Steam-modified sol-gel method for TiO2-based nanosized particles

TiO2-based nanoparticles were synthesized using a steam-modified sol-gel method. Water, acting as the reactant was sprayed as steam into an organic solvent containing a precursor. Each droplet of water acted as a small volume of reactant in the hydrolysis reaction. Titanium isopropoxide was used as a metal alkoxide precursor to synthesize TiO2 and CeO2/TiO2. The crystallite size reduction of the particles obtained by this steam-modified sol-gel method was confirmed by peak broadening, and the crystallite size was calculated using Rietveld refinement. The crystal sizes observed via transmission electron microscopy (TEM) imaging agreed with results obtained from Rietveld refinement. The particle size of TiO2 synthesized using the water method was 31.4 nm, that of TiO2 synthesized using the steam method was 8.62 nm, CeO2/TiO2 synthesized using the water method was 13.58 nm, and that of CeO2/TiO2 synthesized using the steam method was 7.21 nm. Scattering signals of TiO2 water and CeO2/TiO2 water were not observed; TiO2 synthesized with the steam method showed a size distribution centered at 8.55 nm when measured by small-angle X-ray scattering (SAXS), whereas CeO2/TiO2 synthesized using the steam method showed a particle-size average of 7.16 nm. The size measured by SAXS was similar to the size results obtained by Rietveld refinement and the particle-size analysis using TEM imaging. Each particle formed through steam hydrolysis comprised one crystal, indicating that each particle was a complete crystal. The change in the electronic structure with different water addition processes was confirmed by X-ray absorption near edge structure (XANES).