The purpose of this study is to investigate the dielectric properties of fuel oils and their ethanol mixtures in the THz spectral region. We presented frequency dependent absorption coefficients, refractive indices, and dielectric constants calculated from the measurements of pure and mixtures of fuel oils. As the mixing ratio changes, meaningful shifts were observed in refractive index and absorption coefficient of the mixtures. For pure liquids, we used Debye model which provides a good estimate for the dielectric parameters of pure liquids in microwave region and also in the THz region. Bruggeman model, which is used for describing the interaction between liquids in binary mixtures, did not work for ethanol mixtures of gasoline within our assumptions. However, these mixtures were modeled successfully with a modified Debye model in which the mixture behavior was described with a basic contribution approach. The results suggest that there is no strong interaction between the ethanol and the molecules in the gasoline. We concluded that this new approach offers a simple and useful method to determine the concentration of ethanol in gasoline with 3% (by volume) maximum error.

2,3-Dihydro-5-(10-(2,3-dihydrothieno[3,4-b][1,4]dioxin-5-yl)anthracen-9-yl)thieno [3,4-b][1,4]dioxine (DTAT) was synthesized via linking 3,4-ethylenedioxy thiophene (EDOT) on anthracene by Stille coupling. Homopolymer P(DTAT) was achieved by electrochemical techniques. The polymer, P(DTAT) was electrosynthesized by anodic oxidation of the corresponding monomer in the presence of 0.1 M LiClO4 as the supporting electrolyte in acetonitrile (ACN) solution. Copolymer of DTAT in the presence of EDOT was synthesized via potentiodynamic method in ACN/LiClO4 (0.1 M) solvent-electrolyte couple. Structural characterizations of the sample was carried out via 1H-Nuclear Magnetic Resonance (NMR) and Fourier Transform Infrared Spectroscopy (FTIR). Electrochemical behaviors of the monomer and polymers were determined by Cyclic Voltammetry (CV). Electrochromic and spectroelectrochemical behavior of the polymers were investigated on ITO glass electrode, and their ability of employment in device construction was examined. Spectroelectrochemistry analysis of P(DTAT) revealed an electronic transition at 505 nm corresponding to &amp / #960 / -&amp / #960 / * transition with a band gap of 1.57 eV. In order to investigate electronic structure of the copolymers obtained by different applied potentials, spectroelectrochemistry studies were performed. Electrochromic investigations showed that P(DTAT) switches between yellow and blue while P(DTAT-co-EDOT) was found to be multichromic, switching between claret red neutral state, a gray and a red intermediate state, and a blue oxidized state. Switching time of the polymers was evaluated by a kinetic study upon measuring the percent transmittance (%T) at the maximum contrast point. Dual type polymer electrochromic devices (ECDs) based on P(DTAT-co-EDOT) with poly(3,4-ethylenedioxythiophene) (PEDOT) were constructed. Spectroelectrochemistry and electrochromic switching of the device was studied. They were found to have good switching times and reasonable contrasts.

A novel electroactive monomer 5,8-Di(1H-pyrrol-2-yl)-2, 3-di(thiophen-2-yl) quinoxaline (PTQ) was successfully synthesized via Stille Coupling reaction between quinoxaline and pyrrole. Nuclear magnetic resonance (1H NMR and 13C NMR) and Mass spectroscopy were used to characterize the monomer. The monomer was electrochemically polymerized in the presence of tetrabutylammonium perchlorate (TBAP) as supporting electrolyte in dichloromethane. Monomer reveals relatively low oxidation potential at +0.70V. Spectroelectrochemical behaviors and switching ability of homopolymer were investigated by UV-Vis spectroscopy and cyclic voltammetry. Two &amp / #960 / -&amp / #960 / * transitions were observed at 400 nm and 815 nm with a low band gap, 1.0 eV. Polymer possesses 66% optical contrast in the Near IR region, which may be promising in NIR electrochromic device applications. Spectroelectrochemical behaviors and switching ability of copolymers were investigated by UV-Vis spectroscopy and cyclic voltammetry. Copolymers of PTQ in the presence of BiEDOT and BEBT were synthesized via potentiodynamic method in DCM/TBAP (0.1 M) solvent-electrolyte couple. P(PTQ-co-BiEDOT) reveals oxidation potential at +0.45V, whereas P(PTQ-co-BEBT) reveals oxidation potential at +0.70V. The spectroelectrochemical behavior of the P(PTQ-co-BiEDOT) and P(PTQ-co-BEBT) in comparison to homopolymer revealed solid evidence of copolymerization based upon the differences in the spectral signatures. Switching time of the polymers was evaluated by kinetic studies upon measuring the percent transmittance (%T) at the maximum contrast point.

