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Ag-doped TiO2 nanoparticles with different metallic content (0.5, 2.0, and 5.0% m/m) were prepared using a simple and cost-effective method based on a sol–gel technique, followed by thermal treatment.

Nominally Sr 2+n Ce 2 Ti 5+n O 16+3n dielectric ceramics were prepared by conventional solid-state ceramic route. The structure and microstructural features of the ceramics were investigated by X-ray diffraction, X-ray photoelectron spectroscopy, and scanning electron microscopy. At optimized sintering conditions, it is shown that Ce 4+ ions reduce to Ce 3+ ions, which leads to the correct formula Sr 2+n Ce 2 Ti 5+n O 15+3n for the materials. The ceramics present a cubic SrTiO 3 -like structure, where Ce 3+ ions and their associated vacancies randomly share the A-sites with the Sr 2+ cations. Therefore, this solid solution could be alternatively described by Sr 1-3x/2 Ce x TiO 3 , where x e 0.40 is not necessarily an integer. For 0 e n e 10 (0.40 > x > 0.133), these materials have dielectric constant and Q u xf in the range of 113-185 and 6000-11000 GHz (at 2 GHz), respectively. However, the relatively high positive temperature coefficients of resonance frequencies decrease substantially to values five times lower than those commonly observed for SrTiO 3 .

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New TiO2/WO3 films were produced by the layer-by-layer (LbL) technique and successfully applied as self-cleaning photocatalytic surfaces. The films were deposited on fluorine doped tin oxide (FTO) glass substrates from the respective metal oxide nanoparticles obtained by the sol-gel method. Thirty alternative immersions in pH = 2 TiO2 and pH = 10 WO3 sols resulted in ca. 400 nm thick films that exhibited a W(VI)/Ti(IV) molar ratio of 0.5, as determined by X-ray photoelectron spectroscopy. Scanning electron microscopy, along with atomic force images, showed that the resulting layers are constituted by aggregates of very small nanoparticles (<20 nm) and exhibited nanoporous and homogeneous morphology. The electronic and optical properties of the films were investigated by UV-vis spectrophotometry and ultraviolet photoelectron spectroscopy. The films behave as nanoscale heterojunctions, and the presence of WO3 nanoparticles caused a decrease in the optical band gap of the bilayers compared to that of pure LbL TiO2 films. The TiO2/WO3 thin films exhibited high hydrophilicity, which is enhanced after exposition to UV light, and they can efficiently oxidize gaseous acetaldehyde under UV(A) irradiation. Photonic efficiencies of ξ = 1.5% were determined for films constituted by 30 TiO2/WO3 bilayers in the presence of 1 ppm of acetaldehyde, which are ∼2 times higher than those observed for pure LbL TiO2 films. Therefore, these films can act as efficient and cost-effective layers for self-cleaning, antifogging applications.

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