Chemistry Commons^™

Synthesis And Characterization Of Anhydrous Proton Conducting Polymer Electrolytes For Fuel Cell Applications, Buddika Mayomi Liyanage

Electronic Theses and Dissertations

Anhydrous H+ ion conducting and high temperature capability of polymer electrolytes are being investigated for use in applications such as batteries, fuel cells, electro chromic windows and light emitting devices. Fuel cells are efficient electrochemical energy conversion devices; they can generate greener energy from chemical fuels. The polymer electrolyte membrane is heart of most fuel cell designs separating the oxidant and fuel chambers and providing the medium to conduct H+ ions between the anode and the cathode. Our goal is to understand the molecular level details of anhydrous H+ conductivity through the synthesis and characterization of polymer electrolytes based on …

Biophysical Characterization Of A Proline Mutant Of Neural Cadherin, Keshia S. Dykes

Electronic Theses and Dissertations

Cadherins are calcium dependent glycoproteins whose homophilic interactions mediate cell-cell adhesion in solid tissues. They are comprised of an extracellular region, a transmembrane region and a cytoplasmic region. The extracellular region plays a critical role in cadherin-mediated cell adhesion, and has five tandemly repeated ectodomains (ec1-ec5), with three calcium binding sites situated in each interface between the domains. Dimerization of cadherin occurs through formation of adhesive interactions between extracellular domains of cadherins from neighboring cells. Adhesive interaction occurs at the interfaces of ec1 domains of two molecules originating from different cell surfaces. Dimerization is critically dependent on the binding of …

Degradation Of Hexachlorobenzene, Pentachlorophenol And Pentachloroanisole Using Activated Magnesium In An Acidified Ethanol/Ethyl Lactate Cosolvent System, Amel Garbou

Electronic Theses and Dissertations

For many centuries, chemists have dedicated many labor-intensive hours to improving the quality of life for mankind by developing synthetic methods for the production of compounds which fulfill the needs and meet the demands of society. However, the innovation of such compounds has frequently come at the cost of detrimental side-effects that do not always present themselves until many years, or even decades, following their initial application. Many compounds in this category come in the form of globally-distributed halogenated molecules which are toxic to many living organisms, susceptible to bioaccumulation and resistant to biodegradation processes. Such compounds are classified as …

Analysis Of Benzopyrenes And Benzopyrene Metabolites By Fluorescence Spectroscopy Techniques, Bassam Al-Farhani

Electronic Theses and Dissertations

Polycyclic aromatic hydrocarbons (PAHs) are some of the most common and toxic pollutants encountered worldwide. Presently, monitoring is restricted to sixteen PAHs, but it is well understood that this list omits many toxic PAHs. Among the "forgotten" PAHs, isomers with molecular weight 302 are of particular concern due to their high toxicological properties. The chromatographic analysis of PAHs with MW 302 is challenged by similar retention times and virtually identical mass fragmentation patterns. The first original component of this dissertation evolves from a high-resolution spectroscopic approach specifically developed to fulfil this gap. Herein, 4.2 K Laser-Excited Time-Resolved Shpol'skii Spectroscopy (4.2K …

Anodic Metal Dissolution In Haloaluminate Molten Salts/Ionic Liquids, Chen Wang

Electronic Theses and Dissertations

The anodization of Aluminium was investigated in the low-melting, mixed halide molten salt system, lialbr4-naalcl4-kalcl4 (30-50-20 m/o), and in the Lewis acidic Chloroaluminate ionic liquid, aluminum chloride-1-ethyl-3-methylimidazolium chloride (alcl3-etmeimcl) using rotating disk electrode voltammetry. In both cases, at modest overpotentials, the anodization reaction proceeds under mixed kinetic/mass-transport control. However, at larger positive overpotentials and correspondingly higher anodization rates, the reaction transitions to a mass transport-limited process governed by the dissolution of a passive layer of alcl3(s) and/or albr3(s) on the electrode surface. In alcl3-etmeimcl, the passive current density scales linearly with the concentration of alcl4- in the ionic liquid. The …

