Chemistry Commons^™

Novel Modes Of Synchronization And Extreme Events In Coupled Chemical Oscillators, David Allen Mersing

Graduate Theses, Dissertations, and Problem Reports (ETD)

We experimentally and computationally investigate dynamical behaviors in coupled chemical oscillators. These networks of chemical oscillators are created using catalytic Ru(bpy)₃²⁺ loaded cation exchange beads submerged in catalyst-free Belousov-Zhabotinsky (BZ) solutions. Various network structures are created by utilizing the photosensitive nature of the Ru(bpy) ₃²⁺ catalyst. The response of the oscillators due to light stimuli can be characterized by constructing a phase response curve (PRC). The PRC quantifies the excitatory and inhibitory responses of BZ oscillators due to applied light perturbations as a function of the oscillators' phase. Different initial concentrations of reactants in the BZ reaction …

Electrochemical And Mass Spectrometry Methods For Identification Of Gunshot Residues (Gsr) In Forensic Investigations, Kourtney A. Dalzell

Graduate Theses, Dissertations, and Problem Reports (ETD)

Gun violence continues to be one of most significant challenges straining the USA society causing thousands of human lives lost every year. In 2020 alone, firearm-related incidents including homicide, accidents, and suicides, reached a staggering number of over 43,000.^1,2 With the increase in these types of incidents, several service areas in crime laboratories are heavily impacted by the number of cases run on a yearly basis. These include firearm examinations, gunshot residue (GSR) analysis, bullet hole identification, and shooting distance determination, which are crucial to support a criminal investigation and, overall, the justice system in our country. These areas …

Study Of Resonantly Stabilized Radicals In Combustion Environments, James H. Lee

Graduate Theses, Dissertations, and Problem Reports (ETD)

Resonantly stabilized radicals (RSRs) play an important role in combustion environments due to their high stability resulting from resonance. Many RSRs such as the propargyl, allyl, or benzyl radicals are precursors to the formation of polycyclic aromatic hydrocarbons (PAHs), which can aggregate to form soot. Due to their stability, these RSRs can accumulate in combustion environments in significant quantities. The primary way these radical species are consumed in flames or by reactions with other abundant radicals, by self-recombination of propargyl to form benzene, or in the form of other abundant radicals such as the hydroxyl radical. Experimentally determining the pathways …

Development Of Capillary Vibrating Sharp-Edge Spray Ionization For Improving Continuous Flow Mass Spectrometry Analysis, Chong Li

Graduate Theses, Dissertations, and Problem Reports (ETD)

Capillary Vibrating Sharp-Edge Spray Ionization (cVSSI) is new ionization technique developed in the year of 2018. This ionization technique has attractive features such as simplicity, compactness, ease of manipulation, low costs, compatible with continuous flow, etc. However, the development of high performance cVSSI for mass spectrometry analysis is a process that needs unremitting optimizations. In this dissertation, I demonstrate the development of cVSSI for improving continuous flow mass spectrometry analysis. The chapter 2 focuses on improving the ionization efficiency of cVSSI through reducing the droplet size. Three strategies were tested to reduce the droplet size of VSSI. The most effective …

Synthetic Methods For Improved Scope And Efficiency Of Copper-Catalyzed Regioselective Alkene Boracarboxylation, Steven William Knowlden

Graduate Theses, Dissertations, and Problem Reports (ETD)

The synthesis of carboxylic acids is important to the chemistry community, owing to the broad applicability of these compounds as fine chemicals and pharmaceuticals. Method development over the last decade has focused on the preparation of carboxylic acids through transition metal catalysis utilizing CO₂ as a C1 synthon. Copper-catalyzed heteroelement(bora and sila)-carboxylation protocols provide functional group rich carboxylic acid products, yet remain underdeveloped and thus underutilized. Consequently, catalytic reductive difunctionalization methodologies in which CO₂ and B(pin) (pin = pinacolate: 2,3-dimethyl-2,3-butanediolate) are installed across the double bond of a vinyl arene were recently developed. These boracarboxylation protocols provided novel, …

