Physical Sciences and Mathematics Commons^™

Investigations Into Ambient Ionization Mechanisms: Electrospray Ionization And Direct Analysis In Real Time Mass Spectrometry, Stephen Colin Gibson

Doctoral Dissertations

Mass spectrometry (MS) is an important tool for chemical analyses. Despite the MS requirement for generation of analyte gas-phase ions, many ion source designs afford little-to-no fragmentation, allowing characterization of intact molecules. However, this does not assure that detected ions are representative of the analytes’ natural state. Ionization mechanisms are generally complex and rarely fully understood. Fundamental research into these mechanisms provides greater insight into the relationship between solution chemistry and mass spectra. Work herein addresses aspects of two ambient ionization mechanisms: electrospray ionization (ESI) and Direct Analysis in Real Time (DART).

Ions produced by ESI are dispersed into a …

Synthesis And Thermodynamic Analysis Of Volatile Beta-Diketone Complexes Of Select Lanthanides Via Gas-Phase Separations, Daniel Hanson

Doctoral Dissertations

Rapid separation techniques for fission and activation products have long been desired to supplant the slow solution-based methodologies currently used. In this work, rare earth elements were derivatized with β [beta]-diketones to synthesize rare earth complexes with high volatility suitable for gas-phase separations. Rare earth elements samarium and dysprosium were combined with hfac (1,1,1,5,5,5-hexafluoro-2,4-pentadione) and fod (6,6,7,7,8,8,8-heptafluoro-2,2-dimethyl-3,5-octanedione) and analyzed using a gas-phase separation technique. Rare earth elements praseodymium and europium were combined with dpm (2,2,6,6-tetra-methyl-3,5-heptanedione) and similarly analyzed. Employing the data from the separations, the entropy (Δ [delta] S) and enthalpy (Δ [delta] H) of adsorption were evaluated mathematically based …

Photo-Switchable Control Of Membrane Properties Of Liposomes And Biochemical Processes, Andrew Michael Bayer

Doctoral Dissertations

Liposomes are promising agents for drug delivery. They have the ability to encapsulate therapeutic drugs, resulting in decreased toxicity and prolonged circulation time. However, many obstacles to achieving broad utility in liposomal drug delivery still exist, including the ability to control release of therapeutic drugs and modulate surface reactivity. A primary focus of this dissertation involves the development of synthetic photocleavable lipids for controlled release from membranes.

Phosphatidylcholine (PC) is a natural lipid that comprises the majority of structural membranes. It contributes heavily to the formation of lipid bilayers in cell membranes, and modifications to the bilayer can induce membrane …

Computational Studies For Optimization And Design Of Extracting Agents For Separation Of Lanthanides And Actinides, Deborah Andrea Penchoff

Doctoral Dissertations

Rare earths and actinides are of great interest given their varied applications in energy conversion and storage, such as in catalysis and batteries, and for advanced technological applications related to optical and magnetic properties (including electronics and automotive), amongst others. Many of the rare earth elements are considered endangered species due to their unique properties which have no clear alternatives that will maintain performance for important applications. The optimal approach is to find readily available alternatives for critical materials to ensure a certain standard of living and quality of life for future generations, but it is very likely that reusing …

Synthesis And Characterization Of Ln[Hfac]X And Ln[Fod]X Complexes For Thermochromatographic Separations, Matthew L. Marsh

Chancellor’s Honors Program Projects

No abstract provided.

Pressure-Induced Magnetic Crossover Driven By Hydrogen Bonding In Cuf2(H2o)2(3-Chloropyridine), Kenneth R. O'Neal, Tatiana V. Brinzari, Joshua B. Wright, Chunli Ma, Santanab Giri, John A. Schlueter, Qian Wang, Puru Jena, Zhenxian Liu, Janice L. Musfeldt

Chemistry Publications and Other Works

Hydrogen bonding plays a foundational role in the life, earth, and chemical sciences, with its richness and strength depending on the situation. In molecular materials, these interactions determine assembly mechanisms, control superconductivity, and even permit magnetic exchange. In spite of its long-standing importance, exquisite control of hydrogen bonding in molecule-based magnets has only been realized in limited form and remains as one of the major challenges. Here, we report the discovery that pressure can tune the dimensionality of hydrogen bonding networks in CuF2(H2O)2(3-chloropyridine) to induce magnetic switching. Specifically, we reveal how the development of exchange pathways under compression combined with …

Composition Dependence Of The Flory-Huggins Interaction Parameter In Polymer Blends: Structural And Thermodynamic Calculations, Travis H. Russell

