Preparation of aluminum-containing mesoporous silica films

Aluminum-containing mesoporous silica films were synthesized by the solvent evaporation method using tetraethoxysilane, aluminum tri(sec-butoxide), and octadecyltrimethylammonium chloride as the silica source, the alumina source, and a supramolecular template, respectively. The Al/Si ratios were 0.004-0.031 in the present synthesis. The resulting films with the Al/Si ratios of 0.004, 0.013, and 0.022 were highly transparent in the wavelength region of 200-800 nm. The porous structures of the aluminum-containing films were characterized by X-ray diffraction, transmission electron microscopy, and nitrogen adsorption, Although the hexagonal pore arrangements were disordered to some extent by the addition of aluminum, the pore size uniformity was confirmed by the nitrogen adsorption isotherms. The cation exchange ability was evaluated by the adsorption of a cationic azobenzene derivative, p-(w-dimethylhydroxyethylammonioethoxy)-azobenzene bromide, which was not adsorbed effectively on a siliceous mesoporous film. The cation exchange ability of the aluminum-containing mesoporous silica films was semiquantitatively controlled by the amount of added aluminum.