Synthesis of new electroactive monomers are highly desired since these compounds can be utilized as active layers in many device applications such as ECDs, LEDs and solar cells. EDOT (3,4 ethylenedioxythiophene) and thiophene bearing polymers were also proven to be excellent candidates as electrochromic materials. Benzotriazole can be coupled to EDOT and thiophene to yield materials that can be polymerized to give donor acceptor type polymers. These materials are promising candidates as components in fast switching polymeric electrochromic devices. Donor acceptor type materials / 2-dodecyl-4-(2,3-dihydrothieno [3,4- b][1,4]dioxin-5-yl)-7- (2,3-dihydrothieno[3,4-b] [1,4] dioxin-7-yl)-2H-benzo [d][1,2,3]triazole and 2-dodecyl-4,7-di(thiophen-2-yl)-2H-benzo[d][1,2,3]triazole were synthesized via N-alkylation, bromination, stannylation and Stille coupling reactions. Electrochemical and electrochromic properties of the polymers were examined in detail.

Thermal rearrangements of Berson TMMs have been investigated. For this purpose, the potential energy surface of the singlet S state has been explored to test Benson&rsquo / s Schemes 1-2 (Figure 1.10 and 1.11). It is verified that the enyne 9c plays a central role in connecting the two portions of the reaction path (Berson Schemes 1 and 2). Connectivity of successive minima on a given surface has been verified by intrinsic reaction coordinate (IRC) computations. Density functional theory (DFT) and multiconfiguration self consistent field (MCSCF) methods have been employed for these purposes. Further, single point coupled-cluster singles and doubles with perturbative triples (CCSD(T)) energy computations have been carried out at optimized DFT or MCSCF geometries. All transition states (TS) connecting each neighboring minimum have been located in the proposed mechanisms. It is concluded that the proposed mechanisms are confirmed by the theoretical calculations. The computed activation energy and enthalpy of reaction values are in good agreement with the available experimental values, only differing by a few kcal mol-1.

Throughout this thesis work, surface nanocarbon synthesis on metal catalyst surfaces was investigated as the first step of carbon nanotube production mechanism. Study was aimed to make a comparison between the performances of selected catalyst surfaces and to find most probable mechanism for the nanocarbon synthesis on the metal catalyst surface. Formation of nanocarbon from the acetylene as carbon source on the selected Fe(111), Ni(111) and Ni(100) surfaces were studied by means of quantum mechanics. Density functional theory (DFT) was implemented periodically by using Vienna Ab-initio Simulation Package (VASP) code for the computations required. Relative energy profiles of the interested mechanisms were generated by the usage of equilibrium geometry calculations, climbing image nudged elastic band (CI-NEB) calculations and transition state calculations. Formation step of surface nanocarbon, with the decomposition of the carbon source, is the rate determining step of carbon nanotube production. Therefore, results of the nanocarbon synthesis study were related to carbon nanotube synthesis. For the mechanistic study, surface-acetylene complex was obtained by the adsorption of the acetylene on the chosen catalyst surface. Then three different mechanisms were studied for the dehydrogenation process. These processes were named as direct hydrogen-hydrogen interaction, hydrogen atom desorption and surface-hydrogen interaction methods. Among these methods surface-hydrogen interaction methods resulted in minimum activation barriers for all three surfaces used and said to be the most probable mechanism. Finally, relative energy profiles of the mechanisms were compared for the Fe(111), Ni(100) and Ni(111) surfaces and performance of Fe(111) for CNT synthesis was found better than the others.

