This paper describes mass-based energy phase-space projection of microwave-assisted synthesis of transition metals (zinc oxide, palladium, silver, platinum, and gold) nanostructures. The projection uses process energy...This paper describes mass-based energy phase-space projection of microwave-assisted synthesis of transition metals (zinc oxide, palladium, silver, platinum, and gold) nanostructures. The projection uses process energy budget (measured in kJ) on the horizontal axes and process density (measured in kJg−1) on the vertical axes. These two axes allow both mass usage efficiency (Environmental-Factor) and energy efficiency to be evaluated for a range of microwave applicator and metal synthesis. The metrics are allied to the: second, sixth and eleventh principle of the twelve principle of Green Chemistry. This analytical approach to microwave synthesis (widely considered as a useful Green Chemistry energy source) allows a quantified dynamic environmental quotient to be given to renewable plant-based biomass associated with the reduction of the metal precursors. Thus allowing a degree of quantification of claimed “eco-friendly” and “sustainable” synthesis with regard to waste production and energy usage.展开更多
Microwave irradiation is considered an important approach to Green Chemistry, because of its ability to rapidly increase the internal temperature of polar-organic compounds that lead to synthesis times of minutes rath...Microwave irradiation is considered an important approach to Green Chemistry, because of its ability to rapidly increase the internal temperature of polar-organic compounds that lead to synthesis times of minutes rather than hours when compared to conventional thermal heating. This works describes a dual allometry test for the discrimination between the solvents and reagents used in the microwave-assisted synthesis of transition metal (zinc oxide, palladium silver, platinum, and gold) nanostructures. The test is performed in log-log process energy phase-space projection, where the synthesis data (kJ against kJ·mol<sup>-1</sup>) has a power-law signature. The test is shown to discriminate between recommended Green Chemistry, problematic Green Chemistry, and Green Chemistry hazardous solvents. Typically, recommended Green chemistry exhibits a broad y-axes distribution within an upper exponent = 1 and lower exponent = 0.5. Problematic Green Chemistry exhibits a y-axes narrower distribution with an upper exponent = 0.94 and lower exponent = 0.64. Non-Green Chemistry hazardous data exhibits a further narrowing of the y-axes distribution within upper exponent = 0.87 and lower exponent = 0.66. In all three cases, the y-axes is aligned to original database power-law signature. It is also shown that in the x-axes direction (process energy budget) the grouped order of magnitude decreases from four orders for recommended Green Chemistry solvent and reagent data, through two orders for non-Green Chemistry hazardous material and down to one order for problematic Green Chemistry.展开更多
Photoelectrochemical(PEC) water splitting offers the capability of harvesting, storing, and converting solar energy into clean and sustainable hydrogen energy. Metal oxides are appealing photoelectrode materials becau...Photoelectrochemical(PEC) water splitting offers the capability of harvesting, storing, and converting solar energy into clean and sustainable hydrogen energy. Metal oxides are appealing photoelectrode materials because of their easy manufacturing and relatively high stability. In particular, metal oxides prepared by electrochemical anodization are typical of ordered nanostructures, which are beneficial for light harvesting, charge transfer and transport, and the adsorption and desorption of reactive species due to their high specific surface area and rich channels. However, bare anodic oxides still suffer from low charge separation and sunlight absorption efficiencies. Accordingly, many strategies of modifying anodic oxides have been explored and investigated. In this review, we attempt to summarize the recent advances in the rational design and modifications of these oxides from processes before, during, and after anodization. Rational design strategies are thoroughly addressed for each part with an aim to boost overall PEC performance. The ongoing efforts and challenges for future development of practical PEC electrodes are also presented.展开更多
Metal oxide nanostructures (CuO, Co3O4, ZnO and α-Fe2O3) have been successfully fabricated by a simple and efficient method: heating the appropriate metals in air at low temperatures ranging from 200 to 400℃. The...Metal oxide nanostructures (CuO, Co3O4, ZnO and α-Fe2O3) have been successfully fabricated by a simple and efficient method: heating the appropriate metals in air at low temperatures ranging from 200 to 400℃. The chemical composition, morphology and crystallinity of the nanostructures have been characterized by micro-Raman spectroscopy, X-ray diffraction, scanning electron microscopy and transmission electron microscopy. Two mechanisms: vapor-solid and surface diffusion play dominant roles in the growth of metal oxide nanostructures starting with low melting point metals (Zn and Cu) and high melting point metals (Fe and Co), respectively. With sharp ends and large aspect ratio, the metal oxide nanostructures exhibit impressive field-induced electron emission properties, indicating their potentials as future electron source and displays. The water wettability and anti-wettability properties of iron oxide nanoflakes were also discussed in this work.展开更多