Identifying And Minimizing Sources Of Variability Within Modern Spectroscopic Techniques For The Forensic Analysis Of Glass, Oriana Christy Ovide

Graduate Theses, Dissertations, and Problem Reports (ETD)

Broken glass is a trace material frequently found at crime scenes such as hit-and-runs, burglaries, assaults, and homicides. Existing research encompassing the forensic analysis of glass evidence is vast. Published studies cover the analysis and interpretation of various types of glass. However, organizations such as the National Institute of Justice (NIJ), National Institute of Standards and Technology Organization of Scientific Area Committees (NIST-OSAC), and American Society of Trace Evidence Examiners (ASTEE) continue to identify glass-specific research needs to strengthen the scientific foundations of the field. Current gaps within the forensic glass community involve understanding modern glass formulations, re-evaluating the performance …

Analysis Of Forensically Relevant Evidence Using Electrochemistry, Spectroscopy, And Mass Spectrometry Tools, Colby Edward Ott

Graduate Theses, Dissertations, and Problem Reports (ETD)

Forensic science relies on the use of multiple techniques in the assessment of evidence to increase the accuracy and reliability of the results. However, with the rapidly changing drug landscape due to the introduction of novel psychoactive substances, many traditional screening methods are no longer sensitive or selective enough for use. Additionally, many screening methods such as chemical color tests are prone to false positive and negative results and are subjective. Therefore, the goal of this dissertation was to develop a novel analytical scheme that can provide a more efficient, rapid, and sensitive method that will facilitate adoption in the …

Calcite Depression In Bastnaesite-Calcite Flotation System Using Organic Acids, Emmy Muhoza

Graduate Theses, Dissertations, and Problem Reports (ETD)

Bastnaesite is the primary source of light REEs, namely cerium (Ce), lanthanum (La), praseodymium (Pr), neodymium (Nd), to name a few. Bastnaesite is typically concentrated using the froth flotation beneficiation method. Flotation of bastnaesite suffers from high reagent consumption due to the similar surface characteristics of bastnaesite and associated gangue minerals, including calcite. Additionally, complex stages of high-temperature conditioning are often required to suppress the detrimental impact of dissolved calcium ions on the flotation of bastnaesite. This research seeks to investigate the capabilities of organic acids in the bastnaesite-calcite flotation systems to selectively depress calcite minerals and effectively chelate calcium …

Synthesis, Characterization, And Activation Of Pyridine Dipyrrolide Supported Vanadium-Nitrogen Multiple Bonds, Jordan Cruz Martinez

Graduate Theses, Dissertations, and Problem Reports (ETD)

The chemistry of coordination complexes of vanadium supported by pyridine di-pyrrolide pincer ligands was probed via the synthesis and investigation of a variety of compounds from the trivalent starting material, (^MesPDP^Ph)VCl(thf)₂. Under reducing conditions and subsequent addition of terpyridine, a redox transfer series (1-, 0, 1+) stemming from the neutral product (^MesPDP^Ph)V(terpy) was isolated and characterized by X-ray crystallography. The precise bond lengths, in conjunction with bulk magnetic susceptibility, allowed for a detailed study of the redox non-innocence of polypyridyl ligands in these systems.

Metathesis of the halide starting material …

Establishing The Relative Composition Of Functionalized Thiols In Mixed Ligand Gold Nanoparticles By 1h-Nmr Spectroscopy, Matthias Carroll

All Master's Theses

Functionalized gold nanoparticles (AuNPs) are of interest for their optical and electrical properties, specifically the surface plasmon resonance phenomenon and potential applications for medicine and nano-circuitry. In this study, the ligand composition of small (~5 nm diameter) thiol functionalized AuNPs with mixed ligand monolayers was investigated to better understand how the molar feed ratio of ligands used during their synthesis influences the composition of ligands on the particle’s surface. The system under study was a combination of two ω-functionalized thiols, mercapto ethoxy ethoxy ethanol (MEEE) and mercapto pentyl trimethyl ammonium chloride (MPTMA). UV/Visible spectrophotometry, dynamic light scattering, and electron …

