The influence of surfactants on the roughness of titania sol-gel films

Substrate dipping in a composite sol-gel solution was used to prepare both smooth and rough thin films of titanium dioxide (TiO2) on commercial fiberglass. The deposition of a composite film was done in a beaker using a solution of titanium (IV) isopropoxide as the sol-gel precursor and cetyltrimethyl ammonium bromide as the surfactant. In order to establish a correlation between experimental conditions and the titanium oxide produced, as well as the film quality, the calcined samples were characterized using Raman spectroscopy, UV-vis spectrophotometry, scanning electron microscopy and atomic force microscopy. One of the most important results is that a 61-nm TiO2 film was obtained with a short immersion of fiberglass into the sol-gel without surfactant. In other cases, the deposited film consisted of a titanium precursor gel encapsulating micelles of surfactant. The gel films were converted to only the anatase phase by calcining them at 500 degrees C. The resulting films were crystalline and exhibited a uniform surface topography. In the present paper, it was found that the TiO2 films prepared from the sol-gel with a surfactant showed a granular microstructure, and are composed of irregular particles between 1.5 and 3 mu m. Smooth TiO2 films could have useful optical and corrosion-protective properties and, on other hand, roughness on the TiO2 films can enhance the inherent photocatalytic activity. (c) 2006 Elsevier Inc. All rights reserved.