Doctoral Dissertations

Flory-Huggins Theory has been the basis for understanding polymer solvent and blended polymer thermodynamics for much of the last 60 years. Within this theory, a parameter (χ) [chi] was included to quantify the enthalpic energy of dispersion between distinct components. Thin film self-assembly of polymer melts and block copolymers depends critically on this parameter, and in application, χ has generally been assumed to be independent of the concentrations of the individual components of the system. However, Small-Angle Neutron Scattering data on isotopic polymer blends, such as polyethylene and deuterated polyethylene, have shown a roughly parabolic concentration dependency for …

Structural Dynamics And Charge Transport In Room Temperature Ionic Liquids, Philip James Griffin

Doctoral Dissertations

Room temperature ionic liquids are an important class of materials due to their chemical tunability and numerous advantageous physicochemical properties. As a result, ionic liquids are currently being investigated for use in a wide array of chemical and electrochemical applications. Despite their great potential, however, the relationship between the chemical structure and physicochemical properties of ionic liquids is not well understood.

To this end, this dissertation presents experimental studies of the reorientational structural dynamics and charge transport properties of a variety of room temperature ionic liquids using quasielastic light scattering spectroscopy and broadband dielectric spectroscopy.

Studies of a series of …

Ab Initio Studies Of Proton Transport In Proton Exchange Membranes, Jeffrey Keith Clark

Doctoral Dissertations

A molecular-level understanding of the factors that contribute to transport properties of proton exchange membranes (PEMs) for fuel cell applications is needed to aid in the development of superior membrane materials. Ab initio electronic structure calculations were undertaken on various PEM ionomer fragments to explore the effects of local hydration, side chain connectivity, protogenic group separation, and specific side chain chemistry on proton dissociation and transfer at low hydration. Cooperative interactions between both intra- and inter-molecular acidic groups and hydrogen bond connectivity were found to enhance proton dissociation at very low degrees of hydration. The energetics associated with proton transfer …

Methods For Quantitative Local Structure Analysis Of Crystalline Materials Employing High Performance Computing, Tara Marie Michels-Clark

Doctoral Dissertations

A fundamental computational methodology was investigated to extract quantitative local structure information from single crystal diffuse scattering data. The principles of a highly efficient, parallelizable local structure analysis using massively parallel computing resources at Oak Ridge National Laboratory (ORNL) are demonstrated on an organic hydrocarbon compound containing stacking faults, Tris(bicyclo[2.1.1]hexeno)benzene. A probabilistic model of the stacking variations with a five layer interaction depth was developed. The final model structure motif statistics are verified using the steady state distribution of Markov matrix representing the four to five layer transitions. The computations revealed that highly parallelizable “structure-clones” could replace less computationally efficient …

Understanding The Plasmonic Properties Of Metallic Nanostructures With Correlated Photon- And Electron-Driven Excitations, Vighter Ozezinimize Iberi

Doctoral Dissertations

The collective oscillation of the conduction band electrons in metal nanostructures, known as plasmons, can be used to manipulate light on length scales that are smaller than the diffraction limit of visible light. In this dissertation, a correlated approach is used to probe localized surface plasmon resonances (LSPRs) in metallic nanostructures, and their application to surface-enhanced spectroscopy. This correlated approach involves the measurement of LSPRs with dark-field optical microscopy (resonance-Rayleigh scattering), and electron energy-loss spectroscopy (EELS) in a scanning transmission electron microscope (STEM). Structural parameters of the exact same nanostructures obtained from the STEM are subsequently used in performing fully …

Synthesizing Strong Donor Macrocyclic Tetracarbene Metal Complexes For Catalytic Aziridination, Steven Alan Cramer

Doctoral Dissertations

A small ringed macrocyclic tetracarbene ligand was developed due to the inherent ability of N-heterocyclic carbenes (NHCs) to stabilize high oxidation states of transition metals. This new strong donor ligand was prepared by first synthesizing an 18-atom ringed macrocyclic tetraimidazolium ligand precursor. The tetraimidazolium can be prepared by a two-step procedure. This ligand precursor was deprotonated to prepare a monomeric platinum tetracarbene complex.

A new iron macrocyclic tetra-carbene complex was synthesized by an in situ strong base deprotonation strategy of the ligand precursor. The iron tetracarbene complex was found to catalyze the aziridination of a wide array of functionalized aryl …

Double-Hinged Di-1,2,4-Triazoles For Synthesis Of Breathing Mofs, Christopher Ray Murdock

Doctoral Dissertations

Employing semi-rigid di-1,2,4-triazoles as ligands has led to the formation of a plethora of Metal-Organic Framework (MOF) architectures. The ability for the ligands to exhibit multiple conformations through a “hinge” effect allows for the formation of a multitude of MOF topologies and dimensionalities. Employment of a di-triazole containing a central trans-butene moiety was initially studied and led to the formation of two three-dimensional copper MOFs. The frameworks can be synthesized independently, but a reaction occurs in water wherein the kinetic product is used as a reagent to synthesize the topologically distinct thermodynamic product.

