Physical Sciences and Mathematics Commons^™

Total Internal Reflection: Applications In Nonlinear Microscopy And Fluorescence Anisotropy, Brandon Colon

Doctoral Dissertations

As technology advances to harness new energies and to create new cures, the sophistication of analysis grows not only in depth but in efficiency. Total internal reflection (TIR) has been coupled to microscopy leveraging its unique optical phenomenon on a breadth of topics. In this dissertation, the work presented will show how TIR was applied in two different instrumental analyses to evaluate two unique and complex systems. The first project features TIR paired with the transient absorption microscopy (TAM), a nonlinear optical technique, to gauge solvent mixing and diffusion in microreactors. Microreactors gained acclaim for their ability to produce high …

Instrument Development For High Sensitivity Size Characterization Of Lipid Vesicles And Other Biological Macromolecules Via Taylor Dispersion Analysis, Meagan Moser

Doctoral Dissertations

Just as humans communicate with other humans, the cells in our bodies communicate with each other through various, often complex, mechanisms. Cell-to-cell transmission of small molecules, lipids, proteins, peptides, or nucleic acids can be mediated by extracellular lipid vesicles called exosomes. Exosomes have been found to play a role in the delivery of regulatory molecules from one cell to another, serving as a universal communication mechanism. Currently, there is an emerging focus on characterizing exosome communication dynamics. Understanding exosome mechanisms of cell-to-cell communication requires accurate measurements of the spatiotemporal and chemical dynamics of exosome secretion. No current analytical approach offers …

Application Of Single-Ion Conducting Polymer Electrolytes (Sicpes), Sheng Zhao

Doctoral Dissertations

Polymer electrolytes have been widely studied as a potential candidate for next generation batterie with improved safety and higher energy density. Especially, single-ion conducting polymer electrolytes (SICPEs) have attracted significant attention due to their almost unity lithium-ion transport number, which is believed to help suppress lithium dendrite growth and extend battery cycle life. However, there is still a long way to go before they can be practically applied in batteries, due to their relatively low ionic conductivity at ambient temperature. Therefore, the main goal of this work is to explore various methods that can improve the ionic conductivity of SICPEs …

Ultrasound-Driven Fabrication Of Nanosized High-Entropy Materials For Heterogeneous Catalysis, Francis Uchenna Okejiri

Doctoral Dissertations

High-entropy materials (HEMs) have emerged as a new class of multi-principal-element materials with great technological prospects. As a unique class of concentrated solid-solution materials, HEMs, formed on the premise of incorporating five or more principal elements into a single crystalline phase, provide an excellent opportunity to access superior catalytic materials ‘hiding’ in the unexplored central regions of a multicomponent phase space of higher orders.

However, the fabrication of HEMs is energy-intensive, typically requiring extreme temperatures and/or pressures under which agglomeration of particles occurs with a commensurate decrease in surface area. For most catalytic applications, non-agglomerated particles with high surface areas …

Production And Adsorption Of Volatile Tellurium Hexafluoride, Stephanie H. Bruffey

Doctoral Dissertations

Research and development supporting the management of off-gases from nuclear fuel reprocessing has historically been focused on the off-gas streams that arise from aqueous reprocessing technology. With the advent of advanced reactor designs off-gas streams arising from advanced reprocessing methodology, such as that of FV [fluoride volatility] processing, also merit consideration. This work focuses on TeF₆ [tellurium hexafluoride], one of the most volatile radioactive compounds produced during FV, and investigates TeF₆ production, measurement, and abatement technologies.

To assist in on-line monitoring of TeF₆ by Fourier-transformed infrared spectroscopy, this work systematically used the ideal gas law and Beer’s …

Analytical Considerations And Methods For Comprehensive Analysis Of Bacterial Phospholipidomics Using Hilic-Ms/Ms, David Thomas Reeves

Doctoral Dissertations

Omics technologies have rapidly evolved over the last half century through vast improvements in efficient extraction methodologies, advances in instrumentation for data collection, and a wide assortment of informatics tools to help deconvolute sample data sets. However, there are still untapped pools of molecules that warrant further analytical attention. As the frontline defense of the cell against exterior influences, the phospholipid membrane is key in structure, defense, and signaling, but current omics studies are only just now catching up to the potential hidden within cellular lipid profiles. Examination of shifts in phospholipid speciation and character could provide researchers with a …

