When stacking two-dimensional(2D)materials with a lattice mismatch and/or a small twist,moirésuperlattice emerges with fascinating electronic and optical properties.The fabrication of such stacked 2D materials us...When stacking two-dimensional(2D)materials with a lattice mismatch and/or a small twist,moirésuperlattice emerges with fascinating electronic and optical properties.The fabrication of such stacked 2D materials usually requires multiple transfer and stack processes,assisted by a certain transfer medium which needs to be removed afterwards,and it is very challenging to maintain pristine and clean surfaces/interfaces for these stacked structures.In this work,we report a facile direct bonding method for fabrication of twisted MoS_(2) bilayers with ultra-clean surfaces/interfaces.Novel interlayer interactions are revealed in the as-fabricated high-quality samples,leading to twist-angle related dispersion behavior of various Raman modes,such as layer breathing modes,shear modes and E_(2g)modes,as well as indirect bandgap excitons.Field-effect transistors(FETs)of twisted MoS_(2) bilayers also exhibit angle-dependent performance,which could be attributed to the band structure evolution.This facile method holds significance for the future integration of pre-designed multilayer 2D materials and paves a way to explore underlying physical mechanisms and potential applications.展开更多
The rise of smart wearable devices has driven the demand for flexible,high-performance optoelectronic devices with low power and easy high-density integration.Emerging Two-dimensional(2D)materials offer promising solu...The rise of smart wearable devices has driven the demand for flexible,high-performance optoelectronic devices with low power and easy high-density integration.Emerging Two-dimensional(2D)materials offer promising solutions.However,the use of 3D metal in traditional 2D devices often leads to Fermi-level pinning,compromising device performance.2D metallic materials,such as graphene and 2H-phase NbSe_(2),present a new avenue for addressing this issue and constructing high-performance,low-power photodetectors.In this work,we designed an all-2D asymmetric contacts photodetector using Gr and NbSe_(2)as electrodes for the 2D semiconductor WSe_(2).The asymmetric Schottky barriers and built-in electric fields facilitated by this architecture resulted in outstanding photovoltaic characteristics and self-powered photodetection.Under zero bias,the device exhibited a responsivity of 287 mA/W,a specific detectivity of 5.3×10^(11)Jones,and an external quantum efficiency of 88%.It also demonstrated an ultra-high light on/offratio(1.8×10^(5)),ultra-fast photoresponse speeds(80/72μs),broad-spectrum responsiveness(405980 nm),and exceptional cycling stability.The applications of the Gr/WSe_(2)/NbSe_(2)heterojunction in imaging and infrared optical communication have been explored,underscoring its significant potential.This work offers an idea to construct all-2D ultrathin optoelectronic devices.展开更多
Ultrathin van der Waals(vdW)magnets provide a possibility to access magnetic ordering in the two-dimensional(2D)limit,which are expected to be applied in the spintronic devices.Raman spectroscopy is a powerful charact...Ultrathin van der Waals(vdW)magnets provide a possibility to access magnetic ordering in the two-dimensional(2D)limit,which are expected to be applied in the spintronic devices.Raman spectroscopy is a powerful characterization method to investigate the spin-related properties in 2D vdW magnets,including magnon and spin–lattice interaction,which are hardly accessible by other optical methods.In this paper,the recent progress of various magnetic properties in 2D vdW magnets studied by Raman spectroscopy is reviewed,including the magnetic transition,spin-wave,spin–lattice interaction,symmetry tuning induced by spin ordering,and nonreciprocal magneto-phonon Raman scattering.展开更多
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) n...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.展开更多
Within the(2+1)-dimensional Korteweg–de Vries equation framework,new bilinear B¨acklund transformation and Lax pair are presented based on the binary Bell polynomials and gauge transformation.By introducing an a...Within the(2+1)-dimensional Korteweg–de Vries equation framework,new bilinear B¨acklund transformation and Lax pair are presented based on the binary Bell polynomials and gauge transformation.By introducing an arbitrary functionφ(y),a family of deformed soliton and deformed breather solutions are presented with the improved Hirota’s bilinear method.By choosing the appropriate parameters,their interesting dynamic behaviors are shown in three-dimensional plots.Furthermore,novel rational solutions are generated by taking the limit of the obtained solitons.Additionally,twodimensional(2D)rogue waves(localized in both space and time)on the soliton plane are presented,we refer to them as deformed 2D rogue waves.The obtained deformed 2D rogue waves can be viewed as a 2D analog of the Peregrine soliton on soliton plane,and its evolution process is analyzed in detail.The deformed 2D rogue wave solutions are constructed successfully,which are closely related to the arbitrary functionφ(y).This new idea is also applicable to other nonlinear systems.展开更多
Magnetic order in two-dimensional systems was not supposed to exist at finite temperature.In recent years,the successful preparation of two-dimensional ferromagnetic materials such as CrI_(3),Cr_(2) Ge_(2) Te_(6),and ...Magnetic order in two-dimensional systems was not supposed to exist at finite temperature.In recent years,the successful preparation of two-dimensional ferromagnetic materials such as CrI_(3),Cr_(2) Ge_(2) Te_(6),and Fe_(3)GeTe_(2) opens up a new chapter in the remarkable field of two-dimensional materials.Here,we report on a theoretical analysis of the stability of ferromagnetism in Fe_(3)GeTe_(2).We uncover the mechanism of holding long-range magnetic order and propose a model to estimate the Curie temperature of Fe_(3)GeTe_(2).Our results reveal the essential role of magnetic anisotropy in maintaining the magnetic order of two-dimensional systems.The theoretical method used here can be generalized to future research of other magnetic two-dimensional systems.展开更多
