Physical Sciences and Mathematics Commons^™

Study Of Non-Covalent Interactions Using Molecular Rotors And Balances, Daniel Onyekachi Madukwe

Theses and Dissertations

The main focus of this dissertation is on the quantification of non-covalent interactions using molecular rotors and balances. While molecular rotors were used to measure kinetic effects of weak non-covalent interactions, molecular balances were used to measure their thermodynamic effects. Chapters 1 and 2 focus on the use of molecular rotors in measuring and studying the kinetic effects of the hydrogen bonding interaction on the bond rotation transition states. Chapters 3 and 4 focus on the quantification of lone pair – lone pair and sp²-CH/π interactions respectively, using molecular balances. These studies were carried out in the …

Computational Studies Of Bond Dissociation Energies And Organic Reaction Mechanisms, Shehani Thishakkya Wetthasinghe

Theses and Dissertations

This dissertation presents the progress of two independent projects. Chapter 2 and Chapter 3 focus on the first project, which involves material exploration utilizing machine learning techniques. We explore the potential use of cobaltocenium (CoCp⁺₂) derivatives as metal cations in anion exchange membranes (AEMs) for alkaline fuel cells, highlighting their superior thermal and alkaline stability compared to ammonium derivatives. The stability of CoCp⁺₂ can be fine-tuned by varying the substituent groups attached to the cyclopentadienyl ring (Cp) in CoCp⁺₂ .These derivatives encompass a variety of electron-donating and electron-withdrawing groups as substituents on both …

Identification Of New Disinfection Byproducts In Drinking Water And Impacts Of Algae, Md. Tareq Aziz

Theses and Dissertations

The disinfection of water has been hailed as one of the most important triumphs for public health in the 20th century. Drinking water treatment plants produce safe drinking water by inactivating microorganisms through the use of disinfectants, including chlorine, chloramine, chlorine dioxide, UV irradiation, and ozone. However, these disinfectants also produce toxic disinfection by-products (DBPs), through reactions with natural organic matter and anthropogenic pollutants, as well as bromide and iodide present in source waters. The presence of bromide and iodide results in the formation of bromo- and iodo-DBPs which are much more toxic than DBPs containing chlorine. DBPs are always …

Expanding On The Solid State Chemistry Of F-Element Chalcogenides, Logan Skyler Breton

Theses and Dissertations

An overarching goal in solid state chemistry is to achieve predictability regarding the synthesis of compounds with desired properties. While this goal is far from being reached, solid state chemists are hard at work synthesizing and characterizing new materials to further our understanding of structure-property relationships, and to expand our fundamental knowledge to rationalize the outcomes of solid-state syntheses. With the advent of new solid state synthetic methods, novel compounds exhibiting exciting properties are still being discovered today. The infancy of these synthetic methods promises a myriad of undiscovered compounds with potentially interesting properties which has resulted in a recent …

Machine-Learning Classification To Predict The Dimensionality Of Hybrid Organic-Inorganic Halide Perovskites, Yatiwelle Koralalage Samuditha Sandaru Yatiwella

Theses and Dissertations

Low dimensional hybrid perovskites have demonstrated remarkable performance in photovoltaic applications, primarily due to their exceptional optical and electronic properties. As the search for potential candidates for novel materials continues, understanding the structure of these materials is crucial for investigating their stability. In this study, we implement a framework to find novel material based on a machine-learning model. The machine learning model was trained to predict the dimensionality of the polyhedral network based on the connectivity of the polyhedral network in different directions. The polyhedral connectivity of low-dimensional structures can be classified into three dimensions: 0D, 1D, and 2D. This …

The Synthesis Of Novel Rare Earth Thiosilicates Using The Boron Chalcogen Mixture Method For An Interest In Their Magnetic And Optical Properties, Adam Alexander King

Theses and Dissertations

The chalcogens or the group sixteen elements excluding oxygen, are of interest due to their wide variety of structures and compositions, which gives the potential for a plethora of desired physical properties. This is due to their increased ability to catenate, forming stable chalcogen-chalcogen bonds. When the chalcogens combine with certain main group elements and transition metals they form anionic framework building blocks known as chalcometallates. One such chalcometallate of interest is the thiosilicates, compounds containing Si-S bonds as the anionic frameworks. These compounds are of interest due to their potentials in both their optical and magnetic properties. However, traditional …

