Physical Sciences and Mathematics Commons^™

Scanning Electron Microscopy (Sem) Investigation Of Morphology Changes In The Reduction Of Silica Nanoparticles To Elemental Silicon, Allison M. Cairns

University Honors Theses

The application of silicon nanoparticles varies from energy storage materials, to drug-delivery, and molecular recognition. Various chemical and physical properties of the Si nanoparticles arise from their morphology. This paper aims to reveal the morphology of Si nanoparticles following magnesiothermic reduction of silica (SiO₂) nanoparticles. Two sets of SiO₂ nanoparticles were used, commercially available NanoXact nanoparticles and laboratory-synthesized Stöber nanoparticles. A Zeiss Sigma VP FEG SEM was used to examine the morphology. Following the magnesiothermic reduction, the nanoparticles were etched with HF. Ten sets of images were taken of both Stöber and NanoXact nanoparticles: 1,2: the SiO …

Interactions Between The Azoarcus Ribozyme And Manganese (Ii) Divalent Cations, Joshua Martwick

University Honors Theses

The RNA world hypothesis suggests that RNA systems were the first form of life on the planet, beginning to appear approximately 4 billion years ago. Group I introns are self-splicing RNA elements in extant organisms and use Mg²⁺ as the principle divalent cation to promote catalysis. The group I intron ribozyme from Azoarcus is frequently used in origin of life studies, partially due to its autocatalytic abilities - the Azoarcus ribozyme is able to be broken into fragments and reassemble itself into its fully functional ribozyme. Previous work identified metal binding sites on the Azoarcus ribozyme which use both …

Applications Of Triplet-Photosensitizers And Development Of Photochemical Methods, Luke V. Lutkus

Dissertations and Theses

Photochemistry focuses on various aspects of the interaction of light with molecules. This work entails new methodology for fundamental measurements of photochemistry along with novel applications of triplet-photosensitizers. Herein described are two separate methodologies developed for the determination of the quantum yield. A method for the singlet oxygen quantum yield was developed that utilizes the reaction between singlet oxygen and dimethyl sulfoxide (DMSO) to produce dimethyl sulfone. The rate of the reaction is measured by the pressure decrease that results from the consumption of oxygen from the headspace of a sealed system. It was found that the rate of pressure …

Analysis Of E-Cigarette Liquids And Aerosols By Nmr Spectroscopy: Compositions, Boiling Points, And Degradation Profiles, Anna Katherine Duell

Dissertations and Theses

Electronic cigarettes (e-cigarettes) are an increasingly popular tobacco product used by ~3% of adults and 21% of 12th grade students (as reported for the prior 30-days in surveys) in the United States in 2018. As of 2019, this number went up to ~25% for 12th grade students. Due to how quickly e-cigarettes gained popularity and the rapid design changes that have ensued, there has not been enough time to accurately assess the effects of e-cigarettes, particularly for long-term use. The liquids used in e-cigarettes (e-liquids) can degrade when vaped in an e-cigarette, so understanding the variables that can modulate degradation …

The Process Of Establishing Theoretically Grounded Measures Of Science And Chemistry Identity For Use In Undergraduate Chemistry Courses, Kathryn Nicole Hosbein

Dissertations and Theses

Identity has been theorized to aid in student persistence toward science, engineering, technology, and math (STEM) degrees. However, before we can explore the impacts of learning environments on identity, and subsequently persistence, robust measures that can aid in understanding how identity is fostered need to be available. This research study aims to create measures of identity by expanding an existing physics identity framework and contextualizing it to science and chemistry identities. Development of the measures was carried out through two distinct phases that provided evidence for reliability and multiple aspects of validity.

The first phase of the study used qualitative …

Assessing The Efficacy Of Virtual Experiments In The General Chemistry Laboratory, Cory Jerome Hensen

Dissertations and Theses

As more students enroll in chemistry courses, institutions are faced with increasing costs and limited laboratory space to keep up with the demand. One solution some institutions have turned to is the incorporation of virtual experiments into the curriculum, as this can lower costs and increase the availability of laboratory space. Some institutions have offered sections that complete all of their experiments in a virtual environment, others have offered sections that alternate between a traditional hands-on experiment and a virtual experiment, and some institutions have replaced only select experiments throughout the curriculum with a virtual experiment. To begin to be …

