Sharif Digital Repository

Due to the increasing consumption of fuel, the use of new methods with high efficiency to remove sulfur from fossil fuels is felt more than ever. Hydrogenation and oxidation of sulfur organic matter, such as thiophenes, is an old method of desulfurization of liquid fuels. Using a photocatalyst, everything can be done in an environment that is very low cost. In this study, the photocatalytic elimination of dibenzothiophene was investigated. For this purpose, carbon-doped thiamine dioxide was used as the photocatalytic base, which is synthesized by hydrothermal method. This method is the same source of titanium and carbon. To increase the performance of the catalyst, platinum metal was loaded... 

Dye-sensitized solar cells (DSSCs) are Photoelectrochemical cells using wide band gap nanoporous oxide semiconductors sensitized by dye molecules. For achieving high efficiency DSSCs preparation of photoanode electrode with high surface aea which leads to adequate dye absorption is necessary. In order to achieve proper morphology, thickness, particles size and porosity, producing a TiO2 nano-structured paste is required. TiO2 powder was prepared using sol-gel method. following a calcination process at 300 degrees, XRD patterns showed presence of anatase and brookite structures with average crystallite size of 9 nm. Additives such as diethylene glycol, acetylacetone and Triton X-100 were used... 

One of the basic resources for lithium extraction is brine which is very abundance in Iran. It is important to characterize these brines and their compositions to select a suitable method for lithium recovery from them. By investigation of the local brines and determining lithium and other alkali metals composition in them, the ion exchange process using titanium dioxide ion-sieve with nanotube morphology is suggested as highly effective method for lithium extraction from Iranian brines. Due to high advantages of hydrothermal process, TiO2 nanotubes were produced by this method and the optimum parameters of hydrothermal reactions were reported. In this way, hydrogen titanate nanotubes with... 

In this thesis, we focus on studying and fabrication of doped titanium dioxide electrodes and their application in nanostructured dye sensitized solar cells (DSSCs). For this purpose, non-metallic nitrogen (N) and metallic neodymium (Nd) elements were selected. N-doped titanium dioxide nanoparticles were synthesized via solvothermal method and their structural and optoelectrical properties were investigated in comparison to undoped titanium dioxide synthesized by the same method. Based on the obtained results, doping of titanium dioxide by nitrogen resulted in shifting the Fermi level up-ward, increase in charge carriers density, shift of optical absorbance to higher wavelength, and decrease... 

In this research, carbon nanotubes (CNTs) and CNT coated by titanium dioxide (TiO2) were used as adsorbents for desulfurization. Photocatalytic oxidation by titanium dioxide Degussa P-25 nanoparticles (as photocatalyst) immobilized on a porous and low-density support called “perlite” and CNT/TiO2 was perused. TiO2-coatings were prepared by liquid phase deposition method.This is a wet process for the formation of metal oxide thin films on substrates. The coating of nanotubes with TiO2 was confirmed by IR and EDAX and morphological properties were observed by SEM analysis.The physical properties of adsorbents were determine using BET.Dibenzothiophene (DBT)dissolved in acetonitrile was used as... 

We present a systematic study of the composition, electronic structure, and the band gap energy in pure, Cu-doped and O-vacancy@Cu-doped TiO2 using periodic density functional theory (DFT) calculations by several techniques implemented by Abinit code. Herein, the effect of Cu impurity and O-vacancy in three famous crystalline structures of TiO2 i.e. rutile, anatase and brookite, with 6.25% and 12.5% of Cu impurity were investigated. Bulk titania was modeled using 2×2×1, 2×1×1 and 1×1×1 super cells (24 atoms with formula of Ti8O16) and 2×2×2, 2 2×1 and 1×2×1 super cells (48 atoms with formula of Ti16O32) for rutile, anatase and brookite phases, respectively. One Ti atom replaces with Cu atom... 