The Owl Sensor: A Smart Nanostructure For Single Nucleotide Variation Analysis, Rebekah Karadeema

Electronic Theses and Dissertations

Analysis of single nucleotide variations (SNVs) in DNA and RNA sequences is extensively used in healthcare for detection of genetic mutations and analysis of drug resistant pathogens. Here we developed a nucleic acid sensor able to differentiate between a fully matched analyte and one with a SNV in a wide temperature range of 5°C-32°C. The sensor, dubbed here the 'Owl Sensor' due to the complex's resemblance to owl eyes, utilizes recent developments in DNA nanotechnology and synthetic biology to self-assemble a fluorescent DNA nanostructure called a Double Crossover, or DX Tile, capable of differentiating SNVs in a large temperature range, …

Theoretical-Experimental Study Of The Two-Photon Circular Dichroism Of Helicenes And Aromatic Amino Acids In The Uv Region: From The Structure-Property Relationship To The Final Implementation, Yuly Katherine Vesga Prada

Electronic Theses and Dissertations

Two-photon circular dichroism (TPCD) has been recognized for its exceptional spectroscopic ability for the structural and conformational analysis of chiral systems due to its high sensitivity to small peptide structural distortions. In 2008, Hernandez and co-workers demonstrated TPCD experimentally by the development of the Double L-scan technique. Since then, we have been working on a systematic theoretical-experimental study of chiral molecules using TPCD. In this dissertation, I present my contribution to the continuation to the study of the structure-property relationship of TPCD in molecules with axial chirality in solution, as well as the implementation of the TPCD measurements in the …

Multidimensional Room-Temperature Fluorescence Microscopy For The Nondestructive Analysis Of Forensic Trace Textile Fibers, Nirvani Mujumdar

Electronic Theses and Dissertations

The purpose of this dissertation is to advance nondestructive methodology for forensic fiber examination. Non-destructive techniques that can either discriminate between similar fibers or match a known to a questioned fiber – and still preserve the physical integrity of the fibers for further court examination - are highly valuable in forensic science. A challenging aspect of forensic fiber examinations involves the comparison of fibers colored with visually indistinguishable dyestuffs. This is not an uncommon situation, as there are numerous indistinguishable fibers pre-dyed with commercial dyes of virtually identical colors. Minimal chemical structural variations are actually encouraged by the dye patent …

Study Of Polychlorinated Biphenyl Dechlorination By Zero Valent Magnesium With And Without Activated Carbon In Acidified Ethanol-Ethyl Lactate System, Fiona Zullo

Electronic Theses and Dissertations

Polychlorinated biphenyls (PCBs) are synthetic organic chemicals that ca de detected in the environment worldwide. PCBs were banned in the U.S in 1979 owing to their toxicity and persistence in the environment. Today PCBs are classified as human carcinogens and are among the top ten of the U.S Environmental Protection Agency's (EPA) most toxic chemicals. Many researchers have shown soil to be contaminated with PCBs at concentrations as high as 750 ppm. Given the toxicity of PCBs, there is an urgent need to extract and degrade such chemicals from contaminated soil in a cost effective way. Prior work revealed a …

The Unique Electrochemical Reactivity Of Small Metal Nanoparticles., Rafael A. Masitas

Electronic Theses and Dissertations

This dissertation describes the factors controlling metal nanoparticle (NP) oxidation, using Au oxidation in Br- and Ag oxidation in acid as model systems. We found that the oxidation potential depends on size, surface charge, and electrode material. Size has a dramatic effect, shifting about 200 mV from > 200 nm diameter down to 4 nm diameter. The shift is more dramatic below 4 nm. 2.3 nm average diameter Au NPs oxidized in the 300-500 mV range and 1.5 nm average diameter Au NPs displayed several sharp peaks from 200 mV to as low as -200 mV. These smallest Au NPs show …