The fascinating Dirac cone in honeycomb graphene,which underlies many unique electronic properties,has inspired the vast endeavors on pursuing new two-dimensional(2D)Dirac materials.Based on the density functional the...The fascinating Dirac cone in honeycomb graphene,which underlies many unique electronic properties,has inspired the vast endeavors on pursuing new two-dimensional(2D)Dirac materials.Based on the density functional theory method,a 2D material Zn3Si2 of honeycomb transition-metal silicide with intrinsic Dirac cones has been predicted.The Zn3Si2 monolayer is dynamically and thermodynamically stable under ambient conditions.Importantly,the Zn3Si2 monolayer is a room-temperature 2D Dirac material with a spin-orbit coupling energy gap of 1.2 meV,which has an intrinsic Dirac cone arising from the special hexagonal lattice structure.Hole doping leads to the spin polarization of the electron,which results in a Dirac half-metal feature with single-spin Dirac fermion.This novel stable 2D transition-metal-silicon-framework material holds promises for electronic device applications in spintronics.展开更多
Layered magnetic materials,such as MnBi_(2)Te_(4),have drawn much attention owing to their potential for realizing twodimensional(2D)magnetism and possible topological states.Recently,FeBi_(2)Te_(4),which is isostruct...Layered magnetic materials,such as MnBi_(2)Te_(4),have drawn much attention owing to their potential for realizing twodimensional(2D)magnetism and possible topological states.Recently,FeBi_(2)Te_(4),which is isostructural to MnBi_(2)Te_(4),has been synthesized in experiments,but its detailed magnetic ordering and band topology have not been clearly understood yet.Here,based on first-principles calculations,we investigate the magnetic and electronic properties of FeBi_(2)Te_(4)in bulk and 2D forms.We show that different from MnBi_(2)Te_(4),the magnetic ground states of bulk,single-layer,and bilayer FeBi_(2)Te_(4)all favor a 120°noncollinear antiferromagnetic ordering,and they are topologically trivial narrow-gap semiconductors.For the bilayer case,we find that a quantum anomalous Hall effect with a unit Chern number is realized in the ferromagnetic state,which may be achieved in experiment by an external magnetic field or by magnetic proximity coupling.Our work clarifies the physical properties of the new material system of FeBi_(2)Te_(4)and reveals it as a potential platform for studying magnetic frustration down to 2D limit as well as quantum anomalous Hall effect.展开更多
Reducing CO_(2) to hydrocarbon fuels by solar irradiation provides a feasible channel for mitigating excessive CO_(2) emissions and addressing resource depletion.Nevertheless,severe charge recombi‐nation and the high...Reducing CO_(2) to hydrocarbon fuels by solar irradiation provides a feasible channel for mitigating excessive CO_(2) emissions and addressing resource depletion.Nevertheless,severe charge recombi‐nation and the high energy barrier for CO_(2) photoreduction on the surface of photocatalysts com‐promise the catalytic performance.Herein,a 2D/2D Bi_(2)MoO_(6)/BiOI composite was fabricated to achieve improved CO_(2) photoreduction efficiency.Charge transfer in the composite was facilitated by the van der Waals heterojunction with a large‐area interface.Work function calculation demon‐strated that S‐scheme charge transfer is operative in the composite,and effective charge separation and strong redox capability were revealed by time‐resolved photoluminescence and electron para‐magnetic resonance spectroscopy.Moreover,the intermediates of CO_(2) photoreduction were identi‐fied based on the in situ diffuse reflectance infrared Fourier‐transform spectra.Density functional theory calculations showed that CO_(2) hydrogenation is the rate‐determining step for yielding CH_(4) and CO.Introducing Bi_(2)MoO_(6) into the composite further decreased the energy barrier for CO_(2) photoreduction on BiOI by 0.35 eV.This study verifies the synergistic effect of the S‐scheme heterojunction and van der Waals heterojunction in the 2D/2D composite.展开更多
Covalent organic frameworks(COFs)have emerged as a kind of rising star materials in photocatalysis.However,their photocatalytic activities are restricted by the high photogenerated electron-hole pairs recombination ra...Covalent organic frameworks(COFs)have emerged as a kind of rising star materials in photocatalysis.However,their photocatalytic activities are restricted by the high photogenerated electron-hole pairs recombination rate.Herein,a novel metal-free 2D/2D van der Waals heterojunction,composed of a two-dimensional(2D)COF with ketoenamine linkage(TpPa-1-COF)and 2D defective hexagonal boron nitride(h-BN),is successfully constructed through in situ solvothermal method.Benefitting from the presence of VDW heterojunction,larger contact area and intimate electronic coupling can be formed between the interface of TpPa-1-COF and defective h-BN,which make contributions to promoting charge car-riers separation.The introduced defects can also endow the h-BN with porous structure,thus providing more reactive sites.Moreover,the TpPa-1-COF will undergo a structural transformation after being integrated with defective h-BN,which can enlarge the gap between the conduction band position of the h-BN and TpPa-1-COF,and suppress electron backflow,corroborated by experimental and density functional theory calculations results.Accordingly,the resulting porous h-BN/TpPa-1-COF metal-free VDW heterojunction displays out-standing solar energy catalytic activity for water splitting without co-catalysts,and the H_(2) evolution rate can reach up to 3.15 mmol g^(−1) h^(−1),which is about 67 times greater than that of pristine TpPa-1-COF,also surpassing that of state-of-the-art metal-free-based photocatalysts reported to date.In particular,it is the first work for constructing COFs-based heterojunctions with the help of h-BN,which may provide new avenue for designing highly efficient metal-free-based photocatalysts for H_(2) evolution.展开更多
A mathematical model for nonlocal vibration and buckling of embedded two-dimensional(2 D) decagonal quasicrystal(QC) layered nanoplates is proposed. The Pasternak-type foundation is used to simulate the interaction be...A mathematical model for nonlocal vibration and buckling of embedded two-dimensional(2 D) decagonal quasicrystal(QC) layered nanoplates is proposed. The Pasternak-type foundation is used to simulate the interaction between the nanoplates and the elastic medium. The exact solutions of the nonlocal vibration frequency and buckling critical load of the 2 D decagonal QC layered nanoplates are obtained by solving the eigensystem and using the propagator matrix method. The present three-dimensional(3 D) exact solution can predict correctly the nature frequencies and critical loads of the nanoplates as compared with previous thin-plate and medium-thick-plate theories.Numerical examples are provided to display the effects of the quasiperiodic direction,length-to-width ratio, thickness of the nanoplates, nonlocal parameter, stacking sequence,and medium elasticity on the vibration frequency and critical buckling load of the 2 D decagonal QC nanoplates. The results show that the effects of the quasiperiodic direction on the vibration frequency and critical buckling load depend on the length-to-width ratio of the nanoplates. The thickness of the nanoplate and the elasticity of the surrounding medium can be adjusted for optimal frequency and critical buckling load of the nanoplate.This feature is useful since the frequency and critical buckling load of the 2 D decagonal QCs as coating materials of plate structures can now be tuned as one desire.展开更多