Assessment Of Quechers Extraction Protocol For The Lc-Ms/Ms Detection Of Emerging Fentanyl Analogs In Biological Specimens For Clinical And Forensic Purposes, Kylea M. Morris

Graduate Theses, Dissertations, and Problem Reports (ETD)

Drug abuse within the United States is a dynamic and pervasive issue that affects the quality and life expectancy of our society. One of the major drug classes that are constantly utilized is opioids. Opioids are prescribed for pain management in patients suffering from cancer and other medical illnesses. Long-term use of opioids could lead to tolerance in humans, which poses a risk of reaching fatal overdose levels. Unfortunately, opioids are abused recreationally, and in some instances, individuals are unaware of the presence of dangerous synthetic drugs like fentanyl, hidden in materials such as heroin, cocaine, oxycodone, and methamphetamine. Recent …

Photocatalytic Degradation Of Lignin By Supported Silver Nanoparticles, Ning Wei

Theses and Dissertations--Chemical and Materials Engineering

Lignin is the second most abundant form of biomass on earth. The phenolic structure and high carbon to oxygen ratio make lignin an attractive renewable source of fuel and chemicals. However, its recalcitrance and heterogeneous nature prove difficult for decomposing lignin’s polymer structure and separation of the products. This work has focused on the use of low-energy catalytic approaches to overcome these barriers. A mimic of the lignin degrading enzyme laccase, consisting of a copper cluster Cu4Py4I4 modified with AgNO3, was developed to function similarly to the laccase active site. The prepared copper complex solution was found to be active …

A Highly Conductive, Flexible, And 3d-Printable Carbon Nanotube-Elastomer Ink For Additive Bio-Manufacturing, Andy Shar, Phillip Glass, Daeha Joung Ph.D.

Undergraduate Research Posters

The synthesis of a highly conductive, flexible, 3D-printable, and biocompatible ink has been of great interest in the field of bio-based additive manufacturing. Various applications include ultra-sensitive, microscale tactile sensors, patient-customizable scaffolds for cardiac and nerve tissue regeneration, and flexible electrocardiogram (ECG) electrodes. Here, a novel elastomeric carbon nanocomposite is presented consisting of amino-functionalized carbon nanotubes (CNT-NH₂) homogenously dispersed in a one-part room-temperature vulcanizing (RTV) silicone matrix. The use of acetone as a swelling solvent aids in electrical percolation through the elastomer matrix. CNT-NH₂ ratios can be tuned to fit various needs; higher tensile strength is favored …

Review Of The Effects Of Asphalt Fume Emission (Vocs And Pahs) In Vitro, In Vivo And Human Studies, Omran Taqi, Nastassja Lewinski, Elham Fini, Eran Rozewski, Judith Klein-Seetharaman

Undergraduate Research Posters

Review of the effects of Asphalt fume emission (VOCs and PAHs) in vitro, in vivo and human studies

Omran Taqi, Nastassja Lewinski¹

1) Department of Chemical and Life Science Engineering, Virginia Commonwealth University, Richmond, VA

Background

Asphalt is abundantly available around human operations including road paving and roofing sites. However, their emissions and fumes (specifically volatile organic compounds (VOCs) and polycyclic aromatic hydrocarbons (PAHs)) have been found to have adverse effects on health. Asphalt fumes are a class 2A carcinogen and exposure can increase the risk of lung cancer, asthma, headache, fatigue, and other cardiovascular diseases.

