81.58（1）, β= 69.63（1）, γ = 68.02（1）°, V= 940.1（3）A3, Dc = 1.427 g/cm^3, Z = 1, F（000） = 418 and R = 0.0442. A 2D layer structure is formed via the cation-cation π…π and C-H…π interactions observed in the solid state of the complex.

A Fluorine-Functionalized 3D Covalent Organic Framework with Entangled 2D Layers

Constructing three dimensional(3D)covalent organic frameworks(COFs)through the entanglement of two dimensional(2D)nets is a promising but underdeveloped strategy.Herein,we report the design and synthesis of a fluorine functionalized 3DCOF(3D-An-COF-F)formed by entangled 2D sql nets.The structure of 3D-An-COF-F was determined by the combination of continuous rotation electron diffraction technique and modelling based on the chemical information from real space.Interestingly,compared to the isostructural 3D-An-COF without F atom s,3DAn-COF-F showed an improved CO_(2)sorption ability and higher CO_(2)/N_(2)selectivity.Our study not only demonstrated the generality of constructing 3D COFs with entangled 2D nets by introducing bulky groups vertically in planar building blocks,but also will expand the diversity of 3D COFs for various applications.

High-sensitivity shortwave infrared photodetectors of metal-organic frameworks integrated on 2D layered materials

Photodetectors operating in the shortwave infrared region are of great significance due to their extensive applications in both commercial and military fields.Narrowbandgap two-dimensional layered materials(2DLMs)are considered as the promising candidates for constructing nextgeneration high-performance infrared photodetectors.Nevertheless,the performance of 2DLMs-based photodetectors can hardly satisfy the requirements of practical applications due to their weak optical absorption.In the present study,a strategy was proposed to design high-performance shortwave infrared photodetectors by integrating metalorganic frameworks(MOFs)nanoparticles with excellent optical absorption characteristics and 2DLM with high mobility.Further,this study demonstrated the practicability of this strategy in a MOF/2DLM(Ni-CAT-1/Bi_(2)Se_(3))hybrid heterojunction photodetector.Due to the transfer of photo-generated carriers from the MOF to Bi_(2)Se_(3),the MOF nanoparticles integrated on the Bi_(2)Se_(3) layer can increase the photocurrent by 2-3 orders of magnitude.The resulting photodetector presented a high responsivity of 4725 A W^(−1) and a superior detectivity of 3.5×10^(13) Jones at 1500 nm.The outstanding performance of the hybrid heterojunction arises from the synergistic function of the enhanced optical absorption and photogating effect.In addition,the proposed device construction strategy combining MOF photosensitive materials with 2DLMs shows a high potential for the future high-performance shortwave infrared photodetectors.

Multilayered PdTe_(2)/thin Si heterostructures as self-powered flexible photodetectors with heart rate monitoring ability

Two-dimensional layered material/semiconductor heterostructures have emerged as a category of fascinating architectures for developing highly efficient and low-cost photodetection devices.Herein,we present the construction of a highly efficient flexible light detector operating in the visible-near infrared wavelength regime by integrating a PdTe2 multilayer on a thin Si film.A representative device achieves a good photoresponse performance at zero bias including a sizeable current on/off ratio exceeding 105,a decent responsivity of~343 mA/W,a respectable specific detectivity of~2.56×10^(12)Jones,and a rapid response time of 4.5/379μs,under 730 nm light irradiation.The detector also displays an outstanding long-term air stability and operational durability.In addition,thanks to the excellent flexibility,the device can retain its prominent photodetection performance at various bending radii of curvature and upon hundreds of bending tests.Furthermore,the large responsivity and rapid response speed endow the photodetector with the ability to accurately probe heart rate,suggesting a possible application in the area of flexible and wearable health monitoring.