We investigate a modified surface wave splitter with a double-layer structure, which consists of symmetrical metallic grating and an asymmetrical dielectric, using the finite-difference time-domain (FDTD) simulation...We investigate a modified surface wave splitter with a double-layer structure, which consists of symmetrical metallic grating and an asymmetrical dielectric, using the finite-difference time-domain (FDTD) simulation method. The metal/dielectric interface structure at this two-side aperture can support bound waves of different wavelengths, thus guiding waves in opposite directions. The covered dielectric films play an important role in the enhancement and confinement of the diffraction wave by the waveguide modes. The simulation result shows that the optical intensities of the guided surface wave at wavelengths of 760-nm and 1000-nm are about 100 times and 4-5 times those of the weaker side, respectively, which means that the surface wave is split by the proposed device.展开更多
Intrinsic luminescence from metal nanostructures complements conventional scattering and absorption behaviors and has many interesting and unique features. This phenomenon has attracted considerable research attention...Intrinsic luminescence from metal nanostructures complements conventional scattering and absorption behaviors and has many interesting and unique features. This phenomenon has attracted considerable research attention in recent years because of its various potential applications. In this review, we discuss recent advances in this field, summarize potential applications for this type of luminescence, and compare theoretical models to describe the phenomena. On the basis of the excitation process, the characteristic features and corresponding applications are summarized briefly in three parts, namely, continuous-wave light, pulsed laser, and electron excitation. A universal physical mechanism likely operates in all these emission processes regardless of differences in the excitation processes; however, there remains some debate surrounding the details of the theoretical model. Further insight into these luminescence phenomena will not only provide a deeper fundamental understanding of plasmonic nanostructures but will also advance and extend their applications.展开更多
Metal nanostructures have been of great research interest in recent years due to their physicochemical, plasmonic properties and potential applications. A lot of work has been done on the controlled synthesis of metal...Metal nanostructures have been of great research interest in recent years due to their physicochemical, plasmonic properties and potential applications. A lot of work has been done on the controlled synthesis of metal nanostructures for various applications. In this review, we try to focus on recent developments in synthesis and applications of metal nanostructures. Firstly, we summarized different preparation methods and then briefly explained their potential applications.展开更多
Metal organic frameworks(MOFs) represent a class of porous material which is formed by strong bonds between metal ions and organic linkers. By careful selection of constituents, MOFs can exhibit very high surface area...Metal organic frameworks(MOFs) represent a class of porous material which is formed by strong bonds between metal ions and organic linkers. By careful selection of constituents, MOFs can exhibit very high surface area, large pore volume, and excellent chemical stability.Research on synthesis, structures and properties of various MOFs has shown that they are promising materials for many applications, such as energy storage, gas storage, heterogeneous catalysis and sensing. Apart from direct use, MOFs have also been used as support substrates for nanomaterials or as sacrificial templates/precursors for preparation of various functional nanostructures. In this review, we aim to present the most recent development of MOFs as precursors for the preparation of various nanostructures and their potential applications in energy-related devices and processes. Specifically, this present survey intends to push the boundaries and covers the literatures from the year 2013 to early 2017,on supercapacitors, lithium ion batteries, electrocatalysts, photocatalyst, gas sensing, water treatment, solar cells, and carbon dioxide capture.Finally, an outlook in terms of future challenges and potential prospects towards industrial applications are also discussed.展开更多
Open-shell graphene nanostructures(GNs)are promising candidates for future spintronics and quantum technologies.Recent progress based on on-surface synthetic approach has successfully created such GNs on metallic surf...Open-shell graphene nanostructures(GNs)are promising candidates for future spintronics and quantum technologies.Recent progress based on on-surface synthetic approach has successfully created such GNs on metallic surfaces.Meanwhile,the doping effect of metallic surfaces is inevitably present and can significantly tune their electronic and magnetic properties.Here,we investigate the zigzag end states of open-shell 7-armchair graphene nanoribbons(7-AGNRs)on Au(111),Au(100)and Ag(111)surfaces.Combined with the manipulation of a scanning tunneling microscope,we demonstrate that the end states can be tuned from empty states to singly occupied states and to doubly occupied states by substrate doping.Furthermore,the singly occupied states can be finely tuned,with the occupancy number of the states and related magnetic behaviors uncovered by experiments at different temperatures and magnetic fields.Our results provide a comprehensive study of the magnetic response of open-shell GNs on metallic surfaces at different doping levels.展开更多
