GaAs-based nanomaterials are essential for near-infrared nano-photoelectronic devices due to their exceptional optoelectronic properties.However,as the dimensions of GaAs materials decrease,the development of GaAs nan...GaAs-based nanomaterials are essential for near-infrared nano-photoelectronic devices due to their exceptional optoelectronic properties.However,as the dimensions of GaAs materials decrease,the development of GaAs nanowires(NWs)is hindered by type-Ⅱquantum well structures arising from the mixture of zinc blende(ZB)and wurtzite(WZ)phases and surface defects due to the large surface-to-volume ratio.Achieving GaAs-based NWs with high emission efficiency has become a key research focus.In this study,pre-etched silicon substrates were combined with GaAs/AlGaAs core-shell heterostructure to achieve GaAs-based NWs with good perpendicularity,excellent crystal structures,and high emission efficiency by leveraging the shadowing effect and surface passivation.The primary evidence for this includes the prominent free-exciton emission in the variable-temperature spectra and the low thermal activation energy indicated by the variable-power spectra.The findings of this study suggest that the growth method described herein can be employed to enhance the crystal structure and optical properties of otherⅢ-Ⅴlow-dimensional materials,potentially paving the way for future NW devices.展开更多
Mechanically activated disproportionation of Nd 12 Fe 82 B 6 alloy by ball milling in hydrogen atmosphere was experimentally investigated. The aspects of thermodynamics and kinetics for the mechanically activated disp...Mechanically activated disproportionation of Nd 12 Fe 82 B 6 alloy by ball milling in hydrogen atmosphere was experimentally investigated. The aspects of thermodynamics and kinetics for the mechanically activated disproportionation of the NdFeB alloy were discussed. Both the evolution of the disproportionation reaction and the corresponding microstructure change of the alloy during milling were characterized by X ray diffraction (XRD) analysis. The results show that the matrix phase Nd 2Fe 14 B of the as cast Nd 12 Fe 82 B 6 alloy can be disproportionated into a mixture of Nd hydride (H 5Nd 2), FeB/Fe 2B, and α Fe, by ball milling under hydrogen pressure of 0.2 MPa. The as disproportionated phases are of the size about 20 nm, suggesting that ball milling in hydrogen is an effective route for low temperature disproportionation processing of the NdFeB alloy to ensure a full nano structured as disproportionated microstructure. This is the basis for synthesizing Nd 2Fe 14 B/ α Fe nano composites with magnetic exchange coupling effect by subsequent desorption recombination processing.展开更多
Well-crystallized with excellent luminescent cessfully synthesized by a simple solid-state properties, Tb（BO2）3 nanorods were first suc- method with Ag as catalyst. The result of X- ray diffraction showed that the T...Well-crystallized with excellent luminescent cessfully synthesized by a simple solid-state properties, Tb（BO2）3 nanorods were first suc- method with Ag as catalyst. The result of X- ray diffraction showed that the Tb（BO2）3 nanorods could be well-crystallized at 700 ℃. As-prepared straight nanorods of Tb（BO2）3 had the typical diameters in the range of 100-200 nm, the thickness of 30 50 nm, and the length up to 3 μm by transmission electron microscopy, and the corresponding selected area electron diffraction indicated that the nanorod calcined at 700 ℃ was single-crystalline. Based on the fact that Ag nanoparticles attached to the tips and middles of the Tb（BO2）3 nanorods, a growth model of the Tb（BO2）3 nanorods was proposed. Photoluminescence spectra under excitation at 369 nm showed that these Tb（BO2）3 phosphors had a green emission at 546 nm, which is ascribed to 5D4→7F5 transition. The effect of calcining temperature on the structures, morphologies, and luminescent properties of Tb（BO2）3 phosphors were studied.展开更多
Cu2O@Cu2O core-shell nanoparticles (NPs) were prepared by using solution phase strategy. It was found that Cu2O@Cu2O NPs were easily converted to Cu2O@Cu NPs with the help of polyvinylpyrrolidine (PVP) and excessive a...Cu2O@Cu2O core-shell nanoparticles (NPs) were prepared by using solution phase strategy. It was found that Cu2O@Cu2O NPs were easily converted to Cu2O@Cu NPs with the help of polyvinylpyrrolidine (PVP) and excessive ascorbic acid (AA) in air at room temperature, which was an interesting phenomenon. The features of the two kinds of NPs were characterized by XRD, TEM and extinction spectra. Cu2O@Cu NPs with different shell thicknesses showed wide tunable optical properties for the localized surface plasmon (LSP) in metallic Cu. But Cu2O@Cu2O NPs did not indicate this feature. FTIR results reveal that Cu+ ions on the surface of Cu2O shell coordinate with N and O atoms in PVP and are further reduced to metallic Cu by excessive AA and then form a nucleation site on the surface of Cu2O nanocrystalline. PVP binds onto different sites to proceed with the reduction utill all the Cu sources in Cu2O shell are completely assumed.展开更多
