Chemistry Commons^™

Elucidating The Pd Active Sites Of Bimetallic Gold-Palladium Catalysts Using Chemisorption And Titration Techniques, Andrew T. Boucher

Electronic Theses and Dissertations

A bimetallic nanoparticle catalyst combines two different metals on an oxide support, which can increase the selectivity towards useful products that may be too tightly bound to a monometallic catalyst. To explore the surface properties of such a system, we made a group of four PdAu bimetallic catalysts with varying gold mass loadings to compare with a parent Pd catalyst. The parent catalyst was synthesized using ion exchange, and gold was added to this parent Pd catalyst using incipient wetness impregnation (IWI) to create four bimetallic catalysts. All catalysts were characterized using H₂ and CO chemisorption in tandem with …

Enhanced Mechanical Strength Of Soybean Oil-Based Non-Isocyanate Polyurethane Adhesive For Wood Application By Introducing Nanofillers, Vatsal Chaudhari

Electronic Theses & Dissertations

Polyurethane (PU) is a versatile material that finds extensive use in various industries including bedding, construction, automotive, and packaging. Historically, this particular polymer relied significantly on petrochemical resources, a practice that was considered to have negative environmental impacts. The conventional method for preparing PU involves the use of isocyanate, which is a disadvantage due to its negative impact on the environment and human health. The resolution of this problem entails identifying an appropriate substitute for petroleum-derived products that minimize their impact on both the environment and human health. The researchers earlier utilized soybean oil, for the formulation of PUs in …

Exploring Soybean Oil-Based Polyol And Effect Of Non-Halogenated Flame Retardants In Rigid Polyurethane Foam, Sahithi Kondaveeti

Electronic Theses & Dissertations

To address the increasing demand for sustainable biomaterials due to the depletion of fossil fuel resources and growing environmental concerns, a new type of biodegradable and environmentally friendly rigid polyurethane foam (RPUF) has been synthesized. These foams are derived from chemically modified soybean oil-based polyol obtained from soybean oil by epoxidation followed by a ring-opening reaction. Polyurethane foam is generally used in construction, furniture, and automobile industries but is highly flammable and releases toxic gases and smoke during combustion. In this study, a highly efficient synergistic effect halogen-free flame-retardant (FR) melamine salt, 2-carboxyethyl(phenyl)phosphinic acid melamine salt (CMA) was synthesized from …

Material Formulation And Process Optimization Towards Fabricating Robust 3d Printed Structures, Austin Riggins

Doctoral Dissertations

This dissertation focuses on understanding and addressing the fundamental physicochemical phenomena that lead to weak interfaces and structural warpage in material extrusion 3D printing. Polymeric feedstocks used for this manufacturing technique were manipulated through the incorporation of additives that alter the dynamics of the matrix during and after printing. In Chapter II, adhesion between layers of structures printed from PEEK was strengthened through a combination of low-molecular weight additive incorporation and post-printing thermal annealing. Chapter III reports a method for decreasing the irreversible thermal strain of structures printed from poly(lactic acid) by introducing nanographene and photoinitiator additives into the feedstock …

Understanding The Interaction Of Environmental Contaminants With Polystyrene Nanoparticles And Dna Using Nuclear Magnetic Resonance Spectroscopy And Density Functional Theory, Saduni Arachchi

All Dissertations

The objective of the thesis is to study the effect of environmental pollutants on polystyrene nanoparticles and biomolecules. This is done in two different techniques, particularly NMR and density functional theory. In this thesis, we use a combination of 1H NMR, Saturation-Transfer Difference (STD) NMR and relaxation experiments to study the interactions, kinetics and dynamics of antibiotics with polystyrene nanoparticles. (PS NPs) Density functional theory (DFT) is used to study the binding of commonly used non-oxidative hair dyes to biomolecules (DNA and amino acids) and PS particles.