Electrochemical Formation Of One-Dimensional Metal Nanostructures Across Microgaps Electrodes For Resistive Switching And Optical Sensing Applications., Nidhi Shah

Electronic Theses and Dissertations

This dissertation focuses on the electrochemical formation of one-dimensional (1D) Ag nanostructures (in particular nanowires and nanochains) directly on electrode surfaces or gap of two electrodes. Ag nanowires (NWs) and nanorods (NRs) grow directly on glass/indium tin oxide (ITO) surfaces from electrode-attached Au nanoparticle seeds in the presence of cetyltrimethylammonium bromide (CTAB) at appropriate potentials with a 5-15 % yield and the average length ranging from 100 nm to 3 µm for growth times of 30 to 120 min. This method failed when trying to grow Ag NRs/NWs across 5 µm Au electrode gaps. Interestingly, applying voltage in air leads …

Optical And Sensing Properties Of Various Shaped Gold Nanoplates And Highly Controlled Asymmetric Gold Nanoplate/Nanosphere Coupled Assemblies., Aiqin Fang

Electronic Theses and Dissertations

With the development of a strategy to correlate the dark-field light scattering spectra of individual nanostructures with scanning electron microscopy (SEM) and atomic force microscopy (AFM) images of the same nanostructures, we were able to investigate several interesting optical properties of Au nanoplates (NPs) and asymmetrically-coupled Au nanospheres (NSs) attached to Au NPs with a high level of control. The light scattering spectra of the NP/NS coupled structures depend strongly on the location of NS attachment on the NP. Attachment of multiple NSs at the edge/vertex sites leads to a unique synergistic effect. In contrast to the uniform distribution of …

Linkage Analysis And Compositional Studies Of Β-Glucan From Saccharomyces Cerevisiae And Compositional Studies Of Mannan From Candida Albicans, Clara Arthur

Electronic Theses and Dissertations

The efficacy of a novel carbohydrate extraction procedure was investigated with methylation analysis and alditol acetate method by Gas Chromatography-Mass Spectrometry. A published extraction procedure for β-glucans was compared to one developed in house. Both procedures gave a dominant glucose peak in the Gas chromatogram indicative of successful β-glucan isolation. Further linkage studies showed four linkage positions for β-glucans isolated with the published method; terminal, 1,3-linkage, 1,6-linkage and 1,3,6-linkage, while β-glucans isolated using the new method showed six linkage positions; terminal, 1,3-linkage, 1,6-linkage, 1,4-linkage, 1,2,3-linkage and 1,3,6-linkage. Diminishing β-glucan linkage peaks in the chromatogram for the published method indicated structure …

Methodology Study Of N-Deacetylation Of 4-Acetamido-Perfluoroalkylbenzenesulfonimide, Grace Abban

Electronic Theses and Dissertations

In order to improve the synthetic route for diazonium perfluoroalkyl benzenesulfonylimide (PFSI) zwitterionic monomers, N-deacetylation of the coupling product was proposed to replace the reduction of aromatic amine intermediates. A series of hydrolysis methods, such as acid and base catalyzed refluxing, were explored for the N-deacetylation to obtain the PFSI aromatic amine. Factors such as temperature, concentration of acid/base and the time needed for the reaction to take place were investigated in an attempt to optimize the reaction condition. The basic hydrolysis was preferred since it was expected to carry out the N-deacetylation and debromination in one …

Candida Albicans Hyphal Mannan Is Structurally Distinct From Yeast Mannan, Francis Kwofie

Electronic Theses and Dissertations

C. albicans is a polymorphic fungal pathogen which has the ability to shift from yeast to hyphae. C. albicans cell wall is composed of glucan, chitin, mannoprotein and mannan. It is not possible, using standard extraction methods, to isolate mannan from C. albicans hyphae. To isolate hyphal mannan, we developed a simplified alkali extraction method. Using this method it was determined that hyphal mannan has a much lower molecular weight, a smaller polymer distribution and altered conformation structure when compared to yeast mannan. The hyphal mannan was found to contain little to no acid-labile portion with only α-Man-PO₄ groups …

