Fabrication and Characterization of Self-Assembled Multilayer Nanostructure Titania with High Preferential (101) Orientation on Alumina Thin Films by Layer-by-Layer Dip-Coating Method

摘要

This study describes the fabrication of multilayer microporous alumina-titania self-assembled thin-film by dip-coating using sol-gel method on glass substrate. First layer of mesoporous alumina film was synthesized using alumina sol composed of aluminium tri-sec-butylate as precursor, 2-propanol, as solvent and ethyl acetoacetateas chelating agent. Titania overlayer nanoparticles (15-43 nm) were grown on alumina layer by the controlled hydrolysis of titanium (IV) isopropoxide. Thin films consisted of titania with extremely preferential (101) orientation as a novel means to enhance porosity. Thermogravimetry-differential thermal analyses, X-ray diffraction and scanning electron microscopy were employed to investigate the growth and morphology of the films. The results reveal that the thin films consist of stacked, nearly spherical, nanocrystalline particles, and that 500℃ is optimal temperature for the smallest crystal size (15.2 nm) of TiO_2 thin films. It is argued that the extremely preferential (101) orientation of anatase TiO_2 is a result of self-assembly induced by interaction of titania/air and titania/alumina interfaces that force the titania micelles to align and to reorganise.