Novel composite titanium dioxide (TiO2) films of 10 μm thickness were prepared and characterized with an emphasis on evaluating their photovoltaic properties. The films contained 13 nm TiO2 nanocrystals (NCs) with anatase crystalline phase deposited on FTO substrates, composited with CdSe quantum dots (QDs), gold nanoparticles (Au NPs), and poly(3-octylthiophene) (P3OT) in different configurations and combinations. With the introduction of Au NPs or P3OT into the TiO2/QDs films, the photocurrent increased to ∼85% and ∼150%, respectively, while the photoconversion efficiency increased by ∼167% and ∼177%, respectively. An interesting synergistic effect was observed when Au NPs and P3OT were used in conjunction. The configuration of TiO2/Au/QDs/P3OT film exhibited a photocurrent of 906 μA (an enhancement of ∼285%) and a photoconversion efficiency of 0.661% (an enhancement of ∼600%) compared to that of TiO2/QDs films. Such significant enhancement is attributed to the ability of the Au NPs to facilitate charge separation and improve electron injection as well as P3OT’s ability to inject electrons and enhance hole transport. These properties, when combined with the QD’s strong photoabsorption in the visible, led to the overall increase in photocurrent generation, fill factor, and consequently photoconversion efficiency.

WO x /TiO 2 catalysts were synthesized by impregnating aqueous (NH 4 ) 2 WO 4 on hydrous titania nanotubes. The materials were annealed in air at 500 °C and characterized by X-ray diffraction (XRD), Raman spectroscopy, high-resolution transmission electron microscopy (HRTEM), high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM), and X-ray photoelectron spectroscopy (XPS); their catalytic activity was evaluated in the oxidation reaction of dibenzothiophene (DBT). After annealing at 500 °C, the structure of the support transformed from orthorhombic, with nanotubular morphology, to tetragonal, yielding anatase nanoparticles decorated by tungsten nanoparticles on its surface. During this transformation, the nanotubes released residual Na + ions from the interlayer space, which reacted with tungstate species to change the W coordination from octahedral to tetrahedral, yielding e1 nm Na x (WO 4 ) nanoparticles on the surface of anatase TiO 2 . These nanoparticles were highly active for the DBT oxidation, showing a linear dependence on the W surface density at concentrations below 6.9 W/nm 2 . In TiO 2 oversaturated with tungsten nanoparticles, the intrinsic kinetic velocity (r DBT ) of the DBT oxidation reached its maximum value; 6.9 W /nm 2 is then the optimum surface density concentration to attain a high catalytic activity in the DBT oxidation.

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