Visible-light-responsive ternary metal tungstate(MWO_4) photocatalysts are being increasingly investigated for energy conversion and environmental purification applications owing to their striking features, including ...Visible-light-responsive ternary metal tungstate(MWO_4) photocatalysts are being increasingly investigated for energy conversion and environmental purification applications owing to their striking features, including low cost,eco-friendliness, and high stability under acidic and oxidative conditions. However, rapid recombination of photoinduced electron–hole pairs and a narrow light response range to the solar spectrum lead to low photocatalytic activity of MWO_4-based materials, thus significantly hampering their wide usage in practice. To enable their widespread practical usage, significant efforts have been devoted, by developing new concepts and innovative strategies. In this review, we aim to provide an integrated overview of the fundamentals and recent progress of MWO_4-based photocatalysts. Furthermore, different strategies, including morphological control, surface modification, heteroatom doping, and heterojunction fabrication, which are employed to promote the photocatalyticactivities of MWO_4-based materials, are systematically summarized and discussed. Finally, existing challenges and a future perspective are also provided to shed light on the development of highly efficient MWO_4-based photocatalysts.展开更多
Nanostructured (ns) materials, i.e., polycrystalline materials with grain sizes in the nanometer regime (typically below 100 nm), have drawn considerable attention in the past decades due to their unique propertie...Nanostructured (ns) materials, i.e., polycrystalline materials with grain sizes in the nanometer regime (typically below 100 nm), have drawn considerable attention in the past decades due to their unique properties such as high strength and hardness. Wear resistance of ns materials, one of the most important properties for engineering materials, has been extensively investigated in the past decades. Obvious differences have been identified in friction and wear behaviors Between the ns materials and their corresponding coarse-grained (cg) counterparts, consistently correlating with their unique structure characteristics and mechanical properties. On the other hand, the superior tribological properties of ns materials illustrate their potential applications under contact loads. The present overview will summarize the important progresses achieved on friction and wear behaviors of ns metallic materials, including ultrafine-grained (ufg) materials in recent years. Tribological properties and effects on friction and wear behaviors of ns materials will be discussed under different wear conditions including abrasive wear, sliding wear, and fretting wear. Their correlations with mechanical properties will be analyzed. Perspectives on development of this field will be highlighted as well.展开更多
Particulate reinforced metallic matrix composites have attracted considerable attention due to their lightweight, high strength, high specific modulus, and good wear resistance. A1/B4C composite strips were produced i...Particulate reinforced metallic matrix composites have attracted considerable attention due to their lightweight, high strength, high specific modulus, and good wear resistance. A1/B4C composite strips were produced in this work by a modified accumulative roll bonding process where the strips were rotated 90° around the normal direction between successive passes. Transmission electron microscopy and X-ray diffraction analyses reveal the development of nanostructures in the Al matrix after seven passes. It is found that the B4C reinforcement distribution in the matrix is improved by progression of the process. Additionally, the tensile yield strength and elongation of the processed materials are increased with the increase of passes.展开更多
Nanostructured metals possess various excellent properties and offer the potential for a wide range of applications.Improvements in the properties and performance of nanostructured metal components motivate a complete...Nanostructured metals possess various excellent properties and offer the potential for a wide range of applications.Improvements in the properties and performance of nanostructured metal components motivate a complete characterization of the microstructures and crystallographic orientations of nanostructured metals with nanoscale spatial resolution.Two well developed orientation mapping techniques for such characterization are electron backscatter diffraction(EBSD)in the scanning electron microscope and precession electron diffraction(PED)using diffraction spots in the transmission electron microscope.However,these methods can only characterize the structure in two dimensions.It is still a great challenge to characterize grains in three dimensions,i.e.from the interior of the nanostructured metals.Recently,three-dimensional orientation mapping in the transmission electron microscope(3 D-OMi TEM)was developed and further improvements of this technique are introduced in this paper.Utilization of these orientation mapping techniques for structural and orientational characterizations are demonstrated by examples of surface-deformed metals with gradient nanostructures,and a sputtered gold film of nano-islands containing nanograins.The merits and challenges of each of these techniques are discussed and suggestions for further developments are proposed.展开更多
