Sharif Digital Repository

Among the xenobiotic compounds, chlorophenols are considered to be as the most dangerous compounds for the environment and living organisms. These compounds are abundantly found in the wastewater of many chemical industry factories. In this research, by using Gaussian software and density functional theory at the level of B3LYP / 6-31G (d, p),the adsorption of molecules such as phenol, 2-chlorophenol, 4-chlorophenol and 2,4-dichlorophenol over graphene, nitrogen and boron doped graphene sheet are studied. The most stable configurations were determined and adsorption energies were calculated. In addition, to understand the adsorption mechanism, electron properties such as state density and... 

Titanium nitride-carbon nanocomposites are synthesized by the reaction of TiCl4 and NaN3 in supercritical benzene medium that also serves as a carbon source. In order to improve the crystallinity of the as-prepared precursor (SI), it is further heat-treated at 1000 ˚C for 3-10 h using anhydrous ammonia and UHP nitrogen atmospheres at 1000 ˚C (SIII-SV). Moreover, to improve electrochemical behavior, the synthesized nanocomposite (SIV) is modified with Pt nanoparticles using a polyol process. For better understanding of synthesized catalyst nature and justifying their variant ORR activity several analyses are done. X-ray diffraction (XRD), Raman spectrum, field emission scanning electron... 

World population growth, depletion of fossil fuels resources depletion and increased air pollution resulting from their consumption, human society has had to replace fossil fuels with renewable sources. In this context, the production of hydrogen using solar energy is feasible candidate to replace fossil fuels, which can be produced by water splitting in a photoelectrochemical (PEC) cell using an appropriate photocatalyst. This clean production method has been attended by many researchers in recent years. The most common photocatalyst for the conversion of sunlight to hydrogen by splitting water is Titanium dioxide (TiO2). But high energy gap and fast electron-hole recombination rate in TiO2... 

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) ... 

This thesis is focused on the preparation and use of polysaccharides as extractive phases in various extraction methods, such as the micro solid phase extraction (µ-SPE), needle trap microextraction (NTME) and thin film microextraction (TFME).In the first research, feasibility of the online µ-SPE method using cellulose acetate (CA) fibers was investigated. For this purpose, CA fibers were prepared by electrospinning technique and then placed into µ-SPE cartridge. With this method, it was possible to simultaneously extract the drug compounds in the urine and plasma samples. The enrichment factor and limits of detection (LODs) were obtained in the range of 194-210 and 1.0-2.4 μg L-1,... 

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... 

Graphene is a newly developed nanomaterial that has resived considerable attention in recent years. Graphene – based structures having remarkable properties, e.g. high specific surface area, ultrahigh electrical conductivity and good biocompability, are ideal choices for nanomedical applications such as biosensors and cell culture scaffolds. So, in this project 2D graphene and 3D graphene foam structures were synthesized by chemical vapor deposition (CVD) method and their electrical and biological properties were evaluated. First step of this project was to design and make a CVD system suitable for the synthesis of high quality graphene structures, i.e. single layer graphene and 3D graphene... 

In this thesis, the thermal and thermoelectric properties of graphene-based nanostructures are numerically investigated. The transport parameters, including Seebeck coefficient, electrical conductance, and thermal conductance are obtained as well as the thermoelectric figure of merit. The Hamiltonian matrix is set up using a third nearestneighbor atomistic tight-binding approximation and the dynamical matrix using a 4th nearest neighbor force constant approximation. Both ballistic and diffusive regimes are considered in this work. For transport investigation, the Landauer formula and the nonequilibrium Green’s function techniques are used. The role of temperature, geometrical parameters,... 

Depleting resources and heavy pollution of fossil fuels have drawn the world's attention to clean energy and the most ideal one is hydrogen. Water splitting is one of the most effective ways to produce hydrogen and due to slow kinetic rate different kind of catalysts (optical, electrochemical, etc.) are developed for this reaction. In this work a ZIF-67 and N-doped graphene quantum dots composite is developed and its electrocatalytic performance in oxygen evolution reaction is evaluated. The synthesized graphene quantum dots are between 2-4 nm and the incorporation of nitrogen atom in their structure was verified by FTIR analysis. The metal-organic framework which is produced in this work... 

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... 

Using free laccase, enzymatic decolorization of two azo dyes were optimized. The optimum conditions with the aim of maximizing the decolorization of AB92 dye (92.30%) were: dye concentration = 11.85 mg L-1, pH = 5.1, and enzyme concentration = 98.37 mg L-1. While, these conditions to achieve the maximum decolorization yield of DR23 (95.60%) were: dye concentration = 17.68 mg L-1, pH 3.7 and enzyme concentration =97.89 mg L-1.In the second part, the laccase enzyme was covalently immobilized onto GO nanosheets. At the concentration of graphene oxide and laccase enzyme equal to 1 mg mL-1 and 0.9 mg mL-1, respectively, the enzyme loading was 156.5 mg g-1 and the immobilization efficiency was... 

