Ordered Mesoporous Thin Films of Rutile TiO2 Nanocrystals Mixed with Amorphous Ta2O5

Ordered mesoporous thin films of composites of rutile TiO₂ nanocrystals with amorphous Ta₂O₅ are fabricated by evaporation‐induced self‐assembly followed by subsequent heat treatment beyond 780 °C. Incorporation of selected amounts of Ta₂O₅ (20 mol %) in the mesoporous TiO₂ film, together with the unique mesoporous structure itself, increased the onset of crystallization temperature which is high enough to ensure the crystallization of amorphous titania to rutile. The ordered mesoporous structure benefits from a block‐copolymer template, which stabilizes the mesostructure of the amorphous mixed oxides before crystallization. The surface and in‐depth composition analysis by X‐ray photoelectron spectroscopy suggests a homogeneous intermixing of the two oxides in the thin film. A detailed X‐ray absorption fine structure measurement on the composite film containing 20 mol % Ta₂O₅ and heated to 800 °C confirms the amorphous nature of the Ta₂O₅ phase. Photocatalytic activity evaluation suggests that the rutile nanocrystals in the synthesized ordered mesoporous thin film possess good ability to assist the photodegradation of rhodamine B in water under illumination by UV light.