Synthesis Of Phenothiazinium Derivatives, Selorm J. Fanah

Electronic Theses and Dissertations

Photodynamic therapy (PDT) employs photosensitizing drugs for treating cancer. Once introduced into the body and localized in tumor cells, these photosensitizers are irradiated with light to produce active singlet oxygen radicals which kill cancer cells. The current drugs used in PDT have low quantum yield and always require a high energy radiation (normally laser). There is always a need for more effective drugs that have a high quantum yield and can be activated by visible light, in order to eliminate side effects caused by laser radiations.

In this work we synthesized derivatives of phenothiazine and phenothiazinium chromophores from the commercially …

Application Of Surface Chemistry At The Interface Of Mesoporous Tio2 Films For Stable And High Efficiency Dye-Sensitized Solar Cells., Tulashi Luitel

Electronic Theses and Dissertations

Solar energy is widely believed to be the most promising renewable energy source to fulfill the ever-increasing energy demand from human society now and into the future. Dye-sensitized solar cells (DSSCs) have been explored as a potentially low-cost alternative to silicon solar cell technology due to their lower fabrication costs compared to crystalline semiconductor photovoltaics. However, the optimized efficiency for DSSCs has not been achieved yet, and the chemical stability between dye and semiconductor has also not been addressed completely. In this research, we applied the following four main strategies to prepare photoanodes used in DSSCs with the aim of …

Phosphinimine Zinc Complexes And Neutral Phosphinimines For Ring Opening Polymerization Of Lactides., Rajesh Thapa

Electronic Theses and Dissertations

Achiral arenesulfonates ligands having a (NNN) or (NNO) side arm have been developed (Chapter 2) and their respective zinc ethyl complexes, NNNZnEt 3.2 and NNOZnEt 3.3, have been synthesized and characterized using spectroscopic methods (Chapter 3). NNNZnEt as well as NNOZnEt complexes are stable under nitrogen atmosphere. In the NNOZnEt 3.3 complex the protons associated with the pendant (dimethylamino)ethyl arm are broad indicating that a fluxional process is operative, most likely dissociation of the (dimethylamino)ethyl arm at 25 °C in CD2Cl2. The fluxional behavior present in the 1H NMR spectrum of 3.2 could be arrested by cooling the CD2Cl2 solution …

Sulfur-Oxidation Enhances Nitrile Hydration In Bioinspired Ruthenium Complexes : Catalytic, Kinetic, And Dft Investigations., Davinder Kumar

Electronic Theses and Dissertations

The current dissertation focuses on the effects of sulfur‒oxidation on nitrile hydration activity of a series of ruthenium(II) complexes inspired by nitrile hydratase (NHase). NHase catalytically hydrates nitriles to amides at a low spin non‒heme Fe(III) or non‒corrin Co(III) metal center. The active‒site employs a N2S3X type donor set using two carboxamido nitrogens and three cofacial cysteinic sulfurs that are present in distinct oxidation states as sulfinate (RSO2¯), sulfenate (RSO¯), and thiolate (RS¯). The apical site is occupied by substrate or solvent. A lack of sulfur‒oxidation renders the enzyme inactive. Three precatalysts, LnRuPPh3 (n = 1‒3), are employed to assess …

Analysis Of Anacardic Acid On The Surface Of Pelargonium × Hortorum Using Matrix Assisted Laser Desorptoin Ionization Mass Spectrometry Imaging., Bryan Edward Wessel 1989-

Electronic Theses and Dissertations

The biosynthetic pathway leading to the production of anacardic acids (AnAcs) in glandular trichomes on the surface of geranium plants remains unclear. Anacardic acids are salicylic acid derivatives known to possess various medicinal benefits. Gene silencing techniques, such as RNA interference, could be useful in determining specific enzymes involved in the synthesis of AnAcs. However, it is first necessary to develop methodologies to image AnAcs. In this project, both fluorescence (FL) and mass spectral imaging (MSI) were tested. Our results indicate that cellular imaging of AnAcs, via FL, is not suitable because the spectral ranges of absorption and emission of …