Surface-enhanced Raman spectroscopy (SERS) is a powerful vibrational spectroscopy technique for highly sensitive structural detection of low concentration analyte. The SERS activities largely depend on the topograph...Surface-enhanced Raman spectroscopy (SERS) is a powerful vibrational spectroscopy technique for highly sensitive structural detection of low concentration analyte. The SERS activities largely depend on the topography of the substrate. In this review, we summarize the recent progress in SERS substrate, especially focusing on the three-dimensional (3D) noble-metal substrate with hierarchical nanostructure. Firstly, we introduce the background and general mechanism of 3D hierarchical SERS nanostructures. Then, a systematic overview on the fabrication, growth mechanism, and SERS property of various noble-metal substrates with 3D hierarchical nanostructures is presented. Finally, the applications of 3D hierarchical nanostructures as SERS substrates in many fields are discussed.展开更多
In light of the nanostructured surface model, where half-spherical nanoparticles grow out symmetrically from a plane metallic film, the mathematical model for the partial electrical potential around nanospheres is dev...In light of the nanostructured surface model, where half-spherical nanoparticles grow out symmetrically from a plane metallic film, the mathematical model for the partial electrical potential around nanospheres is developed when a uniform external electric field is applied. On the basis of these models, the three-dimensional spatial distribution of the partial electrical potential is obtained and given in the form of a curved surface using a numerical computation method. Our results show that the electrical potential distribution around the nanospheres exhibits an obvious geometrical symmetry. These results could serve as a reference for investigating many abnormal phenomena such as abnormal infrared effects, which are found when CO molecules are adsorbed on the surface of nanostructured transition metals.展开更多
In conventional optics, the Fabry–Pérot(FP) effect is only considered for transparent materials at a macroscopic dimension. Down to the nanometer scale, for absorptive metallic structures, the FP effect has not ...In conventional optics, the Fabry–Pérot(FP) effect is only considered for transparent materials at a macroscopic dimension. Down to the nanometer scale, for absorptive metallic structures, the FP effect has not been directly observed so far. It is unclear whether such a macroscopic effect still holds for a subwavelength metallic nanostructure. Here, we demonstrate the probing of FP interference in a series of nanometer-thick Au films with subwavelength hole arrays. The evidence from both linear and second harmonic generation signals, together with angle-resolved investigations, exhibit features of a FP effect. We also derive an absorptive FP interference equation, which well explains our experimental results. Our results for the first time experimentally confirm the long-persisting hypothesis that the FP effect holds ubiquitously in a metallic nanostructure.展开更多
Department of Mechanical and Biomedical Engineering, City University of Hong Kong, Kowloon, Hong Kong, Chinagrains to a^1-martensite nanograins with bimodal grain size distribution for lower strain rates to nanotwins ...Department of Mechanical and Biomedical Engineering, City University of Hong Kong, Kowloon, Hong Kong, Chinagrains to a^1-martensite nanograins with bimodal grain size distribution for lower strain rates to nanotwins in the ultrafine/coarse grained austenite phase for higher strain rates. Meanwhile, we will further address the mechanism-based plastic models to describe the yield strength, strain hardening and ductility in nanostructured metals with bimodal grain size distribution and nanotwinned polycrystalline metals. The proposed theoretical models can comprehensively describe the plastic deformation in these two kinds of nanostructured metals and excellent agreement is achieved between the numerical and experimental results. These models can be utilized to optimize the strength and ductility in nanostructured metals by controlling the size and distribution of nanostructures.展开更多
文摘This paper describes mass-based energy phase-space projection of microwave-assisted synthesis of transition metals (zinc oxide, palladium, silver, platinum, and gold) nanostructures. The projection uses process energy budget (measured in kJ) on the horizontal axes and process density (measured in kJg−1) on the vertical axes. These two axes allow both mass usage efficiency (Environmental-Factor) and energy efficiency to be evaluated for a range of microwave applicator and metal synthesis. The metrics are allied to the: second, sixth and eleventh principle of the twelve principle of Green Chemistry. This analytical approach to microwave synthesis (widely considered as a useful Green Chemistry energy source) allows a quantified dynamic environmental quotient to be given to renewable plant-based biomass associated with the reduction of the metal precursors. Thus allowing a degree of quantification of claimed “eco-friendly” and “sustainable” synthesis with regard to waste production and energy usage.