Investigating The Origins Of Toxins Present In Electronic Cigarette Aerosols, Shawna Vreeke

Dissertations and Theses

The purported safety of electronic cigarettes has come under scrutiny with the significant increase of lung related illnesses starting in the summer of 2019. Public view has started to shift towards understanding the potential negative health impact associated with these devices. While many investigations indicate probable hazards present in e-cigarette aerosols, inter-laboratory assessments are wide ranging and can be contradictory. Due to the novelty of this field, relatively little is known about these products. In this work, the identification and quantification of inhalation toxicants such as formaldehyde, acrolein, acetaldehyde and dihydroxyacetone are reported. Results of the investigation of the ability …

Spontaneous Recombination Of Short Rnas To Increase Length And Complexity In Prebiotically Plausible Conditions, Benedict Arthur Smail

Dissertations and Theses

The RNA World hypothesis is an influential theory of how life arose on earth which posits that the earliest life forms carried out essential activities with RNA catalysts instead of proteins. Substantial evidence to support this theory comes from among others, the fact that the ribosome is a ribozyme, the existence of small RNA catalysts capable of high activity, and self-assembling ribozymes such as the Azoarcus ribozyme. Additional support has been provided by the directed evolution of various ribozymes and the reputed prebiotic synthesis of nucleotides and small RNA oligomers. However, it has long been challenging to show how long …

Photoelectrochemical Catalysis Of Hydrogen Peroxide With Tellurium Containing Chromophores, James Eliott Lohman

Dissertations and Theses

Growing concerns over climate change and demand for energy worldwide have made development and implementation of alternative energy sources more necessary than ever. Many of the leading energy alternatives suffer from inconsistent energy production due to fluctuations in availability of natural resources, and the current methods of addressing the issue have tremendous ecological and social ramifications of their own. While fuels like hydrogen gas are providing some promise of relief, the scope of infrastructure changes necessary for implementation and the implicit hazards of the use of such fuels complicate their application as an immediate solution. However, hydrogen peroxide carries far …

Early Detection Of Corrosion Via Hydrogel-Based Spectroelectrochemical Sensors, Capri Ann Price

Dissertations and Theses

The backbone of the industrialized world is comprised of refined, zerovalent metal, a material which thermodynamically favors an oxidative return to more chemically stable states. There are many methods used to slow or delay this process, such as protective coatings, sacrificial anodes, and alloys, but no method can entirely prevent corrosion. This body of work instead proposes detecting the earliest chemical markers of corrosion: that is, metal ions as they solubilize from a metal surface. Such information would allow maintenance personnel to make informed decisions about the necessity or lack thereof of preventive maintenance, and intervene before advanced damage has …

Thiophene-Based Molecular Sensors Towards The Selective Detection Of Mercury(Ii) And Other Metals, Austin Kazuo Shigemoto

Dissertations and Theses

This work describes several thiophene-based molecular sensors and various modifications aimed to improve and understand the photophysical and supramolecular properties, such as the association constant (K_a) and selectivity, towards the development of a selective mercury(II) sensor. From the first generation of sensors containing pyridine and thiophene groups, it was determined that thiophene can offer good selectivity for mercury(II) against other transition metal ions, and provide a ratiometric absorption and fluorescent response. The projects following this focused on improving the K_a of the first generation of sensors through several different strategies. Substitution of thiophene for dibenzothiophene was …

Development Of A Direct Aqueous Synthetic Route For The Production Of Elemental Bismuth Nanoparticles, Colin Jon Hiatt

Dissertations and Theses

Bismuth nanoparticles (Bi NPs) for use as an X-ray contrast material have gained significant traction in recent years due to the high atomic number and generally accepted biological tolerance of bismuth. However, to be considered a viable candidate for use in this application, water solubility is a necessity, which poses a challenge, since bismuth tends to readily oxidize. For this reason, research into the direct aqueous synthesis of Bi NPs is still in its infancy and can be very difficult, as described in Chapter 1. The remaining chapters of the thesis describe the direct aqueous synthesis of Bi NPs starting …

A Study Of Fragmentation And Spontaneous Covalent Self-Assembly Of The Azaorcus Ribozyme From Multiple Small Inactive Rna Fragments, Tharuka Sewwandi Jayathilaka