Computational Investigations Of Bond Breaking Processes Using Dft And Td-Dft Approaches., Saurav Parmar

Electronic Theses and Dissertations

The efficient application of DFT and TD-DFT has been harnessed to study bond-breaking processes in some molecules which play a prominent role in enzymatic reactions. The first application includes Radical S-adenosyl methionine (SAM) enzymes which are fundamentally important sources of organic radicals to initiate diverse radical reactions. Recently a bio-organometallic intermediate (Ω) that contains an Fe‒C bond has been characterized and shown to be a common feature of radical SAM enzymes. The strength of Fe‒C bond in Ω has been computed using broken-symmetry density functional theory (BS‒DFT). Additionally, Fe‒C bond dissociation energy (BDE) in Ω has been compared to that …

Aspects Of Stochastic Geometric Mechanics In Molecular Biophysics, David Frost

All Dissertations

In confocal single-molecule FRET experiments, the joint distribution of FRET efficiency and donor lifetime distribution can reveal underlying molecular conformational dynamics via deviation from their theoretical Forster relationship. This shift is referred to as a dynamic shift. In this study, we investigate the influence of the free energy landscape in protein conformational dynamics on the dynamic shift by simulation of the associated continuum reaction coordinate Langevin dynamics, yielding a deeper understanding of the dynamic and structural information in the joint FRET efficiency and donor lifetime distribution. We develop novel Langevin models for the dye linker dynamics, including rotational dynamics, based …

Stress-Sensing In Flexible Epoxy Adhesives, Christine Rukeyser

Honors Theses

In mechanochemistry, mechanical force causes a chemical change using small molecules, called mechanophores, by covalently connecting them into polymer materials. Stress-sensing mechanophores give a visual signal of mechanical force on the molecular level within a material. To our knowledge, stress-sensing mechanophores have never been incorporated into a commercially available epoxy kit. In this work, the characterization of two 3MTM Scotch-Weld TM Epoxy Adhesive kits: DP100 Plus Clear and DP190 Translucent have been completed through FT-IR Spectroscopy. The addition of the mechanophore spiropyran to the 3M kits will be discussed; as well as preparation and characterization of three dimerized anthracene derivatives. …

Applying Density Functional Theory Simulations To Study The Charge Balancing And Structure Directing Roles Of Fluoride In Zeolite Synthesis, Tongkun Wang

Doctoral Dissertations

Zeolites represent a major cornerstone of today’s energy industry as the most-used petrochemical catalyst by weight in the world. Constituted by tetrahedra of T-atoms including Si, Al, Ge and Ti, zeolites form a huge family of nano-porous crystalline materials which also provide reliable candidates for novel, energy related applications such as efficient separations, hydrogen-purifying/storing and conversions from biomass to biofuel. However, the formation mechanism of zeolite is still not clear, as synthesis processes are complicated by requirements including structure directing agents (SDAs), hydroxide or fluoride medium, and experimental conditions like temperature. Attempts for designing new zeolite structures still fall in …

Atomistic Simulations Of Intrinsically Disordered Protein Folding And Dynamics, Xiping Gong

Doctoral Dissertations

Intrinsically disordered proteins (IDPs) are crucial in biology and human diseases, necessitating a comprehensive understanding of their structure, dynamics, and interactions. Atomistic simulations have emerged as a key tool for unraveling the molecular intricacies and establishing mechanistic insights into how these proteins facilitate diverse biological functions. However, achieving accurate simulations requires both an appropriate protein force field capable of describing the energy landscape of functionally relevant IDP conformations and sufficient conformational sampling to capture the free energy landscape of IDP dynamics. These factors are fundamental in comprehending potential IDP structures, dynamics, and interactions. I first conducted explicit solvent simulations to …

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 …

Syntheses, Photophysics, & Application Of Porphyrinic Metal-Organic Frameworks, Zachary L. Magnuson

USF Tampa Graduate Theses and Dissertations

Porphyrins are a group of heterocyclic macrocycles that play crucial roles in various biological processes such as electron transfer, catalysis, and sensing. Hemoglobin, which carries oxygen in the blood of mammals, and chlorophyll, which drives photosynthesis in plants and algae, are both porphyrins. The ability of porphyrins to bind metal ions and their unique electronic and photophysical properties make them an excellent platform for designing functional materials for various applications, often drawing inspiration from their function in nature. Metal-organic frameworks (MOFs) are a class of porous materials that have been extensively studied in recent years due to their high surface …

Syntheses, Photophysics, & Application Of Porphyrinic Metal-Organic Frameworks, Zachary L. Magnuson