文摘Microwave irradiation is considered an important approach to Green Chemistry, because of its ability to rapidly increase the internal temperature of polar-organic compounds that lead to synthesis times of minutes rather than hours when compared to conventional thermal heating. This works describes a dual allometry test for the discrimination between the solvents and reagents used in the microwave-assisted synthesis of transition metal (zinc oxide, palladium silver, platinum, and gold) nanostructures. The test is performed in log-log process energy phase-space projection, where the synthesis data (kJ against kJ·mol<sup>-1</sup>) has a power-law signature. The test is shown to discriminate between recommended Green Chemistry, problematic Green Chemistry, and Green Chemistry hazardous solvents. Typically, recommended Green chemistry exhibits a broad y-axes distribution within an upper exponent = 1 and lower exponent = 0.5. Problematic Green Chemistry exhibits a y-axes narrower distribution with an upper exponent = 0.94 and lower exponent = 0.64. Non-Green Chemistry hazardous data exhibits a further narrowing of the y-axes distribution within upper exponent = 0.87 and lower exponent = 0.66. In all three cases, the y-axes is aligned to original database power-law signature. It is also shown that in the x-axes direction (process energy budget) the grouped order of magnitude decreases from four orders for recommended Green Chemistry solvent and reagent data, through two orders for non-Green Chemistry hazardous material and down to one order for problematic Green Chemistry.
基金This work was financially supported by the National Key Research and Development Program of China(No.2016YFB0700300)the National Natural Science Foundation of China(Nos.51503014 and 51501008)the Fundamental Research Funds for the Central Universities of China(No.230201818-002A3).
文摘Photoelectrochemical(PEC) water splitting offers the capability of harvesting, storing, and converting solar energy into clean and sustainable hydrogen energy. Metal oxides are appealing photoelectrode materials because of their easy manufacturing and relatively high stability. In particular, metal oxides prepared by electrochemical anodization are typical of ordered nanostructures, which are beneficial for light harvesting, charge transfer and transport, and the adsorption and desorption of reactive species due to their high specific surface area and rich channels. However, bare anodic oxides still suffer from low charge separation and sunlight absorption efficiencies. Accordingly, many strategies of modifying anodic oxides have been explored and investigated. In this review, we attempt to summarize the recent advances in the rational design and modifications of these oxides from processes before, during, and after anodization. Rational design strategies are thoroughly addressed for each part with an aim to boost overall PEC performance. The ongoing efforts and challenges for future development of practical PEC electrodes are also presented.
文摘Metal oxide nanostructures (CuO, Co3O4, ZnO and α-Fe2O3) have been successfully fabricated by a simple and efficient method: heating the appropriate metals in air at low temperatures ranging from 200 to 400℃. The chemical composition, morphology and crystallinity of the nanostructures have been characterized by micro-Raman spectroscopy, X-ray diffraction, scanning electron microscopy and transmission electron microscopy. Two mechanisms: vapor-solid and surface diffusion play dominant roles in the growth of metal oxide nanostructures starting with low melting point metals (Zn and Cu) and high melting point metals (Fe and Co), respectively. With sharp ends and large aspect ratio, the metal oxide nanostructures exhibit impressive field-induced electron emission properties, indicating their potentials as future electron source and displays. The water wettability and anti-wettability properties of iron oxide nanoflakes were also discussed in this work.