Dissertations and Theses

The question about the origins of life often appears as a difficult question to answer. A more reliable candidate molecule for the chemical origins of life would be a molecule that is capable of making copies of itself from simple precursors. With the finding of the catalytic activities of RNA molecules by Thomas Cech and Sid Altman in late 1980s, the term ribozyme was introduced to define an RNA molecule with catalytic activity. The RNA World is a conceptual period in the early stages in the development of life because RNA simultaneously possesses evolvability and catalytic function. An RNA molecule …

Combined Theoretical And Experimental Investigation Of Hydrogen Production Catalysis, Carolyn Noelle Virca

Dissertations and Theses

The widespread use of solar energy has been limited in part by the issue of effective storage. Water splitting is a means of converting solar energy into chemical fuel, in the form of hydrogen gas. It can be performed through both photochemical and electrochemical processes, via the two half reactions of water oxidation and proton reduction. Electrochemically, the catalyst receives electrons from an external circuit, which can be coupled to a renewable source such as a solar cell. Photochemically, a light-absorbing molecule provides an excited electron to a catalyst, which either generates oxygen or hydrogen gas. The work described herein …

The Preparation Of Diaryliodonium Salts For Application In Arylation Chemistry, Thomas Ludwig Seidl

Dissertations and Theses

Diaryliodonium salts offer potential as novel reagents for arylation chemistry. An overall goal and successful outcome of this work has been to further understanding of diaryliodonium salt chemistry by developing practical methods that enable chemists more convenient access to these reagents, for the purpose of reaction development. To this end a robust and convenient preparation method has been developed and resulted in novel commercially available diaryliodonium salts. The remainder of the work described, has focused on understanding the parameters important to diaryliodonium mediated arylation and has resulted in a solid framework that multiple future development efforts can build upon.

A …

Crystal Growth And Surface Modification Of Pyrite For Use As A Photovoltaic Material, Eric Rustad Young

Dissertations and Theses

Pyrite (FeS₂) has recently attracted significant interest as a photovoltaic material due to its promising optical properties, high photon to electron conversion yield, and low-cost raw materials. However, hopes have been tempered by recent discoveries that suggest the presence of hard to remove bulk sulfur defects. This research was focused on engineering and implementing the crystallization of pyrite from a sulfur rich solution to counteract the material's natural tendency to form bulk sulfur defects. Homoeptiaxial layers and single-crystal samples have been grown from tellurium sulfur melts with an Fe:S ratio of 1:4 using both natural and synthetic substrates. …

Development Of A Liquid Contacting Method For Investigating Photovoltaic Properties Of Pbs Quantum Dot Solids, Vitalii Alekseevich Dereviankin

Dissertations and Theses

Photovoltaic (PV) devices based on PbS quantum dot (QD) solids demonstrate high photon-to-electron conversion yields. However, record power conversion efficiencies remain limited mainly due to bulk and interfacial defects in the light absorbing material (QD solids). Interfacial defects can be formed when a semiconductor, such as QD solid, is contacted by another material and may predetermine the semiconductor/metal or semiconductor/metal-oxide junction properties. The objective of the work described in this dissertation was set to explore whether electrochemical contacting using liquid electrolytes can provide sufficient means of contacting the QD solids to investigate their PV performance without introducing the unwanted interfacial …

Copper Nanowires Synthesis And Self-Assembly For Interconnect Applications, Srikar Rao Darmakkolla

Dissertations and Theses

One-dimensional (1D) nanomaterial self-assembly offers an excellent approach to the fabrication of highly complex nanodevices. Despite considerable effort and research, precisely controlling the orientation and positioning of nanowires (NWs) on a large-scale area and assembling into a functional device is still a state of the art problem. This thesis focuses on the dimensionally controlled copper nanowires (Cu NWs) synthesis, and magnetic field assisted self-assembly of cupronickel nanowires (Cu/Ni NWs) into interconnect structures on a carbon doped silicon dioxide (CDO) wafer.