Pressure-dependent phase transition of 2D layered silicon telluride(Si2le3)and manganese intercalated silicon telluride

Two-dimensional(2D)layered silicon telluride(SizTes)nanocrystals were compressed to 12 GPa using diamond anvil cell techniques.Optical measurements show a color change from transparent red to opaque black indicating a semiconductor-to-metal phase transition.Raman scattering was used to observe the stiffening of the crystal lattice and subsequent phase behavior.A possible phase transition was observed.at 9.5±0.5 GPa evidenced by the disappearance of the Atg stretching mode.SizTes was intercalated with elemental manganese to^1 at.%.Intercalation lowers the pressure of the proposed phase transition to 7.5±1 GPa.Raman modes show both phonon stiffening and phonon softening,suggesting negative linear compressibility.These results provide fundamental insight into the high-pressure optical phonon behavior of silicon telluride and illuminate how a specific electron-donating intercalant can chemically alter pressure-dependent optical phonon behavior.

基于图层优化与融合的2D—3D视频转换方法

为了缓解3D片源的不足,在结构化重建技术的基础上提出一种基于图层优化与融合的2D—3D视频转换方法.首先通过分段化结构重建框架得到场景离散的3D结构信息;然后以此为深度线索,使用一种扩展的GrabCut交互式分割方法提取出不同物体所在的图层,在每个图层上先对深度进行稠密扩散,再结合多种约束采用优化算法来增强区域层次感;最后将不同图层的深度根据视觉显著性特征进行融合,从而完成2D—3D视频转换.实验和评估结果表明,该方法可以得到令人满意的转换效果.

Nanocarbon-Enhanced 2D Photoelectrodes:A New Paradigm in Photoelectrochemical Water Splitting

Solar-driven photoelectrochemical(PEC)water splitting systems are highly promising for converting solar energy into clean and sustainable chemical energy.In such PEC systems,an integrated photoelectrode incorporates a light harvester for absorbing solar energy,an interlayer for transporting photogenerated charge carriers,and a co-catalyst for triggering redox reactions.Thus,understanding the correlations between the intrinsic structural properties and functions of the photoelectrodes is crucial.Here we critically examine various 2D layered photoanodes/photocathodes,including graphitic carbon nitrides,transition metal dichalcogenides,layered double hydroxides,layered bismuth oxyhalide nanosheets,and MXenes,combined with advanced nanocarbons(carbon dots,carbon nanotubes,graphene,and graphdiyne)as co-catalysts to assemble integrated photoelectrodes for oxygen evolution/hydrogen evolution reactions.The fundamental principles of PEC water splitting and physicochemical properties of photoelectrodes and the associated catalytic reactions are analyzed.Elaborate strategies for the assembly of 2D photoelectrodes with nanocarbons to enhance the PEC performances are introduced.The mechanisms of interplay of 2D photoelectrodes and nanocarbon co-catalysts are further discussed.The challenges and opportunities in the field are identified to guide future research for maximizing the conversion efficiency of PEC water splitting.

空间发展平板混和层流动的大涡模拟-3D与2D模拟的比较

本文利用大涡模拟方法研究了空间发展平板混合层流动,分别在三维模型和二维模型下,比较了大尺度结构涡的演化过程,以及流向速度、流向脉动速度、横向脉动速度和Reynolds应力的统计时均结果,并与实验结果对照,指出3D模拟无论在物理真实性还是预报结果准确性方面都要明显优于2D模拟。

Research Advances of Typical Two Dimensional Layered Thermoelectric Materials

Thermoelectric technologies have caught our intense attention due to their ability of heat conversion into electricity.The considerable efforts have been taken to develop and enhance thermoelectric properties of materials over the past several decades.Recently,twodimensional layered materials are making the promise for potential applications of thermoelectric devices because of the excellent physical and structural properties.Here,a comprehensive coverage about recent progresses in thermoelectric properties of typical two dimensional(2D)layered materials,including the theoretical and experimental results,is provided.Moreover,the potential applications of 2D thermoelectric materials are also involved.These results indicate that the development of 2D thermoelectric materials take a key role in the flexible electronic devices with thermoelectric technologies.

