Sharif Digital Repository

In the present work, edge-functionalaized graphene was used as electrode material and its electrochemical properties were systematically characterized by electrochemical impedance spectroscopy and cyclic voltammetry. Two methods were applied to modify the gold electrode surface. First method was the self assembling process of graphene nanosheets on gold electrode surface. Second method was simply casting specific amounts of graphene suspension on the gold electrode surface. Nyquist plots show decrease of the charge transfer resistance on the electrode surface at both cases. In cyclic voltammetry studies, first electrode shows no significant changes while the second electrode exhibits... 

Unique and interesting properties of Graphene with two dimentional and CarbonNanotubes rod-like and their increasing applications such as application in electronic industry, sensors, displays, supercapasitors, pharmacy, etc, they hase become an important field of condensed matter and nanotechnology. Crystalization process and the distribution of light atoms and molecules on graphene surface hase become one of the reaserche arease of interest and hase attracted much attention. These studies play an important role in design of nanosensors graphene based. Most of the experimental observatins of surface diffusion in the chemical and physics systems have been classically described and... 

In this project, two types of graphene obtained from chemical and chemical vapor deposition (CVD) methods were studied for gas/vapor sensing applications . In chemical method, oxidation and exfoliation of graphite was performed in liquid phase. AFM, XPS, Raman spectroscopy and Uv-visible spectroscopy were indicated that single layers synthesis of graphene oxide (GO) sheets was formed successfully. Reduction of the GO to reduced graphene oxide (RGO) was chemically done by hydrazine as a conventional reducing agent and melatonin as a green alternative. Photocatalytic reduction and hybridization of GO with TiO2 was also studied. TEM, SEM and AFM analyses confirmed nucleation and growth of TiO2... 

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,... 

Supercapacitors represent a new class of energy storage devices that have been attracted many researchers in last few years. Graphene with unique properties such as superior electrical conductivity and large specific surface area is one of the most suitable materials in supercapacitor applications. Besides, metal oxides are being used as active compounds in supercapacitors due to their role in redox reactions. In this research, synthesis and characterization of supercapacitor electrodes based on graphene and MnO2 nanostructured materials was studied under different conditions. For this purpose, Graphene oxide (GO) was synthesized by Hummers’ method and then, it was deposited on a nickel foam... 

One atom thick layer of pure carbon in bonded and hexagonal lattice is named graphene. graphene has unique mechanical, optical, thermal and electrical properties and because of these properties has grabbed attention. graphene has been made from high pure graphite by different methods such as CVD(chemical vapor deposition) , chemical exfoliation , micromechanical cleavage and colloidal suspension. through these methods, green methods for synthesis of graphene, using eco-friendly reductants during synthesis of graphene instead of hydrazine and recently using waste(not graphite) are attractive for synthesis of graphene. Following this idea , a group has produced graphene from wastes such as... 

One of the different sensing techniques for biosensors is based on surface plasmon resonance which provides high reliability and efficiency. In this project working operating principles of biosensors based on surface plasmon resonance will be examined. For investigation of sensing meachanism we assume that there an array consisting of alternating graphen ribbons which by applying light leads to an effective magnetic field coupling to the localized surface plasmon. The numerical calculations are based on the exact solution of Maxwell's equation using Fuorier Model Method and Matlab coding. In these calculations, the coefficients of transmission, reflection and absorption of light versus... 

The main object of this thesis is preparation and investigation of polyolophine/graphene oxide nanocomposites by using bi-supported Ziegler-Natta catalytic system and in-situ polymerization. Magnesium ethoxide and graphene oxide were used as supports of catalyst. TiCl4 was accompanied by triisobutyl aluminum (tibia) and diisobutyl phthalate (DIBP) as an electron donor constituting Ziegler-Natta catalytic system. Preparation of catalyst and polymerization were taken place in slurry phase under the argon atmosphere. At the beginning of the polymerization experiment, several type of nanocomposites were made under various conditions (such as different Al/Ti molar ratio) to find optimum condition... 

