الفهرس 
Cover EnglishOnly 14 pages are availabe for public view
 |  | from | 132 |  |  |
| | | from | 132 | | |
Abstract
Nanotechnology allows us to design highly efficient photocatalytic nanocomposite which act as an efficient catalyst for reduction of global atmospheric pollution and purification of polluted water. This is very attractive area and one of the most desirable and challenging goals in the research of environmentally-friendly catalysts. TiO2 photocatalysts have been attracting much attention in resent years, because TiO2 photocatalyst can completely decompose toxic and non-biodegradable organic materials into CO2, H2O, and inorganic constituents. Many researches has been undertaken to use TiO2 photocatalyst for purification of polluted water. During the process of purification of polluted water, photocatalyst has to be separated from the treated water. To separate the photocatalyst from water, photocatalyst should be supported on bulk materials such as polymer which has been widely used.In this study, visible light assisted degradation of colored organic pollutant using semiconductor nanoparticles or core-shell nanocomposite have been studied in air and the photodegradation rate have been determined. Rhodamine 6G has been used as a colored organic dye which has absorption spectra in the visible region. The photodegradation rate of the organic dye is monitored by the bleach of the absorption band as a function of time. TiO2 nanoparticles were prepared via sol-gel method and the size of the obtained particles has been determined using TEM. Under 3 h of irradiation with a 150 W xenon lamp, over 70% degradation of pollutants has been observed. A working mechanism involving excitation of surface adsorbed dye, followed by charge Injection into the TiO2 conduction band and formation of reactive √O2−/√HO2 radicals is proposed for the degradation of organics to carbon dioxide. In addition, Core-shell nanocomposite of TiO2 coated with gold and TiO2 coated with Iron oxide have been prepared and characterized via TEM and XRD. The photocatalytic activity of these nanocomposites has been compared to pure TiO2 nanocrystals. Our results indicate that TiO2-gold core-shell particle is more active photocatayst than TiO2 alone because of the charge separation enhancement due to the presence of metal-semiconductor junction. In addition, the effect of the plasmonic gold absorption band enhances the number of photon absorbed per particle. Remarkable increase in the photodegradation rate in presence of sun light using core-shell TiO2-gold core shell particles, on the other hand, the rate of photodegradation over core-shell TiO2-iorn oxide nanocomposite does not change significantly compared to pure TiO2 nanocrystal.