Rapid industrialization advancements have grabbed worldwide attention to integrate a very large number of electronic components into a smaller space for performing multifunctional operations.To fulfill the growing com...Rapid industrialization advancements have grabbed worldwide attention to integrate a very large number of electronic components into a smaller space for performing multifunctional operations.To fulfill the growing computing demand state-of-the-art materials are required for substituting traditional silicon and metal oxide semiconductors frameworks.Two-dimensional(2D)materials have shown their tremendous potential surpassing the limitations of conventional materials for developing smart devices.Despite their ground-breaking progress over the last two decades,systematic studies providing in-depth insights into the exciting physics of 2D materials are still lacking.Therefore,in this review,we discuss the importance of 2D materials in bridging the gap between conventional and advanced technologies due to their distinct statistical and quantum physics.Moreover,the inherent properties of these materials could easily be tailored to meet the specific requirements of smart devices.Hence,we discuss the physics of various 2D materials enabling them to fabricate smart devices.We also shed light on promising opportunities in developing smart devices and identified the formidable challenges that need to be addressed.展开更多
The isolation of the first two-dimensional material, graphene-a monolayer of carbon atoms arranged in a hexagonal lattice-opened new exciting opportunities in the field of condensed matter physics and materials. Its i...The isolation of the first two-dimensional material, graphene-a monolayer of carbon atoms arranged in a hexagonal lattice-opened new exciting opportunities in the field of condensed matter physics and materials. Its isolation and subsequent studies demonstrated that it was possible to obtain sheets of atomically thin crystals and that these were stable, and they also began to show its outstanding properties, thus opening the door to a whole new family of materials, known as two-dimensional materials or 2D materials. The great interest in different 2D materials is motivated by the variety of properties they show, being candidates for numerous applications.Additionally, the combination of 2D crystals allows the assembly of composite, on-demand materials, known as van der Waals heterostructures, which take advantage of the properties of those materials to create functionalities that otherwise would not be accessible. For example, the combination of 2D materials, which can be done with high precision, is opening up opportunities for the study of new challenges in fundamental physics and novel applications. Here we review the latest fundamental discoveries in the area of 2D materials and offer a perspective on the future of the field.展开更多
With the development of the Internet,image encryption technology has become critical for network security.Traditional methods often suffer from issues such as insufficient chaos,low randomness in key generation,and po...With the development of the Internet,image encryption technology has become critical for network security.Traditional methods often suffer from issues such as insufficient chaos,low randomness in key generation,and poor encryption efficiency.To enhance performance,this paper proposes a new encryption algorithm designed to optimize parallel processing and adapt to images of varying sizes and colors.The method begins by using SHA-384 to extract the hash value of the plaintext image,which is then processed to determine the chaotic system’s initial value and block size.The image is padded and divided into blocks for further processing.A novel two-dimensional infinite collapses hyperchaotic map(2DICHM)is employed to generate the intra-block scrambling sequence,while an improved variable Joseph traversal sequence is used for inter-block scrambling.After removing the padding,3D forward and backward shift diffusions,controlled by the 2D-ICHM sequences,are applied to the scrambled image,producing the ciphertext.Simulation results demonstrate that the proposed algorithm outperforms others in terms of entropy,anti-noise resilience,correlation coefficient,robustness,and encryption efficiency.展开更多
Field-effect transistors （FETs） for logic applications, graphene and MoS2, are discussed. These materials have based on two representative two-dimensional （2D） materials, drastically different properties and requi...Field-effect transistors （FETs） for logic applications, graphene and MoS2, are discussed. These materials have based on two representative two-dimensional （2D） materials, drastically different properties and require different consider- ations. The unique band structure of graphene necessitates engineering of the Dirac point, including the opening of the bandgap, the doping and the interface, before the graphene can be used in logic applications. On the other hand, MoS2 is a semiconductor, and its electron transport depends heavily on the surface properties, the number of layers, and the carrier density. Finally, we discuss the prospects for the future developments in 2D material transistors.展开更多