In recent years carbon nanotubes and other carbon nanostructures such as graphene sheets have attracted a lot of attention due to their unique mechanical, thermal and electrical properties. These structures can be used in desalination of sea water, removal of hazardous substances from water tanks, gases separation, and so on. The nano porous single layer graphene membranes are very efficient for desalinating water due to their very low thickness. In this study, the mechanism of passing water and salt ions through nano porous single-layer graphene membrane are simulated using classical molecular dynamics. In the simulation, in order to separate salt ions from the water, the effects of applied... 

Graphene -a two-dimensional monolayer of graphite- was realized for the first time in 2004.Owing to its physical extra ordinary properties, graphene has attracted growing interest in research from fundamental physics to electronics, spintronics, and thermoelectrics. Importantly, it is an attractive material for electronics and spintronics due to its specific physical properties such as high electron mobility and gate tunable carrier concentration. Furthermore,achievement of room-temperature spin transport with relatively long spin relaxation time makes graphene nanoribbons the best candidate for spintronics. Based on the theoretical predictions, the weak spin-orbit interaction in graphene... 

By the use of flexible substrates like metal foils and meshes and plastic ones, fabrication of flexible dye sensitized solar cells are possible. Flexible dye sensitized solar cell, not only is utilized in portable, light electronic devices, but is also conductive to industrial roll to roll fabrication which enables the implementation of high throughput production lines and its associated potential reduction in manufacturing costs. This thesis has concentrated on fabrication of flexible dye sensitized solar cells by use of stainless steel mesh as substrate of photo-anode, because of its satisfying stability in electrolyte, flexibility, transparency and low cost. In this research, an efficient... 

In this thesis, a novel graphene oxide (GO)/sodium alginate (SA)/polyacrylamide (PAM) ternary nanocomposite hydrogel with excellent mechanical performance has been fabricated through freeradical polymerization of acrylamide (AAm) and SA in the presence of GO in an aqueous system followed with ionically crosslinking of calcium ions. Physical and chemical characteristics of the composite were investigated by Fourier transform infrared spectroscopy and scanning electron microscopy. The swelling behaviors of the composite hydrogels were investigated under varying conditions of time and pH. The optimized swelling capacity in standard conditions was found to be 1711% per gram of the hydrogel. The... 

The aim of this study was to investigate the rate of increase in temperature of a phantom equivalent to body tissue by different groups of magnetic iron nanoparticles in the external magnetic field to kill cancer cells based on the hyperthermia method. To achieve this goal, three groups of dextran magnetic nanoparticles with different properties and reduced iron oxide-graphene oxide magnetic nanoparticles by M-rGO supercritical synthesis method were used. After XRD, FTIR, SEM, FESEM, VSM, TEM characterization tests, these materials were placed in a phantom made of agarose gel and with the same properties, in a magnetic field with fixed characteristics for all groups and during the process of... 

In this report, a combination of in-situ chemical synthesis and electrolysis methods was applied for the preparation of zinc oxide/graphene quasi core-shell nanoparticles. Pure zinc oxide was also prepared using the same method at different temperatures. The degree of 100 ◦C was selected for synthesizing of ZnO-GO quasi core-shell (zinc oxide as a core and few layer of graphene oxide as a shell). The particle size was 15±2 nm in all samples. In both processes, oxygen was the main reason for the connection between the core and the shell. Unlike chemical process that has all kind of functions in electrolysis process, one kind of function was produced and confirmed by FTIR. XRD patterns also... 

Ease of solar hydrogen production using water splitting and its environmental benefits, distinct hydrogen from other energy carriers. Hydrogen is the most abundant material in the world that make up more than 90% of the world compounds. So applying this material as a clean fuel is the best way to prevent environmental problems caused by fossil fuels. For efficient hydrogen production from water, a suitable electrocatalyst with low overpotential, high mechanical strength and reasonable catalytic activity must be utilized. In this research, cobalt based electrocatalyst was used considering that electrodepositon conditions play an important role in its final efficiency. On the other hand,... 

Graphene، a molecular single layer of graphite، has tremendous applications in materials science for the development of nanocomposites، tissue engineering and supercapacitors. Graphene application and its developing applications depend on its essential properties such as excellent mechanical and thermal properties. Accordingly، investigation on graphene has drawn significant attention to itself. Hence، exploitation of these important properties including the induction of graphene sheets in polymer matrix seems to be essential. In the present survey، salep، a biodegradable polysaccharide، has been used for either the reduction of graphene oxide or functionalization of graphene. Then، reduced... 

Due to the increase in greenhouse gases in earth’s atmosphere in recent years and its devastating environmental outcomes, there has been an increase in research trying to reduce these gases especially CO2. Flue gas is one of the most important sources of CO2 emission. Among the many techniques of removal, capturing and CO2 separation from flue gas, physical adsorption by a solid adsorbent is considered as a suitable and economic option. Among the solid adsorbent that are used for adsorption of CO2, Metal-Organic frameworks have many interesting features such as high specific surface area and high internal free volume. Among the Metal-Organic frameworks, MIL-53 (Al) and MIL-101 (Cr) are two...