In order to discover the main causes of elevator group accidents in edge computing environment, a multi-dimensional data model of elevator accident data is established by using data cube technology, proposing and impl...In order to discover the main causes of elevator group accidents in edge computing environment, a multi-dimensional data model of elevator accident data is established by using data cube technology, proposing and implementing a method by combining classical Apriori algorithm with the model, digging out frequent items of elevator accident data to explore the main reasons for the occurrence of elevator accidents. In addition, a collaborative edge model of elevator accidents is set to achieve data sharing, making it possible to check the detail of each cause to confirm the causes of elevator accidents. Lastly the association rules are applied to find the law of elevator Accidents.展开更多
Two-dimensional(2D)ferromagnetic materials have important applications in optics,spintronics,biomedicine,and energy conversion fields.To achieve higher integration and continue Moore's Law,it is necessary to searc...Two-dimensional(2D)ferromagnetic materials have important applications in optics,spintronics,biomedicine,and energy conversion fields.To achieve higher integration and continue Moore's Law,it is necessary to search for 2D ferromagnetic materials.However,the low Curie temperature(Tc)of most 2D ferromagnetic materials seriously hinders their practical applications.Therefore,the search for room-temperature 2D ferromagnetic materials is of great significance for the advancement of technological applications.This article provides a systematic and comprehensive review of the synthesis methods of room-temperature 2D ferromagnetic materials that have been discovered and created to date,as well as an overview of the physical properties of the 2D ferromagnetic materials.Finally,the challenges and prospects of the room-temperature 2D ferromagnetic materials in the fields of synthesis and application are briefly summarized.展开更多
Metal halide perovskites,as a new generation of optoelectronic materials,have attracted a great deal of interest due to their remarkable intrinsic properties.Due to the excellent optoelectronic properties,the perovski...Metal halide perovskites,as a new generation of optoelectronic materials,have attracted a great deal of interest due to their remarkable intrinsic properties.Due to the excellent optoelectronic properties,the perovskite crystals are widely used in lasers,photodetectors,X-ray detectors and solar cells.Considering the device performance and fabrication requirements,proper thickness of the crystal is required to avoid carrier loss and simultaneously ensure sufficient light absorption,which can realize the full potential of its excellent carrier transport property.Thus,the fabrication of perovskite crystal in a thin film with an adjustable thickness is highly desirable.The space-confined method has been demonstrated to be an effective way of preparing perovskite with controlled thickness.In this method,the thickness of perovskite can be regulated flexibly in a geometric confined space.Moreover,the size,quality and architecture of perovskite crystal films are also major concerns for practical photoelectric devices,which can also be optimized by the space-confined method owing to its good adaptability towards various modified strategies.In a word,the space-confined method is not only a simple and conventional way to adjust the thickness of perovskite crystal films,but also provides a platform to optimize their size,quality and architecture through applying appropriate strategies to the confined space.Herein,we review the space-confined growth of perovskite crystal films.Particularly,various modified strategies based on the space-confined method applied to the optimization of thickness,size,quality and architecture are highlighted.Then the stability investigating and component regulating of perovskite crystal films would be also mentioned.Furthermore,the correlation between the perovskite thickness and the device performance is discussed.Finally,several key challenges and proposed solutions of perovskite thin films based on the space-confined method are discussed.展开更多