Research on two-dimensional(2D)materials is one of the most active fields in materials science and nanotechnology.Among the members of the 2D family,layered hydroxides(LHs)represent an exceptional case of study due to...Research on two-dimensional(2D)materials is one of the most active fields in materials science and nanotechnology.Among the members of the 2D family,layered hydroxides(LHs)represent an exceptional case of study due to their unparalleled chemical versatility which allows the modulation of their physicochemical properties at will.Nowadays,LHs based on earth-abundant metals are key materials in the areas of energy storage and conversion,hybrid materials or magnetism.α-Co hydroxides(Simonkolleite-like structures)are promising phases with tuneable electronic and magnetic properties by ligand modification.However,even in the simple case ofα-Co^(Ⅱ)hydroxychlorides,the preparation of well-defined large 2D crystals is not straightforward,hindering the development of fundamental studies.Herein,we present the synthesis of 2D hexagonal crystals with outstanding sizethickness relationship(diameter>5μm and thickness of 20±7 nm)by a simple homogeneous synthesis taking place at room temperature.In structural terms,no differences are observed between our layered materials and those obtained hydrothermally.However,dynamic susceptibility measurements alert about different arrangements of the magnetic sublattices,which have been rationalized with structural DFT calculations.This work provides an extremely easy bottom-up method to obtain high-quality 2D crystals based onα-CoIIhydroxides,paving the way for the development of fundamental studies and applications.展开更多
We review experimental and theoretical results on thermal transport in semiconductor nanostructures（multilayer thin films, core/shell and segmented nanowires）, single-and few-layer graphene, hexagonal boron nitride,...We review experimental and theoretical results on thermal transport in semiconductor nanostructures（multilayer thin films, core/shell and segmented nanowires）, single-and few-layer graphene, hexagonal boron nitride, molybdenum disulfide, and black phosphorus. Different possibilities of phonon engineering for optimization of electrical and heat conductions are discussed. The role of the phonon energy spectra modification on the thermal conductivity in semiconductor nanostructures is revealed. The dependence of thermal conductivity in graphene and related two-dimensional（2 D） materials on temperature, flake size, defect concentration, edge roughness, and strain is analyzed.展开更多
Synthetic two-dimensional（2 D） polymers have totally different topology structures compared with traditional linear or branched polymers. The peculiar 2 D structures bring superior properties. Although, from linear ...Synthetic two-dimensional（2 D） polymers have totally different topology structures compared with traditional linear or branched polymers. The peculiar 2 D structures bring superior properties. Although, from linear to 2 D polymers, the study of these new materials is still in its infancy, they already show potential applications especially in optoelectronics, membranes, energy storage and catalysis, etc. In this review, we summarize the recent progress of the 2 D materials from three respects：（1） Chemistry—different types of polymerization reactions or supramolecular assembly to construct the 2 D networks were described;（2） Preparation methods—surface science, crystal engineering approaches and solution synthesis were introduced;（3） Functionalization and some early applications.展开更多
Hydrogen(H2)is considered to be a promising substitute for fossil fuels.Two-dimensional(2D)nanomaterials have exhibited an efficient electrocatalytic capacity to catalyze hydrogen evolution reaction(HER).Particularly,...Hydrogen(H2)is considered to be a promising substitute for fossil fuels.Two-dimensional(2D)nanomaterials have exhibited an efficient electrocatalytic capacity to catalyze hydrogen evolution reaction(HER).Particularly,phase engineering of 2D nanomaterials is opening a novel research direction to endow 2D nanostructures with fascinating properties for deep applications in catalyzing HER.In this review,we briefly summarize the research progress and present the current challenges on phase engineering of 2D nanomaterials for their applications in electrocatalytic HER.Our summary will be of significance to provide fundamental understanding for designing novel 2D nanomaterials with unconventional phases to electrochemically catalyze HER.展开更多
The interface crack problems in the two-dimensional(2D)decagonal quasicrystal(QC)coating are theoretically and numerically investigated with a displacement discontinuity method.The 2D general solution is obtained base...The interface crack problems in the two-dimensional(2D)decagonal quasicrystal(QC)coating are theoretically and numerically investigated with a displacement discontinuity method.The 2D general solution is obtained based on the potential theory.An analogy method is proposed based on the relationship between the general solutions for 2D decagonal and one-dimensional(1D)hexagonal QCs.According to the analogy method,the fundamental solutions of concentrated point phonon displacement discontinuities are obtained on the interface.By using the superposition principle,the hypersingular boundary integral-differential equations in terms of displacement discontinuities are determined for a line interface crack.Further,Green’s functions are found for uniform displacement discontinuities on a line element.The oscillatory singularity near a crack tip is eliminated by adopting the Gaussian distribution to approximate the delta function.The stress intensity factors(SIFs)with ordinary singularity and the energy release rate(ERR)are derived.Finally,a boundary element method is put forward to investigate the effects of different factors on the fracture.展开更多
基金supported by Guangdong Major Project of Basic and Applied Basic Research(Grant No.2021B0301030002)the National Key Research and Development Program(Grant No.2021YFA1202900)the National Natural Science Foundation of China(Grant Nos.62204166 and 62404145)。
文摘When stacking two-dimensional(2D)materials with a lattice mismatch and/or a small twist,moirésuperlattice emerges with fascinating electronic and optical properties.The fabrication of such stacked 2D materials usually requires multiple transfer and stack processes,assisted by a certain transfer medium which needs to be removed afterwards,and it is very challenging to maintain pristine and clean surfaces/interfaces for these stacked structures.In this work,we report a facile direct bonding method for fabrication of twisted MoS_(2) bilayers with ultra-clean surfaces/interfaces.Novel interlayer interactions are revealed in the as-fabricated high-quality samples,leading to twist-angle related dispersion behavior of various Raman modes,such as layer breathing modes,shear modes and E_(2g)modes,as well as indirect bandgap excitons.Field-effect transistors(FETs)of twisted MoS_(2) bilayers also exhibit angle-dependent performance,which could be attributed to the band structure evolution.This facile method holds significance for the future integration of pre-designed multilayer 2D materials and paves a way to explore underlying physical mechanisms and potential applications.
