TiO2/SiO2 nanocomposite with molar ratio 1:1 was synthesized by a free calcination sol-gel method using titanium tetra chloride and tetraethylorthosilicate as raw materials. In the composite, TiO2 nanocrystals are highly dispersed in the amorphous SiO2 matrix and the mater showed size quantization effect arising from the presence of extremely small titanium oxide species having a low coordination number. Thermal phase transformation studies of the as-prepared composite were carried out by means of X-ray diffraction (XRD) patterns and thermogravimetry–differential scanning calorimetry (TG–DSC) analyses. The studies showed existence of anatase phase in all the tested temperatures. When temperature exceeds 400oC, brookite phase was formed beside anatase phase. At 950oC amorphous silica matrix was transformed to crystobalite and brookite phase disappeared. Finally, small peaks of rutile phase were detectable at 1100oC.

Mesoporous TiO2-SiO2 nanocomposite (TS) was synthesized via sol-gel method and Amino-functionalized using 3-(aminopropyl) triethoxysilane. prepared amino-functionalized TiO2-SiO2 (NH2TS) was evaluated for eliminating radioactive Th(IV) ion in comparison with (TS). The prepared nanocomposites were characterized using FT-IR, XRD, DSC-TGA, SEM, EDS, BET, and BJH analyses. DSC and TGA analyses revealed that the total organic content of the NH2TS was at about 4%. According to the XRD patterns, synthesized nanocomposites exhibited only the crystalline anatase phase, and the sizes of the anatase crystallites in the prepared TS and NH2TS calculated to be 10. 4 and 14. 1nm, respectively. Moreover, the pore diameters of TS and NH2TS estimated to be 4. 65 and 3. 632 nm according to their BJH plot. The kinetic data of Th(IV) uptake process on both of two nanocomposites corresponded well to the pseudo-second-order equation. Adsorption thermodynamic parameters including the standard enthalpy, entropy, and Gibbs free energy revealed that the ion exchange reactions on both of NH2TS and TS nanocomposites were endothermic and spontaneous processes. The results indicated that NH2TS exhibited higher adsorption affinity toward Th(IV) compared to TS. Moreover, based on the Langmuir model, the maximum adsorption capacity of NH2TS nanocomposite towards the Th (IV) was found to be 1000 mg/g.

Sol-gel derived TiO2 was prepared and decorated with Au nanoparticles by photo deposition technique and examined by means of TEM, XRD, EDX, DRS, and BET-BJH analyses. The band gap was related to the Au decorated TiO2 (Au/T) and the synthesized plain TiO2 were obtained from DRS curves by 3.07 and 3.2 eV. The Au/T showed an enhanced visible light photocatalytic activity towards the Crystal violet (CV) dye in comparison to the plain TiO2 because of surface plasmon resonance phenomenon of the gold nanoparticles. A cooperative working mechanism involving the possible photoactivation of gold nanoparticles as well as surface bounded dye was proposed for the photocatalytic performance of Au/TiO2 system. During the decolorization of the CV dye, two reaction pathways including demethylation of amine sites of the chromophore system and breaking of the whole conjugated chromophore skeleton competing each other. The demethylation of amine sites of CV dye took place predominantly through the raid of OH species to the dye N, N-dimethyl groups, in a stepwise manner.

Electronic spectra and LDI mass spectra changes accompanying photodegradation of acridine yellow (AY) adsorbed on the surface of prepared via templated sol–gel synthesis TiO2, SiO2, and TiO2/SiO2 mesoporous films have been investigated and the main photodegradation products have been determined. The results of calculations show the adsorption energy of the molecular state of AY to be the greatest for the complex with titania–silica where Lewis acidic sites are present, the smallest one being related to the complex with titania what corresponds to the experimental data. Effectiveness of acridine yellow photodegradation on the surfaces of mesoporous films under UV irradiation increases in a row SiO2\TiO2/SiO2\TiO2. Electronic and laser desorption/ ionization mass spectra and theoretical modeling give evidence that efficient photobleach of AY localized at the surface of anatase films proceeds through the following steps: 1-N-demethylation/deamination; 2-photodimerization; 3-photodegradation.

This paper presents the wet chemical synthesis of WO3/TiO2 nanocomposites using hydrothermally prepared monoclinic WO3 and anatase TiO2 nanoparticles as composite matrices and filler, respectively. The nanocomposites were prepared in different compositions, i. e. WO3: TiO2 ratio (w/w) of (1: 1), (1: 3), and (3: 1). Physicochemical properties of the resultant WO3/TiO2 nanocomposites were evaluated by Xray diffraction (XRD), scanning electron microscopy (SEM), BET N2 adsorption-desorption isotherms, UV/vis, and Raman spectroscopy. The resultant nanocomposites exhibited a mesoporous structure with specific surface area of up to 11. 5 m2 g-1, where TiO2 constituent contributed to higher surface area, especially in (1: 3) ratio, and higher number of defect sites. While there was no impurities in the investigated nanocomposites as revealed by XRD analysis and Raman spectra, the WO3: TiO2 (1: 3) nanocomposites showed the highest light harvesting ability indicated by higher absorption amplitude in both UV and visible regime. Three different kinetic models including pseudo-first-order, pseudo-second order, and Langmuir-Hinshelwood were applied to experimental data. The pseudo-second-order was found to be the best representing model and the adsorption kinetic studies indicated that chemisorption initially dominated the degradation mechanism. Finally, photocatalytic activity of nanocomposites was compared for photodegradation of methylene blue (MB) aqueous medium and in a good agreement with physicochemical properties, WO3: TiO2 (1: 3) nanocomposites yielded the highest MB degradation rate (k ~ 0. 162 min-1) and efficiency (96%) within 120 min under UV irradiation.

Dye-sensitized solar cells based on ordered mesoporous TiO2 films were fabricated by sol-gel technique. X-ray diffraction (XRD) analysis revealed that anatase phase was crystallized at 300oC with initially crystallite size 3.2 nm and the crystallization was improved to 700oC. Surface area analysis showed that the specific surface area of the films decreased from 163.43 to 87.15 m2/g and the pore size increased from 5.05 to 8.75 nm as the annealing temperature increased from 400 to 600oC. The transmittance spectra that measured by UV/Vis spectrophotometer revealed that the transmittance maxima of the films decreased in the visible region and the absorption edges shifted to longer wavelengths. Photovoltaic measurements showed that the power conversion efficiency of the films initially enhanced to the maximum value of 3.61% with the increasing film thickness to 1.7 mm and then declined when the film thickness increased further.

The photo catalytic activity of mesoporous TiO2 modified by the carbon nanotubes (CNTs) and Ag is reported. The mesoporous TiO2 was synthesized by sol-gel method and mechanically mixed with functionalized multi-wall carbon nanotubes which was decorated by different amount of Ag. Mesoporous TiO2 and the nano composite were characterized by XRD, SEM, TEM, BET surface area analysis, FTIR, AAS, UV-Visible, DRS-UV and UV-Vis absorption spectroscopy. The photo activity of nano composite containing mesoporous TiO2, MWCNT and Ag were evaluated by the degradation of methyl orange (MO) in aqueous solution under UV irradiation. Results showed that the CNT which was decorated with the 15.5% of Ag could facilitate the phocatalytic activity of mesoporous TiO2.