Previous reports about the growth of large graphene single crystals on polycrystalline metal substrates usually adopted the strategy of suppressing the nucleation by lowering the concentration of the feedstock, which ...Previous reports about the growth of large graphene single crystals on polycrystalline metal substrates usually adopted the strategy of suppressing the nucleation by lowering the concentration of the feedstock, which greatly limited the rate of the nucleation and the sequent growth. The emerging liquid metal catalyst possesses the characteristic of quasi-atomically smooth surface with high diffusion rate. In principle, it should be a naturally ideal platform for the lowdensity nucleation and the fast growth of graphene. However,the rapid growth of large graphene single crystals on liquid metals has not received the due attention. In this paper, we firstly purposed the insight into the rapid growth of large graphene single crystals on liquid metals. We obtained the millimeter-size graphene single crystals on liquid Cu. The rich free-electrons in liquid Cu accelerate the nucleation, and the isotropic smooth surface greatly suppresses the nucleation.Moreover, the fast mass-transfer of carbon atoms due to the excellent fluidity of liquid Cu promotes the fast growth with a rate up to 79 μm s^-1. We hope the research on the growth speed of graphene on liquid Cu can enrich the recognition of the growth behavior of two-dimensional(2 D) materials on the liquid metal. We also believe that the liquid metal strategy for the rapid growth of graphene can be extended to various 2 D materials and thus promote their future applications in the photonics and electronics.展开更多
Emerging two-dimensional(2D)materials have stimulated tremendous scientific and industrial interests due to their diverse and tunable physical,chemical,and mechanical properties.The scalable production of high-quality...Emerging two-dimensional(2D)materials have stimulated tremendous scientific and industrial interests due to their diverse and tunable physical,chemical,and mechanical properties.The scalable production of high-quality wafer-scale 2D materials has become significantly essential to bring us closer to practical industrial applications,particularly in electronic devices.Vapor-phase growth provides attractive opportunities for the synthesis of large-area and high-quality 2D materials.In this review,we will emphasize vapor-phase growth strategies from three aspects,including suppressing nucleation,seamless stitching,and evolutionary selection growth.We discuss the general understanding of the related fundamental mechanism and specific parameter optimization from precursors and substrate design to the adjusting of growth parameters(temperature and pressure).Meanwhile,we present other strategies to produce various kinds of wafer-scale 2D materials.Finally,we conclude the current challenges and future directions in this developing field.This work may inspire researchers to better design routes in the synthesis of wafer-scale 2D materials with high quality.展开更多
The combination of visual and textual information in image retrieval remarkably alleviates the semantic gap of traditional image retrieval methods,and thus it has attracted much attention recently.Image retrieval base...The combination of visual and textual information in image retrieval remarkably alleviates the semantic gap of traditional image retrieval methods,and thus it has attracted much attention recently.Image retrieval based on such a combination is usually called the content-and-text based image retrieval(CTBIR).Nevertheless,existing studies in CTBIR mainly make efforts on improving the retrieval quality.To the best of our knowledge,little attention has been focused on how to enhance the retrieval efficiency.Nowadays,image data is widespread and expanding rapidly in our daily life.Obviously,it is important and interesting to investigate the retrieval efficiency.To this end,this paper presents an efficient image retrieval method named CATIRI(content-and-text based image retrieval using indexing).CATIRI follows a three-phase solution framework that develops a new indexing structure called MHIM-tree.The MHIM-tree seamlessly integrates several elements including Manhattan Hashing,Inverted index,and M-tree.To use our MHIM-tree wisely in the query,we present a set of important metrics and reveal their inherent properties.Based on them,we develop a top-k query algorithm for CTBIR.Experimental results based on benchmark image datasets demonstrate that CATIRI outperforms the competitors by an order of magnitude.展开更多
Lattice symmetry is vital to the properties of two-dimensional(2D)materials,yet their fixed symmetry cannot meet the increasing requirements in highly eficient and programmable electrical transport.If the structural d...Lattice symmetry is vital to the properties of two-dimensional(2D)materials,yet their fixed symmetry cannot meet the increasing requirements in highly eficient and programmable electrical transport.If the structural diversity of 2D materals,as demon-strated by 1T'-WTez,is improved without any phase transition or structural reconstruction,excellent metallic 1T'-WTez would be possibly used for inte-grated devices.Here,we realized meta symmetry of 1T'-WTez by using an edge-induced mechanism,which is recognized as the combination of the intrin-sic C2v symmetry and sixfold axes.On account of the dynamically controlled growth,the meta symmetric 1T'-WTez with^94.9%purity is obtained for the first time.Meta symmetry will also keep the intrinsic electrical properties of 1T'-WTez over the node.Such meta symmetry could not only enrich the structural diversity of 1T'-WTez,but also be extended to other low-symmetry 2D materials,which would be promising for customized circuits and devices.展开更多