USF Tampa Graduate Theses and Dissertations

Porphyrins are a group of heterocyclic macrocycles that play crucial roles in various biological processes such as electron transfer, catalysis, and sensing. Hemoglobin, which carries oxygen in the blood of mammals, and chlorophyll, which drives photosynthesis in plants and algae, are both porphyrins. The ability of porphyrins to bind metal ions and their unique electronic and photophysical properties make them an excellent platform for designing functional materials for various applications, often drawing inspiration from their function in nature. Metal-organic frameworks (MOFs) are a class of porous materials that have been extensively studied in recent years due to their high surface …

Experimental And Simulation Study Of Reactive Silver Ink Droplet Evaporation, Weipeng Zhang

Electronic Thesis and Dissertation Repository

The evaporation of particle-free silver ink droplets on heated substrates directly impacts the morphology of the resultant silver particles and films. In this thesis, COMSOL Multiphysics simulations of the solvent (water-ethylene glycol mixture) droplet evaporation process are used to explain the microflows, mass transfers, and heat distribution responsible for the experimental observations. The reactive ink incorporates fluoro-surfactant FS-31 and poly (acrylamide) (PAM) to suppress the coffee-ring effect that negatively impacts the electrical conductivity. Experiments show that the droplet evaporation process results in varied silver particle morphology, depending on the locations within the droplet, leading to uneven surfaces. Large particles (3 …

Metal Organic Frameworks (Mofs) Supported Single Atom Catalysts (Sacs) For Solar Fuel Conversion, Humphrey Chiromo

Dissertations (1934 -)

The continual reliance on non-renewable energy sources from fossil fuels to meet the world’s energy demand is causing serious environmental problems such as air pollution and global warming, hence there is a need of an alternative clean sustainable energy source. Exploration of clean sustainable renewable energies shows great promise to replace fossil fuels to meet global energy needs. Among the renewable energy sources, solar energy represents one of the most promising alternative energy sources due to its abundance and sustainability. However, the major challenge is the harvesting and storage of solar energy. One of the promising approaches to resolve these …

Protein Stability In Solution And In The Gas Phase., Yousef Haidar

Electronic Thesis and Dissertation Repository

Electrospray Ionization mass spectrometry (ESI-MS) is widely used for probing proteins, yet many aspects of this technique remain elusive. Using MS, ion mobility spectrometry (IMS), and circular dichroism (CD) spectroscopy, this thesis sheds light on the stability differences of proteins in the gas phase and solution. After a general introduction (Chapter 1), Chapter 2 scrutinizes some aspects of native ESI. Our data highlight the significance of cone voltage in maintaining a native-like fold and show the advantage of using NH₄Ac in protein experiments. Chapter 3 focuses on hydrogen/deuterium exchange (HDX)-MS. Several studies have reported that D₂O …

Quantifying Temperature-, Pressure-, And Nuclear Quantum Effects On Hydrophobic And Hydrophilic Water-Mediated Interactions, Justin T. Engstler

Dissertations, Theses, and Capstone Projects

Water-mediated interactions (WMIs) are responsible for diverse processes in aqueous solutions, including protein folding and nanoparticle aggregation. WMI may be affected by changes in temperature and pressure, and hence, they can alter chemical/physical processes that occur in aqueous environments. Traditionally, attention has been focused on hydrophobic interactions while, in comparison, the role of hydrophilic and hybrid (hydrophobic–hydrophilic) interactions have been mostly overlooked. Here, we study the role of T and P on the WMI between nanoscale (i) hydrophobic–hydrophobic, (ii) hydrophilic–hydrophilic, and (iii) hydrophilic–hydrophobic pairs of (hydroxylated/non-hydroxylated) graphene-based surfaces. We find that hydrophobic, hydrophilic, and hybrid interactions are all sensitive to …

Synchrotron Study Of Phase Transition And Heterostructures In Metal Oxide Semiconductors, Bingyu Dong

