Sharif Digital Repository

In this thesis, gas sensors were fabricated based on resonance frequency shift of quartz crystal with covering of polymer fibers and carbon nanostructure materials.¬ Sensing materials were used in two different types of polyvinylpyrrolidone (PVP) and Graphene oxide. Electrospining was used as an efficient, simple and low cost approach for producing polymer and composite fibers with 280nm to 4um diameters. In addition, the effects of changing various parameters such as the concentration of polymer solution and electrospining process time were investigated. Images taken with a scaning electron microscope indicated that the concentration of polymer solution effectively can affect morphology,... 

Poly vinyl alcohol/graphene oxide (GO) nanocomposites were made through solution casting method. The nanocomposite were characterized by XRD , FTIR , FESEM , DSC and mechanical measurements. Graphene oxide was irradiated by gamma ray at 35 KGy in a 50/50 water-ethanol solution and then added to PVA aqueous solution in various GO concentrations (0.3 , 0.7 , 1 wt%) and sonicated. The resulting suspensions were cast into petri dishes to make thin films. Also PVA/GO Hydrogels were prepared by gamma irradiation at 20 KGy. It was observed that GO uniformly dispersed within PVA indicating strong interaction through forming hydrogen bonds between hydroxyl groups of PVA and GO surface. Tensile... 

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 research,Graphene Oxide nanoplatelets (GO) were synthesized by chemically modified Hummer's method.After the GO nanosheets electrochemically reduced to graphene, nanoparticles imposed to this thin film.This optimized nanostructure coating was utilized for investigating the Hydrogen Evolution Reaction (HER) over the copper substrate. In order to optimize the kinetic of electrodeposition and reduction, diverse electrochemical approaches such as cyclic voltammetry, chronoamperometic and potentiometric as well as pulse electrodeposition methods were employed. Electrochemical procedures were aligned by Design of Experiment (DOE) ... 

In the first part, a novel electrochemical sensor based on nanocellulose-carbon nanoparticles (NC–CNPs) nanocomposite film modified glassy carbon electrode (GCE) is developed for the analysis of metoclopramide (MCP). The electrochemical behavior of MCP was investigated on the surface of the modified electrode using cyclic voltammetry (CV). Characterization of the surface morphology and properties of NC/CNPs was carried out by scanning electron microscopy (SEM), atomic force microscopy (AFM) and electrochemical impedance spectroscopy (EIS). Effective experimental variables, such as scan rate, pH of the supporting electrolyte, drop size of the casted modifier suspension and accumulation... 

Thin film graphene oxide(GO) membranes have been promising potential for gas purification due to thin lamellar microstructure, stable a few atom thick layers and very short intersheet distances. In this research, the nanoporous graphene oxide membranes have been prepared by vacuum and pressurized ultrafiltration on the modified polyacrylonitryle(mPAN) sublayer for helium separation from Nitrogen and carbon dioxide gas mixture. The separation performance of synthesized GO membrane was controlled by varying parameters such as concentration of stabilized aqueous GO solution, pores size range of support and its surface properties, centrifuge time, applied pressure after synthesis, humidity,... 

Implant-associated infections are one of the most serious complications in orthopaedic and trauma surgery as it may result in poor functional outcome, implant failure, chronic osteomyelitis or even death. Great concerns have been taken to reduce implant-associated infections through progressing in operating standards, minimizing the possibility of contamination during surgery, reducing the establishment of infection by perioperative antibiotic prophylaxis, and confining of pathogenic strains by patient isolation. In spite of these preventions, the percentage of postoperative infections is still rising. Composite coatings with bone-bioactivity and drug-eluting capacity are considered as... 

The investigations on hydrophobic surfaces have attracted lots of intrests in science and technology. Silica sols have been used extensively in the area of producing hydrophobic coatings. On the other hand, carbon-based materials have attracted of a great deal of scientific interest in recent years. The purpose of this research is synthesis and investigation on the properties of Silica- Graphene Oxide nanocomposite coating.Graphene Oxide synthesized by using Hummer’s method. Silica nanoparticles were prepared using sol-gel process and tetraethylorthosilicate (TEOS) as precursor. The surface hydroxyl groups of silica nanoparticles are replaced with Methyl groups by treatment with... 

The most abundant source of deuterium, of course, is natural water. Other potential natural sources are natural gas and petroleum. Of these, natural water is by far the most significant. Until 1943, all the heavy water produced commercially was made by electrolysis. The largest single producer of heavy water was the Norsk Hydro Company, which operated the world's largest electrolytic hydrogen plant at Rjukan, Norway. In a detailed laboratory investigation of the effect of cell variables on the deuterium separation factor in electrolysis of water, Brun and co-workers [B13] have found that a: depends on the cathode material, electrolyte composition, and cell temperature, generally as... 

One of the most important world issues is environmental constraints regarding the pollutants released by transportation fuels and refinery products, sulfur reduction being one of the most significant objectives. Deep hydrodesulfurization processes result in great sulfur reduction in refinery streams. However, such harsh process conditions increase undesired side reactions and facilitate coke formation as well as affecting the surfaces. More effective alternatives for hard process conditions are highly active and selective hydrodesulfurization catalysts, which enable the process to be performed at milder pressure and reaction conditions. Catalyst bases play a very important role in hydrogen... 

In recent years, temporary skin grafts based on natural biopolymers modified with carbon nanostructures has received considerable for wound healing applications. In this study, Nanofibrous structures that mimic the native extracellular matrix and promote cell adhesion have attracted considerable interest for biomedical applications. Chitosan-polyvinylpyrrolidone (CS/PVP) films containing graphene oxide (GO) nanosheets (~1 nm thickness and micrometer length) were prepared by solvent casting methods. Experimental results showed that PVP concentration had a critical role on the water vapor permeability, transparency, hydrophilicity and thermal stability of the nanocomposite films. Antibacterial... 