A Study Of The Catalytic And Chemical Properties Of Palladium And Palladium-Silver Monolayer Protected Clusters., Luther Benjamin Hutcherson

Electronic Theses and Dissertations

This thesis describes a study of the ligand chemistry of Pd Monolayer-Protected Clusters (MPCs) synthesized in the presence of octylamine. MPCs consists of a metal core surrounded by various organic stabilizers. Pd MPCs coated with alkanethiols, alkylamine, dendrimers, surfactants, and polymers have recently been explored for catalysis applications.Pd MPCs coated with alkylamines are more catalytically active than alkanethiols for hydrogentation/isomerization of allyl alcohol, but at shorter chain lengths are unstable in H2. We explored Pd MPCs synthesized in the presence of octylamines and discovered that the ligands attach to Pd as octanenitrile. This amine to nitrile conversion is catalyzed by …

Effects Of Select Vitamin E Isoforms On The Production Of Polyunsaturated Fatty Acid Metabolites In Colorectal Cancer, Martha A. Borketey

Electronic Theses and Dissertations

Vitamin E exhibits anti-tumor activity by regulating pathways in cancer cells, potentially the lipoxygenase (LOX) pathway. We studied the effects of alpha tocopherol (AT), gamma tocopherol (GT), gamma tocotrienol (GT3), and an alpha-gamma tocopherol mixture (ATGT) on the production of the LOX metabolites 13-hydroxyoctadecaenoic acid (HODE), 15-hydroxyeicosatetraenoic acid (HETE), 12-HETE, and 5-HETE in colorectal cancer. These metabolites were examined in the HCT-116 cell line after 24 h treatment with select vitamin E isoforms and quantified by LC/MS/MS. Under physiological conditions, we find that treatment with varying vitamin E isoforms have different effects on the production of 13-HODE, 15-HETE, 12-HETE, and …

Optimized Acid/Base Extraction And Structural Characterization Of Β-Glucan From Saccharomyces Cerevisiae, Shardrack O. Asare

Electronic Theses and Dissertations

β-glucan is a major component of the fungal cell wall consisting of (1→3)-β linked glucose polymers with (1→6)-β linked side chains. The published classical isolation procedure of β-glucan from Saccharomyces cerevisiae is expensive and time-consuming. Thus, the aim of this research was to develop an effective procedure for the extraction of glucans. We have developed a new method for glucan extraction that will be cost effective and will maintain the native structure of the glucan. The method that we developed is 80% faster and utilizes ¹/₃ of the reagents compared to the published classical method. Further, the method …

Synthesis And Characterization Of Five New Tetrakis(N-Phenylacetamidato) Dirhodium(Ii) Amine Complexes And One Molybdenum Cofactor Described Crystallographically, Cragin K. Harris

Electronic Theses and Dissertations

Six new crystal structures were determined using a Rigaku Mercurcy 375/MCCD(XtaLab mini) diffractometer. The structure of a molybdenum cofactor was solved resulting in an R1 (R1 = Σ ||Fo| - |Fc|| / Σ |Fo|) of 3.61% despite the presence of a disordered DMSO molecule. New Tetrakis(N-phenylacetamidato) Dirhodium(II) complexes were synthesized and characterized. Two 2,2-cis-[Rh2(NPhCOCH3)4]•(C3H4N2)x where x= 1 or 2 were successfully crystallized and solved with R1 values below 5%. Additional studies were conducted via NMR to observe formation of both products. Three potential catalysts were synthesized starting with 3,1-[Rh₂(NPhCOCH₃)₄]. The resulting compounds were a …

Rapid Scan Electron Paramagnetic Resonance (Epr) And Digital Epr Development, Zhelin Yu

