Physical Sciences and Mathematics Commons^™

Binding Interactions Of Biologically Relevant Molecules Studied Using Surface-Modified And Nanostructured Surfaces, Palak Sondhi

Dissertations

This research focuses on the field of surface nanobioscience, wherein different nanosurfaces that will be used as working electrodes in the electrochemical cell are manufactured and surface modified to understand the critical binding interactions between biologically significant molecules like proteins, carbohydrates, small drug molecules, and glycoproteins. This research is essential if we are to determine whether a synthetic molecule can serve as a therapeutic candidate or diagnose a disease in its early stages. In order to fully understand the binding interactions, the study begins with defining some of the fundamental concepts, principles, and analytical tools for biosensing.

Afterwards, we addressed …

High Resolution Intracavity Laser Absorption Spectroscopy Of Transition Metal-Containing Diatomic Molecules, Kristin Bales

Dissertations

Three transition metal-containing diatomic molecules have been studied using intracavity laser spectroscopy. Many of the transitions were recorded using a Fourier-transform spectrometer for detection, allowing collection at Doppler-limited resolution for the gas phase molecules. Several vibrational bands in two electronic transition systems of tantalum fluoride (TaF) have been analyzed, and new molecular constants provided. Transitions involving six electronic states of tungsten sulfide (WS) have been analyzed, with new and updated constants provided, including a deperturbation analysis of three vibrational bands in two of the states. Finally, a fresh perspective on two electronic states of tungsten oxide (WO) included a deperturbation …

V-Shaped Temperature Dependences And Pressure Dependence Of Elementary Reactions Of Hydroxyl Radicals With Several Organophosphorus Compounds, Xiaokai Zhang

Dissertations

Organophosphorus compounds have brought increasing attention since they are widely used as flame-retardants, which can take effect in combustion via reactions with reactive radicals. These reactions are influenced by variables such as temperature and pressure, resulting in a temperature and pressure dependent rate constant. Studying this reaction kinetics has great importance in both combustion reaction and atmospheric environment.

This study is focused on kinetics of several elementary reactions of combustion importance. The kinetics of hydroxyl radicals were studied using pulsed laser photolysis coupled to transient UV-vis absorption spectroscopy over the 295 - 837 K temperature range and the 1 - …

Investigation Of Carbon Dioxide Oxidation Reaction Pathways On Rh(111) Via Reflection Absorption Infrared Spectroscopy (Rairs), Elizabeth A. Jamka

Dissertations

CO oxidation, RAIRS, Rh(111), Surface Science, UHV

Designing Dynamic And Degradable Polymeric Materials With Thiol-X Chemistries, Reese Sloan

Dissertations

With plastic production poised to increase in coming years, there arises a need to develop new polymeric materials designed to combat the global pollution crisis. A commonly utilized approach in addressing this challenge is to employ a responsive functional moiety into the polymer architecture. Thiol-X reactions, a commonly utilized class of “click” reactions, have garnered broad implementation in new stimuli-responsive materials. This work specifically focuses on utilizing radical-mediated thiol-ene coupling and base-catalyzed thiol-isocyanate reactions to develop a library of ternary thiol-ene/thiourethane covalent adaptable networks (CANs) and hydrolytically labile poly(thioether ketal) thermoplastics. CANs are a class of network materials capable of …

Mechanism Of Sila- And Germafluorenes For Biological Applications, Shelby Jarrett

Dissertations

2,7-disubstituted silafluorenes and germafluorenes, originally designed for OLED applications, are a class of fluorescent dyes that have gained recent interest as probes for bioimaging and as biosensors to monitor cellular dynamics and interactions. Desirable biological probes absorb in the visible region, have high extinction coefficients, high quantum yield and excellent photostability. Here, their spectral properties are investigated under aqueous conditions for relevant biological applications. These molecules display intense blue fluorescence in the solid state and in solution, have high extinction coefficients, and exhibit appreciable solubility in aqueous solution. To better understand potential applications, the mechanism of fluorescence was investigated. It …

Controlling Degradation With Force And Light, Brad Davis

Dissertations

Stimuli-responsive polymers respond to changes in their environment by altering their physical and chemical properties. Their responsiveness allows them to be used as sensors, mechanical actuators, delivery systems, and can yield either elongated lifetimes through healing mechanisms or shortened lifetimes through triggered degradation. Still a growing field in polymer science, researchers seek to expand the capabilities of these materials by improving their specificity, range, and mechanisms of both the stimuli and the response. The work presented explores stimuli-responsive materials, focusing on mechanical and light stimuli, and how to gain control of the response by specific changes in the polymeric material. …

Doping Of Conjugated Polymers: Preparation, Characterization And Device Fabrication, Kan Tang

Dissertations

Semiconducting conjugated polymers (CPs) as emerging materials for advanced electronic applications such as sensors, OPVs, and OEFTs has become an intriguing research topic in the past decades. It opens a new avenue of “flexible” electronics, which has shown great potential in next-generation electronic devices.