基金Liming Gao acknowledges funding from the National Natural Science Foundation of China(No.61727805).
文摘The rise of smart wearable devices has driven the demand for flexible,high-performance optoelectronic devices with low power and easy high-density integration.Emerging Two-dimensional(2D)materials offer promising solutions.However,the use of 3D metal in traditional 2D devices often leads to Fermi-level pinning,compromising device performance.2D metallic materials,such as graphene and 2H-phase NbSe_(2),present a new avenue for addressing this issue and constructing high-performance,low-power photodetectors.In this work,we designed an all-2D asymmetric contacts photodetector using Gr and NbSe_(2)as electrodes for the 2D semiconductor WSe_(2).The asymmetric Schottky barriers and built-in electric fields facilitated by this architecture resulted in outstanding photovoltaic characteristics and self-powered photodetection.Under zero bias,the device exhibited a responsivity of 287 mA/W,a specific detectivity of 5.3×10^(11)Jones,and an external quantum efficiency of 88%.It also demonstrated an ultra-high light on/offratio(1.8×10^(5)),ultra-fast photoresponse speeds(80/72μs),broad-spectrum responsiveness(405980 nm),and exceptional cycling stability.The applications of the Gr/WSe_(2)/NbSe_(2)heterojunction in imaging and infrared optical communication have been explored,underscoring its significant potential.This work offers an idea to construct all-2D ultrathin optoelectronic devices.
基金Project supported by Beijing Natural Science Foundation,China(Grant No.JQ18014)the National Natural Science Foundation of China(Grant No.12074371)Strategic Priority Research Program of Chinese Academy of Sciences(Grant No.XDB28000000),and CAS Interdisciplinary Innovation Team.
文摘Ultrathin van der Waals(vdW)magnets provide a possibility to access magnetic ordering in the two-dimensional(2D)limit,which are expected to be applied in the spintronic devices.Raman spectroscopy is a powerful characterization method to investigate the spin-related properties in 2D vdW magnets,including magnon and spin–lattice interaction,which are hardly accessible by other optical methods.In this paper,the recent progress of various magnetic properties in 2D vdW magnets studied by Raman spectroscopy is reviewed,including the magnetic transition,spin-wave,spin–lattice interaction,symmetry tuning induced by spin ordering,and nonreciprocal magneto-phonon Raman scattering.
基金Project supported by the National Natural Science Fundation of China (Grant Nos. 61731019, 60908012, 61575008, and 61775007)the Beijing Natural Science Foundation (Grant Nos. 4182015 and 4202010)。
文摘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.
基金Project supported by the National Natural Scinece Foundation of China(Grant Nos.11671219,11871446,12071304,and 12071451).
文摘Within the(2+1)-dimensional Korteweg–de Vries equation framework,new bilinear B¨acklund transformation and Lax pair are presented based on the binary Bell polynomials and gauge transformation.By introducing an arbitrary functionφ(y),a family of deformed soliton and deformed breather solutions are presented with the improved Hirota’s bilinear method.By choosing the appropriate parameters,their interesting dynamic behaviors are shown in three-dimensional plots.Furthermore,novel rational solutions are generated by taking the limit of the obtained solitons.Additionally,twodimensional(2D)rogue waves(localized in both space and time)on the soliton plane are presented,we refer to them as deformed 2D rogue waves.The obtained deformed 2D rogue waves can be viewed as a 2D analog of the Peregrine soliton on soliton plane,and its evolution process is analyzed in detail.The deformed 2D rogue wave solutions are constructed successfully,which are closely related to the arbitrary functionφ(y).This new idea is also applicable to other nonlinear systems.
基金Project supported by the Fundamental Research Funds for the Central Universities,China(Grant No.XJS200503)the Post-Doctoral Research Project of Shaanxi Province,China。
文摘Magnetic order in two-dimensional systems was not supposed to exist at finite temperature.In recent years,the successful preparation of two-dimensional ferromagnetic materials such as CrI_(3),Cr_(2) Ge_(2) Te_(6),and Fe_(3)GeTe_(2) opens up a new chapter in the remarkable field of two-dimensional materials.Here,we report on a theoretical analysis of the stability of ferromagnetism in Fe_(3)GeTe_(2).We uncover the mechanism of holding long-range magnetic order and propose a model to estimate the Curie temperature of Fe_(3)GeTe_(2).Our results reveal the essential role of magnetic anisotropy in maintaining the magnetic order of two-dimensional systems.The theoretical method used here can be generalized to future research of other magnetic two-dimensional systems.
基金the National Natural Science Foundation of China(Grant Nos.11674136 and 11564022)Yunnan Province for Recruiting High-Caliber Technological Talents,China(Grant No.1097816002)+3 种基金Reserve Talents for Yunnan Young and Middle-aged Academic and Technical Leaders,China(Grant No.2017HB010)the Academic Qinglan Project of KUST(Grant No.1407840010)the Analysis and Testing Fund of KUST(Grant No.2017M20162230010)the High-level Talents of KUST(Grant No.1411909425)。
文摘The fascinating Dirac cone in honeycomb graphene,which underlies many unique electronic properties,has inspired the vast endeavors on pursuing new two-dimensional(2D)Dirac materials.Based on the density functional theory method,a 2D material Zn3Si2 of honeycomb transition-metal silicide with intrinsic Dirac cones has been predicted.The Zn3Si2 monolayer is dynamically and thermodynamically stable under ambient conditions.Importantly,the Zn3Si2 monolayer is a room-temperature 2D Dirac material with a spin-orbit coupling energy gap of 1.2 meV,which has an intrinsic Dirac cone arising from the special hexagonal lattice structure.Hole doping leads to the spin polarization of the electron,which results in a Dirac half-metal feature with single-spin Dirac fermion.This novel stable 2D transition-metal-silicon-framework material holds promises for electronic device applications in spintronics.