Methods

We used …

Oxidative Damage To Brain Cells Underlies: (I) Resistance To Radiation And Increased Tumor Cell Growth In Glioblastoma; (Ii) Apoe Allele Status And Pentose Phosphate Pathway Proteins In Alzheimer Disease Mouse Models, Nicole Rummel

Theses and Dissertations--Chemistry

Oxidative phosphorylation occurs within the inner mitochondrial membrane producing ATP for the cell’s energy needs. The Electron Transport Chain carries out the transfer of electrons from electron carriers through a series of proteins to form a proton gradient across the inner mitochondrial membrane. This gradient acts as the energy source needed to put a phosphate onto ADP and form ATP. With the large amounts of free electrons and oxygen within the mitochondria, an inevitable by-product of free radicals in the form of superoxide are produced. Superoxide (O^-̇₂) is a reactive radical that can react further to …

Synthesis Of 6,6- And 7,7-Difluoro-1-Acetamidopyrrolizidines And Their Oxidation Catalyzed By The Nonheme Fe Oxygenase Lolo, Nabin Panth

Theses and Dissertations--Chemistry

One of the remarkable steps in loline alkaloid biosynthesis is the installation of an ether bridge between two unactivated C atoms in 1-exo-acetamidopyrrolizidine (AcAP). LolO, a 2-oxoglutarate-dependent nonheme Fe oxygenase, catalyzes both the hydroxylation of AcAP and the resulting alcohol's cycloetherification to give N-acetylnornoline (NANL). The mechanism of hydroxylation is well understood, but the mechanism of the oxacyclization is not. I synthesized difluorinated analogs of AcAP in an attempt to further understand the mechanism of the unusual cycloetherification step.

I prepared 6,6-F₂-AcAP in eight steps from N,O-protected 4-oxoproline. The key step was a Dieckmann …

Crystal Engineering Of Asymmetric And Pyrene Fused Annulenes For Use In Organic Electronic Materials, Garrett Fregoso

Theses and Dissertations--Chemistry

Since the development of TiPS Pentacene, the use of trialkylsilylethynyl groups has become a commonly utilized moiety for stabilizing, solubilizing, and directing crystal packing of acenes and acene-like compounds, leading to the development of a well-defined series of trends that aid in the prediction of crystal packing for the development of organic semiconducting materials. While these trends have been extensively studied in mainly symmetric linear systems, it is important to determine how, if at all, asymmetry of the aromatic core affects these well-defined trends. This constitutes the basis of Chapter 2, which explores the crystal engineering and physical properties of …

Mass Spectrometric Analysis Of Lignin Model Compounds: Fundamental Investigations Of Ionization And Supramolecular Interactions For Lignocellulosic Biomass Applications, Kimberly Dean

Theses and Dissertations--Chemistry

Lignocellulosic biomass is pivotal for the development of renewable energy sources and materials essential to mitigate the exploitation of fossil fuels causing climate change and environmental pollution issues. The conversion of biomass into fuel requires the hydrolysis of cellulose and a biproduct of this process is the isolation of millions of tons of lignin as biorefinery waste. Lignin is a complex high molecular weight polymer whose structure remains undefined and critically limits potential industrial applications of lignocellulosic biomass. The advancement of analytical methods for structural elucidation of lignin and its ensemble of phenolic compounds is therefore essential to advance this …

The Role Of Charge On Dna Packaging And Integrity Within Reconstituted Peptide-Dna Assemblies, Ehigbai Oikeh

Theses and Dissertations--Chemistry

In nature, DNA exists primarily in a highly compacted form. The compaction of DNA in vivo is mediated by cationic proteins; histone in somatic nuclei and arginine-rich peptides called protamines in sperm chromatin. The packaging in the sperm nucleus is significantly higher than somatic nuclei resulting in a final volume roughly 1/20^th that of a somatic nucleus. This tight packaging results in a near crystalline packaging of the DNA helices. While the dense packaging of DNA in sperm nuclei is considered essential for both efficient genetic delivery as well as DNA protection against damage by mutagens and oxidative species, …

Development Of Fluorescence Based Approaches To Understand Astrocyte Biology In The Context Of Nicotine And Nicotinic Receptor Activity, Surya P. Aryal