Several nanostructured photocatalysts were prepared by sol-gel, hydrothermal and precipitation methods. The products were characterized by X-ray diffraction (XRD), nitrogen adsorption, UV-VIS diffuse reflectance spectroscopy, fourier transform infrared absorption spectroscopy (FT-IR), transmission electron microscopy (TEM), scanning electron microscopy (SEM). Their Photocatalytic activities were evaluated by degradation of organic pollutants in liquid-solid system. In this research work, the influence of metal oxide, copper oxide, on structure of nanocrystalline mesoporous titanium dioxide were evaluated. Different molar percentages of copper oxide on the surface of titanium dioxide were... 

Textile industry wastewaters are one of the important sources of environmental contamination because they produce large quantities of highly colored effluents. In recent years, use of advanced oxidation processes by producing highly active and reactive components such as hydroxyl radicals has been proposed. In this study, two oxygenated photocatalytic systems including UV/ZnO and UV/TiO2 were examined for degradation of C.I. reactive orange 16 dye as a typical organic pollutant in textile effluents. A thin gap annular photoreactor was designed and applied for the experiments. The photoreactor provided large surface area exposed to UV light, where in the solution layer renewal on the UV... 

Dye Sensitized Solar cell (DSC) is the third class of solar cell, which consists of a nanocrystalline, mesoporous of semiconductor(The best one is Tio2), covered with a monolayer of dye molecules, platinum coated on FTO as a counter electrode and a redox electrolyte. This Photovoltaic cell which is promising low-cost materials, works on electron separation of dye molecule, and electron injection to semiconductor’s conduction photo- electrode structure and its porosity is affected the DSC’s performance. Recently, use of electrophoretic deposition (EPD) for TiO2 electrode (which best found for photo-electrode in DSC) fabrication has gained increased interests. In this method charged particles... 

Today organometallic perovskites are very important in fabrication of solar cells. This materials have advantages like high mobility of charge carriers, changing in range of light aborption with changing in structures atoms, having longer charge carrier diffusion lengths than other materials, high stability and efficiency, Low-cost fabrication process, having capability of studying and processing in low temperatures and having flexibility because of Weak chemical bond in perovskite structure. Due to the low stability and rapid decomposition of this material with the presence of light and moisture, in this study has tried to use PbS quantum dots which is used in sensitive dye solar cells as... 

This study investigates the effect of titanium dioxide and magnesium oxide additives on hydroxyapatite synthesized by sol-gel and composite with the predominant phase of hydroxyapatite by in situ method to improve mechanical properties. Scaffold samples were synthesized with nanometer-sized hydroxyapatite and composite powder particles by gel casting and sintered at 1200 ° C. Then, to evaluate the synthesized powders, simultaneous thermal analysis (STA), X-ray diffraction test, FTIR test, FESEM, EDS, and MAP analysis were used. Also, to evaluate the mechanical properties of the scaffolds, a compressive test was used, and to evaluate the scaffolds' density, the Archimedes method was used.... 

In this thesis, pure –known as T- and chromium doped titanium dioxide nanoparticles –known as -CTx- with different dopant atomic ratio (0.1 to 5 %at.) were synthesized using a facile, fast and efficient method. FESEM and XRD studies showed no morphologic and structural change via Cr doping of nanoparticles (size in the range of 20-30 nm). However, according to DRS analysis, Cr intrusion in TiO2 crystal structure, drastically reduced band gap energy of pure TiO2 from 3.14 eV to 1.81 eV for CT3 powder and improved absorption range of UV-Vis spectrum. Mott-Schottky plots indicated that, Cr doping, caused reduction in donor density of TiO2 and an upward shift in the conduction band edge.... 

Different structures of TiO2 photoelectrodes were fabricated with different structures and arrangement modes of the layers. TiO2 Nanoparticles were synthesized by solvothermal method and the effect of solvothermal processing parameters on morphology and crystal structure of nanoparticles was studied. Hierarchical and spherical TiO2 particles were synthesized to use in photoanode electrode as light scattering particles. FE-SEM and XRD analyses revealed that TiO2 nanoparticles had uniform and nanometer grains with particle size around 20nm and average crystallite size of 4nm. The optical properties of TiO2 particles were studied through UV–Vis absorption and DRS analysis. The indirect optical... 