文摘We investigate a modified surface wave splitter with a double-layer structure, which consists of symmetrical metallic grating and an asymmetrical dielectric, using the finite-difference time-domain (FDTD) simulation method. The metal/dielectric interface structure at this two-side aperture can support bound waves of different wavelengths, thus guiding waves in opposite directions. The covered dielectric films play an important role in the enhancement and confinement of the diffraction wave by the waveguide modes. The simulation result shows that the optical intensities of the guided surface wave at wavelengths of 760-nm and 1000-nm are about 100 times and 4-5 times those of the weaker side, respectively, which means that the surface wave is split by the proposed device.
文摘Intrinsic luminescence from metal nanostructures complements conventional scattering and absorption behaviors and has many interesting and unique features. This phenomenon has attracted considerable research attention in recent years because of its various potential applications. In this review, we discuss recent advances in this field, summarize potential applications for this type of luminescence, and compare theoretical models to describe the phenomena. On the basis of the excitation process, the characteristic features and corresponding applications are summarized briefly in three parts, namely, continuous-wave light, pulsed laser, and electron excitation. A universal physical mechanism likely operates in all these emission processes regardless of differences in the excitation processes; however, there remains some debate surrounding the details of the theoretical model. Further insight into these luminescence phenomena will not only provide a deeper fundamental understanding of plasmonic nanostructures but will also advance and extend their applications.
文摘Metal nanostructures have been of great research interest in recent years due to their physicochemical, plasmonic properties and potential applications. A lot of work has been done on the controlled synthesis of metal nanostructures for various applications. In this review, we try to focus on recent developments in synthesis and applications of metal nanostructures. Firstly, we summarized different preparation methods and then briefly explained their potential applications.
基金financial support from Ningbo Municipal Government (Innovation Team 2012882011,3315 Plan,2014A35001-1)the EPSRC (EP/J000582/1,GR/R68078)
文摘Metal organic frameworks(MOFs) represent a class of porous material which is formed by strong bonds between metal ions and organic linkers. By careful selection of constituents, MOFs can exhibit very high surface area, large pore volume, and excellent chemical stability.Research on synthesis, structures and properties of various MOFs has shown that they are promising materials for many applications, such as energy storage, gas storage, heterogeneous catalysis and sensing. Apart from direct use, MOFs have also been used as support substrates for nanomaterials or as sacrificial templates/precursors for preparation of various functional nanostructures. In this review, we aim to present the most recent development of MOFs as precursors for the preparation of various nanostructures and their potential applications in energy-related devices and processes. Specifically, this present survey intends to push the boundaries and covers the literatures from the year 2013 to early 2017,on supercapacitors, lithium ion batteries, electrocatalysts, photocatalyst, gas sensing, water treatment, solar cells, and carbon dioxide capture.Finally, an outlook in terms of future challenges and potential prospects towards industrial applications are also discussed.
基金supported by the Guangdong Major Project of Basic and Applied Basic Research(Grant No.2021B0301030002)the National Natural Science Foundation of China(Grant Nos.11974431,and 11774434)the support from the Hundreds of Talents Program of Sun Yat-sen University and Guangdong Science and Technology Project(Grant No.2021QN02X859)。
文摘Open-shell graphene nanostructures(GNs)are promising candidates for future spintronics and quantum technologies.Recent progress based on on-surface synthetic approach has successfully created such GNs on metallic surfaces.Meanwhile,the doping effect of metallic surfaces is inevitably present and can significantly tune their electronic and magnetic properties.Here,we investigate the zigzag end states of open-shell 7-armchair graphene nanoribbons(7-AGNRs)on Au(111),Au(100)and Ag(111)surfaces.Combined with the manipulation of a scanning tunneling microscope,we demonstrate that the end states can be tuned from empty states to singly occupied states and to doubly occupied states by substrate doping.Furthermore,the singly occupied states can be finely tuned,with the occupancy number of the states and related magnetic behaviors uncovered by experiments at different temperatures and magnetic fields.Our results provide a comprehensive study of the magnetic response of open-shell GNs on metallic surfaces at different doping levels.