基金funding support from the Singapore MOE Ac RF 308 Tier 2(Grant No.T2EP50220-0026)funding support from Shandong Provincial Natural Science Foundation(Grant No.ZR2023QA012)+3 种基金the Special Fund-ing in the Project of Qilu Young Scholar Program of Shandong Universityfunding support from Australian Research Council Future Fellowship(Grant No.FT220100290)funding support from the AINSE postgraduate awardfunding support from the Research and Development Administration Office at the University of Macao(Grants Nos.MYRG2022-00088-IAPME and SRG2021-00003-IAPME)。
文摘Layered magnetic materials,such as MnBi_(2)Te_(4),have drawn much attention owing to their potential for realizing twodimensional(2D)magnetism and possible topological states.Recently,FeBi_(2)Te_(4),which is isostructural to MnBi_(2)Te_(4),has been synthesized in experiments,but its detailed magnetic ordering and band topology have not been clearly understood yet.Here,based on first-principles calculations,we investigate the magnetic and electronic properties of FeBi_(2)Te_(4)in bulk and 2D forms.We show that different from MnBi_(2)Te_(4),the magnetic ground states of bulk,single-layer,and bilayer FeBi_(2)Te_(4)all favor a 120°noncollinear antiferromagnetic ordering,and they are topologically trivial narrow-gap semiconductors.For the bilayer case,we find that a quantum anomalous Hall effect with a unit Chern number is realized in the ferromagnetic state,which may be achieved in experiment by an external magnetic field or by magnetic proximity coupling.Our work clarifies the physical properties of the new material system of FeBi_(2)Te_(4)and reveals it as a potential platform for studying magnetic frustration down to 2D limit as well as quantum anomalous Hall effect.
文摘Reducing CO_(2) to hydrocarbon fuels by solar irradiation provides a feasible channel for mitigating excessive CO_(2) emissions and addressing resource depletion.Nevertheless,severe charge recombi‐nation and the high energy barrier for CO_(2) photoreduction on the surface of photocatalysts com‐promise the catalytic performance.Herein,a 2D/2D Bi_(2)MoO_(6)/BiOI composite was fabricated to achieve improved CO_(2) photoreduction efficiency.Charge transfer in the composite was facilitated by the van der Waals heterojunction with a large‐area interface.Work function calculation demon‐strated that S‐scheme charge transfer is operative in the composite,and effective charge separation and strong redox capability were revealed by time‐resolved photoluminescence and electron para‐magnetic resonance spectroscopy.Moreover,the intermediates of CO_(2) photoreduction were identi‐fied based on the in situ diffuse reflectance infrared Fourier‐transform spectra.Density functional theory calculations showed that CO_(2) hydrogenation is the rate‐determining step for yielding CH_(4) and CO.Introducing Bi_(2)MoO_(6) into the composite further decreased the energy barrier for CO_(2) photoreduction on BiOI by 0.35 eV.This study verifies the synergistic effect of the S‐scheme heterojunction and van der Waals heterojunction in the 2D/2D composite.
基金supported by the National Natural Science Foundation of China(Nos.22101105,52071171,52202248)the Research Fund for the Doctoral Program of Liaoning Province(2021-BS-086)+6 种基金Liaoning BaiQianWan Talents Program(LNBQW2018B0048)Shenyang Science and Technology Project(21-108-9-04)Australian Research Council(ARC)through Future Fellowship(FT210100298,FT210100806)Discovery Project(DP220100603)Linkage Project(LP210100467,LP210200504,LP210200345,LP220100088)Industrial Transformation Training Centre(IC180100005)schemesthe Australian Government through the Cooperative Research Centres Projects(CRCPXIII000077).
文摘Covalent organic frameworks(COFs)have emerged as a kind of rising star materials in photocatalysis.However,their photocatalytic activities are restricted by the high photogenerated electron-hole pairs recombination rate.Herein,a novel metal-free 2D/2D van der Waals heterojunction,composed of a two-dimensional(2D)COF with ketoenamine linkage(TpPa-1-COF)and 2D defective hexagonal boron nitride(h-BN),is successfully constructed through in situ solvothermal method.Benefitting from the presence of VDW heterojunction,larger contact area and intimate electronic coupling can be formed between the interface of TpPa-1-COF and defective h-BN,which make contributions to promoting charge car-riers separation.The introduced defects can also endow the h-BN with porous structure,thus providing more reactive sites.Moreover,the TpPa-1-COF will undergo a structural transformation after being integrated with defective h-BN,which can enlarge the gap between the conduction band position of the h-BN and TpPa-1-COF,and suppress electron backflow,corroborated by experimental and density functional theory calculations results.Accordingly,the resulting porous h-BN/TpPa-1-COF metal-free VDW heterojunction displays out-standing solar energy catalytic activity for water splitting without co-catalysts,and the H_(2) evolution rate can reach up to 3.15 mmol g^(−1) h^(−1),which is about 67 times greater than that of pristine TpPa-1-COF,also surpassing that of state-of-the-art metal-free-based photocatalysts reported to date.In particular,it is the first work for constructing COFs-based heterojunctions with the help of h-BN,which may provide new avenue for designing highly efficient metal-free-based photocatalysts for H_(2) evolution.