A Novel Luminescent Zinc(Ⅱ) Coordination Polymer with 2D → 3D Polythreaded Motif

A new zinc（Ⅱ） compound, [Zn（BTA）（UCA）]n （1, HBTA = 1,2,3-benzotriazole, HUCA = 4-imidazoleacrylic acid）, has been synthesized via the hydrothermal reactions of Zn（OAC）2.2H20, HBTA and HUCA. The crystal structure is of monoclinic, space group P21/c with a = 7.450（3）, b = 18.911 （8）, c = 9.198（4） A, fl = 94.317（8）°, V = 1292.2（9） A3, C12HgNsO2Zn, Mr = 320.63, Z = 4, Dc = 1.648 g/cm3, F（000） = 648,/z = 1.909 mm-1, R= 0.0255 and wR= 0.0655 for 2104 observed reflections （I 〉 2a（/））. Single-crystal X-ray diffraction analysis revealed that compound 1 features a two-dimensional （2D） layered framework based on benzotriazole controlled dinuclear [Zn2（BTA）2] subunits. Furthermore, these 2D layers are threaded into a 3D supramolecular framework via the direction of intermolecular hydrogen bonds and π-π interactions. In addition, the thermal stability and fluorescence property of compound 1 were also investigated.

Recent advances in two-dimensional layered and non-layered materials hybrid heterostructures

With the development of Moore's law, the future trend of devices will inevitably be shrinking and integration to further achieve size reduction. The emergence of new two-dimensional non-layered materials(2DNLMs) not only enriches the 2D material family to meet future development, but also stimulates the global enthusiasm for basic research and application technologies in the 2D field. Van der Waals(vd W) heterostructures, in which two-dimensional layered materials(2DLMs)are physically stacked layer by layer, can also occur between 2DLMs and 2DNLMs hybrid heterostructures, providing an alternative platform for nanoelectronics and optoelectronic applications. Here, we outline the recent developments of2DLMs/2DNLMs hybrid heterostructures, with particular emphasis on major advances in synthetic methods and applications. And the categories and crystal structures of 2DLMs and 2DNLMs are also shown. We highlight some promising applications of the heterostructures in electronics, optoelectronics, and catalysis. Finally, we provide conclusions and future prospects in the 2D materials field.

2D–3D dual carbon layer confined ultrasmall VN nanoparticles for improving lithium-ion storage in hybrid capacitors

Lithium-ion capacitors(LICs) of achieving high power and energy density have garnered significant attention. However, the kinetics unbalance between anode and cathode can impede the application of LICs. Vanadium nitride(VN) with a high theoretical specific capacity(~ 1200 m Ah·g^(-1)) is a better pseudocapacitive anode to match the response of cathode in LICs. However, the insertion/extraction of Li-ions in VN's operation results in significant volume expansion. Herein, the VN/N-r GO-5composite that three-dimentional(3D) dicyandiamidederived-carbon(DDC) tightly wrapped VN quantum dots(VN QDTs) on two-dimentional(2D) reduced graphene oxid(r GO) was prepared by a facile strategy. The VN QDTs can reduce ion diffusion length and improve charge transfer kinetics. The 2D r GO as a template provides support for nanoparticle dispersion and improves electrical conductivity. The 3D DDC tightly encapsulated with VN QDTs mitigates agglomeration of VN particles as well as volume expansion. Correspondingly, the LICs with VN/Nr GO-5 composite as anode and activated carbon(AC) as cathode were fabricated, which exhibits a high energy density and power density. Such strategy provides a perspective for improving the electrochemical properties of LIC anode materials by suppressing volume expansion and enhancing conductivity.

轴向磁场电机永磁体空载涡流损耗减小方法对比研究

减少轴向磁场电机永磁体空载涡流损耗的方法主要有:减小定子槽开口宽度、增大气隙长度、永磁体分块、使用屏蔽层和磁性槽楔等。基于轴向磁场电机的简化二维分析模型,分析了减小定子槽开口宽度和增大气隙长度、使用屏蔽层和磁性槽楔降低空载涡流损耗的效果。通过三维电磁场仿真,研究了永磁体不同分块方式对减少空载涡流损耗的效果。研究结果表明,减小定子槽开口宽度的效果最佳;虽然增加气隙长度可以显著减小涡流损耗,但永磁体用量迅速增加;永磁体分块减小涡流效果较好,且周向分块方式最好;屏蔽层起反作用;使用分段磁性槽楔效果比减小定子槽开口宽度稍微差一点,但加工难度要低些。