基金support of NSFC 51702284Fundamental Research Funds for the Central Universities (112109*172210171)+2 种基金the Startup Foundation for Hundred-Talent Program of Zhejiang University (112100-193820101/001/022)support of the NSFC 21501138the Science Research Foundation of Wuhan Institute of Technology (K201513)
文摘Visible-light-responsive ternary metal tungstate(MWO_4) photocatalysts are being increasingly investigated for energy conversion and environmental purification applications owing to their striking features, including low cost,eco-friendliness, and high stability under acidic and oxidative conditions. However, rapid recombination of photoinduced electron–hole pairs and a narrow light response range to the solar spectrum lead to low photocatalytic activity of MWO_4-based materials, thus significantly hampering their wide usage in practice. To enable their widespread practical usage, significant efforts have been devoted, by developing new concepts and innovative strategies. In this review, we aim to provide an integrated overview of the fundamentals and recent progress of MWO_4-based photocatalysts. Furthermore, different strategies, including morphological control, surface modification, heteroatom doping, and heterojunction fabrication, which are employed to promote the photocatalyticactivities of MWO_4-based materials, are systematically summarized and discussed. Finally, existing challenges and a future perspective are also provided to shed light on the development of highly efficient MWO_4-based photocatalysts.
基金the National Major Project of Fundamental Research(Grant No.2005CB623604)National Natural Science Foundation of China(Grant Nos.50431010 and 50621091)Shenyang Science and Technology Project(Grant No.1071107-1-00).
文摘Nanostructured (ns) materials, i.e., polycrystalline materials with grain sizes in the nanometer regime (typically below 100 nm), have drawn considerable attention in the past decades due to their unique properties such as high strength and hardness. Wear resistance of ns materials, one of the most important properties for engineering materials, has been extensively investigated in the past decades. Obvious differences have been identified in friction and wear behaviors Between the ns materials and their corresponding coarse-grained (cg) counterparts, consistently correlating with their unique structure characteristics and mechanical properties. On the other hand, the superior tribological properties of ns materials illustrate their potential applications under contact loads. The present overview will summarize the important progresses achieved on friction and wear behaviors of ns metallic materials, including ultrafine-grained (ufg) materials in recent years. Tribological properties and effects on friction and wear behaviors of ns materials will be discussed under different wear conditions including abrasive wear, sliding wear, and fretting wear. Their correlations with mechanical properties will be analyzed. Perspectives on development of this field will be highlighted as well.
文摘Particulate reinforced metallic matrix composites have attracted considerable attention due to their lightweight, high strength, high specific modulus, and good wear resistance. A1/B4C composite strips were produced in this work by a modified accumulative roll bonding process where the strips were rotated 90° around the normal direction between successive passes. Transmission electron microscopy and X-ray diffraction analyses reveal the development of nanostructures in the Al matrix after seven passes. It is found that the B4C reinforcement distribution in the matrix is improved by progression of the process. Additionally, the tensile yield strength and elongation of the processed materials are increased with the increase of passes.
基金supported by the National Key Research and Development Program of China(2016YFB0700400)National Natural Science Foundation of China(Nos.51327805,51971045,51971043and 51671039)the support of the“111 Project”(B16007)by the Ministry of Education and the State Administration of Foreign Experts Affairs,China.