CONSPECTUS:Liquid metal exhibits the unique advantages of both the liquid and metal,including excellent deformability,high thermal conductivity,and electrical conductivity.The exploration of liquid metal is a new oppo...CONSPECTUS:Liquid metal exhibits the unique advantages of both the liquid and metal,including excellent deformability,high thermal conductivity,and electrical conductivity.The exploration of liquid metal is a new opportunity and revolution for the application of metal materials,including the flexible devices,catalysis,microfluidic,and drug delivery.In addition to the above applications,the characteristics of excellent inclusive ability with the majority of the elements and abundant vacancies in the bulk make it a new type of reaction medium different from traditional aqueous and organic solutions,exhibiting great potential in the precise construction of materials.To date,the research of using liquid metal as a reaction system to synthesize materials is still in its infancy.When acting as a reaction system,the vacancies inside and the smooth layering surfaces without grain boundaries allow liquid metals to encapsulate heterogeneous atoms,confine the precursors in atomically thick layers and realize the self-limiting growth of 2D material.Besides,the good rheological property makes it possible to construct 2D arrays on its surface.Except for the properties mentioned above,as a kind of metal,its excellent electrical conductivity and ductility provide a new idea for the preparation of composite materials in the energy field.Indeed,liquid metals provide attractive prospects in manufacturing advanced materials including 2D materials and functional composite materials.Thus,this Account aims to focus on the controllable fabrication of 2D materials and functional composite materials by liquid metals.Based on the characteristics of the surface layering and solidification and of excellent fluidity,the self-limited growth and ordered arrangement of 2D materials on liquid metal surfaces can be achieved,which enriches the material structures and leads to new properties.By constructing an in situ synthesis and observation system,the growth and assembly behavior of 2D materials on the liquid metal can be observed directly.Combining the electrical property,deformability,ductility,and high inclusive ability with other materials,the liquid metal reaction system can also realize the preparation of new functional composite materials toward various applications,such as the energy field.Except for the 2D materials and functional composite materials mentioned here,liquid metals also provide more possibilities for fabricating other promising materials,like wafer-scale semiconductors,magic-angle graphene,flexible functional materials,biomedical materials,and so on.The research concerning the manufacturing of advanced materials on liquid metals is still in its infancy.We believe that the development of related technologies offering in-depth investigation and theoretical understanding on liquid metals will lay a solid foundation for the basic research and practical application of more advanced materials.展开更多
Self-assembly is deemed to be an effective and inspiring strategy to construct programmable and innovative super-ordered structures.Here,we have,for the first time,achieved the large-area super-ordered two-dimensional...Self-assembly is deemed to be an effective and inspiring strategy to construct programmable and innovative super-ordered structures.Here,we have,for the first time,achieved the large-area super-ordered two-dimensional(2D)emptiness arrays in graphene by silicon dioxide self-assembly pre-occupancy.The prominent uniform periodicity of 2D emptiness arrays in graphene can be flexibly adjusted.The synergistic interaction between the pre-occupancy structural unit and graphene contributes to the successful acquisition of 2D emptiness arrays.The realization of 2D emptiness arrays by self-assembly pre-occupancy strategy would shed light on the rational redaction,fabrication and research of complex 2D super-ordered structure systems and facilitate their applications for various fields,such as highly integrated functional devices,precise location acquisition systems,sensing,separation,and so on.展开更多
Two-dimensional(2 D) transition metal phosphides(TMPs) are predicted with many novel properties and various applications. As a member of TMPs family, molybdenum phosphide(MoP) exhibits many exotic physicochemical prop...Two-dimensional(2 D) transition metal phosphides(TMPs) are predicted with many novel properties and various applications. As a member of TMPs family, molybdenum phosphide(MoP) exhibits many exotic physicochemical properties. However, the synthesis of high-quality2 D MoP single crystals is not reported due to the lack of reliable fabrication method, which limits the exploration of 2 D MoP. Here, we report the growth of high-quality ultrathin MoP single crystals with thickness down to 10 nm on liquid metals via chemical vapor deposition(CVD). The smooth surface of liquid Ga is regarded as a suitable growth substrate for producing 2 D MoP single crystals. The Mo source diffuses toward the Ga surface due to the high surface energy to react with phosphorus source, thus to fabricate ultrathin MoP single crystals. Then, we study the second harmonic generation(SHG) of 2 D MoP for the first time due to its intrinsic noncentrosymmetric structure. Our study provides an new approach to synthesize and explore other 2 D TMPs for future applications.展开更多