基金the National Natural Science Foundation of China(Nos.12072166 and 11862021)the Program for Science and Technology of Inner Mongolia Autonomous Region of China(No.2021GG0254)the Natural Science Foundation of Inner Mongolia Autonomous Region of China(No.2020MS01006)。
文摘A mathematical model for nonlocal vibration and buckling of embedded two-dimensional(2 D) decagonal quasicrystal(QC) layered nanoplates is proposed. The Pasternak-type foundation is used to simulate the interaction between the nanoplates and the elastic medium. The exact solutions of the nonlocal vibration frequency and buckling critical load of the 2 D decagonal QC layered nanoplates are obtained by solving the eigensystem and using the propagator matrix method. The present three-dimensional(3 D) exact solution can predict correctly the nature frequencies and critical loads of the nanoplates as compared with previous thin-plate and medium-thick-plate theories.Numerical examples are provided to display the effects of the quasiperiodic direction,length-to-width ratio, thickness of the nanoplates, nonlocal parameter, stacking sequence,and medium elasticity on the vibration frequency and critical buckling load of the 2 D decagonal QC nanoplates. The results show that the effects of the quasiperiodic direction on the vibration frequency and critical buckling load depend on the length-to-width ratio of the nanoplates. The thickness of the nanoplate and the elasticity of the surrounding medium can be adjusted for optimal frequency and critical buckling load of the nanoplate.This feature is useful since the frequency and critical buckling load of the 2 D decagonal QCs as coating materials of plate structures can now be tuned as one desire.
文摘Rapid industrialization advancements have grabbed worldwide attention to integrate a very large number of electronic components into a smaller space for performing multifunctional operations.To fulfill the growing computing demand state-of-the-art materials are required for substituting traditional silicon and metal oxide semiconductors frameworks.Two-dimensional(2D)materials have shown their tremendous potential surpassing the limitations of conventional materials for developing smart devices.Despite their ground-breaking progress over the last two decades,systematic studies providing in-depth insights into the exciting physics of 2D materials are still lacking.Therefore,in this review,we discuss the importance of 2D materials in bridging the gap between conventional and advanced technologies due to their distinct statistical and quantum physics.Moreover,the inherent properties of these materials could easily be tailored to meet the specific requirements of smart devices.Hence,we discuss the physics of various 2D materials enabling them to fabricate smart devices.We also shed light on promising opportunities in developing smart devices and identified the formidable challenges that need to be addressed.
基金financial support through the project Medium-Sized Centre programme R-723-000-001-281support from EU Flagship Programs (Graphene CNECTICT-604391 and 2D-SIPC Quantum Technology)European Research Council Synergy Grant Hetero2D, the Royal Society, EPSRC grants EP/N010345/1, EP/ P026850/1, EP/S030719/1.
文摘The isolation of the first two-dimensional material, graphene-a monolayer of carbon atoms arranged in a hexagonal lattice-opened new exciting opportunities in the field of condensed matter physics and materials. Its isolation and subsequent studies demonstrated that it was possible to obtain sheets of atomically thin crystals and that these were stable, and they also began to show its outstanding properties, thus opening the door to a whole new family of materials, known as two-dimensional materials or 2D materials. The great interest in different 2D materials is motivated by the variety of properties they show, being candidates for numerous applications.Additionally, the combination of 2D crystals allows the assembly of composite, on-demand materials, known as van der Waals heterostructures, which take advantage of the properties of those materials to create functionalities that otherwise would not be accessible. For example, the combination of 2D materials, which can be done with high precision, is opening up opportunities for the study of new challenges in fundamental physics and novel applications. Here we review the latest fundamental discoveries in the area of 2D materials and offer a perspective on the future of the field.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.62105004 and 52174141)the College Student Innovation and Entrepreneurship Fund Project(Grant No.202210361053)+4 种基金Anhui Mining Machinery and Electrical Equipment Coordination Innovation Center,Anhui University of Science&Technology(Grant No.KSJD202304)the Anhui Province Digital Agricultural Engineering Technology Research Center Open Project(Grant No.AHSZNYGC-ZXKF021)the Talent Recruitment Special Fund of Anhui University of Science and Technology(Grant No.2024yjrc175)the Graduate Innovation Fund Project of Anhui University of Science and Technology(Grant Nos.2024cx2067,2024cx2107,and 2024cx2064)Seed Support Project for Postgraduate Innovation,Entrepreneurship and Practice at Anhui University of Science and Technology(Grant No.2024cxcysj084).
文摘With the development of the Internet,image encryption technology has become critical for network security.Traditional methods often suffer from issues such as insufficient chaos,low randomness in key generation,and poor encryption efficiency.To enhance performance,this paper proposes a new encryption algorithm designed to optimize parallel processing and adapt to images of varying sizes and colors.The method begins by using SHA-384 to extract the hash value of the plaintext image,which is then processed to determine the chaotic system’s initial value and block size.The image is padded and divided into blocks for further processing.A novel two-dimensional infinite collapses hyperchaotic map(2DICHM)is employed to generate the intra-block scrambling sequence,while an improved variable Joseph traversal sequence is used for inter-block scrambling.After removing the padding,3D forward and backward shift diffusions,controlled by the 2D-ICHM sequences,are applied to the scrambled image,producing the ciphertext.Simulation results demonstrate that the proposed algorithm outperforms others in terms of entropy,anti-noise resilience,correlation coefficient,robustness,and encryption efficiency.
基金supported by the National Basic Research Program of China (Grant No. 2013CBA01600)the National Natural Science Foundation of China (Grant Nos. 61261160499 and 11274154)+2 种基金the National Science and Technology Major Project of the Ministry of Science and Technology of China (Grant No. 2011ZX02707)the Natural Science Foundation of Jiangsu Province, China (Grant No. BK2012302)the Specialized Research Fund for the Doctoral Program of Higher Education of China (Grant No. 20120091110028)
文摘Field-effect transistors （FETs） for logic applications, graphene and MoS2, are discussed. These materials have based on two representative two-dimensional （2D） materials, drastically different properties and require different consider- ations. The unique band structure of graphene necessitates engineering of the Dirac point, including the opening of the bandgap, the doping and the interface, before the graphene can be used in logic applications. On the other hand, MoS2 is a semiconductor, and its electron transport depends heavily on the surface properties, the number of layers, and the carrier density. Finally, we discuss the prospects for the future developments in 2D material transistors.
