Sharif Digital Repository

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... 

A new magnetic catalytic nanocomposite of Hal-MT-Cys-Ag/MNCD was fabricated and utilized for catalyzing reductive de-colorization of methyl orange and rhodamin B in aqueous media at room temperature. To prepare this material, Cl-functionalized halloysite nanoclay was successively reacted with melamine and 2,4,6-trichloro-1,3,5-triazine to furnish multi-nitrogen containing ligand on halloysite surface. Then, magnetic carbon dots were crafted through a facile method and decorated with Ag nanoparticles and cysteine to furnish Cys-Ag/MNCD species. The final nanocomposite was obtained via incorporation of this latter species onto functionalized halloysite. This was characterized through the XRD,... 

A triple photocatalytic composite of biochar, metal-organic framework and phosphomolybdic acid was prepared through solvothermal treatment of iron (III) chloride hexahydrate, terephthalic acid, lavandulifolia-derived biochar and phosphomolybdic acid. The composite was thoroughly characterized and utilized for photodegradation of organic dyes under visible light irradiation. Investigations of reaction variables confirmed that, the highest yield of 96.2% for a cationic Rhodamine-B (RhB) dye was achieved at ambient temperature when using 0.07 g of catalyst at pH of 7 and a dye concentration of 10 ppm. The activity of the composite was superior compared to its individual components implying... 

There are many industries in the world that produce colorized wastewater. Because of the complex structure and good solubility of dyes, such industries have problem treating this wastewaters. On the other hand, because of the toxicity of these materials for water living, dye removal from discharged wastewater of these industries is very important. In recent years, researchers have become interested in the synthesis of dye Nano adsorbents and they have published many works on this subject. The important parameters in the synthesis of such adsorbent include; non-toxicity, high adsorption capacity and easy separation. In this project, cellulose was extracted from bagasse and then CMC was... 

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, an adsorptive affinity membrane has been prepared based on the combination of the nanofiber structure’s intrinsic characteristic in the dye adsorption and its membrane filtration properties. Electrospinning method has been used to prepare chitosan/poly(vinyl alcohol) (PVA) nanofibers. The morphology and properties of the prepared nanofibrous membranes were characterized using Fourier-transform infrared spectroscopy (FT-IR), field-emission scanning electron microscopy (FE-SEM), image processing, atomic force microscopy (AFM), and thermogravimetric analysis (TGA). Also, the major drawback of electrospun nanofibrous membranes (ENMs) is their low mechanical resistance. So,... 

Distributed feedback dye lasers are among the suitable candidates for spectroscopic applications due to their capability of producing widely tunable picosecond pulses in UV-IR region. However, the pulsewidth sensitivity of the laser to pump intensity fluctuations hinders its suitability for precision applications. In this thesis, by utilizing widely used Self Q-Switching model, we showed that if the dye solution is pumped by a narrow (sub-nanosecond) pulse, the laser can operates in the single-pulse output mode with a better stability over a wide range of pump intensity. After that, we used a dynamical model based on the induced polarization and Maxwell equations, where the obtained results... 

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... 

This research is focused on fabrication of TiO2 layers by electrophoretic deposition (EPD) for application as photoanode in Dye Sensitized Solar Cell (DSC). DSCs are third generation of solar cells, also known as the Grätzel cell, after its inventor Michael Grätzel. A DSC is composed of a porous layer of wide band gap semiconductor such as TiO2 and ZnO, covered with a molecular dye that absorbs sunlight, and a counter electrode contacted by a liquid redox electrolyte. Dye Sensitized semiconductor (photoanode) has important role in conversion of photon to electricity. To achieve higher efficiency, preparation of photoanode with high surface area resulted to enough dye adsorption is necessary.... 

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 this thesis, it reports the fabrication of novel magnetic nanocomposites combining the unique properties of magnetic nanoparticles and cross-linked basic polymers that their surface functionalized by suitable groups such as carboxylate groups, pentaethylenehexamine and so on to achieve the maximum adsorption capacity of dyes and heavy metal ions. The performance of the magnetic nanocomposites for removal of anionic and cationic dyes and heavy metal ions were evaluated in different conditions of pH, contact time and initial concentrations. Moreover, the adsorption mechanism was investigated by kinetic models and isotherm studies. The results showed that the abovementioned adsorbents can... 