However, due to the nature of CP materials and related solution processing techniques, unlike almost perfectly crystalline silicon materials, CPs in the solid-state often exhibit much lower crystallinity if it is not complete amorphous, which severely hinder the electronic property and optical property of the materials. The crystallinity of CPs in a film is often uniquely …

Identification Of New Pathways For Co Oxidation On Rh(111) & Spatial And Structural Control Of O-Induced Reconstruction Of Ag(111), Marie Turano

Dissertations

Understanding the fundamentals of oxygen surface structures under a variety of conditions is pivotal to determining reactivity of heterogeneous catalysis. Exposure of catalytically active metal surfaces to high oxygen coverages results in a myriad of surface structures. A further complication is the formation of subsurface oxygen (Osub) or oxygen present in the near subsurface region of the metal. It is known to form in transition metals yet the absorption of oxygen and resultant formation of Osub is not equivalent across all catalytically relevant metals. As a result, it is difficult to predict the stability and efficacy of the formation of …

An Atomistic Study Of The Effects On Mechanical Properties And Bonding Interactions Of Carbon Nanofillers In Nylon 6 Nanocomposites, Michael Roth

Dissertations

Polymers have potential for a wide range of applications. The effectiveness of polymers can be further enhanced through the addition of nanofillers that improve thermal, mechanical, and electrical properties of the polymer. Carbon based nanofillers such as carbon nanotube (CNT), graphene, and carbon nanofibre (CNF) are of particular interest due to their high properties and high aspect ratios. However, limited understanding of the governing interactions of these nanofillers with polymers limits the effectiveness of the final nanocomposite.

The first facet of this dissertation focuses on determining the dominating interactions between pristine CNT and graphene with nylon 6 monomer and the …

Engineering Multifunctional And Morphologically Diverse Polymer Brush Surfaces, Cassandra M. Reese

Dissertations

The combination of surface-initiated polymerization (SIP) and post-polymerization (PPM) serves as a powerful approach to fabricate complex, multifunctional polymer films, which can be precisely tuned for desired surface engineering applications. Careful manipulation of PPM parameters such as reaction conditions, the tethered brush parameters, and the physical properties of the unbound post-modifier greatly influence the depth of penetration of the post-modifier and the polymer brush compositional heterogeneity. This dissertation focuses on engineering polymer brush surfaces with multifunctional chemistries and tunable morphologies by investigating the PPM parameters that dictate the distribution of post-modifiers on grafted polymer brush surfaces.

The first chapter of …

High Resolution Near-Infrared/Visible Intracavity Laser Spectroscopy Of Small Molecules, Jack Harms

Dissertations

Intracavity laser spectroscopy has been used to study the electronic structure of several small molecules. The molecules studied as part of this dissertation include germanium hydride (GeH), copper oxide (CuO), nickel chloride (NiCl), platinum fluoride (PtF), platinum chloride (PtCl), and copper hydroxide (CuOH). This work encompasses five peer-reviewed publications and two submitted manuscripts.

Effect Of Network Structure On Free Volume And Gas Transport Properties Of Thiol-Ene And Epoxy-Amine Networks, Ramesh Krishnan Ramakrishnan

Dissertations

Network parameters such as cross-link density or intermolecular interactions were used as effective parameters to control polymer chain packing or free volume and thereby control the mass transport properties of networks.

A series of polyethylene glycol (PEG) based thiol-ene elastomeric networks having a broad range of molecular weight between cross-links, M_c, (inverse of cross-link density) was prepared. The specific volume of the networks was studied as a function of temperature and pressure using high pressure dilatometry, and the obtained PVT data was fit using Simha-Somcynsky equation of state (S-S eos) analysis. Fractional free volume, quantified through S-S eos …

Synthetic And Theoretical Studies For Cyclization Reactions To Form C-C And C-N Bonds, Nicholas Jentsch

Dissertations

Natural product total synthesis provides an alternative method for obtaining medicinally relevant compounds in a more efficient process with higher yields than what nature can provide. Natural products pose significant synthetic challenges due to the unique heterocyclic skeletons with fused and spirocyclic ring systems. Therefore, it is paramount to develop efficient reaction methodologies targeting substructures such as cyclic ureas and spiro[4.5]decanes which are prominent among marine natural products and Lycopodium alkaloids, respectively. Presented here is a compilation of research seeking to develop synthetic methods for the construction of cyclic moieties such as those previously mentioned. The objectives that are addressed …

