Physical Sciences and Mathematics Commons^™

High-Pressure Studies On The Transition From Red Phosphorus To Black Phosphorus, Heng Xiang

Electronic Thesis and Dissertation Repository

Black phosphorus (BP) is a promising material in many research fields. However, the transition process from amorphous red phosphorus (ARP) is elusive and hence hinders large scale synthesis and applications. This work describes the application of the high-pressure method to study the transition process from ARP to BP.

In this thesis, the following three objectives were achieved: (1) to understand the mechanism of the transition, (2) to facilitate the synthesis of BP by taking the advantage of less pure ARP, (3) to propose new methods of synthesizing BP-based materials, such as the moderately oxidized BP and the black phosphorus/ amorphous …

X-Ray Absorption Spectroscopy, X-Ray Diffraction And Optical Luminescence Studies Of Phase Transition Of Titania Nanotubes, Lu Yao

Electronic Thesis and Dissertation Repository

The one-dimensional (1D) TiO₂ nanotubes (NTs) and their derivatives have been extensively studied due to their wide applications, such as photocatalysts, solar cell, paints and so on. Since TiO₂ has a wide band gap (~3.0 eV), its photo-absorption as the photocatalyst only occurs in the UV region that wastes mostly solar energy. Therefore, the solution to higher photocatalytic efficiency has been sought for some time. This thesis presents a study of the size-dependent phase transitions of TiO₂ NTs using synchrotron-based X-ray techniques. The chemical environment including local symmetry and the luminescence origin of the TiO₂ NTs …

Electrochemical Investigation Into The External Failure Modes Of Oil And Gas Pipelines, Maxwell Goldman

Electronic Thesis and Dissertation Repository

Carbon steel is the material of choice for transmission pipelines for the oil and gas industry across the globe due to its mechanical properties, and low cost. Carbon steel is only resistffxidant, and the types of anions present in the exposure environment. Transmission pipelines are coated with non-conductive polymeric coatings and can be protected by cathodic protection in order to mitigate exterior corrosion. The primary goals of this thesis were to determine the role of anions, cathodic charging with hydrogen, and steel microstructure on different failure modes of carbon steel.

The corrosion mechanism of carbon steel in the presence of …

Galvanic Corrosion Of Copper-Coated Carbon Steel For Used Nuclear Fuel Containers, Thalia E. Standish

Electronic Thesis and Dissertation Repository

Carbon steel vessels coated with ∼3 mm of Cu have been proposed for the permanent disposal of used nuclear fuel in a deep geological repository (DGR) in Canada. In the event of an undetected defect in the Cu coating that exposes the steel substrate, galvanically accelerated corrosion of steel is, in principle, possible. To investigate this scenario, the progression of steel corrosion at the base of novel simulated through-coating defects was monitored electrochemically and imaged non-destructively using X-ray micro-computed tomography (micro-CT) as a function of time, O₂ availability (including anoxic conditions), and coating method (cold spray deposition (with and …

Saponin Penetration And Interactions With Membranes, Sarai Guerrero

Electronic Thesis and Dissertation Repository

The saponin QS21 has been used and studied for years as an adjuvant agent to improve vaccines for both humans and animals. However, how the saponin interacts with the membrane and itself remains poorly understood. We studied the QS21-A majority isomer using all-atom classical molecular dynamics simulations in model bilayers composed of cholesterol and either DOPC or DPPC. As this is one of the few computational studies on QS21-A, we had very few resources to compare our results to. Nevertheless, we were able to gain insight into possible configurations that QS21-A takes after penetration, the effect of the bilayer on …

Synthesis Of Polycarbamate‒Based Nanoassemblies And Previously Inaccessible Polyglyoxylates, Rebecca Yardley

Electronic Thesis and Dissertation Repository

Self-immolative polymers (SIPs) are a subclass of degradable polymers that can be triggered to depolymerize when exposed to a specific stimulus. The main advantages of SIPs are the controlled and predictable depolymerization, signal amplification, and tunability of the polymer regarding which stimuli it responds to. The work presented in this thesis details the synthesis, characterization, and applications of two different families SIPs: polycarbamates (PCBs) and polyglyoxylates (PGs). PCBs are known to have depolymerization rates that are sensitive to environmental conditions surrounding them. In efforts to modify the depolymerization, PCB was incorporated into amphiphilic diblock copolymers, first with multi-stimuli-responsive poly(2-(dimethylamino)ethyl methacrylate) …

Synthesis Of Functionalized Tetrahydropyridine Derivatives Via Sncl4-Promoted [4+2] Cycloaddition Of Donor-Acceptor Cyclobutanes And Nitriles, David Tong

Electronic Thesis and Dissertation Repository

The formation of carbon-heteroatom bonds is pivotal in obtaining structural frameworks present in a variety of important natural products and bioactive molecules. In that regard, Lewis-acid promoted cycloadditions of strained carbocycles have proven to be powerful tools for the construction of heterocyclic frameworks. The Pagenkopf group was the first to discover the cycloaddition of donor-acceptor (DA) cyclopropanes with nitriles. Since the strain energy of cyclobutane is comparable to that of cyclopropane, our group has sought to extend to the comparatively unexplored homologous cyclobutane scaffold. Disclosed here is the first [4+2] cycloaddition of nitriles with DA cyclobutanes via Lewis-acid activation. This …

Investigations Of The High Pressure Effects On Structural Properties And Co2 Adsorption Performance Of Mofs Using Vibrational Spectroscopy, Shan Jiang

Electronic Thesis and Dissertation Repository

The pre- and post-combustion carbon dioxide capture has drawn much attention in the past few decades owing to the increasing concentration of CO₂ in the atmosphere. Among all the potential solid adsorbents for CO₂ capture, metal-organic frameworks (MOFs) are a promising class of materials due to their large surface areas, high tunability and their high selectivity for gas adsorption applications. It has been widely demonstrated that the application of high external pressure in gigapascal level can substantially tune the structure, pore size and opening of porous material. Consequently, the structural, as well as gas adsorption properties of these …