Interfaces And Dynamics In Polymeric 3d Printing And Crystalline Polymer Blends, Stevenson C. Perryman

Doctoral Dissertations

This dissertation presents experimental work that provide a foundation to rationally improve fused filament fabrication (FFF) and immiscible blend compatibilization. Objects generated from additive manufacturing processes, such as FFF, have intrinsic structural weaknesses which include two project specific examples: structural anisotropy and irreversible thermal strain. Due to low adhesion between individual print layers that results in macroscopic defects, the mechanical strength of printed objects when force is applied perpendicular to the build orientation is drastically reduced. In the first dissertation chapter, we present a protocol to produce interlayer covalent bonds by depositing multi-amine additives between individual layers of a print …

Designing Polymer Materials For Improved Additive Manufacturing, Kaizhong Guan

Masters Theses

Currently, two of the most used additive manufacturing methods for polymers are selective laser sintering (SLS) and fused filament fabrication (FFF). Although at high market size, they both have imperfections. The materials for SLS are limited and the objects manufactured by FFF existing anisotropic behavior. Targeting on these drawbacks, this thesis has proposed a novel method to prepare polypropylene (PP) microsphere which is suitable for SLS with low cost and scalable potential; and a novel material with polycarbonate as matrix that has shown a decrease in anisotropy after FFF printing.

The PP microsphere in this thesis was prepared via liquid-liquid …

Exploring The Potential Of Ionothermal Syntheses For High-Performance Lithium-Ion Battery Anode Materials, Runming Tao

Doctoral Dissertations

Renewable energy storage systems are regarded as the solution to the environmental and energy crises caused by the burning of fossil fuels in vehicles. Unfortunately, owning to the limits to the electrochemical performance of the current anode materials, lithium-ion batteries [LIBs] are still lacking strength in the charging rate-capability and thereby cannot fulfill future application requirements in electrical vehicles [EVs].

Particularly, graphite with a high theoretical specific capacity of 372 mAh/g is unsuitable for EVs due to the safety concerns of passivating solid-electrolyte interphase [SEI] resulted from the low operation potential of 0.1 V versus Li/Li⁺. The other …

Influence Of Physical Variability Of Highly Weathered Sedimentary Rock On Nitrate In Area 3 Of The Enigma Field Research Site At Y-12, Erin Kelly

Masters Theses

Uranium processing and waste storage in unlined waste ponds leached contaminants into the groundwater at Y-12, Oak Ridge, Tennessee, from the 1950s to 1980s. Groundwater wells near the S-3 ponds have had the highest nitrate concentrations of groundwater anywhere in the world (>10,000 mg/L). For reference, the maximum contaminant level for nitrate in drinking water set by the U.S. Environmental Protection Agency is 10 mg/L. Since 2012, the ENIGMA (Ecosystems and Networks Integrated with Genes and Molecular Assemblies) group has been characterizing, monitoring, and conducting field experiments to understand the interactions between contaminants, microbes, and the subsurface. The goals …

Using Applied Field, Pressure, And Light To Control Magnetic States Of Materials, Amanda J. Clune

Doctoral Dissertations

Due to their low energy scales, flexible architectures, and unique exchange pathways, molecule-based multiferroics host a number of unique properties and phase transitions under external stimuli. In this dissertation, we reveal the magnetic- and pressure-driven transitions in [(CH₃)₂NH₂]Mn(HCOO)₃ and (NH₄)₂[FeCl₅(H₂O)], present a detailed investigation of these materials away from standard equilibrium phases, and develop rich two- and three-dimensional phase diagrams.

The first platform for exploring phase transitions is [(CH₃)₂NH₂]Mn(HCOO)₃. This type-I multiferroic contains Mn centers linked by …

Development Of Catalysts For The Ring-Opening Polymerization Of Cyclic Esters And The Coordination-Insertion Polymerization Of Olefins, Alicia Doerr

Doctoral Dissertations

Over the past few decades, interest in the design and synthesis of tailorable polymeric materials has grown due to the well documented correlation between structure, property, and function. However, in order to obtain polymers with desired microstructures, well controlled synthetic methods are needed. Therefore, the continued investigation of homogeneous, single-site polymerization catalysts is important to gain a deeper understanding of how systematic modifications of polymerization conditions, ligand scaffold, metal center identity, cocatalyst or activator identity, etc. affect the catalytic activity, selectivity, and/or polymer topology obtained when using these catalysts for the polymerization of a variety of monomers. This dissertation will …