Electronic Theses and Dissertations

Rapid scan electron paramagnetic resonance (EPR) was developed in the Eaton laboratory at the University of Denver. Applications of rapid scan to wider spectra, such as for immobilized nitroxides, spin-labeled proteins, irradiated tooth and fingernail samples were demonstrated in this dissertation. The scan width has been increased from 55 G to 160 G. The signal to noise (S/N) improvement for slowly tumbling spin-labeled protein samples that is provided by rapid scan EPR will be highly advantageous for biophysical studies. With substantial improvement in S/N by rapid scan, the dose estimation for irradiated tooth enamels became more reliable than …

Measurement Of Particulate Transition Metals And Atmospheric Processing Of Iron, Benton T. Cartledge

Electronic Theses and Dissertations

The work presented herein details the measurement of particle-bound metals in environmental samples with specific interests in iron (Fe) in atmospheric particulate matter. Metals were measured in ambient PM_2.5 to study the effects and contributions of a light rail system on the concentrations of metals in atmospheric particles. Particulate matter samples were collected on board trains, near the tracks, and at an urban background location in Denver, CO. Metals were found to be enriched in particles collected on board the trains more so than at the other locations. Fe speciation was also measured in the soluble fraction of the …

Synthesis And Characterization Of New Probes For Use In Fluorescence And X-Ray Ct Bioimaging, Simon Tang

Electronic Theses and Dissertations

The pursuit of more suitable drugs intended for possible biological applications are a continuously growing topic of research within the scientific community. One of these suitable qualities includes the need for hydrophilicity and or some appropriate delivery system for the drug to enter into biological systems. A system of analyzing and following these compounds would then, however, be necessary to conduct any kind of mechanistic or interaction studies for he said drug within the biological system. Just to name a few, fluorescence and X-ray computed tomography (CT) methods allow for imaging of biological systems but require the need of compounds …

Fluorescent Biological Aerosol Particles In Coastal Canada And The Link To Atmospheric Ice Nuclei, Jixiao Li

Electronic Theses and Dissertations

Bioaerosols are a subgroup of atmospheric aerosols and are often linked to the spread of human, animal and plant diseases. Bioaerosols also may play an indirect effect on environmental processes, including the formation of precipitation and alteration of the global climate through their role as nuclei for cloud droplet formation. Several types of biological organisms (e.g., fungi and bacteria) have been shown to be effective ice nuclei (IN) and cloud condensation nuclei (CCN).

During 21 days in August 2013 we participated in a collaborative international campaign at a rural, coastal site near the village of Ucluelet on the west coast …

New Methods For Measuring Transient Interactions Between Proteins And Curved Membranes, Philip P. Cheney

Electronic Theses and Dissertations

Variations in the physical deformation of the plasma membrane play a significant role in the sorting and behavior of the proteins that occupy it. Determining the interplay between membrane curvature and protein behavior required the development and thorough characterization of a model plasma membrane with well defined and localized regions of curvature. This model system consists of a fluid lipid bilayer that is supported by a dye-loaded polystyrene nanoparticle patterned glass substrate. As the physical deformation of the supported lipid bilayer is essential to our understanding of the behavior of the protein occupying the bilayer, extensive characterization of the structure …

The Effects Of Molecular Chaperones On Tau Fibril Assembly, Ahmed Omran

Electronic Theses and Dissertations

The accumulation of microtubule-associated protein tau into fibrillar aggregates is the hallmark of Alzheimer’s disease and other neurodegenerative disorders, collectively referred to as tauopathies. Fibrils can propagate from one cell to the next and spread throughout the brain. However, a study shows that only small aggregates can be taken up by cultured neuronal cells. The mechanisms that lead to the breakage of fibrils into smaller fragments remain unknown. In yeast, the AAA+ chaperone HSP104 processes the reactivation of protein aggregates and is responsible for fragmentation of fibrils. This study focused on investigating the effects of molecular chaperones on tau fibrils …