基金supported by the European Research Council(ERC Starting Grant No.2D-Pnicto Chem 804110)the Spanish MICINN(PID2019-111742GA-I00 and Unit of Excellence“María de Maeztu”CEX2019-000919-M)+2 种基金the Deutsche Forschungsgemeinschaft DFG(FLAG-ERA AB694/2-1)the Generalitat Valenciana(CIDEGENT/2018/001 and i Di FEDER/2018/061 co-financed by FEDER)CONICET for financial support and CNEA Computing Clusters for computer time(density functional theory calculations).
文摘Research on two-dimensional(2D)materials is one of the most active fields in materials science and nanotechnology.Among the members of the 2D family,layered hydroxides(LHs)represent an exceptional case of study due to their unparalleled chemical versatility which allows the modulation of their physicochemical properties at will.Nowadays,LHs based on earth-abundant metals are key materials in the areas of energy storage and conversion,hybrid materials or magnetism.α-Co hydroxides(Simonkolleite-like structures)are promising phases with tuneable electronic and magnetic properties by ligand modification.However,even in the simple case ofα-Co^(Ⅱ)hydroxychlorides,the preparation of well-defined large 2D crystals is not straightforward,hindering the development of fundamental studies.Herein,we present the synthesis of 2D hexagonal crystals with outstanding sizethickness relationship(diameter>5μm and thickness of 20±7 nm)by a simple homogeneous synthesis taking place at room temperature.In structural terms,no differences are observed between our layered materials and those obtained hydrothermally.However,dynamic susceptibility measurements alert about different arrangements of the magnetic sublattices,which have been rationalized with structural DFT calculations.This work provides an extremely easy bottom-up method to obtain high-quality 2D crystals based onα-CoIIhydroxides,paving the way for the development of fundamental studies and applications.
基金Project supported by the Republic of Moldova through the projects 15.817.02.29F and 17.80013.16.02.04/Ua
文摘We review experimental and theoretical results on thermal transport in semiconductor nanostructures（multilayer thin films, core/shell and segmented nanowires）, single-and few-layer graphene, hexagonal boron nitride, molybdenum disulfide, and black phosphorus. Different possibilities of phonon engineering for optimization of electrical and heat conductions are discussed. The role of the phonon energy spectra modification on the thermal conductivity in semiconductor nanostructures is revealed. The dependence of thermal conductivity in graphene and related two-dimensional（2 D） materials on temperature, flake size, defect concentration, edge roughness, and strain is analyzed.
基金financially supported by the National Natural Science Foundation of China(No.21604046)the National Young Thousand Talents Program,Shandong Provincial Natural Science Foundation,China(No.ZR2016XJ004)
文摘Synthetic two-dimensional（2 D） polymers have totally different topology structures compared with traditional linear or branched polymers. The peculiar 2 D structures bring superior properties. Although, from linear to 2 D polymers, the study of these new materials is still in its infancy, they already show potential applications especially in optoelectronics, membranes, energy storage and catalysis, etc. In this review, we summarize the recent progress of the 2 D materials from three respects：（1） Chemistry—different types of polymerization reactions or supramolecular assembly to construct the 2 D networks were described;（2） Preparation methods—surface science, crystal engineering approaches and solution synthesis were introduced;（3） Functionalization and some early applications.
基金financially supported by the Key Grant for Special Professors in Jiangsu Province(No.RK030STP18001)the Scientific Research Foundation of Nanjing University of Posts and Telecommunications(No.NY218150)“1311 Talents Program”of Nanjing University of Posts and Telecommunications and the National Postdoctoral Program for Innovative Talents(No.BX20190156)。
文摘Hydrogen(H2)is considered to be a promising substitute for fossil fuels.Two-dimensional(2D)nanomaterials have exhibited an efficient electrocatalytic capacity to catalyze hydrogen evolution reaction(HER).Particularly,phase engineering of 2D nanomaterials is opening a novel research direction to endow 2D nanostructures with fascinating properties for deep applications in catalyzing HER.In this review,we briefly summarize the research progress and present the current challenges on phase engineering of 2D nanomaterials for their applications in electrocatalytic HER.Our summary will be of significance to provide fundamental understanding for designing novel 2D nanomaterials with unconventional phases to electrochemically catalyze HER.
基金the National Natural Science Foundation of China (Nos. 11572289,1171407,11702252,and 11902293)the China Postdoctoral Science Foundation (No. 2019M652563)。
文摘The interface crack problems in the two-dimensional(2D)decagonal quasicrystal(QC)coating are theoretically and numerically investigated with a displacement discontinuity method.The 2D general solution is obtained based on the potential theory.An analogy method is proposed based on the relationship between the general solutions for 2D decagonal and one-dimensional(1D)hexagonal QCs.According to the analogy method,the fundamental solutions of concentrated point phonon displacement discontinuities are obtained on the interface.By using the superposition principle,the hypersingular boundary integral-differential equations in terms of displacement discontinuities are determined for a line interface crack.Further,Green’s functions are found for uniform displacement discontinuities on a line element.The oscillatory singularity near a crack tip is eliminated by adopting the Gaussian distribution to approximate the delta function.The stress intensity factors(SIFs)with ordinary singularity and the energy release rate(ERR)are derived.Finally,a boundary element method is put forward to investigate the effects of different factors on the fracture.