With the emergence of nanotechnology, mankind has obtained the capability to manipulate materials at nanoscale and this led to the invention of a new group of novel materials like carbon nanotubes, graphene and quantum nanodots. Silicene nanoribbons (SiNRs) are one of the newest members of this nanomaterial family which has been synthesized very recently by deposition on silver substrates. A SiNR sheet is made up of a layer of two dimensional honeycomb structure solely composed of silicon atoms. In this thesis, structural and mechanical properties of SiNR are being investigated with the help of classical empirical molecular dynamics simulation technique. In the first part of this thesis, structural properties of SiNR sheets have been investigated. This investigation has been carried out by performing classical molecular dynamics simulations using atomistic many-body potential energy functions at many different SiNR sheet lengths and widths, at low and room temperatures with and without periodic boundaries. It has been found that SiNR sheets do not have perfectly flat honeycomb geometry. It has also been found that finite length models are more likely to form tubular structures resembling distorted silicon nanotubes at room temperature. In the second part of this thesis, mechanical properties of SiNRs have been investigated. Mechanical properties of silicene nanoribbons of varying width have been investigated under 5% and 10% uniaxial strain via classical Molecular-Dynamics simulations at 1 K&deg / and 300 K&deg / temperatures by the aid of atomistic many-body potential energy functions. It has been found that under strain, SiNRs show such material properties: they are very ductile, they have considerable toughness and despite their low elasticity, they have a very long plastic range before fragmentation.

In this work, adsorption of cadmium and lead from waste solutions by activated carbon was investigated. The activated carbons were produced from ion exchange resins and agricultural wastes in previous thesis studies under different conditions. BET surface areas of the activated carbons were given in previous studies. They were further characterized in this study. Slurry pH was measured by change in pH of water in which activated carbon was added. Methylene blue numbers were determined by adsorption of methylene blue onto activated carbons. Isoelectric points were determined by measuring zeta potential of activated carbons at different equilibrium pH. Results of the first part of sorption experiments showed a strong dependency of adsorption on pH since adsorption mechanism was exchange of heavy metal ions with H+ ions on the surface. Activated carbon produced from hazelnut shell had the highest removal efficiency with 95% Pb removal and 50% Cd removal at pH 6. However, activated carbon produced from apricot stone removed only 25% and 80% of Cd and Pb, respectively at the same pH. Initial concentration had positive effect on percent removal as shown by the second part of sorption experiments. This can be explained with saturation of available active sites as initial concentration increased. Activated carbon produced from hazelnut shell could remove 42% of Cd and 85% of Pb, but the one produced from synthetic resin couldn&amp / #8217 / t remove Cd and Pb more than 20% and 35%, respectively at initial concentration of 100 mg/l. Langmuir and Freundlich isotherms were plotted and both isotherms were in good agreement with experimental data.

The purpose of this study is to simulate Pt&ndash / IB (IB=Ag, Au, Cu) and PtPd bimetallic catalysts with Monte Carlo method for 201, 586, 1289, and 2406 atom containing clusters in the temperature range between 298&ndash / 1000K. The simulations were based on a coordination-dependent potential model in which binary interaction parameters were used. The binary interaction parameters were determined from the available thermodynamic data and classical thermodynamics mixing rules. The equilibrium structure of the clusters was dictated as a perfect cubo-octohedral shape. In the first part of this study, Pt&ndash / Ib bimetallics were modelled in order to test the Monte Carlo program against the previously published work. In the second part of the study, the surface composition of PtPd bimetallic catalysts as a function of temperature and cluster size were estimated in order to offer further insight to the catalytic activity for CO oxidation reaction. It was found that at low temperatures Pd segregation took place on the catalyst. The Monte Carlo predictions were in good agreement with the published experimental data on the surface compositions.

Fiber loop ring down (FLRD) spectroscopy is a sensitive spectroscopic technique that is based on absorption and it is convenient for trace chemical detection. Different FLRD systems are being improved in order to increase their sensitivity. In FLRD spectroscopy, detection of a sample is done by measuring of a leaking light at each trip within an optical cavity. Intensity of leaking light has an exponential decay where it is reduced by absorption of sample and scattering of light. In this project, two FLRD set-ups at 1535 nm and 808 nm were designed. In both set-ups, optical fiber and optical fiber couplers are used to form a cavity. At 1535 nm, a FLRD set-up is constructed by utilizing a pulsed laser and used for characterization of thin films, various pure liquids and fluorescein solutions. Two different sensor regions are designed with free space collimators and ferrules for the measurement of thin films and liquids, respectively. The future endeavor of the set-up is improvement for reliability and reproducibility of the system. For visible and NIR regions, a fiber coupled laser with four colors as 642 nm, 785 nm, 808 nm and 852 nm laser is used to design of a FLRD set-up. 808 nm laser is selected to build a prototype of the FLRD system. The construction of a closed loop FLRD set-up is completed and the system is characterized. Ultimate aim in our project is to be able to do trace detection at visible and NIR regions where the chemical sensitivity is higher.