Acoustic and optical phonons in EVOH-TiO2 nanocomposite films: Effect of aggregation

Films of an organic-inorganic nanocomposite material formed by a polymeric matrix (ethylene-vinyl alcohol copolymer-EVOH) and nanometric TiO2 particles (ca. 10 nm) have been obtained with photo-catalytic properties in the elimination of pathogens. Optical spectroscopy experiments have been performed in order to characterize the films and evaluate their properties as a function of TiO2 doping in the range between 0.25 and 13 wt%. Anatase TiO2 nanoparticles seem to be well-dispersed up to 2% but aggregation for higher doping originates the two different regimes observed in the acoustic modes as well as in the optical absorption in the visible spectral range.