Preparation of highly ordered titanium dioxide porous films: Characterization and photocatalytic activity

Abstract

The highly ordered titanium dioxide (TiO2) porous films was fabricated by a single-step assembly method in which the fabrication of opal structure and the infiltration of TiO2 sot particles into the voids between templates were carried out simultaneously. The polystyrene microspheres with diameters ranging between 480 and 1000 nm were used as the template, and titanium tetrabutoxide, a precursor of TiO2, was prepared in an acidic solution to fill the voids between the template microspheres during the formation of opal structure, The properties of the highly ordered TiO2 porous materials were examined by scanning electron microscopy (SEM), thermogravimetry (TA), differential scanning calorimetry (DSC), X-ray diffraction (XRD) and specific surface area analyzer. Thermal analyses showed that polystyrene can be completely removed at 425 degrees C and the phase transformation of TiO2 from amorphous to crystalline anatase occurred at 360 degrees C. SEM images clearly demonstrated that these films have a highly ordered three-dimensional porous structure arranged mainly in hexagonal orientation. The XRD patterns indicated that the crystalline phase of TiO2 is mainly anatase with crystallite sizes of 7.0-9.7 nm. In addition, the ratio of rutile to anatase increased slightly with the increase in hole diameters of the ordered TiO2 porous films. The specific surface areas of the ordered TiO2 porous film ranged between 59 and 84 m(2) g(-1), and the determined adsorption pore sizes in walls between templates were in the range 5.1-6.0 nm, which indicates that the fabricated TiO2 film is a macrostructured mesoporous material. The ordered TiO2 porous films showed high photocatalytic activity in degradation of methylene blue (MB) solution. The degradation rate increased linearly with the increase in hole diameters of the TiO2 films ranging between 480 and 1000 nm. Results obtained in this study clearly show the feasibility of using one-step method to fabricate the highly ordered TiO2 materials as potential supports for heterogeneous catalysis. (C) 2007 Elsevier B.V. All rights reserved.