A Novel Two-dimensional Layer Compound Built up by Hexapolyoxotungstates and Coordinated Sodium Chains

The 2D-layer compound ([Na-2(C8H12N2O3)(4)(C2H6SO)(4)(W6O19)](n) 1, M-r = 2133.98) synthesized by the reaction of sodium tungstate and barbitone sodium in the solution of DMSO and water has been characterized by IR and Raman spectra, elemental analysis and TGA. X-ray diffraction analysis indicates that Compound 1 crystallizes in the monoclinic system, space group C2/c with a 14.8026(4), b = 17.3012(3), c = 19.6379(5) A, beta = 98.6300 degrees, V = 4972.4(2) angstrom(3), Z = 4, F(000) 3928, D-c = 2.851 and mu = 14.101 mm(-1). 1 has a two-dimensional layer structure with hexapolyoxotungstate building blocks and coordinated sodium chains.

THE NAVIER-STOKES EQUATIONS IN STREAM LAYER AND ON STREAM SURFACE AND A DIMENSION SPLIT METHODS

In this paper,we proposal stream surface and stream layer.By using classical tensor calculus,we derive 3-D Navier-Stokes Equations(NSE)in the stream layer under semigeodesic coordinate system,Navier-Stokes equation on the stream surface and 2-D Navier-Stokes equations on a two dimensional manifold. After introducing stream function on the stream surface,a nonlinear initial-boundary value problem satisfies by stream function is obtained,existence and uniqueness of its solution are proven.Based this theory we proposal a new method called"dimension split method"to solve 3D NSE.

Hydrothermal Synthesis and Characterization of a Two-dimensional Layer Based on Keggin POM Cluster Units:[Cu_2(DMPz)_2PMo_(12)O_(40)]·HDMPz

The title compound, [Cu2（DMPz）2PMo12O40]·HDMPz （1, DMPz = 2,5-dimethyl pyrazine）, has been synthesized and characterized by single-crystal X-ray diffraction analysis. It crystallizes in triclinic, space group P1 with a = 11.075（2）, b = 11.551（2）, c = 11.886（2） A.α = 106.352（2）, β = 109.862（3）, γ = 109.504（1）°, V = 1206.8（3） A3, C18H26CU2Mo12N6O40P, Mr = 2275.78, Z = 1, Dc = 3.131 g/cm3, μ = 4.011 mm^-1, F（000） = 1073, S = 1.066, the final R = 0.0389 and wR = 0.1056 for 3739 observed reflections with I 〉 2σ（I）. The structural analysis indicates that the title compound is composed of Keggin clusters [PMo12O40]3- connected by one-dimensional [CB（DMPz）]2n^2n＋ chains to form a two-dimensional grid layer with holes occupied by monoprotonated DMPz molecules. In the solid of the title compound, the 2D grid layers are stacked together in an ABAB packing mode.

基于Hydrus-2D模型的层状下凹式绿地水文特性研究

下凹式绿地对缓解内涝积水、控制地表径流和污染、美化城市环境等具有重要作用.为了研究下凹式绿地在低渗透性土壤下的水力性能,基于贵阳月亮湖海绵公园的红黏土土壤性质和碎石颗粒级配.依据非饱和土壤水分运动理论,运用Hydrus-2D模型软件,对层状下凹式绿地的雨水蓄积性能进行数值模拟研究.通过设计不同降雨强度0.05、0.08、0.09、1.30 cm/min,分析土壤和蓄水层各因素对层状下凹式绿地雨水蓄积性能的影响.结果表明:低渗透性土壤的土壤饱和含水量(即θmax)是影响层状下凹式绿地雨水蓄积性能最敏感的参数;增大蓄水层骨料粒径和蓄水层深度可有效增加层状下凹式绿地的蓄排水性能.