Electronic Thesis and Dissertation Repository

Transition metal oxides, including titanium dioxide (TiO₂), zinc oxide (ZnO) and Tin dioxide (SnO₂) are widely recognized semiconducting photocatalysts. This project engages in a detailed examination of the phase transition of TiO₂ and the synthesis of heterostructured metal oxides using an eco-friendly method of ball-milling. A variety of spectroscopy and microscopy techniques have been used to analyze the products. Synchrotron-based techniques: X-ray Absorption near-edge spectroscopy (XANES), X-ray Emission Spectroscopy and X-ray excited optical luminescence (XEOL) can demonstrate the local structure and bonding. The finding highlights a phase transition in TiO₂ and the formation of …

The Effect Of Hydrogen Peroxide On The Corrosion Dynamics Of Carbon Steel, Kwang Soak Gabriel O'Donnell

Electronic Thesis and Dissertation Repository

The Used Fuel Container (UFC) is a key barrier in Canada’s nuclear fuel disposal plan. Understanding the radiation-induced corrosion of the carbon steel (CS) vessel is critical for predicting the long-term integrity of the UFC. Developing a mechanistic understanding of CS corrosion and the effect of solution parameters is essential.

This work investigates the effects of H₂O₂, the key radiolytic oxidant, on CS corrosion dynamics in small, stagnant solutions. Elementary processes are identified, corrosion rates are calculated, and the effects of H₂O₂ concentration are investigated. Corrosion was studied by quantifying the concentrations of …

Dinitrogen Functionalization Using A Molybdenum Atom: Bridging The Gap Between Small And Coordination Complexes Via Quantum Mechanical Methods, Maria Virginia White

Doctoral Dissertations

Chemistry devotes a significant amount of its research to understanding small molecule activation from an electronic structure perspective to help with the investigation of the reaction pathways of catalytically active substances that can promote biomimetic catalysis. A large portion of the energy used annually in our planet is used for the artificial nitrogen fixation (Haber-Bosch process), which renders dinitrogen activation a subject of study. Molybdenum, a fourth row transitional metal, has demonstrated its effectiveness as an essential component of the dinitrogen reduction catalytic process. To better understand the multiple dinitrogen molybdenum binding modes, the work described herein combines wave function …

Theoretical Studies Of Adsorption And Reactivity At The Gas-Solid Interface, Carson J. Mize

Doctoral Dissertations

Catalytic transformations of small molecules is of great interest for both laboratory and industrial practices. Two specific transformations are ethylene to ethylene oxide and combinations of azides and alkenes into aziridine molecules. Ethylene oxide is an epoxide used as a feed-stock for many bulk reactions and commercial products such as antifreeze and various sterilization techniques, while molecules with the aziridine functional group are used for many ring opening and closing techniques as well as in pharmaceuticals and other drug treatments. For production of ethylene oxide, the combination of oxygen adsorbed onto a silver crystal is the known catalysts for thus …

Chirality, Symmetry-Breaking, And Chemical Substitution In Multiferroics, Kiman Park

Doctoral Dissertations

Multiferroic materials attract significant attention due to their potential utility in a broad range of device applications. The inclusion of heavy metal centers in these materials enhances their magnetoelectric properties, yielding fascinating physical phenomena such as the Dzyaloshinskii–Moriya interaction, nonreciprocal directional dichroism, enhancement of spin-phonon coupling, and spin-orbit-entangled ground states. This dissertation provides a comprehensive survey of magnetoelectric multiferroics containing heavy metal centers and explores spectroscopic techniques under extreme conditions. A microscopic examination of phase transitions, symmetry-breaking, and structure-property relationships enhances the fundamental understanding of coupling mechanisms.

In A2Mo3O8 (A = Fe, Zn, Ni, and Mn), we use optical spectroscopy …

Advances In One-Electron Self-Interaction-Correction Methods For Accurate And Efficient Self-Interaction-Free Density Functional Calculations, Selim Romero

Open Access Theses & Dissertations

Density functional theory (DFT) is a widely used computational method for studying electronic structures of atoms, molecules, and solids. It provides an exact theory for obtaining ground state energy from the ground state density. However, since the exact exchange-correlation functional remains unknown, approximate exchange-correlation functionals called approximate density approximations (DFAs) are used. The foundation of many DFAs is the local spin density approximation (LSDA). It serves as the starting point for constructing various DFAs. However, DFAs are prone to self-interaction errors (SIE) due to the improper cancellation of the approximate exchange energy and the Coulomb energy. This issue impacts the …

