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Derivation of Optical Functional Materials by Host-guest Assembly of Mesoporous Silica Films

Author: LiuWei
Tutor: LeiJiaZuo
School: Wuhan University of Technology
Course: Applied Chemistry
Keywords: silica mesoporous films metal semiconductor host-guest assembly nanoparticles optical materials
CLC: O613.72
Type: Master's thesis
Year: 2006
Downloads: 167
Quote: 0
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Abstract


Ordered mesoporous silica films, which have important potential applications in optical device, separation and catalysis fileds, have been chosen as the research object of this thesis. On the bases of the formation of ordered mesoporous silica films, metal and semiconductor nanoparticles were incorporated to the mesoporous silica films. Mesoporous composted films with special optical functions are obtained. The main contents are as follows.Mesoporous silica films are fabricated by an evaporation induced self-assembly （EISA） procedure using the nonionic alkyl （ethylene oxide） surfactant as a template. By change the concentration of surfactant in a chosen conditions, Well-ordered 3D-cubic, 2D-hexagonal, and worm-like mesoporous silica films have been synthesized. Also Well-ordered 3D-cubic, 2D-hexagonal, and disordered mesoporous silica films have been synthesized with the same concentration of non-ionic surfactants, depending on the kind of acids. The effects of conditions on the mesophases were investigated by X-ray diffraction and high-resolution transmission, electron microscope. The action mechanism has also been discussed.Mesoporous silica films embedded with Ag nanoparticles have been synthesized directly by a Sol-gel dip-coating process, combining alkyl （ethylene oxide） surfactant as temple and tetraethoxysilane as inorganic precursor. The addition of Ag+ ions to the reaction sol prior to the formation of films, followed by the heat treatment at 150℃ led to the creation of Ag nanoparticies. The formation of Ag nanoparticles and the change of its surface plasma resonance absorption were characterized by Uv-vis. The small angle XRD test indicates that the films had an ordered hexagonal mesoporous structure, which the unit cell parameter was about 4.26nm. The TEM graphs and EDS spectra of the samples have verified directly the presence of mono-dispersed Ag nanoparticles within the films, due to the confine effects of mesopores to them.Binary semiconductor CdS nanoparticles have been prepared inside the channels of mesoporous silica film using an in situ formation method. The approach combines formation of the origanic-silica hybrib mesoporous filim with thiol groups in the channel surface, absorption of Cd2+, and heating in N2 atmosphere at high temperature. The mesostructure order was retained after the growth of the nanoparticles, as pointed out by small-angle X-ray diffraction measurements. Electron microscopy characterizations unambiguously demonstrate that the mesoporous structure allows to control the particle size and the organization of CdS nanoparticles. The mean particles diameter is 3 nm, which is compatible with the pore dimensions. And a blue shift is observed in UV-Vis absorption spectrum, indicating the quantum size effect of nanocrystalline CdS.

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CLC: > Mathematical sciences and chemical > Chemistry > Inorganic Chemistry > Non-metallic elements and their compounds > Part Ⅳ family of non-metallic elements (carbon and silicon ) and its compounds > Si Si
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