文摘Nanostructured metals possess various excellent properties and offer the potential for a wide range of applications.Improvements in the properties and performance of nanostructured metal components motivate a complete characterization of the microstructures and crystallographic orientations of nanostructured metals with nanoscale spatial resolution.Two well developed orientation mapping techniques for such characterization are electron backscatter diffraction(EBSD)in the scanning electron microscope and precession electron diffraction(PED)using diffraction spots in the transmission electron microscope.However,these methods can only characterize the structure in two dimensions.It is still a great challenge to characterize grains in three dimensions,i.e.from the interior of the nanostructured metals.Recently,three-dimensional orientation mapping in the transmission electron microscope(3 D-OMi TEM)was developed and further improvements of this technique are introduced in this paper.Utilization of these orientation mapping techniques for structural and orientational characterizations are demonstrated by examples of surface-deformed metals with gradient nanostructures,and a sputtered gold film of nano-islands containing nanograins.The merits and challenges of each of these techniques are discussed and suggestions for further developments are proposed.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11304188,51171139,and 51201122)the Specialized Research Fund for the Doctoral Program of Higher Education,China(Grant No.20120201120049)
文摘Surface-enhanced Raman spectroscopy (SERS) is a powerful vibrational spectroscopy technique for highly sensitive structural detection of low concentration analyte. The SERS activities largely depend on the topography of the substrate. In this review, we summarize the recent progress in SERS substrate, especially focusing on the three-dimensional (3D) noble-metal substrate with hierarchical nanostructure. Firstly, we introduce the background and general mechanism of 3D hierarchical SERS nanostructures. Then, a systematic overview on the fabrication, growth mechanism, and SERS property of various noble-metal substrates with 3D hierarchical nanostructures is presented. Finally, the applications of 3D hierarchical nanostructures as SERS substrates in many fields are discussed.
基金Project supported by the Natural Science Foundation of Fujian Province,China(Grant No.2010J01210)
文摘In light of the nanostructured surface model, where half-spherical nanoparticles grow out symmetrically from a plane metallic film, the mathematical model for the partial electrical potential around nanospheres is developed when a uniform external electric field is applied. On the basis of these models, the three-dimensional spatial distribution of the partial electrical potential is obtained and given in the form of a curved surface using a numerical computation method. Our results show that the electrical potential distribution around the nanospheres exhibits an obvious geometrical symmetry. These results could serve as a reference for investigating many abnormal phenomena such as abnormal infrared effects, which are found when CO molecules are adsorbed on the surface of nanostructured transition metals.
基金Supported by the National Key Research and Development Program of China under Grant Nos 2017YFA0303603 and 2016YFA0300303the National Natural Science Foundation of China under Grant Nos 11504062,11774408 and 11574383+2 种基金the Strategic Priority Research Program of Chinese Academy of Sciences under Grant No XDB30000000the Chinese Academy of Sciences Interdisciplinary Innovation Teamthe External Cooperation Program of Chinese Academy of Sciences under Grant No GJHZ1826
文摘In conventional optics, the Fabry–Pérot(FP) effect is only considered for transparent materials at a macroscopic dimension. Down to the nanometer scale, for absorptive metallic structures, the FP effect has not been directly observed so far. It is unclear whether such a macroscopic effect still holds for a subwavelength metallic nanostructure. Here, we demonstrate the probing of FP interference in a series of nanometer-thick Au films with subwavelength hole arrays. The evidence from both linear and second harmonic generation signals, together with angle-resolved investigations, exhibit features of a FP effect. We also derive an absorptive FP interference equation, which well explains our experimental results. Our results for the first time experimentally confirm the long-persisting hypothesis that the FP effect holds ubiquitously in a metallic nanostructure.
基金supportedby the Chinese Ministry of Science and Technology of China (2012CB932203)the Research Grants Council of the Hong Kong Special Administrative Region of China(CityU8/CRF/08 and GRF/CityU519110)the Croucher Foundation CityU9500006 and PolyU Postdoctoral Fellowship Project (G-YX3S)
文摘Department of Mechanical and Biomedical Engineering, City University of Hong Kong, Kowloon, Hong Kong, Chinagrains to a^1-martensite nanograins with bimodal grain size distribution for lower strain rates to nanotwins in the ultrafine/coarse grained austenite phase for higher strain rates. Meanwhile, we will further address the mechanism-based plastic models to describe the yield strength, strain hardening and ductility in nanostructured metals with bimodal grain size distribution and nanotwinned polycrystalline metals. The proposed theoretical models can comprehensively describe the plastic deformation in these two kinds of nanostructured metals and excellent agreement is achieved between the numerical and experimental results. These models can be utilized to optimize the strength and ductility in nanostructured metals by controlling the size and distribution of nanostructures.