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 °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 μm. 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.