A variety of spherical and structured activated charcoal supported Pt/Fe3O4 composites with an average particle size of ~100 nm have been synthesized by a self-assembly method using the difference of reduction potenti...A variety of spherical and structured activated charcoal supported Pt/Fe3O4 composites with an average particle size of ~100 nm have been synthesized by a self-assembly method using the difference of reduction potential between Pt （Ⅳ） and Fe （Ⅱ） precursors as driving force. The formed Fe3O4 nanoparticles （NPs） effectively prevent the aggregation of Pt nanocrystallites and promote the dispersion of Pt NPs on the surface of catalyst, which will be favorable for the exposure of Pt active sites for high-efficient adsorption and contact of substrate and hydrogen donor. The electron-enrichment state of Pt NPs donated by Fe304 nanocrystallites is corroborated by XPS measurement, which is responsible for promoting and activating the terminal C=O bond of adsorbed substrate via a vertical configuration. The experimental results show that the activated charcoal supported Pt/Fe3O4 catalyst exhibits 94.8% selectivity towards cinnamyl alcohol by the transfer hydrogenation of einnamaldehyde with Pt loading of 2.46% under the optimum conditions of 120 ℃ for 6 h, and 2-propanol as a hydrogen donor. Additionally, the present study demonstrates that a high-efficient and recyclable catalyst can be rapidly separated from the mixture due to its natural magnetism upon the application of magnetic field.展开更多
Ce^(3+)/Tb^(3+) co-doped and Ce^(3+)/Tb^(3+)/Eu^(3+) tri-doped β-NaYF_(4) photoluminescent microcrystals using oleic acid as surfactant were synthesized using the solvothermal method.Their microstructural characteris...Ce^(3+)/Tb^(3+) co-doped and Ce^(3+)/Tb^(3+)/Eu^(3+) tri-doped β-NaYF_(4) photoluminescent microcrystals using oleic acid as surfactant were synthesized using the solvothermal method.Their microstructural characteristics and photoluminescence properties were investigated in detail.They have the shape of hexagonal prism bipyramids with uniform particle size,which decreases with the concentrations of Tb^(3+) and Eu^(3+).The energy transfer processes of both the Ce^(3+)→Tb^(3+) and the Ce^(3+)→Tb^(3+)→Eu^(3+) were systematically studied.Compared with Eu^(3+) or Tb^(3+) single-doped β-NaYF_(4) microcrystals,the sensitization by Ce^(3+) for the photoluminescence of Tb^(3+) and Eu^(3+) leads to a broad excitation spectral bandwidth in the ultraviolet (UV) range.Meanwhile,the corresponding optical absorption efficiency is greatly enhanced.High energy transfer efficiencies have been observed from Ce^(3+) to Tb^(3+) and from Tb^(3+) to Eu^(3+).展开更多
A series of Dy^(3+)/Eu^(3+) single doped and co-doped SrLaAlO_(4) phosphors was synthesized by the traditional high-temperature solid-state method,and their structure,morphology and optical properties were characteriz...A series of Dy^(3+)/Eu^(3+) single doped and co-doped SrLaAlO_(4) phosphors was synthesized by the traditional high-temperature solid-state method,and their structure,morphology and optical properties were characterized.The X-ray diffraction(XRD) shows a small amount of doping with Dy^(3+) and Eu^(3+) does not change the crystal structure of the matrix SrLaAlO_(4) and the best synthesis temperature is 1450℃.The scanning electron microscopy(SEM) indicates the particle size directly ranges from 1 to 5μm roughly and the energy dispersive spectroscopy(EDS) patterns show that SrLaAlO_(4):Dy^(3+) phosphor and SrLaAlO_(4):Dy^(3+),Eu^(3+) phosphor were successfully synthesized.SrLaAlO_(4):Dy^(3+) phosphor can be effectively excited by near-ultraviolet light,producing two strong emission lights at 483 nm(blue light) and 579 nm(yellow light),presenting a cold white light;SrLaAlO_(4):Eu^(3+) phosphor can be effectively excited by nearultraviolet light,producing red lights at 622 nm;the characteristic emission peaks of Dy^(3+) and Eu^(3+)can be shown simultaneously under the same excitation wavelength in SrLaAlO_(4):Dy^(3+), Eu^(3+) phosphor.By changing the relative doping concentration ratio of Dy^(3+) and Eu^(3+),the modulation of SrLaAlO_(4):Dy^(3+),Eu3+phosphor from cold white to warm white light can be achieved.In addition,the study of the luminescent mechanism and lifetime shows that there is energy transfer between Dy^(3+) and Eu^(3+) in SrLaAlO_(4):Dy^(3+),Eu^(3+) phosphor.展开更多
基金This work is supported by the National Natural Science Foundation of China （No.51372248, No.51432009 and No.51502297）, Instrument Developing Project of the Chinese Academy of Sciences （No.yz201421）, the CAS/SAFEA International Partnership Program for Creative Research Teams of Chinese Academy of Sciences, China.
