Rod-shaped PbW O4 microcrystals of length 1 μm were fabricated by a hydrothermal route and subsequent calcination. Pt nanoparticles（NPs） of different contents（0.5 wt%,1 wt% and 2 wt%） were subsequently deposited ...Rod-shaped PbW O4 microcrystals of length 1 μm were fabricated by a hydrothermal route and subsequent calcination. Pt nanoparticles（NPs） of different contents（0.5 wt%,1 wt% and 2 wt%） were subsequently deposited on the PbW O4 microcrystals,producing robust Pt/PbW O4 composite microcrystals. The PbW O4 microcrystals and Pt/PbW O4 photocatalysts were characterized by X-ray diffraction,N2 sorption measurements,scanning electron microscopy,transmission electron microscopy,and X-ray photoelectron,photoluminescence,Fourier-transform infrared,and ultraviolet-visible diffuse reflectance spectroscopies. The photocatalytic performances of the catalysts were evaluated by the consecutive photocatalytic degradation of acid orange II dye. The Pt/PbW O4 composite microcrystals exhibited high photocatalytic activity and stability. The deposition of Pt NPs produced surface plasmon resonance（SPR）,which induced a large visible light absorption. A Pt NP content of 1-2 wt% resulted in an ~2 times increase in photocatalytic activity,compared with the activity of Pt/PbW O4. The crystal structure and high crystallinity of PbW O4 resulted in its favorable photocatalytic property,and the SPR effect of the Pt NPs promoted visible light harvesting. The Pt NPs also enhanced the separation of photo-generated electrons and holes,which further promoted the photocatalytic reaction.展开更多
The structure of Tb∶Mo∶PbWO4 crystals was investigated by Raman spectra and the results showed that the spectra were varied differently by doping dopants in different ranges of shift. Rotation-vibration, curving-vib...The structure of Tb∶Mo∶PbWO4 crystals was investigated by Raman spectra and the results showed that the spectra were varied differently by doping dopants in different ranges of shift. Rotation-vibration, curving-vibration and non-symmetrical stretching-vibration had been investigated on the spectra. Rotation-vibration intensity of [WO4]2-group is weakened and curving-vibration intensity is undergirded; low Mo6+ doping enhances the intensity of non-symmetrical stretching-vibration, with the concentration of Mo6+ increasing, the intensity is weakened. So it could be inferred that Tb3+ ion replaced the vacancy of Pb, when achieving at a certain concentration, Tb3+ ion would substitute for the lattice of Pb2+, Mo6+ ion would substitute for W lattice and generate [MoO4]2-new group, these are the main reason for the properties changing. Furthermore it could suggest that the impurity ions doped in tetrahedral positions, strongly affect the electron-phonon coupling in [WO4]2-, which makes the intensities of the vibration changed regularly.展开更多
In high energy physics experiments,large arrays of scintillation crystals have b een used in electromagnetic calorimeters for precision measurements of photons a nd electrons.The large crystal calorimeters and their u...In high energy physics experiments,large arrays of scintillation crystals have b een used in electromagnetic calorimeters for precision measurements of photons a nd electrons.The large crystal calorimeters and their use has been a key factor in the high energy physics programs.Table 1 lists parameters of crystal calorime ter projects of the past (Crystal Ball),present(L3) and future (CMS) in high ene rgy physics.In future high energy collider,however,scintillating crysta ls face a new challenge:the radiation damage caused by the increased background radiation level.It would reach about 1000 rad/day for lead tungstate (PbWO 4) crystal at LHC.Lead tungstate is a new fast and dense scintillating crystal and has been s elected as scintillator for the construction of calorimeter in CMS experiment of Large Hadron Collider (LHC) at CERN(European Organization for Nuclear Research ) next century.82000 large sized PWO scintillating crystals will be assembled in the calorimeter of the CMS experiment,and they will be produced both in China a nd in Russia from now until to 2004.展开更多
基金supported by the National Natural Science Foundation of China(2106700421567008+5 种基金21263005)Project of Jiangxi Province Natural Science Foundation China(20133BAB21003)Training Programs of Innovation and Entrepreneurship for Undergraduates of Jiangxi Province(201310407046)The Landing Project of Science and Technology of Colleges and Universities in Jiangxi Province(KJLD14046)Young Scientist Training Project of Jiangxi Province(20122BCB23015)Yuanhang Engineering of Jiangxi Province~~
文摘Rod-shaped PbW O4 microcrystals of length 1 μm were fabricated by a hydrothermal route and subsequent calcination. Pt nanoparticles（NPs） of different contents（0.5 wt%,1 wt% and 2 wt%） were subsequently deposited on the PbW O4 microcrystals,producing robust Pt/PbW O4 composite microcrystals. The PbW O4 microcrystals and Pt/PbW O4 photocatalysts were characterized by X-ray diffraction,N2 sorption measurements,scanning electron microscopy,transmission electron microscopy,and X-ray photoelectron,photoluminescence,Fourier-transform infrared,and ultraviolet-visible diffuse reflectance spectroscopies. The photocatalytic performances of the catalysts were evaluated by the consecutive photocatalytic degradation of acid orange II dye. The Pt/PbW O4 composite microcrystals exhibited high photocatalytic activity and stability. The deposition of Pt NPs produced surface plasmon resonance（SPR）,which induced a large visible light absorption. A Pt NP content of 1-2 wt% resulted in an ~2 times increase in photocatalytic activity,compared with the activity of Pt/PbW O4. The crystal structure and high crystallinity of PbW O4 resulted in its favorable photocatalytic property,and the SPR effect of the Pt NPs promoted visible light harvesting. The Pt NPs also enhanced the separation of photo-generated electrons and holes,which further promoted the photocatalytic reaction.
文摘The structure of Tb∶Mo∶PbWO4 crystals was investigated by Raman spectra and the results showed that the spectra were varied differently by doping dopants in different ranges of shift. Rotation-vibration, curving-vibration and non-symmetrical stretching-vibration had been investigated on the spectra. Rotation-vibration intensity of [WO4]2-group is weakened and curving-vibration intensity is undergirded; low Mo6+ doping enhances the intensity of non-symmetrical stretching-vibration, with the concentration of Mo6+ increasing, the intensity is weakened. So it could be inferred that Tb3+ ion replaced the vacancy of Pb, when achieving at a certain concentration, Tb3+ ion would substitute for the lattice of Pb2+, Mo6+ ion would substitute for W lattice and generate [MoO4]2-new group, these are the main reason for the properties changing. Furthermore it could suggest that the impurity ions doped in tetrahedral positions, strongly affect the electron-phonon coupling in [WO4]2-, which makes the intensities of the vibration changed regularly.
文摘In high energy physics experiments,large arrays of scintillation crystals have b een used in electromagnetic calorimeters for precision measurements of photons a nd electrons.The large crystal calorimeters and their use has been a key factor in the high energy physics programs.Table 1 lists parameters of crystal calorime ter projects of the past (Crystal Ball),present(L3) and future (CMS) in high ene rgy physics.In future high energy collider,however,scintillating crysta ls face a new challenge:the radiation damage caused by the increased background radiation level.It would reach about 1000 rad/day for lead tungstate (PbWO 4) crystal at LHC.Lead tungstate is a new fast and dense scintillating crystal and has been s elected as scintillator for the construction of calorimeter in CMS experiment of Large Hadron Collider (LHC) at CERN(European Organization for Nuclear Research ) next century.82000 large sized PWO scintillating crystals will be assembled in the calorimeter of the CMS experiment,and they will be produced both in China a nd in Russia from now until to 2004.
