Raman Spectroscopy as a Morphological Probe for TiO2 Aerogels

We report on the application of Raman scattering as a probe to follow the structural evolution of TiO2 aerogels. We have traced the evolution of the 142 and 630 cm-1 Eg anatase peaks as a function of morphology. The results have been analyzed in terms of the q vector relaxation mechanism which predicts a unique relation between particle size and features of the Raman spectra. Since the phonon dispersion of anatase is not known, we have used the analogous rutile dispersion. There is good agreement between the particle sizes evaluated from the model and those determined by X-ray diffraction. Our results demonstrate that Raman spectroscopy can be an effective tool in monitoring the evolution of these aerogel systems.