Expanding Tailorable Nanomaterial Synthesis With Persistent Micelle Templates, Eric R. Williams

Theses and Dissertations

The control of block polymer micelle dimensions while in solution is critical for a range of emerging applications in diverse fields from drug delivery and nanoreactors to use as sacrificial templates for porous nanomaterials. When under kinetic control, micelles will maintain a constant average size and thus aggregation number (N_agg) through the suppression of chain exchange mechanisms. Such kinetic control effectively enables the decoupling of micelle dimensions from solution conditions. In other words, kinetically trapped micelles can resist reorganizations brough about by e.g., the addition of metal nanoparticles. However, such micelles are traditionally governed by a fickle �� …

Structure Property Investigation And Applications Of Self-Assembled Triphenylamine Bis Urea Macrocycles, Md Faizul Islam

Theses and Dissertations

Porous organic crystals can be advantageous as nanoreactors and in sensing, separations, and storage. The Shimizu group utilizes bifurcated urea hydrogen bonding to direct the assembly small building block into pillars and columns affording functional porous crystals. Recently, our group has examined the incorporation of triphenylamines within the framework of bis-urea macrocycles. These macrocycles assemble into columns that contain the solvent of crystallization bound within the channels. Heating the crystals leads to removal of the solvent and activates the host for guest exchange by single-crystal-to-single[1]crystal transformations. Different electron accepting molecules can be encapsulated inside the pore of the host …

Molecular Devices For Measuring Weak Solvophobic Interactions And The Development Of Pedagogical Tools For Organic Chemistry Students, Alexander N. Manzewitsch

Theses and Dissertations

The main topics of this dissertation are: 1) the development and discussion of a new molecular balance for measuring alkyl-alkyl interactions in a wide array of organic solvents, 2) the development of linear solvation energy relationships between solvent interaction parameters and solvent accessible surface area (SASA) in CH-arene interactions, and 3) the development of online resources for helping undergraduate students perform organic chemistry mechanisms problems well.

The solvophobic effect, that is the forced association between two solutes due to intermolecular attraction of the solvent molecules, is ubiquitous in organic chemistry and responsible for many significant phenomena thereof. However, there is …

Sustainable Approaches To Photo-, Thermo-, And Electro-Chemical Reactions Of Amines, James David Sitter

Theses and Dissertations

In recent years, sustainable routes for chemical synthesis have garnered renewed interest. As the world continues to fight pollution and rising costs, it is imperative that new routes of synthesis that continuously fight the issues of pollution and waste are discovered, defined and explored. While traditional synthesis routes that require energy input typically require the burning of fossil fuels to produce heat, the amount of resources that go into the production of these fossil fuels and the sequestration of its waste to minimize its impact on the carbon footprint is enormous. Furthermore, sustainable chemistry research aims to decrease and minimize …

Mapping Per- And Polyfluoroalkyl Substances (Pfas) In South Carolina Surface Waters: Are There Hotspots?, Thomas C. Geiger

Senior Theses

Per- and polyfluoroalkyl substances (PFAS) are synthetic chemicals used in consumer products for their unique chemical properties. PFAS compounds are resistant to water, oil, heat, and grease, making them useful for a wide variety of everyday items such as non-stick cooking pans, food packaging, electronics, carpets, upholstery, paints, adhesives, and personal care products.¹ The resilient nature of PFAS has made these compounds immensely popular with consumers but has since been considered a potential environmental and public health hazard for their ability to bioaccumulate and for their stability in the environment. More than 6000 PFAS have been discovered in the …

Evaluation Of A Radium-Thorium Disequilibrium Sediment Method Used To Model And Assess Porewater And Submarine Groundwater Exchange In The Coastal Marsh, Madeline R. Bodine

Theses and Dissertations

Ground, pore, and surface water exchange has been extensively studied in beach and near shore environments but has been long neglected in saltmarsh systems due to their complexity. Saltmarsh systems are of particular importance as they are the interface between fresh and saltwater. Saltmarshes impact carbon exchange, release and sequestration, and they process particulate matter. Understanding the characteristics of a marsh system such as the nutrient and particulate loads in conjunction with the flux of water exchange through the marsh provides a deeper understanding of these systems and can impact our understanding of the global water and carbon cycles, as …

Self-Assembling Porous Supramolecular Networks Capable Of Post-Synthetic Modification With A New Approach To Reticular Design With Semiconductor Potential, Steven A. Sloope

Theses and Dissertations

In past decades, research in self-assembling supramolecular frameworks have been produced with vast surface area, inherent from their porous nature. Predesigning monomers in a reticular manner allows a framework’s structure to be known before self-assembly occurs. This is very helpful since high porosity is sought after for many purposes such as hosting guests within the framework, post-synthetic modifications, sensing and detection, selective catalysis, semiconduction, etc. Methods of design usually focus on forming intrinsic porosity and unfortunately, sometimes the network formed is not as expected and porosity is lost.