Dinitroxides In Rapid Scan Electron Paramagnetic Resonance Imaging, Lukas B. Woodcock

Electronic Theses and Dissertations

Local tissue physiology is an important parameter in understanding disease behavior. Rapid Scan (RS) electron paramagnetic resonance (EPR) offers a unique, non-invasive tool for investigation of these so-called microenvironments through EPR Imaging (EPRI). Research into advancement of EPRI falls into many categories. Not least among those are advances in instrumentation and methodology. Presented here are updates to a benchtop EPRI instrument operating at 1 GHz targeted at pre-clinical EPRI applications. Newly developed methods for reducing RS-EPR background through inversion of the magnetic field are also demonstrated. EPR applications are limited in native biological systems due to the miniscule concentration of …

Electron-Transfer Mediated Photo-Switching In Nanoparticles, Liaoran Cao

All Dissertations

Previous publications from our lab demonstrated viable approaches to design a photo-switching nanoparticle with arguably superior brightness and photostability resulting in an improved resolution in localization-based microscopy, as compared to other photo-switching dyes or particles. As a follow-up, this dissertation is focused on two major tasks: first, developing nanoparticles with better photo-switching properties for super-resolution imaging; second, trying to achieve a better physical picture of the mechanisms involved in photo-switching, including polaron dynamics, charge transfer, and energy transfer. A new class of photo-switchable nanoparticles was developed by blending conjugated polymer semiconductor with fullerene-based electron acceptors, and further blending with polystyrene …

The Influence Of Allostery Governing The Changes In Protein Dynamics Upon Substitution, Joseph Hess

All Dissertations

The focus of this research is to investigate the effects of allostery on the function/activity of an enzyme, human immunodeficiency virus type 1 (HIV-1) protease, using well-defined statistical analyses of the dynamic changes of the protein and variants with unique single point substitutions ¹. The experimental data¹ evaluated here only characterized HIV-1 protease with one of its potential target substrates. Probing the dynamic interactions of the residues of an enzyme and its variants can offer insight of the developmental importance for allosteric signaling and their connection to a protein’s function. The realignment of the secondary structure elements can …

The Investigation Of Singlet Fission From The Perspective Of Hierarchy Of Pure States (Hops), Tao (James) Chen

Chemistry Theses and Dissertations

This thesis provides a preliminary investigation of singlet fission from the perspective of Hierarchy of pure states (HOPS), which provides a numerical exact solution for the investigation of a series of open quantum systems. Since the inception of the concept of singlet fission about half a century ago, this photo-physical process has attracted the attention of a multitude of researchers and has been extensively studied theoretically and experimentally. However, these previous methods for the investigation of singlet fission focus more or less on tackling the underlying mechanisms of singlet fission from the perspective of perturbation. So far, the HOPS method …

The Investigation Of Singlet Fission From The Perspective Of Hierarchy Of Pure States (Hops), Tao (James) Chen

Chemistry Theses and Dissertations

This thesis provides a preliminary investigation of singlet fission from the perspective of Hierarchy of pure states (HOPS), which provides a numerical exact solution for the investigation of a series of open quantum systems. Since the inception of the concept of singlet fission about half a century ago, this photo-physical process has attracted the attention of a multitude of researchers and has been extensively studied theoretically and experimentally. However, these previous methods for the investigation of singlet fission focus more or less on tackling the underlying mechanisms of singlet fission from the perspective of perturbation. So far, the HOPS method …

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 …

Photophysical Properties Of Synthetic Oligomeric Phenylene Ethynylene, Hugh F. Fritz Jr.

Chemistry and Chemical Biology ETDs

Oligomeric Phenylene Ethynylenes (OPEs) are a class of synthetically prepared compounds with the basic structure of phenylene rings connected by triple-bonded carbon atoms, also known as an ethyne link. This structure can be modified by incorporating functional groups onto one or more of the phenylene rings. The addition of functional groups, such as sulfoxide or imidazole, may alter the photophysical properties in detectable ways. The photophysical techniques used in this report include fluorescence, spectroscopy in the ultraviolet and visible light range (UVVIS), and photon-based excitation using a photo chamber.

One attractive function of OPEs is their antimicrobial property. Previously published …