Titania (TiO2) nanopowders called PC 500, synthesised by the sulphate process, were annealed in air at temperatures of up to 1022K for 30min. The X-ray Diffraction (XRD) indicates that the thermal annealing resulted in coarsening of the average crystallite size from 13 to 72nm. However, Scanning Electron Microscopy (SEM) reveals persistence of platelet-like structures which survive up to temperatures around 900K. This implies that the crystals at least partially grow within the plates in 2D confinement. This implies that direct usage of Scherrer equation in this case should be approached with care. Raman spectra peak positions and the Full-Width-at-Half-Maximum (FWHM) values changed considerably after calcinations crystal growth, while, material composition and oxygen content remain unchanged. The Raman peak behaviour can be cautiously attributed to the first order phonon confinement phenomena, but both, 2D and 3D models of confinement should be accounted. The highest photoactivity, as indicated by photoinduced degradation of a mono azo dye methyl-orange (C14H14N3SO3Na), was observed in material treated at 773K.
|Number of pages||6|
|Journal||Journal of Photochemistry and Photobiology A: Chemistry|
|Early online date||16 Feb 2010|
|Publication status||Published - 5 Mar 2010|