Titanium oxide thin film preparation with sol coatings of plate and spindle-shaped nanoparticles for control of optical transmittance

摘要

A layered titanate sol was prepared at room temperature (298 K) using dialysis of a mixed solution of ethylene glycol solution of TiCl₃, ammonium carbonate aqueous solution, and hydrogen peroxide. A sol with dispersion of plate-shaped layered titanate nanoparticles was obtained. A stable sol with dispersion of spindle-shaped anatase TiO₂ nanoparticles was obtained by heating the sol with dispersion of layered titanate at 368 K for 24 h in a closed vessel. The optical transmittance spectrum of the TiO₂ thin film obtained by coating the sol with dispersion of anatase nanoparticles and firing at 773 K for 1 h showed no interference of an incident light beam into the TiO₂ thin film. Optical characteristics on interference originated from pores among TiO₂ primary nanoparticles in the thin film, which caused incoherent scattering of incident light into the thin film. When the sols containing both of the plate-shaped layered titanate nanoparticles and the spindle-shaped anatase nanoparticles were used as the coating solution, the interparticle pore volume was controlled by the volume ratio of the anatase sol in the coating solution. The effects of interference on the optical transmittance spectra of the thin films depended on the interparticle pore volume.