Pure ZnS and Ni^2+-doped ZnS nanorods (Zn1-xNixS, x=0, 0.01, 0.03, 0.05 and 0.07, mole fraction,%) were synthesized by hydrothermal method. The effects of Ni2+ doping on the phase-structure, morphology, elemental comp...Pure ZnS and Ni^2+-doped ZnS nanorods (Zn1-xNixS, x=0, 0.01, 0.03, 0.05 and 0.07, mole fraction,%) were synthesized by hydrothermal method. The effects of Ni2+ doping on the phase-structure, morphology, elemental composition and optical properties of the samples were investigated by X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), X-ray energy dispersive spectrometry (EDS) and ultraviolet–visible spectroscopy (UV-Vis), respectively. The photocatalytic activity of Zn1-xNixS nanorods was evaluated by the photodegradation of organic dyes Rhodamine B (RhB) in aqueous solution under UV light irradiation. The results show that all samples exhibit wurtzite structure with good crystallization. The morphologies are one-dimensional nanorods with good dispersion, and the distortion of the lattice constant occurs. The band gap of Zn1-xNixS samples is smaller than that of pure ZnS, thus red shift occurs. Ni^2+-doped ZnS nanocrystals can enhance photocatalytic activities for the photodegradation of RhB. Especially, Zn0.97Ni0.03S sample exhibits better photocatalytic performance and photocatalytic stability for the decomposition of RhB.展开更多
We theoretically investigate the wave-vector and temperature-dependent electron transport in a magneticnanostructure modulated by an applied bias.The large spin-polarization can be achieved in such a device,and the de...We theoretically investigate the wave-vector and temperature-dependent electron transport in a magneticnanostructure modulated by an applied bias.The large spin-polarization can be achieved in such a device,and the degreeof spin-polarization strongly depends on the transverse wave-vector and the temperature.These interesting propertiesmay be helpful to spin-polarize electrons into semiconductors,and this device may be used as a spin filter.展开更多
Palladium based catalysts are the most active for methane oxidation. The tuning of their composition, structure and morphology at macro and nanoscale can alter significantly their catalytic behavior and robustness wit...Palladium based catalysts are the most active for methane oxidation. The tuning of their composition, structure and morphology at macro and nanoscale can alter significantly their catalytic behavior and robustness with a strong impact on their overall performances. Among the several combinations of supports and promoters that have been utilized, Pd/CeO2 has attracted a great attention due to its activity and durability coupled with the unusually high degree of interaction between Pd/Pd O and the support. This allows the creation of specific structural arrangements which profoundly impact on methane activation characteristics. Here we want to review the latest findings in this area, and particularly to envisage how the control(when possible) of Pd-CeO2 interaction at nanoscale can help in designing more robust methane oxidation catalysts.展开更多
文摘GaAs-based nanomaterials are essential for near-infrared nano-photoelectronic devices due to their exceptional optoelectronic properties.However,as the dimensions of GaAs materials decrease,the development of GaAs nanowires(NWs)is hindered by type-Ⅱquantum well structures arising from the mixture of zinc blende(ZB)and wurtzite(WZ)phases and surface defects due to the large surface-to-volume ratio.Achieving GaAs-based NWs with high emission efficiency has become a key research focus.In this study,pre-etched silicon substrates were combined with GaAs/AlGaAs core-shell heterostructure to achieve GaAs-based NWs with good perpendicularity,excellent crystal structures,and high emission efficiency by leveraging the shadowing effect and surface passivation.The primary evidence for this includes the prominent free-exciton emission in the variable-temperature spectra and the low thermal activation energy indicated by the variable-power spectra.The findings of this study suggest that the growth method described herein can be employed to enhance the crystal structure and optical properties of otherⅢ-Ⅴlow-dimensional materials,potentially paving the way for future NW devices.
基金National Natural Science Foundation of China(51201118)Foundation of the State Key Laboratory of Refractories and Metallurgy(2016QN11)KLGHEI(KLB11003)
文摘Mechanically activated disproportionation of Nd 12 Fe 82 B 6 alloy by ball milling in hydrogen atmosphere was experimentally investigated. The aspects of thermodynamics and kinetics for the mechanically activated disproportionation of the NdFeB alloy were discussed. Both the evolution of the disproportionation reaction and the corresponding microstructure change of the alloy during milling were characterized by X ray diffraction (XRD) analysis. The results show that the matrix phase Nd 2Fe 14 B of the as cast Nd 12 Fe 82 B 6 alloy can be disproportionated into a mixture of Nd hydride (H 5Nd 2), FeB/Fe 2B, and α Fe, by ball milling under hydrogen pressure of 0.2 MPa. The as disproportionated phases are of the size about 20 nm, suggesting that ball milling in hydrogen is an effective route for low temperature disproportionation processing of the NdFeB alloy to ensure a full nano structured as disproportionated microstructure. This is the basis for synthesizing Nd 2Fe 14 B/ α Fe nano composites with magnetic exchange coupling effect by subsequent desorption recombination processing.
