(36f) Surface-Mediated Growth of Oriented and Well-Defined Nanocrystalline Anatase Titania Films

Anatase TiO2 is an important functional material with a wide range of application. A variety of physical and chemical approaches have been used for preparation of anatase TiO2 films. Simple and inexpensive chemical synthesis approach has been widely studied, including sol-gel methods, electrochemical desposition, Langmuir-Blodgett technique, hydrothermal deposition and biomimetic approach. However, simultaneous control of crystalline morphology and orientation in TiO2 films has not been achieved. In connection with wide applications of anatase TiO2 such as chemical sensing, photocatalysis, optical emission, and energy conversion and storage such as photovoltaics, batteries, and capacitors, anatase TiO2 films with well-controlled nanostructures, crystallographic planes and favorable orientation are very desirable for these applications. In this presentation, we report a new class of anatase TiO2 films consisting of octahedral pyramidal nanocrystals via slow oxidative hydrolysis. The nanocrystalline TiO2 films have been characterized using XRD, TEM, SEM, UV-vis, Raman spectroscopy and other techniques. Well-defined octahedral pyramidal nanocrystals, which are close to equilibrium shape of anatase TiO2, are oriented with [001] axis preferably perpendicular to the substrate. The unique structure of octahedral pyramidal nanocrystals in the TiO2 film lead to anatase (101) surface as the most accessible surface, which may be used in specific site-selective catalysis. The anatase TiO2 film with a new morphology consisting of octahedral pyramidal nanocrystals is an exciting addition to a family of TiO2 films. Because of unique chemical, physical and optical properties of TiO2, we expect this new class of TiO2 films are of great interest for sensor, photovoltaic, and other applications.