Search

In this study, we report the influence of vanadium oxide (VO), as a photosensitive component, on the photoactivity of TiO2 nanotubes (TNTs). A series of TNTs of varying tube diameter were synthesized by the anodization of titanium foils at different voltages, while vanadium oxide was deposited on TNTs by wet chemical deposition. An improvement in the optical properties of nanotubes was observed after the deposition of vanadium oxide. An improvement in the optical properties (redshift in UV-Vis spectra) of TNTs and TNT/VO was noted. The photocatalytic activity was improved with increasing tube diameter, while it was weakened after the deposition of VO. Furthermore, photoactivity was investigated in photodiodes based on TNTs or TNT/VO and single crystals of CH3NH3PbI3. The photoelectric measurement revealed that different TNT diameters did not influence the I-V characteristic of the photodiodes, while the deposition of VO improved the photocurrent for smaller TNTs. [ABSTRACT FROM AUTHOR]

A process of obtaining N-doped TiO 2 nanotubes sensitized by CdS nanoparticles is presented, including detailed characterizations performed along the synthesis. Transparent TiO 2 films consisting of nanotubes, 2.5 µm long and of ~60 nm inner diameter, were obtained after anodization of a titanium film deposited onto FTO glass substrate. N-doping was achieved by annealing of TiO 2 film in ammonia. X-ray Photoelectron Spectroscopy measurements showed that nitrogen was substitutionally incorporated in the TiO 2 matrix, with the N:Ti concentration ratio of 1:100. The doping changed the optical properties of the material in such a way that the absorption edge was shifted from 380 nm to 507 nm, as observed from diffuse reflectance spectra. The influence of the microwave (MW) irradiation on the synthesized CdS quantum dots and their optical properties was investigated. It was shown that the diameter of CdS nanoparticles was increased due to releasing of S 2- ions from dimethyl sulfoxide (DMSO) as a consequence of the MW treatment. The (N)TiO 2 films were then used as substrates for matrix assisted pulsed laser deposition of the CdS quantum dots with DMSO as a matrix. The laser parameters for the deposition were optimized in order to preserve the nanotubular structure open, the latter being an important feature of this type of photoanode. The structure obtained under optimized conditions has an additional absorption edge shift, reaching 603 nm. [ABSTRACT FROM AUTHOR]

Abstract: Nanostructural TiO2/modified multi-wall carbon nanotubes photocatalysts were prepared by hydrolysis of Ti(iso-OC3H7)4 providing chemical bonding of anatase TiO2 nanoparticles onto oxidized- or amino-functionalized multi-wall carbon nanotubes (MWCNT). The processes of functionalization of the MWCNT and the deposition of TiO2 influence the photocatalytic activity of the synthesized nanocomposites. The phase composition, crystallite size, and the structural and surface properties of the obtained TiO2/modified-MWCNT nanocomposite were analyzed from XRD, FEG-SEM, TEM/HRTEM and FTIR data, as well low temperature N2 adsorption. In the photocatalytic study, the TiO2/oxidized-MWCNT catalyst showed the highest and the TiO2/amino functionalized-MWCNT catalysts somewhat lower degradation rates, indicating that the enhancement of photocatalysis was supported by the more effective electron transfer properties of the oxygen- than amino-containing functional groups, which support the efficient charge transportation and separation of the photogenerated electron-hole pairs. [Copyright &y& Elsevier]

The photocatalytic degradation of the synthetic textile dye CI Basic Yellow 28 (BY28) in water, using a recently synthesized P160 TiO2-based catalyst, under Osram ultra-vitalux® lamp (300 W) light, was studied. The effects of the operational parameters, such as initial concentration of catalyst, initial dye concentration and pH, were studied. The salt effect (NaCl, Na2CO3, Na2SO4 and NaNO3) was also investigated. It was found that the optimal concentration of catalyst is 2.0 g L-1. A pseudo first-order kinetic model was illustrated using the Langmuir--Hinshelwood mechanism and the adsorption equilibrium constant and the rate constant of the surface reaction were calculated (KBY = 6.126 L mg-1 and kC = 0.272 mg L min-1, respectively). The photodegradation rate was higher in weak acidic than in high acidic and alkaline conditions. The presence of CO32- ions increased the photodegradation rate while Cl-, SO4-2 and NO3- decreased the reaction rate. The rate of photodegradation of BY28 was measured using UV--Vis spectroscopy. [ABSTRACT FROM AUTHOR]

Abstract: A method for the preparation of efficient TiO2/multi-wall carbon nanotubes nanocomposite photocatalysts by precipitation of anatase TiO2 nanoparticles onto differently oxidized carbon nanotubes is presented. The precursor compound titanium(IV) bromide was hydrolyzed producing pure anatase phase TiO2 nanoparticles decorated on the surface of the oxidized carbon nanotubes. The oxidative treatment of the carbon nanotubes influenced the type, quantity and distribution of oxygen-containing functional groups, which had a significant influence on the electron transfer properties, i.e., the photocatalytic activity of the synthesized nanocomposites. The results of C.I. Reactive Orange 16 photodegradation in the presence of all the synthesized nanocomposites showed their better photocatalytic activity in comparison to the commercial photocatalyst Degussa P-25. [Copyright &y& Elsevier]

The photocatalytic efficiency of a recently synthesized TiO2 powder, denoted P160, for the degradation of the Dye C.I. Reactive Orange 16 in natural and artificial seawater was investigated in comparison to its efficiency in deionized water and the efficiency of a standard TiO2 powder, Degusa P25. It was shown that the photocatalytic efficiency of P160 was slightly higher than that of P25, probably due to slightly higher specific surface area, higher pore volume and larger pores of the powder P160. The efficiency of both photo-catalysts in natural and artificial seawater was significantly lower than in deionized water. The overall rate of dye degradation for both types of photo-catalysts was slightly higher in artificial seawater than in natural seawater, which shows the influence of organic compounds naturally present in seawater on the photocatalysts activity. A saturation Langmuir-type relationship between the initial degradation rate and the initial dye concentration indicated that adsorption plays a role in the photocatalytic reaction. The photodegradation rate constant, k, which represents the maximum reaction rate, had similar values for P25 and P160 in all types of water due to the similar properties of the photocatalysts. [ABSTRACT FROM AUTHOR]

Ordered titania nanotubes (pore diameter ≈ 90 nm and wall thickness ≈ 10 nm) were obtained by the anodization technique and used for the ex-situ deposition of cadmium sulfide quantum dots (CdS QDs) via simple immersion of titania substrates in the CdS colloid. The colloidal dispersion of CdS nanoparticles in water was obtained in the presence of the bifunctional ligand, mercapto silane, which binds to the surface of CdS providing stability to the colloid and preventing further growth of the synthesized nanoparticles. The blue-shift of the optical absorption indicated that the CdS nanoparticles were of quantum dot size. Using the effective mass model, the average particle size was calculated to be 5.4 nm. Transmission electron microscopy provided the verification for the estimated size of the nanoparticles, which was followed by performing selected area electron diffraction to determine the mixed phase (cubic and hexagonal) of the synthesized CdS QDs. Scanning electron microscopy and reflectance spectroscopy were employed to characterize the nanostructures consisting of TiO 2 nanotubes with different loadings of CdS QDs (after 24 h and 72 h immersion). It was demonstrated that mercapto silane efficiently binds CdS QDs onto TiO 2 nanotubes enabling visible-light response of the obtained nanocomposites. [ABSTRACT FROM AUTHOR]