In First part, the electrophoretic deposition method was utilized to immobilize TiO2 particles on stainless steel substrates. In addition, for the first time, statistics-based experimental design using response surface methodology (RSM) was employed to investigate the effect of four key coating parameters (i.e. applied voltage, calcination temperature, photocatalyst weight percentage, and deposition time) on the photocatalytic degradation. Analysis of variance revealed that the proposed model was adequate. X-ray diffraction (XRD) and scanning electron microscope (SEM) were used to evaluate the effects of the parameters on degradation efficiency. The optimum applied voltage, calcination... 

One of the Advanced Oxidation Process (AOP) is Photocatalyst method. Structure of this method is according to three foundation: 1. Catalyst, 2. Source of energy, 3. Wastewater. Progress of human activity around variety of fields such as pharmaceutical, plastic industry, and medical science has produced some micro pollutants such as Bisphenol A (BPA) that has aroused the public concerns in recent years. The half-life of this components in water, air and soil is too long, so typical methods such as biological method, activated sludge and carbon adsorption are inefficient in removing BPA. This work describes a visible light responsive Carbon Quantum Dots(CQDs) embedded on TiO_2 nanoparticles... 

In this study, one dimensional titanium dioxide nanostructures including nanotube and nanowire were synthesized by anodization and hydrothermal methods respectively and were used for PEC glucose sensing. Meanwhile various length of nanotubes was investigated toward glucose sensing. Finally, nanotubes with the length of 2.7 µm were selected as the optimum sample. Finally, to improve sensitivity toward glucose, TiO2 nanotubes were modified by graphene oxide nanosheets which caused several percent increase in PEC sensing performances. In the next stage branched TiO2 nanowires were grew on FTO substrate in various conditions. In spite of acceptable reproducibility of this structure,... 

Solar energy is one of the man's solutions to cope with problems involved in exhaustible fossil resources. In this regard, using photocatalysts is a practical and rational pproach.Nanotechnology facilitates using catalysts and photocatalysts with more productivity.TiO2 semiconductor is one of the most popular material in this field but its efficiency is low by several factors such as being inactive in visible light, recombination and the high cost of using noble metals. In this research, we tried to fix these limitations by creating a p-n junction TiO2 - NiO nanocomposite. The samples are made by three methods: impregnation, ultrasonic assisted modified impregnation with ammonium hydroxide... 

Transition metal oxides and carbon based materials (especially graphene) are common electrode materials in supercapacitors. The metal oxide limitation is due to their high agglomeration and low electrical conductivity. On the other hand graphene base materials due to their unique structure as well as high electrical conductivity and high surface area increase energy storage capability. However, chemically produced graphene generally suffers from high agglomeration and re-stacking after removal from the solution and drying, g, which results in reduced electrochemical performance of graphene sheets in supercapacitors. To take full advantage of these two groups of materials, it is expected that... 

Pure NanoParticles of TiO2 and Nanocomposite catalysts of TiO2 , activated carbon (TiO2/AC) and multi-walled carbon nanotube (TiO2/MWCNT) were prepared by a sol –Gel method using TetraisoPropylorthotitanat (Tipt) as a precursor. The catalysts were characterized by x-ray diffraction (XRD), scanning electron microscopy (SEM), diffuse reflectance uv-vis spectroscopy (DRS) and N2 adsorption – desorption measurements. The photoactivity of samples was evaluated by Acid Blue 92 (AB 92) degradation. The analysis results show that compared with pure Nanoparticles of TiO2, the spherical – shaped TiO2 particles are well – dispersed in TiO2/AC. In TiO2/MWCNT, the coating has special mechanism that...