Abstract
The effect of Fe ion concentration on the morphological, structural, and optical properties of TiO2 films supported on silica (SiO2) opals has been studied. TiO2:Fe2O3 films were prepared by the sol-gel method in combination with a vertical dip coating procedure; precursor solutions of Ti and Fe were deposited on a monolayer of SiO2 opals previously deposited on a glass substrate by the same procedure. After the dip coating process has been carried out, the samples were thermally treated to obtain the TiO2:Fe2O3/SiO2 composites at the Fe ion concentrations of 1, 3, and 5 wt%. Scanning electron microscopy (SEM) micrographs show the formation of colloidal silica microspheres of about 50 nm diameter autoensembled in a hexagonal close-packed fashion. Although the X-ray diffractograms show no significant effect of Fe ion concentration on the crystal structure of TiO2, the μ-Raman and reflectance spectra do show that the intensity of a phonon vibration mode and the energy bandgap of TiO2 decrease as the Fe+3 ion concentration increases.
Highlights
SiO2 microsphere assemblies coated with metal oxide films have been considered as promising candidate materials for applications in photocatalysis due to their large surface area, excellent accessibility to the inner surface, and suitable morphology in comparison with powder materials
It is seen that the SiO2 sphere assembly was obtained in a single-layer form; each sphere is surrounded by six nearest spheres in such a way that this arrangement is the most dense of identical circles packed in a plane
There are fissures suggesting that the packing is not completely homogeneous; this ruptures on the surface are probably produced by the deposition silica method, that is, the glass substrate is immersed into an aqueous solution where the silica microparticles are dispersed and the hexagonal closed packed is not very well controlled
Summary
SiO2 microsphere assemblies coated with metal oxide films have been considered as promising candidate materials for applications in photocatalysis due to their large surface area, excellent accessibility to the inner surface, and suitable morphology in comparison with powder materials. Mesoporous TiO2 films perform quite well in the decomposing of pollutants and in the generation of hydrogen by water splitting [1]. The TiO2 is the most promising catalyst due to its high efficiency, stability, and low cost. It has been used widely in the photocatalytic degradation of phenol. One disadvantage of TiO2 for industrial applications is the need of filtration after the photodegradation process. The research has been focused on modifying the surface or the bulk of a semiconductor catalyst by adding transition metal impurities, which give rise to the mixed oxide semiconductor formation [2]
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