Phonon confinement and size effect in Raman spectra of TiO 2 nanocrystal towards Photocatalysis Application

The detailed micro-Raman study of pure TiO 2 and Si-doped TiO 2 thin film was synthesized by facile dip-coating technique for photocatalytic application, to degrade the organic species in polluted surface water due to the recent environmental crisis by dye industries. The prepared pure TiO 2 and Si-doped TiO 2 thin film were annealed at various temperatures 300 °C and 450 °C. Micro-Raman spectrum of TiO 2 nanostructure confirms the presence of anatase phase. The crystallinity of TiO 2 and uniformity of the film were improved in annealing temperature of 450 °C. The particle size of TiO 2 was calculated on the basis of the phonon confinement model with the theoretical phonon dispersion relation. The phonon confinement effect depends upon the blue shift and broadening of the lower-frequency E g Raman mode of TiO 2 . Also, the compressive stress of TiO 2 was evaluated using a suitable formula. In addition, the dye degradation activity under visible light irradiation process using methylene blue (MB) was analyzed to check the ability of photocatalytic activity of prepared samples, in which, the fast MB degradation kinetics achieved by Si-TiO 2 nanocrystal and it degrades 99% of MB within 60 min. Also, it exhibits more than 90% photodegradation efficiency up to ten recycle than pristine. Moreover, the possible photocatalytic mechanism of the prepared system was discussed.