文摘A variety of spherical and structured activated charcoal supported Pt/Fe3O4 composites with an average particle size of ~100 nm have been synthesized by a self-assembly method using the difference of reduction potential between Pt （Ⅳ） and Fe （Ⅱ） precursors as driving force. The formed Fe3O4 nanoparticles （NPs） effectively prevent the aggregation of Pt nanocrystallites and promote the dispersion of Pt NPs on the surface of catalyst, which will be favorable for the exposure of Pt active sites for high-efficient adsorption and contact of substrate and hydrogen donor. The electron-enrichment state of Pt NPs donated by Fe304 nanocrystallites is corroborated by XPS measurement, which is responsible for promoting and activating the terminal C=O bond of adsorbed substrate via a vertical configuration. The experimental results show that the activated charcoal supported Pt/Fe3O4 catalyst exhibits 94.8% selectivity towards cinnamyl alcohol by the transfer hydrogenation of einnamaldehyde with Pt loading of 2.46% under the optimum conditions of 120 ℃ for 6 h, and 2-propanol as a hydrogen donor. Additionally, the present study demonstrates that a high-efficient and recyclable catalyst can be rapidly separated from the mixture due to its natural magnetism upon the application of magnetic field.
基金Funded by the National Natural Science Foundation of China(Nos.21571095,51362020)the Jiangxi Provincial Department of Education(No.KJLD13008)the Scientific Research Projects of Hunan Education Department(No.18C1442)。
文摘Ce^(3+)/Tb^(3+) co-doped and Ce^(3+)/Tb^(3+)/Eu^(3+) tri-doped β-NaYF_(4) photoluminescent microcrystals using oleic acid as surfactant were synthesized using the solvothermal method.Their microstructural characteristics and photoluminescence properties were investigated in detail.They have the shape of hexagonal prism bipyramids with uniform particle size,which decreases with the concentrations of Tb^(3+) and Eu^(3+).The energy transfer processes of both the Ce^(3+)→Tb^(3+) and the Ce^(3+)→Tb^(3+)→Eu^(3+) were systematically studied.Compared with Eu^(3+) or Tb^(3+) single-doped β-NaYF_(4) microcrystals,the sensitization by Ce^(3+) for the photoluminescence of Tb^(3+) and Eu^(3+) leads to a broad excitation spectral bandwidth in the ultraviolet (UV) range.Meanwhile,the corresponding optical absorption efficiency is greatly enhanced.High energy transfer efficiencies have been observed from Ce^(3+) to Tb^(3+) and from Tb^(3+) to Eu^(3+).
基金Project supported by Outstanding Young and Middle-aged Scientific Innovation Team of Colleges and Universities of Hubei Province(T2020008)。
文摘A series of Dy^(3+)/Eu^(3+) single doped and co-doped SrLaAlO_(4) phosphors was synthesized by the traditional high-temperature solid-state method,and their structure,morphology and optical properties were characterized.The X-ray diffraction(XRD) shows a small amount of doping with Dy^(3+) and Eu^(3+) does not change the crystal structure of the matrix SrLaAlO_(4) and the best synthesis temperature is 1450℃.The scanning electron microscopy(SEM) indicates the particle size directly ranges from 1 to 5μm roughly and the energy dispersive spectroscopy(EDS) patterns show that SrLaAlO_(4):Dy^(3+) phosphor and SrLaAlO_(4):Dy^(3+),Eu^(3+) phosphor were successfully synthesized.SrLaAlO_(4):Dy^(3+) phosphor can be effectively excited by near-ultraviolet light,producing two strong emission lights at 483 nm(blue light) and 579 nm(yellow light),presenting a cold white light;SrLaAlO_(4):Eu^(3+) phosphor can be effectively excited by nearultraviolet light,producing red lights at 622 nm;the characteristic emission peaks of Dy^(3+) and Eu^(3+)can be shown simultaneously under the same excitation wavelength in SrLaAlO_(4):Dy^(3+), Eu^(3+) phosphor.By changing the relative doping concentration ratio of Dy^(3+) and Eu^(3+),the modulation of SrLaAlO_(4):Dy^(3+),Eu3+phosphor from cold white to warm white light can be achieved.In addition,the study of the luminescent mechanism and lifetime shows that there is energy transfer between Dy^(3+) and Eu^(3+) in SrLaAlO_(4):Dy^(3+),Eu^(3+) phosphor.