sp^2 carbon nanomaterials are mainly composed of sp^2-hybridized carbon atoms in the form of a hexagonal network. Due to the p bonds formed by unpaired electrons, sp^2 carbon nanomaterials possess excellent electronic...sp^2 carbon nanomaterials are mainly composed of sp^2-hybridized carbon atoms in the form of a hexagonal network. Due to the p bonds formed by unpaired electrons, sp^2 carbon nanomaterials possess excellent electronic, mechanical, and optical properties, which have attracted great attention in recent years.As the advanced sp^2 carbon nanomaterials, graphene and carbon nanotubes(CNTs) have great potential in electronics, sensors, energy storage and conversion devices, etc. The low-temperature synthesis of graphene and CNTs are indispensable to promote the practical industrial application. Furthermore, graphene and CNTs can even be expected to directly grow on the flexible plastic that cannot bear high temperature,expanding bright prospects for applications in emerging flexible nanotechnology. An in-depth understanding of the formation mechanism of sp^2 carbon nanomaterials is beneficial for reducing the growth temperature and satisfying the demands of industrial production in an economical and low-cost way. In this review, we discuss the main strategies and the related mechanisms in low-temperature synthesis of graphene and CNTs, including the selection of precursors with high reactivity, the design of catalyst, and the introduction of additional energy for the pre-decomposition of precursors. Furthermore, challenges and outlooks are highlighted for further progress in the practical industrial application.展开更多
Currently,most two-dimensional(2D)materials that are of interest to emergent applications have focused on van der Waals–layered materials(VLMs)because of the ease with which the layers can be separated(e.g.,graphene)...Currently,most two-dimensional(2D)materials that are of interest to emergent applications have focused on van der Waals–layered materials(VLMs)because of the ease with which the layers can be separated(e.g.,graphene).Strong interlayer-bonding-layered materials(SLMs)in general have not been thoroughly explored,and one of the most critical present issues is the huge challenge of their preparation,although their physicochemical proper-ty transformation should be richer than VLMs and deserves greater attention.MAX phases are a classi-cal kind of SLM.展开更多
文摘In order to discover the main causes of elevator group accidents in edge computing environment, a multi-dimensional data model of elevator accident data is established by using data cube technology, proposing and implementing a method by combining classical Apriori algorithm with the model, digging out frequent items of elevator accident data to explore the main reasons for the occurrence of elevator accidents. In addition, a collaborative edge model of elevator accidents is set to achieve data sharing, making it possible to check the detail of each cause to confirm the causes of elevator accidents. Lastly the association rules are applied to find the law of elevator Accidents.
基金supported by the College of Chemistry and Molecular Sciences,Wuhan Universitythe National Natural Science Foundation of China(22025303)。
文摘Two-dimensional(2D)ferromagnetic materials have important applications in optics,spintronics,biomedicine,and energy conversion fields.To achieve higher integration and continue Moore's Law,it is necessary to search for 2D ferromagnetic materials.However,the low Curie temperature(Tc)of most 2D ferromagnetic materials seriously hinders their practical applications.Therefore,the search for room-temperature 2D ferromagnetic materials is of great significance for the advancement of technological applications.This article provides a systematic and comprehensive review of the synthesis methods of room-temperature 2D ferromagnetic materials that have been discovered and created to date,as well as an overview of the physical properties of the 2D ferromagnetic materials.Finally,the challenges and prospects of the room-temperature 2D ferromagnetic materials in the fields of synthesis and application are briefly summarized.
基金the National Natural Science Foundation of China(Nos.21673161 and 21905210)the Sino-German Center for Research Promotion(1400)the Postdoctoral Innovation Talent Support Program of China(No.BX20180224).
