| Preparation and photochromism of Keggin-type molybdphosphoric acid/silica mesoporous composite thin films |
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| 作者单位： | ZHANG XueAo（College of Aerospace and Material Engineering, National University of Defense Technology, Changsha 410073, China） ;
WU WenJian（College of Aerospace and Material Engineering, National University of Defense Technology, Changsha 410073, China） ;
MAN YaHui（College of Aerospace and Material Engineering, National University of Defense Technology, Changsha 410073, China） ;
TIAN Tian（College of Aerospace and Material Engineering, National University of Defense Technology, Changsha 410073, China） ;
TIAN XiaoZhou（College of Aerospace and Material Engineering, National University of Defense Technology, Changsha 410073, China） ;
WANG JianFang（College of Aerospace and Material Engineering, National University of Defense Technology, Changsha 410073, China） ; |
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| 基金项目： | 国家高技术研究发展计划(863计划);国防科学技术大学校科研和教改项目 |
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| 摘 要： | Using tetraethoxysilane and 3-aminopropyltriethoxysilane as the silica sources, amino-functionalized organic/inorganic hybrid mesoporous silica thin films with 2-dimensional hexagonal structure have been synthesized by evaporation induced self-assembly process in the presence of cetyltrimethyl ammonium bromide templates under acid conditions. The Keggin-type molybdphosphoric acid (PMo) is incorporated into the mesoporous silica thin films with amino-groups by wetness impregnation, and the PMo/silica mesoporous composite thin films are obtained. The results of X-ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM), and Fourier transform infrared (FTIR) spectra indicate the PMo molecules maintain Keggin structure and are homogeneously distributed inside mesopores. The composite thin films possess excellent reversible photochromic properties, and change from colorless to blue under ultraviolet irradiation. The photochromic mechanism of the composite thin films is studied by ultraviolet-visible (UV-vis), electron spin resonance (ESR) and X-ray photoelectron spectroscopy (XPS) spectra. It is shown that intervalence charge transfer (IVCT) and ligand-to-metal charge transfer (LMCT) are the main reasons of photochromism. PMo anions interact strongly with amino-groups of the mesoporous suface via hydrogen bond and electrostatic force. After ultraviolet irradiation, the charge transfer occurs by reduction of heteropolyanions accompanying the formation of heteropolyblues with multivalence Mo(VI, V), and the bleaching process of composite thin films is closely related to the presence of oxygen.
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| 收稿时间： | 23 July 2006 |
| 修稿时间： | 29 August 2006 |
Preparation and photochromism of Keggin-type molybdphosphoric acid/silica mesoporous composite thin films |
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| Authors: | Zhang XueAo Wu WenJian Man YaHui Tian Tian Tian XiaoZhou Wang JianFang |
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| Institution: | College of Aerospace and Material Engineering, National University of Defense Technology, Changsha 410073, China |
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| Abstract: | Using tetraethoxysilane and 3-aminopropyltriethoxysilane as the silica sources, amino-functionalized organic/inorganic hybrid mesoporous silica thin films with 2-dimensional hexagonal structure have been synthesized by evaporation induced self-assembly process in the presence of cetyltrimethyl ammonium bromide templates under acid conditions. The Keggin-type molybdphosphoric acid (PMo) is incorporated into the mesoporous silica thin films with amino-groups by wetness impregnation, and the PMo/silica mesoporous composite thin films are obtained. The results of X-ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM), and Fourier transform infrared (FTIR) spectra indicate the PMo molecules maintain Keggin structure and are homogeneously distributed inside mesopores. The composite thin films possess excellent reversible photochromic properties, and change from colorless to blue under ultraviolet irradiation. The photochromic mechanism of the composite thin films is studied by ultraviolet-visible (UV-vis), electron spin resonance (ESR) and X-ray photoelectron spectroscopy (XPS) spectra. It is shown that intervalence charge transfer (IVCT) and ligand-to-metal charge transfer (LMCT) are the main reasons of photochromism. PMo anions interact strongly with amino-groups of the mesoporous suface via hydrogen bond and electrostatic force. After ultraviolet irradiation, the charge transfer occurs by reduction of heteropolyanions accompanying the formation of heteropolyblues with multivalence Mo(VI, V), and the bleaching process of composite thin films is closely related to the presence of oxygen. |
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| Keywords: | molybdphosphoric acid silica mesoporous composite thin films preparation photochromism |
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