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

Abstract

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 degrees 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 degrees 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.

New Triblock Copolymer Templates, PEO‐PB‐PEO, for the Synthesis of Titania Films with Controlled Mesopore Size, Wall Thickness, and Bimodal Porosity

“…Typically amphiphilic di‐ or triblock copolymers, composed of hydrophilic and hydrophobic blocks, are employed as structure‐directing agents for mesoporous materials. The majority of amphiphilic block‐copolymer templates reported in literature for the synthesis of ordered mesoporous oxide materials consists of a hydrophilic poly(ethylene oxide) (PEO) block connected to hydrophobic blocks, e.g., PEO‐ block ‐polystyrene (PEO‐PS),15–20 PEO‐ block ‐poly(methyl acrylate) (PMA‐PEO‐PMA21 and PEO‐PMA22), PEO‐ block ‐polyisobutylene (PEO‐PIB),23–25 PEO‐ block ‐poly(ethylene‐co‐butylene) (PEO‐PHB referred to also as “KLE”),24, 26–34 PEO‐ block ‐polyisoprene (PEO‐PI)35–37 as well as PEO‐ block ‐polybutadiene (PEO‐PB) 38. The most common block‐copolymer templates are members of the commercially available Pluronics family, i.e., triblock copolymers PEO‐ block ‐poly(propylene oxide)‐ block ‐PEO (PEO‐PPO‐PEO), which are available with different block sizes 39–44…”

Mesoporous MgTa2O6 thin films with enhanced photocatalytic activity: On the interplay between crystallinity and mesostructure

“…Here, two oxide films, namely, a mesoporous anatase film and a F127-templated MgTa 2 O 6 film, were included as references. The fabrication and characterization of the mesoporous anatase film is reported elsewhere [21]. F127-templated MgTa 2 O 6 films also exhibited an ordered mesoporous structure with concaves, even after calcination at 760 °C; however, the pore-to-pore distance was much smaller and the mesopores were less ordered compared to those templated by KLE.…”

Selective preparation of zero- and one-dimensional gold nanostructures in a TiO2 nanocrystal-containing photoactive mesoporous template

“…As for the TiO 2 crystalline phases, anatase TiO 2 was widely recognized as the most suitable phase for photocatalysis [26,27]; but recent reports suggest that mixed rather than single phases can be even more active [28,29]. Also, since the TiO 2 nanocrystals in our samples possess diameters of a few nanometers, which are almost the optimum size for photocatalysis [26], UV irradiation of the templates should generate charges and influence the shape of the GNSs.…”