Sharif Digital Repository

Liquid phase deposition is a method to grow conformal TiO2 films with good crystallinity on various substrates. The growth depends on the hydrophilicity of the substrate surface and we found that mica is a substrate capable of forming uniform and thick films. Films were grown using an aqueous solution of TiF4 through a hydrolysis-condensation process. We have studied films properties; morphology, porosity and thickness, in terms of growth conditions, i.e. TiF4 concentration, growth temperature, deposition time and pH. The porosity of films was shown to rapidly increase from about 18% to about 25% and remained the same for longer growth times. The growth process of films could be identified... 

TiO2 deposited on a membrane of Ag fibers was prepared as a photoelectrochemical cell electrode. Ag fibers were made by reduction of Ag complexes on cellulose fibers, followed by burning out the template. TiO 2 photocatalyst layers were grown on the fibers by electrophoretic deposition of TiO2 nanoparticles. Ag fibers could be uniformly deposited. Photocatalytic tests by dye decomposition and electrochemical impedance spectroscopy (EIS) under UV illumination demonstrate that Ag fibers act as a good substrate that provides both high surface area and good separation of photogenerated electron-hole pairs and causes the enhancement of photocatalytic activity in comparison with a thin film of... 

Apatite-coated Ag/AgBr/TiO2 was prepared by deposition of Ag as novel metal to generate electron-hole pairs by extending the excitation wavelength to the visible-light region, AgBr, and hydroxy apatite as photosensitive material and adsorption bioceramic, respectively. The energy dispersive X-ray spectrometry clearly showed the presence of Ti, Ag, Ca, and P elements on the surface of catalyst. The bactericidal experiments in dark media indicated that only the novel catalyst shows inhibiting growth of bacteria in this case. A transmission electron microscopy image illustrated that catalyst nanoparticles adhere to the outer membrane of the cell and act as an inhibitor to the nourishment of... 

Titania was deposited on glass fibers with a partial epoxy layer coating from a solution containing TiO2 nanoparticles at T = 90°C, and the adsorption process was examined by X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), Fourier transform infrared (FT-IR) spectroscopy, and photocatalytic activity measurements. XPS data demonstrated that about 25% of the surface was covered with TiO2 nanoparticles, with 10% on the epoxy layer and 15% on the glass body. It was found that TiO2 nanoparticles can be readily adsorbed on epoxy groups, whereas they have a low tendency to adsorb on carbon polymer chains. This difference can be... 

Nanostructured and nanoporous TiO2-Ga2O3 films and powders with various Ti:Ga atomic ratios and high specific surface area (SSA) have been prepared by a new straightforward particulate sol-gel route. Titanium isopropoxide and gallium (III) nitrate hydrate were used as precursors and hydroxypropyl cellulose (HPC) was used as a polymeric fugitive agent (PFA) in order to increase the SSA. X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) revealed that powders contained both rhombohedral α-Ga2O3 and monoclinic β-Ga 2O3 phases, as well as anatase and rutile. It was observed that the Ga2O3 formed from the nitrate precursor retarded anatase-to-rutile transformation.... 

The photocatalytic degradiation of phenol by nanoTiO2 particles coated on perlite as a new composite nano-catalyst was investigated. Titanium dioxide (Degussa P-25) was immobilized on three different supports (perlite granules, glass plates and steel fiber) by a very simple and inexpensive method. Perlite granules have a porosity of more than 95%, which allows them to stay afloat on water surface. This gives the medium a unique characteristic from the processing point of view, which enables it to get wetted with the polluted solution without requiring any pumping and simultaneously be exposed to the radiation source when coated with the photocatalyst. The photocatalytic activity of prepared... 

High specific surface area (SSA) nanocrystalline powders and dip-coated TiO2 thin films have been prepared by a particulate sol-gel route with added polymeric fugitive agents (PFAs), namely trehalose dihydrate (THD), polyethylene glycol (PEG6000) and hydroxypropyl cellulose (HPC). One of the highest SSA reported in the literature, obtained without PFA, was achieved (i.e., 181 m2/g), a value that could be increased up to 304 m2/g, 274 m2/g and 200 m2/g for PEG/TiO2, HPC/TiO2 and THD/TiO2 powders, respectively. Furthermore, the crystallite size varied from 1 nm for as-produced powders up to 4 nm for powders heat-treated at 600 °C. Thin films produced under optimised conditions showed excellent... 

TiO2 nanofibres were prepared using a templating method with tetraisopropylorthotitanate (TiPT) as a precursor. The preparation comprises liquid phase deposition on cellulose fibres followed by thermal removal of the cellulose template. The obtained TiO2 fibrous substance consists of micron-size fibres with a microstructure of nanofibres. It was demonstrated that nanofibres are basically formed through the aggregation of TiO2 nanoparticles and nanorods into chain structures during the thermal treatment process. The measured surface area of the TiO2 fibres was about 250 m2 g-1. It was shown that the pore size distribution is multi-scale and a fractal morphology was demonstrated with two...