Optical study of the photoactivation time of a sol–gel titania suspension in ethanol

The photoactivation time of sol–gel nanostructured titania, in an ethanol suspension, was studied by optical methods in the UV–Vis region. Titania activation was induced using a Hg lamp and the process was analyzed using light transmittance. The Hg lamp light beam was transmitted through the sample and collected with a spectrophotometer as a function of time. The titania powder was thermally treated to observe the effect in the photoactivation. When the photoactivation of the titania suspension occurs, the transmittance falls and afterwards, a constant value is reached. It was found that the activation time depends on the crystalline structure and the crystallite size.