CDO is a low dielectric constant (k) material used for copper interconnects in multilayered complex integrated circuits (ICs). …

Investigation Of Aerosol Optical And Chemical Properties Using Humidity Controlled Cavity Ring-Down Spectroscopy, Xijing Zhu

Dissertations and Theses

Scientists have been observing a change in the climate since the beginning of the 20^th century that cannot be attributed to any of the natural influences of the past. Natural and anthropogenic substances and processes perturb the Earth's energy budget, contributing to climate change. In particular, aerosols (particles suspended in air) have long been recognized to be important in processes throughout the atmosphere that affect climate. They directly influence the radiative balance of the Earth's atmosphere, affect cloud formation and properties, and are also key air pollutants that contribute to a variety of respiratory and cardiovascular diseases. Despite their …

Analysis Of The Acid-Base Balance Of Mainstream Tobacco Smoke And Its Effect On The Gas/Particle Partitioning Of Nicotine, Amy Kathleen Devita-Mcbride

Dissertations and Theses

Tobacco smoke particulate matter (PM) is a complex mixture of condensed organic compounds, with about 5 to 10% water. Its general properties are similar in some respects to that of atmospheric organic aerosol PM and thus provides a useful surrogate when studying atmospheric PM. Due to its ability to undergo acid-base chemistry, nicotine is of particular interest in the tobacco smoke system. The gas/particle partitioning of nicotine depends on the protonation state of nicotine in the particles, so the distribution of nicotine between these phases provides a means of understanding the acid-base balance in the tobacco smoke system. The goal …

Controlling Water Exchange Kinetics And Improving Paracest Imaging, Jacqueline R. Slack

Dissertations and Theses

Generating MR image contrast from exogenous contrast media through chemical exchange saturation transfer (CEST) offers several exciting new possibilities, such as multicolored imaging, the interleaving of pre- and post-contrast images, and the potential to perform ratiometric metabolic imaging. The major limitation of the deployment of CEST imaging is the comparatively high detection limits of exogenous agents and particularly at the low B_¹ power levels required to meet SAR requirements. The large chemical shifts afforded by paramagnetic (paraCEST) agents permit more rapid exchange kinetics and therefore potentially more effective contrast agents. Despite comparatively large chemical shifts, many Ln³⁺ DOTA-tetraamide …

Investigations Of Electronic Cigarette Chemistry: 1. Formation Pathways For Degradation Products Using Isotopic Labeling; And 2. Gas/Particle Partitioning Of Nicotine And Flavor Related Chemicals In Electronic Cigarette Fluids, Kilsun Kim

Dissertations and Theses

Use of electronic cigarettes (e-cigarettes) is rapidly growing around the world. E-cigarettes are commonly used as an alternative nicotine delivery system, and have been advocated as generating lower levels of harmful chemicals compared to conventional cigarettes. Cigarette smoke-like aerosols are generated when e-cigarettes heat e-liquids. The main components of e-cigarette liquids are propylene glycol (PG) and glycerol (GL) in a varying ratio, plus nicotine and flavor chemicals. Both PG and GL are considered safe to ingest in foods and beverages, but the toxicity of these chemicals in aerosols is unknown. Current studies of e-cigarettes have mainly focused on dehydration and …

The Discovery And Development Of Metal-Free Arylation Reactions With Unsymmetrical Diaryliodonium Salts, Sunil Kumar Sundalam

Dissertations and Theses

Functionalizing arenes and heteroarenes has been an active area of research since the 19th century, due to the presence of these molecular structures in many industrially important sectors. A tremendous amount of research has been published in achieving these chemical transformations using stoichiometric reagents and transition metal-catalyzed reactions. However, challenges still remain. An alternative and comparable methodology to metal-catalyzed reactions to overcome the drawbacks will advance this particular area of research is desirable.

Hypervalent iodine compounds offer a promising approach to metal-free arylation reactions. These mild, air and moisture stable compounds have showed significant success as non-toxic and metal-free reagents …

Investigation In To The Stabilizing Effects Of The Modified Base Archaeosine In Trna And The Identification Of The Fluorescent Product Of Base Treatment Of Nad(P)+ Cofactors, Ben Turner

Dissertations and Theses

This dissertation covers two projects linked by their involvement in the modification of tRNA bases.