Theses and Dissertations--Chemistry

Smoking and tobacco use (STU) is a major global health problem and worldwide more than six million people die due to tobacco related diseases each year. Although majority of smokers try to quit smoking several times in their life, traditional therapeutic approaches, which focus only on neuronal cells, have a very low success rate. Understanding the effect of nicotine on glial cells, synaptic communication and blood vasculature in the brain can provide further insights on the neurobiology of substance abuse and can potentially help to design better therapeutic approaches. Glial cells are non-excitable cells in the brain which do not …

Application Of Mass Spectrometry For Characterization Of Plant-Based Phenolics And Alkaloids, Masoumeh Dorrani

Theses and Dissertations--Chemistry

Plant-derived compounds have the potential to produce value-added compounds with a variety of applications. For example, the lignin part of the lignocellulosic biomass, produced in large quantities as waste from the paper and pulp industries, is a rich source of phenolics with potential applications in the renewable energy sector, pharmaceutical, and chemical industries. On the other hand, plant alkaloids are the primary source for developing plant-derived therapeutics. Unfortunately, the recalcitrant nature of plant cell walls, low extraction yields of small secondary metabolites, and the lack of effective analytical methods for a rapid and accurate identification of plant-based compounds and plant’s …

Nanomaterial Synthesis And Real Time Investigation Of Thermal Effects On Nanomaterial And Nano-Interfaces For Real World Applications, Rose H. Pham

Theses and Dissertations--Chemistry

As interest in nanomaterials and nanotechnology continues to grow, so does the need for more efficient and economical synthesis methods to keep up with the demand. The applications for nanomaterials are seemingly endless as they have functions in energy, biomedical, environmental, and many more. Working to develop different morphologies and sizes of nanomaterials will further help expand its utility. With the use of advanced characterization techniques such as in situ transmission electron microscopy (TEM), real time studies on the effects of external forces on nanomaterials are possible under controlled environments. This will give insight on how nanomaterials will perform in …

Development Of Ph-Sensitive And Amine-Reactive Lifters For The Detection Of Latent Fingermarks, Andrei Gregory Mlakar

Graduate Research Theses & Dissertations

Latent fingermarks are among the most common forms of physical evidence left at crime scenes. Being composed largely of eccrine and sebaceous secretions, they are typically invisible unless they are treated with, e.g., powders or cyanoacrylate fumes. Drawbacks to these and other commonly used methods, however, may include limited substrate compatibility, safety hazards, inability to detect older marks, and the need for expensive instrumentation and expert practitioners. Fingermarks on curved, reflective, patterned, or luminescent substrates are particularly challenging to image with most common techniques. After treatment, fingermarks on such difficult substrates may be transferred to, or “lifted” by, flexible adhesives, …

Interfacial Electrochemistry In Metallic Film Fabrication, Eric S. Tuala

Masters Theses

An experimental determination of RC constant at the edge and the center of a disk electrode was done using in situ reflectance spectroscopy on a Au electrode immersed in HClO₄ as electrolyte. The RC constant at the edge of the disk electrode was found much smaller than that at the center. Such differences contribute to the selective removal of the deposited Cu on an Au disk electrode.

Furthermore, the electrochemical corrosion of Cu²⁺ towards Co electrode (called cementation reaction) was investigated using a Co/Pt rotating disk electrode. The Open Circuit Potential of Co electrode in CuSO₄ electrolyte …

A Study Of Π – Π Stacking Interactions In Rhenium Carbonyl Complexes Based On Backbone Functionalized Bis(Pyrazolyl)Methane Ligands, Balamani Guduru

Masters Theses

π – π Stacking interactions are one of the most important non-covalent inter-molecular forces, which play an important role in the architecture of 1D and 2D networks of supramolecular chemistry. This associative contact involves the attractive interactions of aromatic molecules with each other. To describe and study the strength of the π – π stacking interactions, four new bis(pyrazolyl)ethanamine ligands having different aromatic groups (1-pyrenyl, 1-naphthyl, 2-naphthyl, and 9-anthracenyl) known for their propensity to be involved in π – π stacking interactions were prepared by the reaction of one equivalent of bis(pyrazolyl)ethanamine with one equivalent of the corresponding aromatic aldehyde. …

