Copper ion is the essential microelement to many organisms. In this paper, the local structure of Cu2+ in CuBr2 aqueous solutions with different concentrations are investigated by using X-ray absorption fine structure...Copper ion is the essential microelement to many organisms. In this paper, the local structure of Cu2+ in CuBr2 aqueous solutions with different concentrations are investigated by using X-ray absorption fine structure (XAFS) technique. XANES (X-ray Absorption Near Edge Structure) spectra indicate that charge transfer from Br- to Cu2+ decreases with the solution concentration, which lead to a shift of the absorption edge. The shoulder appearing at the rising edge proves to be characteristic of a tetragonal distortion. The Fourier transform magnitudes of EXAFS (Extended X-ray absorption fine structure) data of Cu species suggest that more Cu-Br bonds may exist in high concentrations. A fivefold coordination configuration like a pyramid is used as the fitting parameters. From the analysis of the coordination numbers, the proportion of Cu-O and Cu-Br is 4:1 in the saturated solution. The Br atom is on the equatorial plane of the model. The fitting results agree well with the experiment data.展开更多
Cerium oxide nanoparticles coated by sodium bis(2-ethylexyl) sulphosuccinate(AOT) were prepared by using a microemulsion method.Transmission electron microscopy revealed an average particle siae of 2-3nm.X-ray diffrac...Cerium oxide nanoparticles coated by sodium bis(2-ethylexyl) sulphosuccinate(AOT) were prepared by using a microemulsion method.Transmission electron microscopy revealed an average particle siae of 2-3nm.X-ray diffraction showed that the cerium oxide nanoparticles retain the CeF2-type cubic structures like the bulk crystal.The intermediate valence offormally tetravalent compounds had been detected by x-ray-absorption near-edge structetravalent compounds had been detected by x-ray-absorption near-dege structure(XANES) spectra of Ce LIII absorption in bulk CeO2 and the cerium oxide nanoparticles.Two well resoved white lines can be assigned to the electron configurations of 4f^0L and 4f^1L,respectively,where L denotes a ligand hole.At the same time,the cerium oxide nanoparticles also showed the structural featres of trivalent compounds,in comparison to the trivalent Ce(NO3)3·6H2O.Fuor Lorentzian functions and two arctan functions were used to fit the normalized XANES spectra.The extended x-ray-absorption fine-structure(EXAFS) technique was used to probe the local atomic structures around the absorber Ce.The multielectrorn excitation effect on the EXAFS spectra was eliminated.A cor-shell model was used to deduce the near-neighbour structural parameters around cerium.Bulk CeO2 with eight oxygen atoms located at 2.343A was used as the reference sample to extract the backscattering amplitude and phase shift of the Ce-O bond.One half of the atome locate at the core part with the CeF2-type cubic structures(eight oxyens at 2.343A around Ce),the other half of the atoms are amorphous phase located in the shell part (surface of the nanoparticles) with approximately Ce2O3 structural features (averageed seven oxygens at 2.50A around Ce).展开更多
Uranium is a member of Actinides and plays important role in nuclear science and technology. Electronicand structural investigations of actinide compounds attract major interest in science. The electronic structure an...Uranium is a member of Actinides and plays important role in nuclear science and technology. Electronicand structural investigations of actinide compounds attract major interest in science. The electronic structure andchemical bonding of coffinite USiO_4 are investigated by X-ray Absorption Fine Structure spectroscopy (XAFS). U L_3-edge absorption spectrum in USiO_4 is compared with U L_3-edge spectra in UO_2 and UTe due to their different electronicand chemical structures. The study presents XANES (x-ray Absorption Near-Edge Structure) and Extended XAFS(EXAFS) calculations of USiO_4 thin films. The full multiple scattering approach has been applied to the calculation ofU L_3 edge XANES spectra of USiO_4, UO_2 and UTe, based on different choices of one electron potentials according toUranium coordinations by using the real space multiple scattering method FEFF 8.2 code.展开更多
基金Supported by National Natural Science Foundation of China (Grant No.11005148,10705046,11135008)National Basic Research Program of China (Grant No. 2010CB934501)+1 种基金Special Presidential Foundation of the Chinese Academy of Science (Grant No. 29)Science and Technology Commission of Shanghai Municipality (Grant No. 11JC1414900)
文摘Copper ion is the essential microelement to many organisms. In this paper, the local structure of Cu2+ in CuBr2 aqueous solutions with different concentrations are investigated by using X-ray absorption fine structure (XAFS) technique. XANES (X-ray Absorption Near Edge Structure) spectra indicate that charge transfer from Br- to Cu2+ decreases with the solution concentration, which lead to a shift of the absorption edge. The shoulder appearing at the rising edge proves to be characteristic of a tetragonal distortion. The Fourier transform magnitudes of EXAFS (Extended X-ray absorption fine structure) data of Cu species suggest that more Cu-Br bonds may exist in high concentrations. A fivefold coordination configuration like a pyramid is used as the fitting parameters. From the analysis of the coordination numbers, the proportion of Cu-O and Cu-Br is 4:1 in the saturated solution. The Br atom is on the equatorial plane of the model. The fitting results agree well with the experiment data.
文摘Cerium oxide nanoparticles coated by sodium bis(2-ethylexyl) sulphosuccinate(AOT) were prepared by using a microemulsion method.Transmission electron microscopy revealed an average particle siae of 2-3nm.X-ray diffraction showed that the cerium oxide nanoparticles retain the CeF2-type cubic structures like the bulk crystal.The intermediate valence offormally tetravalent compounds had been detected by x-ray-absorption near-edge structetravalent compounds had been detected by x-ray-absorption near-dege structure(XANES) spectra of Ce LIII absorption in bulk CeO2 and the cerium oxide nanoparticles.Two well resoved white lines can be assigned to the electron configurations of 4f^0L and 4f^1L,respectively,where L denotes a ligand hole.At the same time,the cerium oxide nanoparticles also showed the structural featres of trivalent compounds,in comparison to the trivalent Ce(NO3)3·6H2O.Fuor Lorentzian functions and two arctan functions were used to fit the normalized XANES spectra.The extended x-ray-absorption fine-structure(EXAFS) technique was used to probe the local atomic structures around the absorber Ce.The multielectrorn excitation effect on the EXAFS spectra was eliminated.A cor-shell model was used to deduce the near-neighbour structural parameters around cerium.Bulk CeO2 with eight oxygen atoms located at 2.343A was used as the reference sample to extract the backscattering amplitude and phase shift of the Ce-O bond.One half of the atome locate at the core part with the CeF2-type cubic structures(eight oxyens at 2.343A around Ce),the other half of the atoms are amorphous phase located in the shell part (surface of the nanoparticles) with approximately Ce2O3 structural features (averageed seven oxygens at 2.50A around Ce).
文摘Uranium is a member of Actinides and plays important role in nuclear science and technology. Electronicand structural investigations of actinide compounds attract major interest in science. The electronic structure andchemical bonding of coffinite USiO_4 are investigated by X-ray Absorption Fine Structure spectroscopy (XAFS). U L_3-edge absorption spectrum in USiO_4 is compared with U L_3-edge spectra in UO_2 and UTe due to their different electronicand chemical structures. The study presents XANES (x-ray Absorption Near-Edge Structure) and Extended XAFS(EXAFS) calculations of USiO_4 thin films. The full multiple scattering approach has been applied to the calculation ofU L_3 edge XANES spectra of USiO_4, UO_2 and UTe, based on different choices of one electron potentials according toUranium coordinations by using the real space multiple scattering method FEFF 8.2 code.