The aim of this thesis was creating Titania/RGO coating with electrophoretic method to evaluate the corrosion resistance of stainless steel 316. At first Graphene Oxide were synthesized with modified Hammers method and their physical, chemical and morphological properties have been investigated using XRD, FTIR, EDX, TGA, UV-Vis and Raman analysis. then Graphene Oxide was added to the bath of titanium and was deposited on 316 stainless steel substrates. Moreover, corrosion protection of coating has been examined using Poarization test and Electrochemical Impedance Spectrometry. The effect of deposition parameters on corrosion properties of composite coatings were examined. The key variables... 

The main purpose of this research was functionalizing graphene, in order to achieve higher hydrophobicity, and producing nanocomposite of functionalized graphene and titanium dioxide by hydrothermal method, and sequently invastigation on photocatalytic properties of the powders and corrosion properties of EPD coated samples. Graphene oxide was synthesized by improved Hummers method and reduced and sequently was functionalized through the chemical process with hydrazine and octadecylamine respectively. Then the nanocomposite of functionalized graphene-titania was synthesized by use of titanium isopropoxide precursor and its photocatalytic properties were measured. The analysis of the... 

In this thesis, graphene/titanium oxide and graphene/tungsten oxide composites were synthesized using arc discharge in liquid and their photocatalytic behavior was studied. Based on physical principles of the arc discharge in liquid, geometry of point-point was used for metallic Ti and W electrodes. TiO2 and WO3 nanoparticles and their nanocomposites with graphene and graphene oxide (GO) were studies using DLS, UV-vis, PL, ICP, FTIR, XRD, Raman and TEM characterization. The concentration of aqueous solution of Rhodamine B mixed with graphene/WO3 and GO/WO3 composites and WO3 nanoparticles under ultraviolet light was measured versus time and reached to 0.1, 0.6 and 0.6 of the initial value... 

Platelet nanoparticles could dramatically decrease permeability of polymeric film where increase considerably its physical -mechanical properties. Bio based (Biodegradable) polymeric materials such as starch based polymeric films show very weak mechanical and high oxygen and water vapor permeability. Graphene oxide (GO) could increase mechanical properties of starch based polymer where decrease its permeability dramatically. Addition of chitosan also could increase antibacterial and antifungal of films and decrease permeability of films considerably. In this research nanocomposite of Starch/Chitosan/GO films have been prepared by solution method and its morphology, permeability, physical... 

TiO2 and TiO2-Graphene have been synthesized by hydrothermal method. Their physical, chemical and morphological properties have been investigated using XPS, XRD, FTIR, TEM, EDX, UV-Vis and AFM analyses. Moreover, photocatalytic efficiency of prepared materials has been examined using degradation of methylene blue. AFM image exhibited that monolayer GO with thickness of 10 nm was synthesized using modified Hummer’s method. FTIR analysis represented main characteristic peak of oxygen bond on the surface of GO, whereas for TiO2-Graphene most of oxygen functionalities on the surface were removed partially or completely. Photocatalytic degradation of MB proved this extension of light absorption.... 

In this research, room-temperature flexible humidity sensors using graphene oxide (GO) and partially reduced grapheme oxide (PRGO) are reported. Sensing layer was deposited onto Kapton substrate by spin coating method. Topography of the sensing layer was observed by Optical Microscopy, Atomic Force Microscopy (AFM) and Scanning Electron Microscopy (SEM). Partial reduction of the GO was confirmed by X-ray Diffraction (XRD) data. Humidity sensing properties of the samples that were annealed in different temperatures in the range of 125-200 were measured at room temperature. The sample which was reduced at 125 presented higher response about 106% and shorter recovery time of about 65 s.... 

The purpose of this study is to prepare a catalyst for copper nanoparticles that can be used in C-H activation processes in order to increase copper salt catalytic processes by converting it into a catalyst with characteristics of having recovery cycles, convenient separation and environmental friendliness and being in nano size. Consequently, copper nanoparticles are directly grafted onto graphene oxide, or using para-aminobenzoic acid grafted on graphene oxide. A copper nanoparticle catalyst was used in the reaction to activate the C(sp2)-H bonds of benzoxazole molecule and C-N bonds formation with secendary amines. Using the results of transition electron microscopy (TEM), scanning... 

Heat pipes are useful devices in heat transfer, renewable energies and cooling systems in particular. According to various application of this systems in different industries, performance improvement of this devices has gained much importance. Working fluid is one of the effective factors on pulsating heat pipes. Since heat transfer in PHPs is natural convection and two-phase, specific heat and thermal conductivity of working fluid have an important role in the performance of pulsating heat pipes. In the present study, the effect of using nano-encapsulated PCM along with reduced graphene oxid (RGO) dispersed in water and their mixture as working fluid has on the performance of PHPs has been... 

The main aim of present thesis is to synthesis and characterize of ferrite nanocomposites as a new generation phtocalyst and their application in degradation of various types of environmental pollutants in different irradiation time and dark conditions. Ferrites have been used anchored to carbon allotropes such as graphene oxide and carbon nanotubes, in order to improve their photocalytic activity as well as phase structure, textural and optical properties. Firstly, a new SnS2-BiFeO3/rGO nanocomposite has been prepared to increase the visible-light-responsive photodegradation of organic dyes such as cationic methylene blue (MB) and anionic methyl orange (MO). The obtained results showed...