Synthesis And In Situ Characterization Of Intercalated Transition Metal Oxide Nanomaterials Investigated For Novel Cathode Applications, Ahamed Ullah

Theses and Dissertations--Chemistry

To develop an effective battery cathode material that can be useful for future batteries, the thermal stability and ion diffusion dynamics need to be well understood. In situ transmission electron microscopy (TEM) is a popular and proven technique to study the evolution of local structures during the dynamic processes in the cathode materials. This dissertation will demonstrate the application of high-resolution imaging and in situ heating and biasing in the TEM to study the structure and composition, morphology change, and ion diffusion in the cathode materials.

The three chapters in this dissertation will be focused on the two cathode materials: …

Fundamental Study Of Dopant Effect And Toxicity In Perovskite Materials, Xun Li

Graduate Research Theses & Dissertations

This dissertation comprehensively studies the research on organic-inorganic hybrid perovskite to solve the toxicity issue of perovskite-based solar cells under practical conditions, understand the doping effect on hybrid perovskite materials in optoelectronic applications, and improve the photovoltaic performance of perovskite-based solar cells by composition tailoring. Specifically, an innovative and simple chemical approach was invented for on-device sequestration of toxic Pb leakage caused by severe device damage. To mimic the practical conditions, the sequestration of lead leakage was conducted under cold water, warm water, acid water, dripping water, and water with competitive ions. Crucially, it was found that at least 96% …

The Design And Synthesis Of New Organic Dithiols For Environmental Applications, Shashika Nadishani Bandara

Theses and Dissertations--Chemistry

A thiol molecule, 2,6-pyridinediamidoethanethiol (PB9), was synthesized based on the pyridine-2,6-dicarboxamide scaffold with appended cysteamine groups. PB9 acts as an effective chelator for Pb(II) due to multiple binding sites (N₃S₂) through irreversible binding precipitating Pb(II). Removal of aqueous Pb(II) from solution was demonstrated by exploring the effects of time, initial PB9:Pb(II) ratios, pH, exposure time, and solution temperature. After 15 min the Pb(II) concentrations were reduced from 50.00 ppm to 0.30 ppm (99.4%) and 0.25 ppm (99.5%) for PB9:Pb ratios of 1:1 and 2:1, respectively. Removal of > 93% Pb(II) was observed over multiple pH values with …

1,2-Diamination Of Alkenes Via Reduction Of 1,2,3-Triazolinium Ions, Setareh Saryazdi

Theses and Dissertations--Chemistry

1,2-Diamine substructures are prevalent functional motifs in natural products, pharmaceutical compounds, and ligands. The interesting functionalities of 1,2-diamines have inspired many synthetic chemists to design various methodologies for preparing these structures from simple precursors such as alkenes. In this work, we described two different but related methods using simple and easily accessible reagents for 1,2-diamination of alkenes. In the first method, an alkene undergoes 1,3-dipolar cycloaddition with an organic azide to form a 1,2,3-triazoline. Subsequent N-alkylation of the generated 1,2,3-triazoline gives the 1,2,3-triazolinium ion, which is then hydrogenated over Raney Ni with a balloon of H₂ to produce …

Assembly Mechanism Of Early Hsp90-Cdc37-Kinase Complexes, Dimitra Keramisanou, M.V. Vasantha Kumar, Nicole Boose, Rinat R. Abzalimov, Ioannis Gelis

Advanced Science Research Center

Molecular chaperones have an essential role for the maintenance of a balanced protein homeostasis. Here, we investigate how protein kinases are recruited and loaded to the Hsp90-Cdc37 complex, the first step during Hsp90-mediated chaperoning that leads to enhanced client kinase stability and activation. We show that conformational dynamics of all partners is a critical feature of the underlying loading mechanism. The kinome co-chaperone Cdc37 exists primarily in a dynamic extended conformation but samples a low-populated, well-defined compact structure. Exchange between these two states is maintained in an assembled Hsp90-Cdc37 complex and is necessary for substrate loading. Breathing motions at the …