Design of transition metal oxide mesoporous thin films

摘要

Mesostructured transition metal (Ti, Zr, V, Fe) oxide-based hybrid thin films have been prepared reproducibly, displaying 2D-hexagonal (p6m), 2D-centred rectangular (c2m) or lamellar structure. A combination of time resolved Synchrotron-SAXS and interferometry was applied to study the earlier stages of film formation during dip-coating. The results showed that an intermediary worm-like structure was formed just after the drying line, giving rise to the organised mesophase upon evaporation of residual solvent and HCl. Many variables concerning the solution composition and the processing of the films have been optimised. Water (into the solution and from air moisture) and solution acidity clearly play a major role in the resulting degree of organisation. By carefully adjusting these variables it is possible to combine both high organisation and excellent optical quality. TiO_2 and ZrO_2-based hybrids show thermal stability up to 300-350℃. The elimination of the template can be conducted efficiently and gives rise to high surface area mesoporous films. For the other metal oxide hybrids the inorganic framework is much more fragile, and require a precise sequence of post-treatments to be stabilised.