文摘Metal halide perovskites,as a new generation of optoelectronic materials,have attracted a great deal of interest due to their remarkable intrinsic properties.Due to the excellent optoelectronic properties,the perovskite crystals are widely used in lasers,photodetectors,X-ray detectors and solar cells.Considering the device performance and fabrication requirements,proper thickness of the crystal is required to avoid carrier loss and simultaneously ensure sufficient light absorption,which can realize the full potential of its excellent carrier transport property.Thus,the fabrication of perovskite crystal in a thin film with an adjustable thickness is highly desirable.The space-confined method has been demonstrated to be an effective way of preparing perovskite with controlled thickness.In this method,the thickness of perovskite can be regulated flexibly in a geometric confined space.Moreover,the size,quality and architecture of perovskite crystal films are also major concerns for practical photoelectric devices,which can also be optimized by the space-confined method owing to its good adaptability towards various modified strategies.In a word,the space-confined method is not only a simple and conventional way to adjust the thickness of perovskite crystal films,but also provides a platform to optimize their size,quality and architecture through applying appropriate strategies to the confined space.Herein,we review the space-confined growth of perovskite crystal films.Particularly,various modified strategies based on the space-confined method applied to the optimization of thickness,size,quality and architecture are highlighted.Then the stability investigating and component regulating of perovskite crystal films would be also mentioned.Furthermore,the correlation between the perovskite thickness and the device performance is discussed.Finally,several key challenges and proposed solutions of perovskite thin films based on the space-confined method are discussed.
基金supported by the National Natural Science Foundation of China(21673161)the Sino-German Center for Research Promotion(1400)
文摘Previous reports about the growth of large graphene single crystals on polycrystalline metal substrates usually adopted the strategy of suppressing the nucleation by lowering the concentration of the feedstock, which greatly limited the rate of the nucleation and the sequent growth. The emerging liquid metal catalyst possesses the characteristic of quasi-atomically smooth surface with high diffusion rate. In principle, it should be a naturally ideal platform for the lowdensity nucleation and the fast growth of graphene. However,the rapid growth of large graphene single crystals on liquid metals has not received the due attention. In this paper, we firstly purposed the insight into the rapid growth of large graphene single crystals on liquid metals. We obtained the millimeter-size graphene single crystals on liquid Cu. The rich free-electrons in liquid Cu accelerate the nucleation, and the isotropic smooth surface greatly suppresses the nucleation.Moreover, the fast mass-transfer of carbon atoms due to the excellent fluidity of liquid Cu promotes the fast growth with a rate up to 79 μm s^-1. We hope the research on the growth speed of graphene on liquid Cu can enrich the recognition of the growth behavior of two-dimensional(2 D) materials on the liquid metal. We also believe that the liquid metal strategy for the rapid growth of graphene can be extended to various 2 D materials and thus promote their future applications in the photonics and electronics.
基金The research was supported by the National Natural Science Foundation of China(grants 21673161)the Science and Technology Department of Hubei Province(grant 2017AAA114)+1 种基金the Postdoctoral Innovation Talent Support Program of China(BX20180224)the Sino-German Center for Research Promotion(grant 1400).
文摘Emerging two-dimensional(2D)materials have stimulated tremendous scientific and industrial interests due to their diverse and tunable physical,chemical,and mechanical properties.The scalable production of high-quality wafer-scale 2D materials has become significantly essential to bring us closer to practical industrial applications,particularly in electronic devices.Vapor-phase growth provides attractive opportunities for the synthesis of large-area and high-quality 2D materials.In this review,we will emphasize vapor-phase growth strategies from three aspects,including suppressing nucleation,seamless stitching,and evolutionary selection growth.We discuss the general understanding of the related fundamental mechanism and specific parameter optimization from precursors and substrate design to the adjusting of growth parameters(temperature and pressure).Meanwhile,we present other strategies to produce various kinds of wafer-scale 2D materials.Finally,we conclude the current challenges and future directions in this developing field.This work may inspire researchers to better design routes in the synthesis of wafer-scale 2D materials with high quality.
基金the National Basic Research 973 Program of China under Grant No.2015CB352403the National Key Research and Development Program of China under Grant Nos.2018YFC1504504,2016YFB0700502 and 2018YFB1004400+1 种基金the National Natural Science Foundation of China under Grant Nos.61872235,61729202,61832017,U1636210,61832013,61672351,61472453,61702320,U1401256,U1501252,U1611264,U1711261,U1711262,U61811264Guangdong Province Key Laboratory of Popular High Performance Computers of Shenzhen University under Grant No.SZU-GDPHPCL2017.