文摘Well-crystallized with excellent luminescent cessfully synthesized by a simple solid-state properties, Tb（BO2）3 nanorods were first suc- method with Ag as catalyst. The result of X- ray diffraction showed that the Tb（BO2）3 nanorods could be well-crystallized at 700 ℃. As-prepared straight nanorods of Tb（BO2）3 had the typical diameters in the range of 100-200 nm, the thickness of 30 50 nm, and the length up to 3 μm by transmission electron microscopy, and the corresponding selected area electron diffraction indicated that the nanorod calcined at 700 ℃ was single-crystalline. Based on the fact that Ag nanoparticles attached to the tips and middles of the Tb（BO2）3 nanorods, a growth model of the Tb（BO2）3 nanorods was proposed. Photoluminescence spectra under excitation at 369 nm showed that these Tb（BO2）3 phosphors had a green emission at 546 nm, which is ascribed to 5D4→7F5 transition. The effect of calcining temperature on the structures, morphologies, and luminescent properties of Tb（BO2）3 phosphors were studied.
基金Projects(41172110,61107090)supported by the National Natural Science Foundation of China
文摘Cu2O@Cu2O core-shell nanoparticles (NPs) were prepared by using solution phase strategy. It was found that Cu2O@Cu2O NPs were easily converted to Cu2O@Cu NPs with the help of polyvinylpyrrolidine (PVP) and excessive ascorbic acid (AA) in air at room temperature, which was an interesting phenomenon. The features of the two kinds of NPs were characterized by XRD, TEM and extinction spectra. Cu2O@Cu NPs with different shell thicknesses showed wide tunable optical properties for the localized surface plasmon (LSP) in metallic Cu. But Cu2O@Cu2O NPs did not indicate this feature. FTIR results reveal that Cu+ ions on the surface of Cu2O shell coordinate with N and O atoms in PVP and are further reduced to metallic Cu by excessive AA and then form a nucleation site on the surface of Cu2O nanocrystalline. PVP binds onto different sites to proceed with the reduction utill all the Cu sources in Cu2O shell are completely assumed.
基金Project(51261015)supported by the National Natural Science Foundation of ChinaProject(1308RJZA238)supported by the Natural Science Foundation of Gansu Province,China
文摘Pure ZnS and Ni^2+-doped ZnS nanorods (Zn1-xNixS, x=0, 0.01, 0.03, 0.05 and 0.07, mole fraction,%) were synthesized by hydrothermal method. The effects of Ni2+ doping on the phase-structure, morphology, elemental composition and optical properties of the samples were investigated by X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), X-ray energy dispersive spectrometry (EDS) and ultraviolet–visible spectroscopy (UV-Vis), respectively. The photocatalytic activity of Zn1-xNixS nanorods was evaluated by the photodegradation of organic dyes Rhodamine B (RhB) in aqueous solution under UV light irradiation. The results show that all samples exhibit wurtzite structure with good crystallization. The morphologies are one-dimensional nanorods with good dispersion, and the distortion of the lattice constant occurs. The band gap of Zn1-xNixS samples is smaller than that of pure ZnS, thus red shift occurs. Ni^2+-doped ZnS nanocrystals can enhance photocatalytic activities for the photodegradation of RhB. Especially, Zn0.97Ni0.03S sample exhibits better photocatalytic performance and photocatalytic stability for the decomposition of RhB.
基金Supported by Hubei Province Key Laboratory of Systems Science in Metallurgical Process (Wuhan University of Science and Technology) under Grant No.C201018 the National Natural Science Foundation of China under Grant No.10805035
文摘We theoretically investigate the wave-vector and temperature-dependent electron transport in a magneticnanostructure modulated by an applied bias.The large spin-polarization can be achieved in such a device,and the degreeof spin-polarization strongly depends on the transverse wave-vector and the temperature.These interesting propertiesmay be helpful to spin-polarize electrons into semiconductors,and this device may be used as a spin filter.
文摘Palladium based catalysts are the most active for methane oxidation. The tuning of their composition, structure and morphology at macro and nanoscale can alter significantly their catalytic behavior and robustness with a strong impact on their overall performances. Among the several combinations of supports and promoters that have been utilized, Pd/CeO2 has attracted a great attention due to its activity and durability coupled with the unusually high degree of interaction between Pd/Pd O and the support. This allows the creation of specific structural arrangements which profoundly impact on methane activation characteristics. Here we want to review the latest findings in this area, and particularly to envisage how the control(when possible) of Pd-CeO2 interaction at nanoscale can help in designing more robust methane oxidation catalysts.
