Browsing by Author "Dong, C. L."

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Effect of Fe2O3 coating on ZnO nanowires in photoelectrochemical water splitting: A synchrotron x-ray spectroscopic and spectromicroscopic investigation
(2020-06-01)
Lu, Y. R.
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Wang, Y. F.
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Chang, H. W.
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Huang, Y. C.
;
Chen, J. L.
An array of ZnO/Fe2O3 core-shell nanowires (NW) for the highly efficient absorption of light and carrier collection is developed for use in photoelectrochemical (PEC) water-splitting. The oriented NW architecture favors physical matching, providing a direct electron conduction pathway and reducing the diffusion length of photogenerated holes. This work involves a combination of spectral imaging, spectromicroscopy and in situ x-ray absorption spectroscopy; spectra are obtained under operando conditions. Direct investigation of oriented nanowires using polarization-dependent x-ray spectromicroscopy enables the determination of the relationship between anisotropic electronic orbitals and charge carrier water-splitting efficiency. The results of O K-edge STXM demonstrated that the ZnO/Fe2O3 core-shell NW exhibits strong anisotropy and thus provides higher electron-hole transport efficiency than bare ZnO. In situ XAS revealed that interfacial charge transfer between Fe 3d and Zn 4p states enhances the photoelectrochemical reaction in the ZnO/Fe2O3 core-shell NW. The photogenerated electrons of Fe2O3 are transferred from Fe 3d states to the Zn 4p state under photoelectrochemical conditions.
Effect of Mn substitution on electronic structure of Ca(9)Y(PO(4))(7):Eu(2+), Mn(2+) phosphor determined by X-ray absorption spectroscopy
(2011-10-27)
Lu, Y. R.
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Huang, C. H.
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Chen, T. M.
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Lin, J. H.
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Ma, Y. R.
The single-composition Ca(9)Y(PO(4))(7):Eu(2+), Mn(2+) phosphors were synthesized by a solid-state reaction. The luminescent properties and electronic structures were investigated by photoluminescence (PL) and X-ray absorption near-edge structure (XANES). The PL demonstrated energy transfer and a red-shift as the Mn doping level was increased. The energy transfer is ascribed to charge transfer between Eu and Mn. The change of the PL intensity is caused by the increased O 2p-Mn 3d hybridization. The narrowing of the band gap, which finding is supported by the red-shift, is responsible for the formation of the Mn-related states close to the conduction band minimum. (C) 2011 Elsevier B.V. All rights reserved.
Effect of Mn substitution on electronic structure of Ca9Y(PO4)(7):Eu2+, Mn2+ phosphor determined by X-ray absorption spectroscopy
(2011-10-27)
Lu, Y. R.
;
Huang, C. H.
;
Chen, T. M.
;
Lin, J. H.
;
Ma, Y. R.
The single-composition Ca9Y(PO4)(7):Eu2+, Mn2+ phosphors were synthesized by a solid-state reaction. The luminescent properties and electronic structures were investigated by photoluminescence (PL) and X-ray absorption near-edge structure (XANES). The PL demonstrated energy transfer and a red-shift as the Mn doping level was increased. The energy transfer is ascribed to charge transfer between Eu and Mn. The change of the PL intensity is caused by the increased O 2p-Mn 3d hybridization. The narrowing of the band gap, which finding is supported by the red-shift, is responsible for the formation of the Mn-related states close to the conduction band minimum. (C) 2011 Elsevier B.V. All rights reserved.
Structural distortion and electronic states of Rb doped WO3 by X-ray absorption spectroscopy
(2016-01-01)
Wang, Y. C.
;
Hsu, C. H.
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Hsu, Y. Y.
;
Chang, C. C.
;
Dong, C. L.
Rubidium tungsten bronzes (RbxWO3) have recently attracted much attention due to their intriguing phenomena, such as complex structural phase transitions, strong electron-phonon coupling, and superconducting properties. This study investigates the local atomic and electronic structures of RbxWO3 (0.17 <= x <= 0.33). X-ray powder diffraction patterns showed a hexagonal tungsten bronze (HTB) phase. X-ray absorption spectra (XAS) at the W L-3-edge and Rb K-edge of RbxWO3 were carried out. The XAS analysis indicated a local distorted WO6 octahedron which leads to a splitting of e(g) and t(2g) energy states in the tungsten 5d orbital and this splitting of energy levels exhibited an asymmetrical behavior at x = 0.23 and 0.27. Overall analysis revealed a distortion of local atomic structure of the WO6 octahedra by rubidium doping, leading to the modification of the electronic structures of e(g) and t(2g) states in the tungsten 5d orbital, thereby accounting for the property changes in CDW formation and superconducting transition temperature of these materials.