文摘The combination of visual and textual information in image retrieval remarkably alleviates the semantic gap of traditional image retrieval methods,and thus it has attracted much attention recently.Image retrieval based on such a combination is usually called the content-and-text based image retrieval(CTBIR).Nevertheless,existing studies in CTBIR mainly make efforts on improving the retrieval quality.To the best of our knowledge,little attention has been focused on how to enhance the retrieval efficiency.Nowadays,image data is widespread and expanding rapidly in our daily life.Obviously,it is important and interesting to investigate the retrieval efficiency.To this end,this paper presents an efficient image retrieval method named CATIRI(content-and-text based image retrieval using indexing).CATIRI follows a three-phase solution framework that develops a new indexing structure called MHIM-tree.The MHIM-tree seamlessly integrates several elements including Manhattan Hashing,Inverted index,and M-tree.To use our MHIM-tree wisely in the query,we present a set of important metrics and reveal their inherent properties.Based on them,we develop a top-k query algorithm for CTBIR.Experimental results based on benchmark image datasets demonstrate that CATIRI outperforms the competitors by an order of magnitude.
基金the National Natural Science Foundation of China(No.21673161)the Sino-German Center for Research Promotion(1400)the Fundamental Research Funds for the Central Universities(2042017kf0208).
文摘Lattice symmetry is vital to the properties of two-dimensional(2D)materials,yet their fixed symmetry cannot meet the increasing requirements in highly eficient and programmable electrical transport.If the structural diversity of 2D materals,as demon-strated by 1T'-WTez,is improved without any phase transition or structural reconstruction,excellent metallic 1T'-WTez would be possibly used for inte-grated devices.Here,we realized meta symmetry of 1T'-WTez by using an edge-induced mechanism,which is recognized as the combination of the intrin-sic C2v symmetry and sixfold axes.On account of the dynamically controlled growth,the meta symmetric 1T'-WTez with^94.9%purity is obtained for the first time.Meta symmetry will also keep the intrinsic electrical properties of 1T'-WTez over the node.Such meta symmetry could not only enrich the structural diversity of 1T'-WTez,but also be extended to other low-symmetry 2D materials,which would be promising for customized circuits and devices.
基金supported by the National Natural Science Foundation of China(grants 22025303 and 21905210)the Sino-German Center for Research Promotion(grant no.1400).
文摘CONSPECTUS:Liquid metal exhibits the unique advantages of both the liquid and metal,including excellent deformability,high thermal conductivity,and electrical conductivity.The exploration of liquid metal is a new opportunity and revolution for the application of metal materials,including the flexible devices,catalysis,microfluidic,and drug delivery.In addition to the above applications,the characteristics of excellent inclusive ability with the majority of the elements and abundant vacancies in the bulk make it a new type of reaction medium different from traditional aqueous and organic solutions,exhibiting great potential in the precise construction of materials.To date,the research of using liquid metal as a reaction system to synthesize materials is still in its infancy.When acting as a reaction system,the vacancies inside and the smooth layering surfaces without grain boundaries allow liquid metals to encapsulate heterogeneous atoms,confine the precursors in atomically thick layers and realize the self-limiting growth of 2D material.Besides,the good rheological property makes it possible to construct 2D arrays on its surface.Except for the properties mentioned above,as a kind of metal,its excellent electrical conductivity and ductility provide a new idea for the preparation of composite materials in the energy field.Indeed,liquid metals provide attractive prospects in manufacturing advanced materials including 2D materials and functional composite materials.Thus,this Account aims to focus on the controllable fabrication of 2D materials and functional composite materials by liquid metals.Based on the characteristics of the surface layering and solidification and of excellent fluidity,the self-limited growth and ordered arrangement of 2D materials on liquid metal surfaces can be achieved,which enriches the material structures and leads to new properties.By constructing an in situ synthesis and observation system,the growth and assembly behavior of 2D materials on the liquid metal can be observed directly.Combining the electrical property,deformability,ductility,and high inclusive ability with other materials,the liquid metal reaction system can also realize the preparation of new functional composite materials toward various applications,such as the energy field.Except for the 2D materials and functional composite materials mentioned here,liquid metals also provide more possibilities for fabricating other promising materials,like wafer-scale semiconductors,magic-angle graphene,flexible functional materials,biomedical materials,and so on.The research concerning the manufacturing of advanced materials on liquid metals is still in its infancy.We believe that the development of related technologies offering in-depth investigation and theoretical understanding on liquid metals will lay a solid foundation for the basic research and practical application of more advanced materials.