Characterization Techniques And Cation Exchange Membrane For Non-Aqueous Redox Flow Battery, Kun Lou

Doctoral Dissertations

The motivation of this work comes from one of the major problems of emerging non-aqueous flow battery (NAFB) that a separator or membrane which facilitates conductivity and blocks redox species crossover does not exist. Although many aspects of principles can be mirrored from mature fuel cell and aqueous flow battery, it is found that some well-defined membrane properties in aqueous systems such as swelling, transport and interactions are different in non-aqueous solvents to some extent. However, the approach of this work does follow the way perfluorosulfonate ion exchange membrane (PFSA) facilitated development of fuel cell and aqueous flow battery in …

Stimuli-Responsive Polyelectrolytes: Thermosensitive Zwitterionic Polymers And Charged Shape-Changing Star Molecular Bottlebrushes, Evan M. Lewoczko

Doctoral Dissertations

This dissertation work investigated two classes of stimuli-responsive polyelectrolytes: thermosensitive zwitterionic poly(sulfobetaine methacrylate)s (PSBMAs) and charged shape-changing star molecular bottlebrushes (SMBs). While zwitterionic polymers are explored for numerous applications, their structure-solution behavior relationship was poorly understood. The first part of this dissertation focused on the effects of N-substituents of PSBMAs on their behavior in water. A series of PSBMAs were synthesized, with systematically changed N-substituents, including symmetric N-n-alkyl substituents of various lengths and asymmetric N-substituents comprising one methyl and either one cyclohexyl, phenyl or 2-hydroxyethyl group. The behavior of PSBMAs with symmetric N-substituents …

Fabrication Of Specialized Scintillators For Nuclear Security Applications, Cordell James Delzer

Doctoral Dissertations

Radiation detectors are important for a variety of fields including medical imaging, oil drilling, and nuclear security. Within nuclear security, they can serve a multitude of purposes whether that be imaging, localization, isotopic identification, or even just activity measurement. Even without directly seeing a nuclear material it is often able to notice their existence without a detector. Scintillators make up an important part of these detectors due to their large intrinsic efficiency, low cost, large volume, and relatively low upkeep. Due to the importance of the large number of purposes these scintillators may be used for, it can often be …

Development Of Density-Functional Tight-Binding Methods For Chemical Energy Science, Quan Vuong

Doctoral Dissertations

Density-functional tight-binding (DFTB) method is an approximation to the popular first-principles density functional theory (DFT) method. Recently, DFTB has gained considerable visibility due to its inexpensive computational requirements that confer it the capability of sustaining long-timescale reactive molecular dynamics (MD) simulations while providing an explicit description of electronic structure at all time steps. This capability allows the description of bond formation and breaking processes, as well as charge polarization and charge transfer phenomena, with accuracy and transferability beyond comparable classical reactive force fields. It has thus been employed successfully in the simulation of many complex chemical processes. However, its applications …

Dissolved Organic Carbon And The Potential Role To Stream Acidity In The Great Smoky Mountains National Park, Jason R. Brown

Masters Theses

A substantial societal shift towards environmental awareness has focused research efforts on the impacts of pollution on natural landscapes. Improvements to pollutant regulations and technology have resulted in sizeable reductions of atmospheric deposition of anthropogenic acids, especially nitrates and sulfates, which has altered the role of these ions in the environment. As such, understandings of environmental chemistry dynamics have required regular updating.

Through the National Park Service Vital Signs monitoring program, increases in precipitation pH observed in Great Smoky Mountains National Park (GRSM) has been attributed to the reduction of inorganic acid concentrations. Unfortunately, these improvements have not been uniformly …

Physical Adsorption Of Linear Hydrocarbon Quadrupoles On Graphite And Mgo (100): Effects Of The Compatibility Of Surface And Molecular Symmetries, Andrew J. Pedersen

Doctoral Dissertations

The process of physical adsorption finds a practical role in wide-ranging fields from catalysis, to lubrication, and even optoelectronics. Furthermore, it provides a mechanism to probe the fundamental understanding of intermolecular forces and how symmetries can play a role in the behavior of a system. Linear quadrupoles preferentially adopt square-T configurations when confined in two dimensions. This would lead the system to adopt a four-fold symmetry in the molecular lattice.