Investigation Of Vaporization Enthalpies And Vapor Pressures Of Organic Compounds By Correlation Gas Chromatography, Carissa Nelson

Dissertations

Thermodynamic properties of organic compounds are useful to scientists and manufacturers in many areas of research and technology. This work focuses on measuring and reporting these properties on materials of commercial, environmental and scientific interest. Vaporization enthalpies and vapor pressures of several organic compounds have been studied using correlation gas chromatography (CGC) and are reported here as well as in recent publications. The CGC method allows for the indirect measurement of these properties in instances where these materials are available only in mixtures or in very small amounts.

The qualities of these measurements for any chosen target are directly related …

Thermosetting Polymers Via Azide Alkyne Cycloaddition, Richard H. Cooke Iii

Dissertations

This dissertation exploits properties inherent to azide-alkyne cycloaddition and applies practical solutions to difficult problems. Chapter II addresses structure-property relationships in glassy azido-alkyne matrices by varying the identity of the central linkage within tetrapropargyl bis-aniline-type crosslinkers, and by the addition or omission of Cu(I) catalyst. This systematic study showed that an ether or methylene linkage yielded lower melting tetrapropargyl crosslinkers that were soluble in, and produced homogeneous, networks when cured with, a standard azido resin, di(3-azido-2-hydroxypropyl) ether of bisphenol-A; in contrast, a sulfone linkage yielded a relatively insoluble crosslinker and poorly dispersed, heterogeneous networks when reacted with the same …

Photoelectrochemical Studies On Non-Noble Metal Based Catalysts Towards Tandem Solar Water Splitting, Arun Siddarth Sridhar

Dissertations

Photoelectrochemical (PEC) water splitting makes direct use of solar energy incident on semiconductor photoelectrodes, and it is a convenient, economic option to produce high purity hydrogen at low temperatures. The use of multiple light absorbers can increase overall solar energy utilization and provide a solution to the trade-off between overall band gap and band edge positioning of photoelectrodes specific to solar water oxidation and water reduction. The study of non-noble metal based catalysts for hydrogen evolution reaction (HER) and oxygen evolution reactions (OER) are essential for economic practical commercialization of photo-electrolyzers. This dissertation focuses on the use of a variety …

Structural And Chemical Consequences Of High Oxygen Coverages On Rh(111), Rachael Gabrielle Farber

Dissertations

Partial oxidations of small molecules over metal surfaces are central to many heterogeneously catalyzed reactions. However, the identity of the actual surface species that promote or hinder these reactions has remained elusive for a variety of reasons. Recently, the understanding of the role of surface oxides in catalytic activity has changed. Instead of being thought of as poisons, they are now believed to be effective promoters of selective catalysis.

Rhodium (Rh) effectively promotes oxidation reactions and is a benchmark system for models of heterogeneously catalyzed chemistry. For this reason, Rh(111) was chosen as the model system for this dissertation work. …

Synthesis And Catalytic Evaluation Of Novel C-Alpha-Methyl-Beta-Proline Analogues, And Concise Synthetic Approach To Nh-Fmoc-S-Trityl-C-Alpha-Methyl Cysteine, Hari Kiran Kotapati

Dissertations

In the field of chemistry there is a growing demand for small molecule organocatalysts such as amino acids, more specifically proline and its analogues, which could catalyze various key chemical reactions in the synthesis of several biologically important molecules. Even though natural proline is reported to catalyze various chemical reactions, its use as organocatalyst is limited mainly due to the solubility issues in the reaction media and high catalyst loadings, which is not very ideal for bulk scale manufacturing. To address these limitations we planned to develop unnatural analogues of proline that could catalyze the reactions with lower catalyst loadings …

Property Morphology Correlations Of Organic Semiconductor Nanowires, Frederick Marshall Mcfarland

Dissertations

Chemically doped and non-doped P3HT nanoaggregates are studied to establish a comprehensive understanding of the interplay between their morphology and various optoelectronic properties. One-dimensional nanoaggregates of P3HT are chosen as the model systems here due to their high surface/volume ratio and suitability for microscopic investigations.