基金supported by the National Natural Science Foundation of China(22025303 and 21905210)the Sino-German Center for Research Promotion(GZ 1400)。
文摘Self-assembly is deemed to be an effective and inspiring strategy to construct programmable and innovative super-ordered structures.Here,we have,for the first time,achieved the large-area super-ordered two-dimensional(2D)emptiness arrays in graphene by silicon dioxide self-assembly pre-occupancy.The prominent uniform periodicity of 2D emptiness arrays in graphene can be flexibly adjusted.The synergistic interaction between the pre-occupancy structural unit and graphene contributes to the successful acquisition of 2D emptiness arrays.The realization of 2D emptiness arrays by self-assembly pre-occupancy strategy would shed light on the rational redaction,fabrication and research of complex 2D super-ordered structure systems and facilitate their applications for various fields,such as highly integrated functional devices,precise location acquisition systems,sensing,separation,and so on.
基金supported by the National Natural Science Foundation of China (21673161 and 21905210)the Sino-German Center for Research Promotion (GZ 1400)。
文摘Two-dimensional(2 D) transition metal phosphides(TMPs) are predicted with many novel properties and various applications. As a member of TMPs family, molybdenum phosphide(MoP) exhibits many exotic physicochemical properties. However, the synthesis of high-quality2 D MoP single crystals is not reported due to the lack of reliable fabrication method, which limits the exploration of 2 D MoP. Here, we report the growth of high-quality ultrathin MoP single crystals with thickness down to 10 nm on liquid metals via chemical vapor deposition(CVD). The smooth surface of liquid Ga is regarded as a suitable growth substrate for producing 2 D MoP single crystals. The Mo source diffuses toward the Ga surface due to the high surface energy to react with phosphorus source, thus to fabricate ultrathin MoP single crystals. Then, we study the second harmonic generation(SHG) of 2 D MoP for the first time due to its intrinsic noncentrosymmetric structure. Our study provides an new approach to synthesize and explore other 2 D TMPs for future applications.
基金supported by the National Natural Science Foundation of China (21673161)the Sino-German Center for Research Promotion (1400)the Postdoctoral Innovation Talent Support Program of China (BX20180224)
文摘sp^2 carbon nanomaterials are mainly composed of sp^2-hybridized carbon atoms in the form of a hexagonal network. Due to the p bonds formed by unpaired electrons, sp^2 carbon nanomaterials possess excellent electronic, mechanical, and optical properties, which have attracted great attention in recent years.As the advanced sp^2 carbon nanomaterials, graphene and carbon nanotubes(CNTs) have great potential in electronics, sensors, energy storage and conversion devices, etc. The low-temperature synthesis of graphene and CNTs are indispensable to promote the practical industrial application. Furthermore, graphene and CNTs can even be expected to directly grow on the flexible plastic that cannot bear high temperature,expanding bright prospects for applications in emerging flexible nanotechnology. An in-depth understanding of the formation mechanism of sp^2 carbon nanomaterials is beneficial for reducing the growth temperature and satisfying the demands of industrial production in an economical and low-cost way. In this review, we discuss the main strategies and the related mechanisms in low-temperature synthesis of graphene and CNTs, including the selection of precursors with high reactivity, the design of catalyst, and the introduction of additional energy for the pre-decomposition of precursors. Furthermore, challenges and outlooks are highlighted for further progress in the practical industrial application.
基金This research was supported by the National Natural Science Foundation of China(21673161 and 21473124)the Sino-German Center for Research Promotion(1400)STEM characterization was conducted at the Center for Nanophase Materials Sciences,which is a DOE Office of Science User Facility.Work at Jilin University is supported by the Recruitment Program of Global Youth Experts in China and National Natural Science Founda-tion of China(11404131 and 11674121).
文摘Currently,most two-dimensional(2D)materials that are of interest to emergent applications have focused on van der Waals–layered materials(VLMs)because of the ease with which the layers can be separated(e.g.,graphene).Strong interlayer-bonding-layered materials(SLMs)in general have not been thoroughly explored,and one of the most critical present issues is the huge challenge of their preparation,although their physicochemical proper-ty transformation should be richer than VLMs and deserves greater attention.MAX phases are a classi-cal kind of SLM.