In the year 2004 when the first instance of graphen was built in laboratory, entice the attraction of many research groups. Because in spite of absence of graphen to that time, physicists given the unique properties for it. So it was the time to use that marvel properties which only theoretically available, to design and built one atom thick circuits. In this dissertation for the first time, we want by using method of moment and multilayer green functions in spectral domain, analyze graphene-based ribbon and stepped electrical conductivity distribution waveguides and calculate their characteristics such as propagation constant, surface currents and characteristics impedance with external... 

The main object of the presented thesis is manufacturing ultra high molecular weight polyethylene(UHMWPE)/Graphene nanocomposites by insitu polymerization using Ziegler Natta catalysts. In this study, three types of Ziegler Natta Catalysts such as Magnesium ethoxide supported, single-supported and bi-supported have been studied. Experimental conditions are optimized (from point of productivity and molecular weight) by Design expert software with response surface methodology (Box-Behnken design). Effect of process parameters like temperature, pressure and [Al]/[Ti] molar ratio on productivity and Molecular weight are investigated. Also, the effect of hydrogen presence and type of cocatalyst... 

Although a lot of research has been done on Carbon-based interconnect, there are many important questions unanswered. For example, there is no compact model for the resistance of bundle of CNTs at high frequencies, at which interconnects will be operating due to the scaling. Also there are many studies comparing CNT, GNR, and Cu wires but there is no study to show how much this will impact the design of a chip at today’s Giga Scale Integration. This comprehensive study should include chip performance, power dissipation and total number of metal levels. These two big questions are investigated in this dissertation. In the first part, high frequency behavior of CNT bundles is studied. A... 

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... 

Development of renewable energy production from sun and wind and the development of hybrid electric vehicles seem to be integral components in modern societies in order to overcome the environmental pollution and reduce the use of fossil fuel sources. In such devices energy storage plays an important role and supercapacitor is one the important energy storage devices. Structure of supercapacitor electrodes has considerable effect on supercapacitor performance. Graphene as a 2D carbon structure can improve electrochemical properties of electrodes. Here three different hybrid structure of graphene have been realized. The high capacitance and cyclic stability of graphene nanosheets decorated... 

Liquide phase catalytic exchange (LPCE) between liquid water and hydrogen is an important reaction for separation of the hydrogen isotope from liquid water. One of the application of this reaction is heavy water production. This method is mainly used hydrophobic catalysts with Pt active metal. The use of hydrophobic catalyst is necessary, because liquid water in the LPCE reaction, resulted in block the catalyst pores and loss of catalyst activity. Design of experiment has been done by using of Design Expert 7.0.0 for determination of number of tests and optimization of Pt weight percent. Alumina and carbon (included graphene, single-walled and multi-walled carbon nanotube) supported 5% wt Pt... 

In the present investigation, graphene sheets are simulated as Nano resonators using Kirchhoff plate theory and nonlocal continuum theory. External force and interlayer forces are simulated as harmonic and Winkler-like elastic foundation, respectively. Equations are solved analytically and numerically and corresponding results are presented. Considering a two layer resonator, natural frequencies and oscillation amplitude are investigated by free vibration and forced vibration analysis. Also, the effects of parameters such as small scale, sheets dimensions and inciting frequency on the vibration of the resonator, are displayed  

In this thesis we present fabrication, characterization, and experimental results describing electrical actuation and readout of the mechanical vibratory response of PVP, graphene-doped and ZnO fibers by employing electrical actuation. For a fiber resonator with an approximate radius of 850 nm and length of 100 µm, we observed a resonance frequency around 580 kHz with a quality factor (Q) of about 2511 in air at ambient conditions. Through the use of finite element simulations, we show that the reported frequency of resonance is relevant. Also, the measurements were performed in an enclosed chamber with controlled levels of ethanol vapor. The adsorption of ethanol causes a shift in the... 

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... 

The main purpose of this theses is to synthesize graphene by chemical vapor deposition (CVD) of a hydrocarbon gas such as methane on the nickel foam substrate and then to characterize this kind of graphene. Graphene is a single layer of carbon atoms, discovered in 2004, which has led mankind to new eras in all fields by its extraordinary features such as extra high electron mobility, high thermal conductivity, excellent mechanical strength, optical transparence and extra high specific surface. The advantage of this method compared to other methods is that the graphene generated has a better structural quality. Graphene foam firstly, because of the continuity of the foam structure, has better...