In Chapter 1, we discuss novel ways of network formation, their potential …

The Optimization Of Anion Exchange Membrane Fuel Cells And Water Electrolyzers By Varying Catalyst Design And Changing Gas Inlet Composition, Jasmine D. Bohannon

Theses and Dissertations

Researchers around the globe are looking to avoid the consequences of climate change by shifting away from the burning of fossil fuels as a source of energy. While using fossil fuels have negatively affected the earth’s climate for at least the last hundred and fifty years, the introduction of renewables looks to use abundant and naturally occurring resources. Sources of renewable energy include solar power, wind power, hydropower, geothermal energy, and biomass2 . These sources work by converting the abundant source into mechanical, electrical, or chemical energy that can be used to power industrial plants or residential areas and they …

Small Molecule Activation By Dirhenium Carbonyl Complexes, Meenal Kaushal

Theses and Dissertations

The background of small molecule activation is discussed in Chapter 1. Carbon-hydrogen (C-H) bond activation and carbon-carbon (C-C) bond formation using transition metal complexes are explained using examples from the literature. It also includes the previous work done by Dr. Adams’ lab on C-H bond activation and zwitterions in metal carbonyl complexes.

The reaction of Re₂(CO)₈(µ-C₆H₅)(µ-H) with vinyl acetate yielding three new products has been discussed in Chapter 2. One of the products Re₃(CO)₁₃(µ-η² -C₂H₃), 2.3 further reacts with I₂ resulting in …

Pyridyl Bis-Urea Macrocycles As Supramolecular Synthons And The Design And Synthesis Of Small Molecule Pharmaceuticals Targeting Ly6k, Devan D. Buchanan

Theses and Dissertations

Assembled pyridyl bis-urea macrocycles have been utilized as 1D supramolecular synthons to construct hierarchical assemblies. These macrocycles have both urea and pyridyl functional groups and can form non-covalent interactions with hydrogen or halogen bond donors through symmetric, ditopic acceptor motifs. Bis-urea macrocycles offer interesting capabilities as synthons to organize donors into well-defined crystal structures. In part, this is due to the urea motifs’ propensity to assemble through hydrogen bonding. New, asymmetric pyridyl macrocycles were synthesized, crystallized, and experimentally probed to determine how symmetry affects their assembly and utility as supramolecular synthons.

The Uphadhyay group identified small molecules, including NSC11150, …

Crystal Growth Of Inorganic Halides And Oxide-Halides For Scintillation Applications And Radiation Detection, Gyanendra B. Ayer

Theses and Dissertations

Scintillators, materials which emit light when struck by high energy X-rays and y- rays, are extensively used in various fields including medical imaging, computed tomography, high-energy physics, and more recently in homeland security for the prevention of nuclear and radiological terrorism. While comparing with the traditional scintillators, which have long-term instability, high synthetic cost, toxicity, and hygroscopicity issues, metal halides have been reported to exhibit effective excitonic radioluminescence and greatly contribute in the field of scintillating applications and radiation detection. Currently, the mixed-anion oxide-fluorides have emerged as a prospective new class of scintillators, in which the mixed oxide-fluoride environment …

Novel Synthetic Strategies Toward Polyolefin-Grafted Nanoparticles, Richard Tran Ly

Theses and Dissertations

Surface functionalization of nanoparticles has proven to be a powerful and versatile strategy in the development of various materials with advanced properties. Polymer brush composition can range from complex copolymers to more simplistic polyolefin, and by functionalizing nanoparticle surfaces, mobility of distinct particles can then be tuned and, therefore, control over dispersion in a polymer matrix can be achieved. Presented in this dissertation are new synthetic strategies for the preparation of polymer nanocomposites.

