Preparation of mesoporous titania gel films and their characterization

Mesoporous TiO₂ films with large surface area are attractive due to their many potential applications. Titania gel films, prepared by hydrolysis of Ti(n-C₄H₉O)₄ in ethanol and spin coating on glass substrates, were immersed in surfactant solutions, dried at 90°C, and annealed at temperatures up to 500°C. The as-dried gel films were evaluated by emanation thermal analysis (ETA). The annealed gel films were characterized by XRD, ellipsometry, SEM, and AFM. The annealed xerogel films, about 100nm in thickness, were transparent. The porosity, which was estimated from the refractive indices determined by ellipsometry, increased with immersion in surfactant solutions. The average pore size increased more than two times with surfactant immersion. The pore size and shape correlate with the size and shape of the surfactant micelles. The ETA measurements distinguished the differences in surface area and thermal stability of the surfactant-modified films. The ETA results were evaluated by diffusion structural analysis (DSA), and structural changes in the films during heating were discussed.