The first project focused on an investigation of a role for the modified base Archaeosine, the ubiquitous modification in tRNA in the archaeal domain. Initial work was performed on a set of in vitro prepared tRNA modified to feature either the canonical guanine base at position 15, preQ₀ (TGT product) or Archaeosine (ArcS product). There was very little difference in the thermal stability of tRNAs containing these modifications in the halophilic H. volcanii tRNA^Ser or E. coli tRNA^Gln. In tRNA^{Gln …}

Formulation Of Colloidal Suspensions Of 3-Mercaptopropionic Acid Capped Pbs Quantum Dots As Solution Processable Qd "Inks" For Optoelectronic Applications, Chase Collier Reinhart

Dissertations and Theses

The use of colloidal quantum dots (QDs) for photovoltaic energy conversion is a nascent field that has been dominated for well over a decade by the use of 3-mercaptopropionic acid (3-MPA) capped PbS QDs. These QDs are routinely deposited via an in situ solid state ligand exchange process that displaces the native oleate ligand on the PbS QD surface. This ligand exchange procedure is wasteful of material and has been demonstrated to leave numerous impurities that limit electronic performance of the as-deposited QD devices. Until the last few years there was very little understanding in chemical literature as to many …

Investigations Into The Effects Of Water Exchange And The Structure Of Lanthanide Chelates, Katherine Marie Payne

Dissertations and Theses

Lanthanide chelates are effective agents for improving contrast in MR images. Optimizing the relaxation of inner sphere water molecules is a common focus of research in this field. However, the efforts to design an optimal contrast agent have commonly over-looked the relationship of water position and water exchange kinetics. This work explores structural conformation, the impact of very fast water exchange kinetics on hydration, and differing tumbling rates for regioisomers of a number of lanthanide chelates. We have grown crystals of LnDOTMA and obtained structural data by X-ray diffraction that provide a picture of the chelate during water exchange and …

The Application Of Electrochemical Impedance Spectroscopy To Immediately Diagnose The Protective Quality Of Coatings On Artistic And Architectural Metalwork, Kathryn Nicole Hosbein

Dissertations and Theses

Corrosion is a spontaneous process that causes irreversible damage to nearly all metals, which has world-wide implications for architectural and artistic metalwork, such as bridges, buildings, airplanes and sculptures. Protective coatings such as wax, paint, or polymeric clear coatings are used to prolong the lifetime of metals such as steel and bronze. Unfortunately, these coatings fail over time due to oxidative damage by UV rays and by failure to exclude water that can carry salts and pollutants that cause corrosion of the underlying substrate. The current method of coating assessment is visual inspection but when coating failure is detected at …

Quef And Quef-Like: Diverse Chemistries In A Common Fold, Adriana Bon Ramos

Dissertations and Theses

The tunneling fold (T-Fold) superfamily is a small superfamily of enzymes found in organisms encompassing all kingdoms of life. Seven members have been identified thus far. Despite sharing a common three-dimensional structure these enzymes perform very diverse chemistries.

QueF is a bacterial NADPH-dependent oxidoreductase that catalyzes the reduction of the nitrile group of 7-cyano-7-deazaguanine (preQ₀) to a primary amine (preQ₁) in the queuosine biosynthetic pathway. Previous work on this enzyme has revealed the mechanism of reaction but the cofactor binding residues remain unknown. The experiments discussed herein aim to elucidate the role of residues lysine 80, …

Thermal Decomposition Of Electronic Cigarette Liquids, Robert Paul Jensen

Dissertations and Theses

Electronic cigarette liquid (e-liquid) is a solution of propylene glycol and/or glycerol with varying concentrations of nicotine and flavorants. Inhalation of vaporized e-liquid is a method of nicotine delivery that is growing in popularity and is commonly regarded as safe relative to smoking traditional tobacco products. The thermal decomposition of glycerol and propylene glycol is typical of alcohols and has been investigated, although not exhaustively. In this work, samples of propylene glycol and glycerol were vaporized using an electronic cigarette (e-cigarette) and were analyzed for evidence of decomposition using nuclear magnetic resonance (NMR) spectroscopy. E-cigarettes are shown to degrade glycerol …

Molecular Probes For Pancreatic Cancer Imaging, Lei Wang

Dissertations and Theses

Pancreatic ductal adenocarcinoma (PDAC) has the poorest five-year survival rate of any cancer. Currently, there are no effective diagnostics or chemotherapeutics. Surgical resection is the only curative therapy. However, most patients experience recurrence due largely to challenges in assessing tumor margin status in the operating room. Molecular probes that selectively highlight pancreatic cancer tissue, having the potential to improve PDAC margin assessment intraoperatively, are urgently needed. In this work, a series of red and near-infrared fluorescent probes is reported. Two were found to distribute to normal pancreas following systemic administration. One selectively accumulates in genetically modified mouse models of PDAC, …