The first chapter covers a novel synthetic strategy for ethylene/propylene-like copolymers grafted to silica nanoparticles. This approach utilizes Reversible Addition-Fragmentation Chain Transfer (RAFT) polymerization to promote living …

Disinfection Byproducts In Wastewater, Swimming Pools, And Tea: Identification, Quantification, And Drivers Of Toxicity, Caroline O. Granger

Theses and Dissertations

Drinking water disinfection is considered one of the greatest scientific achievements of the 20th Century because it significantly reduced the number of deaths related to waterborne diseases. However, in 1974 J.J. Rook discovered that chlorine, a commonly used disinfectant, can react with natural organic matter to form disinfection byproducts (DBPs). Since then, more than 700 DBPs have been identified, with several epidemiological and toxicological studies linking DBPs to several adverse health effects such as bladder and colorectal cancer, adverse birth outcomes, and asthma. Due to their ubiquity in disinfected water and their adverse health effects, studying the formation and identifying …

Materials Discovery By Flux Crystal Growth: Synthesis, Structure Determination, Magnetic, And Optical Properties Of Complex Oxides, Oxychlorides, And Oxyfluorides, Darren Andrew Carone

Theses and Dissertations

Exploratory crystal growth has proven to be a successful technique in the synthesis of new compounds with desired properties. This method is very versatile and has various iterations, but results described herein were obtained through flux growth at high temperatures utilizing mixed alkali halide salts. The tunability of these reactions with respect to reactant ratios, reaction temperature, heating/cooling rates, metal precursors, and choice of flux allow for the exploration of phase spaces between a combination of elements and observation of significantly different products and/or structure types from minor tweaks.

Most of the research presented in this dissertation describes results that …

Mechanisms And Impact Of Hypoxia Regulated Inhibins In Cancer, Ben Allen Horst

Theses and Dissertations

Inhibins are heterodimeric ligands within the TGFβ superfamily, comprised of an α-subunit (INHA) and a β-subunit (either INHBA or INHBB) with emergent roles in cancer. Inhibins are biomarkers of disease burden and prognosis in a subset of cancers and utilize the coreceptors betaglycan (TGFBR3) and endoglin (ENG) for physiological or pathological outcomes. Previously, we found inhibin promotes angiogenesis in ovarian cancer however no mechanism of regulation for inhibin expression in cancer has been established. Hypoxia, a driver of tumor growth and metastasis, regulates angiogenic pathways that are targets for vessel normalization and ovarian cancer management. …

Mechanistic Understanding Of Catalytic Processes For Sustainable Chemical Transformations, Pooja J. Ayare

Theses and Dissertations

The current field of catalysis is notably advanced in terms of both conceptual and technical innovation. There is a constant need to design new catalysts and develop catalytic processes to improve the scope, efficiency, and selectivity of various chemical transformations. It is also imperative to design catalytic systems which are effective, truly-recyclable and energy efficient for a sustainable future. This can be done through comprehensive knowledge and understanding of catalyst behavior, reaction kinetics and process designing.

For most industrial processes, the preferred catalysts are heterogeneous because these solid catalysts can be easily separated from the final product. However, they often …

Synthesis Of Carborane Pincer Complexes And Exploration Of The Reactivity Of Metal-Boron Bonds, Hindurangalage Don Asela Chathumal Jayaweera

Theses and Dissertations

Exploration of transition metal complexes with metal-boron bonds for the cooperative bond activation of small molecules in catalysis is one of the recent developments in novel synthetic strategies. The use of boron clusters as a modular platform for the formation of metal-boron bond has been successfully utilized by our and other groups. Carboranes are icosahedral boron-carbon molecular clusters that have gained attraction as multifunctional ligands due to their unique geometry, electronic properties, and versatility of functionalization methods. Their 3-D structure exerts a steric bulk around the exohedral substituent, either metal or non-metal center. Furthermore, due to the cluster geometry, five …

Modification Of Active Sites In Catalytic Materials For Gas-Phase Heterogeneous Catalysis, Deependra Man Shakya

Theses and Dissertations

Heterogeneous catalysis remains at the core of chemical manufacturing industries with 80-90 % of chemical processes relying on the use of catalysts. Unlike homogeneous catalyst that has extremely well-defined active sites, active sites in heterogeneous catalysis are complex and show dynamic behavior under reaction conditions, and change their structures, composition, particle size. The complexity associated with these systems has made the rational design of the catalyst a difficult problem. Highly crystalline metalorganic frameworks (MOFs) as heterogeneous catalysts present the unique opportunity to systematically modify the geometries, ensemble sizes, and compositions of highly dispersed active sites due to their tailorable, and …