Additional testing of reaction conditions with …

Development Of Optical Sensors For Chemical Detection, Jonathan Kelly Fong

Doctoral Dissertations

Detection of biodiesel at low and high concentrations in diesel is highly desired in the aviation and fuel industries. Cross contamination of jet fuel with biodiesel may impact the thermal stability and freezing point which can cause deposits in the fuel system or cause the fuel to gel, leading to jet engine operability problems and possible engine flameout. A dye doped optical sensor utilizing the dye Nile Blue Chloride has been developed for quick and direct detection of biodiesel which mainly contains fatty acid methyl esters (FAME). The sensing mechanism relies on the solvatochromatic properties of the dye which undergoes …

The Development Of Apci Mass Spectrometry Based Systems For Quantitative Real-Time Monitoring Of Process-Scale Homogenous And Heterogeneous Reactions, Zhenqian Zhu

Doctoral Dissertations

The dissertation presents solutions to monitor industrial chemical processes quantitatively in real time by mass spectrometry. Chapter 1 presents the background of atmospheric pressure chemical ionization mass spectrometry (APCI-MS). Chapters 2-6 present methods developed based on flow injection analysis coupled to atmospheric pressure chemical ionization mass spectrometry (FIA/APCI-MS) for quantitative real-time monitoring of homogeneous and heterogeneous reactions conducted at molar concentrations.

Chapter 2 introduces auto-sampling FIA/APCI-MS with the ability to overcome potential sample overloading when molar concentration samples were analyzed without sample pretreatment procedures. A homogenous Michael-addition reaction between phenethylamine and acrylonitrile was conducted at room temperature and monitored quantitatively …

A Study In Conjugated Polymers: From Solution Properties Of P3ht To Synthesis Of Highly Functionalized Conjugated Polymers; Moving Toward Block Copolymers And Beyond, Justin Taylor Roop

Doctoral Dissertations

Conjugated polymers have been the focus of intense research for more than a decade now, and advances in this field are beginning to materialize in the production of high-efficiency opto-electronic materials that may led to the generation of energy without the need for fossil fuels. However, these current materials have not been shown to be capable of reaching efficiency levels high enough to be competitive with the siliconbased solar cells that are the standard today. We embarked on a journey in this work to help the next step in conjugated polymer research be attained. We have done just that through …

A Method To Control Morphology Of Bhj Opvs Using End-Functionalized Poly(3-Hexylthiophene)(P3ht) Grafted To Sqds, William Michael Kochemba

Doctoral Dissertations

Improving the power conversion efficiency of organic photovoltaic devices based on polymer-nanoparticle bulk heterojunctions remains a significant challenge that limits the commercial production of these technologies. There are a number of factors that contribute to the efficiency of photovoltaic devices including absorption, charge generation and charge separation, which ultimately rely on the morphology of the bulk heterojunction active layer. My work aims to improve these processes by developing a method to prepare end-group functionalized π[pi]- conjugated polymers that will be used to decorate the surface of nanoparticles thereby tailoring the interface between the polymer and the nanoparticle. This work involves …

Characterizing The Morphology Of Solvent Annealed Pcbm/P3ht Bilayers Using Gixrd And Raman Spectroscopy, Tyler Evan Mcpherson

Masters Theses

A growing demand for new forms of renewable energy has been at the forefront of scientific research. Organic photovoltaics (OPVs) provide a promising alternative to the expensive inorganic solar cells used today. Poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl C61-butyric acid methyl ester (PCBM) are common donor and acceptor materials used in the active layer of an OPV device. These systems have reached power conversion efficiencies of approximately 12 %. However, little is known about the actual morphology. A better understanding of the morphology would allow researchers to optimize device fabrication to increase the device performance. As-cast devices are limited by the processing …

Using Ultra Performance Liquid Chromatography-Mass Spectrometric Based Metabolomics To Determine The Metabolic Differences Due To Low Temperature Or Genetic Mutation In Salmonella Enterica, Nicole Rhonda Mooney

Masters Theses

Metabolomics aims to identify and quantify all of the small molecules within a cell. The relative concentrations of metabolites within cells grown under different experimental conditions, or different species, can be compared using pool size data. Exposing cellular cultures to isotopically labeled compounds allows the progress of metabolites through metabolic pathways to be tracked, known as flux. In the first experiment, the metabolic effects of exposure to lower than optimal temperatures in wild type Salmonella enterica, i.e. cold shock, were determined. The metabolites involved in glycolysis, the citric acid cycle, and the pentose phosphate pathway had less efficient labeling …

Syntheses Of Precursors To Fluorine-18 Labeled Pet Imaging Agents, Lindsay B. Boling

Chancellor’s Honors Program Projects

No abstract provided.