Atomic force microscopy (AFM) and kelvin probe force microscopy (KPFM) are used to correlate property/morphology characteristics of non-doped P3HT nanowhiskers. Topographical measurements indicate that individually folded P3HT motifs stack via interfacial interactions to form nanowhiskers in solution. Further aging leads to multi-layered nanowhiskers with greater stability and less instances of π-π sliding of interfacial edge-on …

Preparation And Characterization Of Singlet-Oxygen Generating Thiol-Ene Networks Containing Fullerene And Metallofullerene Derivatives, Emily Matthews Barker

Dissertations

This work explores the derivatization of C₆₀ and Sc₃N@C₈₀ with S-, P-, and C- centered radicals, and is the first exploration into the functionalization of Sc₃N@C₈₀ with sulfur and phosphorous. The number of addends bound to C₆₀, as a function of reaction time and molar ratios, as well as, structure-property relationships including thermal stability, solubility, and singlet oxygen generation were explored. Fullerene derivatives exhibiting enhanced solubility were incorporated into two different thiol-ene polymer matrices at varying thiol-ene monomer concentrations (1:1 or 1:0.75 molar equivalents) and at different C₆₀ loadings (0, …

Surface And Interfacial Design And Control Of High Performing Thermoplastics: Polysulfones And Beyond, Katrina Marie Knauer

Dissertations

The study of a class of materials almost always begins with the development of an understanding of properties in the bulk state. However, it is the study of surface critical phenomena that has led to a number of new important insights into polymer behavior. A systematic understanding of physical properties in the immediate vicinity of surface and interfacial layers, which cannot be deduced by simple extrapolation of bulk properties, is of significant importance for advancements in polymer applications where the interface drives performance, such as in membranes, coatings, drug-delivery systems, medical devices, and composites.

First, the surface and interfacial modification …

Atomic Oxygen Adsorption And Absorption On Rh(111) And Ag(111), Jonathan Derouin

Dissertations

A central question in the field of heterogeneous catalysis is how surface structure and subsurface species influence catalytic behavior. One key to answering that question is determining which surface structures and subsurface species are present under catalytically relevant conditions. This dissertation presents results of Auger electron spectroscopy, low energy electron diffraction, temperature programmed desorption, and scanning tunneling microscopy experiments on oxidized Rh(111) and Ag(111) crystals. Exposing Rh(111) to O2 produced a predominately (2 × 1) adlayer, but even after extended dosing, (2 × 2) domains were also present. Exposing Rh(111) to atomic oxygen yielded O coverages greater than 0.5 ML …

Hydrogen Bond-Mediated Structural Order In Hydroxylated Bis-Mpa Dendritic Polymers: Experimental And Molecular Dynamics Simulation Study, Maliha N. Syed

Dissertations

Dendritic architectures are echoed throughout nature. While the significance of these pervasive patterns is not entirely clear, connections between their structures and physical properties are fascinating to contemplate. Particular interest has been paid to a family of synthetically manufactured and commercially available dendritic polymers based on 2,2-bis(hydroxymethyl) propionic acid (bis-MPA) as a monomer. Composed of two hydroxyls and a carboxyl group, bis-MPA based structures hydrogen bond (H-bond) profusely. Given the high concentration and unique spatial orientation of end-groups, as well as the multitude of carbonyl, ester, and ether interior H-bond acceptors, a set of distinct H-bond organizations may be observed …

Investigations Of The Photocatalytic Activity And Self-Cleaning Properties Of Polyhedral Oligomeric Silsesquioxane (Poss) Containing Titania Thiol-Ene Films, Lacrissia Unsonta Jefferson

Dissertations

In this document the film composition, self-cleaning aspect, photocatalytic efficiency, and methods employed to analyze a novel photocatalytic titania-containing thin film was evaluated. A primary objective of this research project was to assess the conditions required to achieve a stable titania dispersion for the photocatalytic coating and to determine the extent to which the presence of additives contributes to this process. Modified titania dispersions were prepared and characterized via dynamic light scattering (DLS), transmission electron microscopy (TEM), fourier transmission infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA). Characterization details of the previous focus on the influence of polyhedral oligomeric silsesquioxane (POSS) …

Investigation Into Select Isoquinolines As A Putative Causal Agent Of Ethanol Addiction In Mammals, Jacob Christopher Strawbridge

Dissertations

Alcohol is the most abused drug in America today. The neurological root of the problem is still a much debated subject and many differing views exist on the nature of alcoholism, be it a social dysfunction or a neurochemical imbalance. Some researchers have proposed that a skewed metabolism of dopamine that results in the formation of tetrahydroisoquinoline (THIQ) alkaloids plays a major role in the neurochemical acquisition and maintenance of alcohol addiction. In an effort to better understand the relationship of THIQ's to alcohol addiction, a series of experiments have been conducted. The chiral separation via high pressure liquid chromatography …