Two archetypal surfaces often studied in physisorption research are MgO (100), which has a four-fold symmetry of alternating charges, and the basal plane of graphite, which has a six-fold symmetry …

Small Molecule Activation By Transition Metal Complexes: Studies With Quantum Mechanical And Machine Learning Methodologies, Justin Kyle Kirkland

Doctoral Dissertations

One of the largest areas of study in the fields of chemistry and engineering is that of activation of small molecules such as nitrogen, oxygen and methane. Herein we study the activation of such molecules by transition metal compounds using quantum mechanical methods in order to understand the complex chemistry behind these processes. By understanding these processes, we can design and propose novel catalytic species, and through the use of data-driven machine learning methods, we are able to accelerate materials discovery.

Fine Tuning Rhii Complexes With Tethered, Axial Coordination: Structural Studies And Application To Diazo-Mediated Cyclopropanation Reactions, Derek Cressy

Doctoral Dissertations

The cyclopropane moiety is an attractive synthetic target due to its application in pharmaceuticals and medicinal research. One effective strategy involves the formation of metal carbenoid species from diazo reagents. The carbenoid then reacts with an olefin substrate to generate the cyclopropane ring. Of the metal complexes that can facilitate this reaction, dirhodium(II) paddlewheel complexes are arguably the most prevalent catalysts. This is because modification of the bridging ligands enables control to be exerted over the catalyst’s chemoselectivity and enantioselectivity. Exploiting the axial site as a control element is often overlooked as strongly coordinated Lewis bases inhibit catalysis. Despite this, …

Spectroscopic Investigations Of Complex Van Der Waals Systems, Sabine N. Neal

Doctoral Dissertations

Complex chalcogenides are superb platforms for revealing the interplay between structure, charge, and magnetism as well as the unusual states of matter that develop under external stimuli. These van der Waals solids can also be exfoliated into few- and single-layer sheets that sport a number of unexpected properties, including quantum confinement, magnetic excitations and size-induced magnetic states, and symmetry breaking. A commonality amongst sheet studies is the role of Raman scattering to assure sample quality, probe even-symmetry vibrational modes, and uncover single-layer properties. Odd-symmetry modes were, however, completely underexplored in few-layer materials. Infrared spectroscopy is well suited for examining the …

Synthesis, Characterization, And Applications Of Nucleobase-Functionalized Conjugated Polymers, Sina Sabury

Doctoral Dissertations

Understanding the effect of the functional groups at the terminus of the side chains is important for developing conjugated polymers through side chain engineering. Nucleobases, which are known for their multi-functionality, have not been deeply studied as functionality in conjugated polymers due to synthetic challenges. The overarching goal of my dissertation is to design, synthesize, characterize conjugated polymers bearing nucleobase functionality in their side chains and demonstrate their utility in various applications. Stille cross-coupling and direct arylation polymerization are used to synthesize adenine- and thymine-containing conjugated polymers. Monomer design requirements for successful polymerization are studied and conditions that optimize polymerization …

Application Of Titrations For Verification Of Small Molecule Interaction In Relation To Amidoximated Fibers For Uranium Extraction From Seawater, Kc Michael Mote

Masters Theses

Nuclear energy is a promising substitute for fossil fuels due to possessing low carbon emissions and providing scalable base-load power. However, one major drawback of using nuclear fuel as an energy source is that it needs a steady source of uranium. While the most economical method of obtaining uranium is through conventional terrestrial mining of the ore uranite, mining uranium ores is both harmful to the environment and limited by the terrestrial uranium supply, which is estimated at only 100 more years. However, more than 1000× more uranium is dissolved in seawater than is reasonably inferred and assured in terrestrial …

Stretching The Applications Of Biomass: Development Of Lignin Based Thermoplastic Elastomers And Composite Materials, Anthony Stephen Bova

Doctoral Dissertations

Bio-based plastics and composites have seen increased industry adoption in recent years due to growing demand for materials with a low carbon footprint. The use of lignin as a feedstock for polymers has seen growing interest as the concept of an integrated cellulosic biorefinery gains traction and advances the need to use all components of separated biomass for value-added applications. Historically, use of lignin in thermoplastic and elastomeric copolymers and blends has been bottlenecked by the inability to introduce lignin content above 30 weight percent due to difficulties with interfacial adhesion of lignin with other soft segments. Efforts to overcome …

Thorium Dioxide Extraction From Monazite Ore, Jason Pan, Niall Phelan Terry, Katherine Glass, Eli Jenkins, Connor High

Chancellor’s Honors Program Projects

No abstract provided.