Population growth and community development has a large role in the demand for fresh water for a variety of uses. In recent decades, over-harvesting and abusing of water resources has led to water crisis. On the other hand, the increase in various pollutants, in addition to environmental hazards, is a threat to groundwater pollution and the existence of valuable fresh water. Due to the potential hazards of emerging pollutants, new treatment technologies such as advanced oxidation and photocatalytic methods are being developed. One of the contaminants resistant to traditional treatment methods is textile contaminants. In this research, by designing and constructing a photocatalytic reactor,... 

With decreasing fresh water availability and growing demand for clean water, alternative water sources are used in many parts of the world. At the same time, the increasing environmental pollution with a variety of manmade chemicals with known or unknown effects on the aquatic wildlife and human health is an uncontested reality. These emerging pollutants include pharmaceuticals and personal care products, pesticides and hormones. Due to the high sensitivity of color pollutants and many concerns about this issue, in this study, by designing and optimizing a falling film reactor, the removal of Basic red 46 dye from water by advanced oxidation method is investigated. The photocatalytic... 

In the current research, Anatase-Rutile Titania hollow spheres were synthesized using hydrothermally prepared carbon spheres as template. Different calcination temperatures were used to remove carbon template and crysalized Titania. The characterizations for the physicochemical properties of prepared samples were carried out by XRD, FESEM, XPS, DRS, UV-Vis and FTIR.It is found that doping of carbon in the crystal structure of Titania hollow sphere, cause red shift in band gap wavelenght and the absorption wavelength edge was expanded to the visible light region and the additional diffusive electronic states were observed on the valence band spectra of samples.The photoelectric conversion... 

In the present work, a series of nanohybrids based on ZIF-8 as a physicochemical stable metal-organic framework (MOF) and different amounts of Chitosan (CS) (0.5–15 wt%) were synthesized and used as adsorbents for anionic (Congo Red, CR) and cationic (malachite green, MG) dyes from contaminated water in single and binary dye solutions. The single adsorbents and their nanohybrids were characterized by FESEM, FTIR, XRD, TGA, BET, and zeta potential measurements. The experimental adsorption results displayed that the synthesized nanohybrids presented higher adsorption capacity for anionic dyes compared to cationic dyes in both single and binary dye solutions. It was deduced that the... 

In this research, the synthesis of the electrospum nano fiber doped zinc oxide and its photocatalyst usage was investigated. The band gap of the zinc oxide in the area of UV leads to deactivation of this material at the visible light. With due the attention to sunny weather in Iran and the fact that about 50 percentage of sunlight is visible light, producing and usage of catalyst materials actived at visible light is economical. Doping is one of the ways of activating ZnO at visible light, so in this research thiourea is used as the source of ZnO doping. The results of the expriments done at visible light and also spectrums of DRS, XPS and XRD prove that the doping is happened. Also, in this... 

It is necessary to monitor pollutants in aquatic samples, because many of these compounds can pose threats to human health and the ecosystem. Separation technology based on magnetic materials has received considerable attention in recent years. The magnetic extraction method is not only convenient, economical and highly efficient, but it also overcomes problems with conventional solid-phase extraction. In order to remove anionic dyes from single and ternary systems, zinc ferrite nanoparticle was synthesized using co-precipitation method and its surface was modified by Cetyltrimethyl ammonium bromide (CTAB) cationic surfactant. Surface characteristics of ZFN-CTAB was studied using Fourier... 

Lately, a wide application of eco-friendly polysaccharide-based hydrogels in waste water treatment has received enormous attention in the literature. The effluents containing dye materials from the processing industries are washed off into rivers and lakes which can be very harmful to creatures. Low-cost biopolymers and biodegradable adsorbents have been researched to be a good tool to minimize the environmental hazards caused by the industrial effluents by removal of these toxic and carcinogenic dyes from the waste effluents. In this study, an eco-friendly superabsorbent hydrogel was prepared by using of sugarcane bagasse, two hydrophilic monomers, magnetic nanoparticle and methylene...