Tailored Nanomaterials For Advancing Fast-Charge Research, Wessel Van Den Bergh

Theses and Dissertations

The demand for fast, energy-dense storage has driven research into nanoscale intercalation materials. Nanoscale materials not only accelerate kinetics but also can modify reaction path thermodynamics, intercalant solubility, and diffusivity. Pioneering works have revealed such nanoscale changes, often without the need to separately probe each fundamental transport process. While electrodes can be designed to have one transport processes dominant, there remain opportunities to better understand energy-dense designs with multiple concomitant transport constraints. The contents herein highlight emerging an method using tailored, energy-dense nanomaterials and the process of elimination to clearly correlate architectural features to performance. For example, this method revealed …

Sustainable Polymers: Upcycling Poly(Vinyl Chloride) And Mimicking Low Density Polyethylene, Ian Baxter

Theses and Dissertations

In this research, increasing the sustainability of polymers was investigated through two main methods. The upcycling of poly(vinyl chloride) and the creation of polymer mimics to create degradable low-density polyethylene. In the first chapter, an overview of the sustainability issues of polymers is presented and approaches are described on how their sustainability may be increased through the upcycling of polymers or the synthesis of degradable polymers that mimic the properties of petrol-based polymers.

Chapter 2 contains the progress on the upcycling of PVC using high oleic soybean oil. Soybean oil can soften PVC making it less brittle than pure PVC. …

Metal Free Bond Activation By Carboranyl Phosphines, Gayathri B. Gange

Theses and Dissertations

In the past few decades, main group-based catalysts have attracted increasing attention as an alternative approach to overcome the most prevailing issues of transition metal catalysts such as high cost, toxicity, and low abundance. Among these main groupbased catalysts, Phosphine based compounds have shown a variety of bond activations due to the strong nucleophilicity from their congener species. To the contrary, unique electron deficient boron-based clusters have the tendency to accept two electrons reversibly due to their electron deficiency. In this study, we have synchronized the electron donor ability of the phosphine with the electron acceptor ability of the ortho …

Well–Defined Donor–Acceptor Materials, Gabrielle A. Leith

Theses and Dissertations

The modularity of multivariant scaffolds such as covalent–organic frameworks (COFs) provides an unprecedented level of control in the alignment of donor (D) and acceptor (A) units, a demand that is driven by the production of optoelectronic, photonic, and spintronic devices. The foray into novel motifs bearing D-A ensembles in frameworks has been applied towards material property modulation for device performance enhancement. This dissertation presents an emerging trend in the development of D-A interfaces by highlighting recent advances probing D-A interactions in porous crystalline matrices and co-crystals, with a focus on energy transfer (ET) and charge transfer (CT) processes in pre-designed …

Photophysics And Electronic Properties Of Photochromic Metal-Organic Frameworks, Corey R. Martin

Theses and Dissertations

Modulation of materials properties through light-based illumination has the capability to expand the technology sector due to stimuli-responsive dynamic behavior that cannot be achieved in traditional materials. For example, reversibly tuning photophysical profiles of such materials allows for switching between discrete states that is a key aspect for the developing logic gates, spatially- and temporally-resolved sensors, and on-demand drug delivery systems. My efforts have focused on employment of metal-organic frameworks (MOFs) as a versatile platform for the material development which contain photochromic moieties allowing for tailoring their electronic properties. Our group has expanded this direction to include heterometallic and actinide-containing …

Adsorption Of Microcystins To Sediment Affects Their Bioavailability And Remediation, Ashley Womer

Theses and Dissertations

The freshwater harmful algae Microcystis spp produces a family of toxins called microcystins1. These species of algae are known to release microcystins from their cells directly into the surrounding water2. This creates an array of human health risks depending on the fate and transport of the toxins in the water column3,4. Risk modelling and previous literature has shown that sediment is a sink for free microcystin, microcystin can be stably adsorbed to sediment for hundreds of years, and its adsorption to sediment is determined by the sediment adsorption partitioning coefficient (Kd)5,6,7. In this work it is hypothesized that the sediment …