The Synthesis Of Heterocycles And Carbocycles And Work Towards Kainic Acid, Mathew L. Piotrowski

Electronic Thesis and Dissertation Repository

This thesis focuses on the synthesis of a variety of heterocycles and carbocycles such as pyrrolidines, dihydrofurans, dihydropyrroles, cyclopentenes, and 2,5-dihydrooxepines. Traditional synthetic methods are discussed first, followed by the manipulation of donor-acceptor cyclopropanes towards the above-mentioned compounds. This leads to a discussion about an important pyrrolidine-containing natural product known as kainic acid. Kainic acid has been studied in the neuroscience field for its biological properties which have led to a better understanding of common human neurological disorders like epilepsy, Huntington’s disease and the after-effects of strokes.

Chapter two focuses on a common rearrangement of donor-acceptor cyclopropanes known as the …

Functionalization Of Indoles And Donor-Acceptor Cyclopropanes And Their Application Towards The Total Synthesis Of Tronocarpine And Dippinine B, Lauren C. Irwin

Electronic Thesis and Dissertation Repository

The work disclosed in this dissertation outlines novel reactions involving indoles and their applications towards the total synthesis of natural products, tronocarpine and dippinine B.

Showcased in Chapter 2 is a novel mode of activation for donor-acceptor cyclopropanes via an external hydrogen bond. The hydrogen bond increases the cyclopropane’s electrophilicity permitting indole nucleophiles to open the ring. The result is 3-postion functionalized indoles.

An external hydrogen-bond donor, HFIP (1,1,1,3,3,3-hexafluoroisopropanol), is used as a solvent to provide the medium necessary for favourable hydrogen-bond interaction with donor-acceptor cyclopropanes. Hydrogen bond activation of donor-acceptor cyclopropanes was successful in generating a multitude of functional …

Novel Avenues Toward Controlling The Photophysical Properties Of Ultra-Small Silicon Quantum Dots, Mohammed Abdelhameed

Electronic Thesis and Dissertation Repository

Quantum dots (QDs) have attracted an increasing attention in the last decade over many conventional organic dyes. This is due to their unique optical properties including broad absorption spectra, high photostability, and size-tunable photoluminescence (PL). However, some toxicity concerns associated with traditional quantum dots have hindered their wide applicability. Interestingly, silicon quantum dots (SQDs) have been shown to be more advantageous than most of QDs thanks to their excellent biocompatibility and biodegradability, low cytotoxicity, and versatile surface functionalization capability. Thus, SQDs are promising candidates for various biological and biomedical applications such as bioimaging, biosensing, and photodynamic therapy. Unfortunately, only a …

Progress Toward Durable Icephobic Materials, Matthew J. Coady

Electronic Thesis and Dissertation Repository

Ice accumulation is a major engineering challenge in many fields including aerospace, power generation, transportation, and infrastructure. A variety of solutions are being researched to address this challenge. Perhaps the most promising method of combating ice accumulation is by applying coatings with low values of interfacial ice adhesion strength, τ_ice. Icephobic materials are those with ice adhesion below 100 kPa, and it has been shown that passive delamination can occur on surfaces with τ_ice below 20 kPa. While various low adhesion surfaces have been prepared, durability concerns pervade applications where surfaces experience repeated icing or freeze-thaw cycles, …

Zinc–Phosphorus Clusters For Solution Synthesis Of Zinc Phosphide Nanoparticles, Kyungseop Lee

Electronic Thesis and Dissertation Repository

Synthesis of zinc phosphide (Zn₃P₂) nanoparticles is an emerging topic of investigation as Zn₃P₂ is a candidate material for the next generation solar cells. Despite the early discovery of its favorable electronic properties that are well-suited for photovoltaic applications, a major focus of synthetic strategy was with vapor/chemical deposition methods. Solution methods with greater control over size, crystal structure and composition at a lower production cost, has been underdeveloped in comparison. In this context, this thesis describes the synthesis, characterization and reactivity of zinc phosphido clusters: [Zn₂(μ-PPh₂)₂(PPh …

Methodologies For Metal Functionalization Of Phosphorus Based Photopolymer Networks, Vanessa Béland

Electronic Thesis and Dissertation Repository

Photopolymer networks with phosphonium cation, alkyl phosphine and olefin functionality were designed, synthesized and functionalized with metals by metathesis, coordination and hydrometallation reactions, respectively. The materials were strategically designed so that the metal functionalization step could be monitored and quantified. In some cases, this involved characterization by IR, NMR, or X-ray spectroscopic techniques, or by comparison to molecular analogues. It was found that by using a bi-functional photopolymer network, the material could be bi-metallized by orthogonal mechanisms. All metallized polymer networks were tested for their suitability as precursors to metal-containing ceramics. The polymers were pyrolyzed, and on analysis it was …

Strategies For The Preparation Of Functional Pendant Group Polymer Materials Via Click Chemistry, Rajeshwar Vasdev

Electronic Thesis and Dissertation Repository

This thesis describes the development of a polymer via a unique masking-unmasking strategy allowing for physical and chemical modification as desired. Modifiable polymers may lead to improved applications in drug delivery, photo-patterning and emissive materials design. In recent years, these potential traits have motivated the search for efficient protocols for the synthetic modification of polymers. Accordingly, click chemistry, characterized by fast, clean and high yielding reactions represents an effective tool for the modification of polymers. To achieve this goal, an efficient methodology is created to incorporate a highly reactive strained alkyne functional group as a modification site to expand the …

Vertical Ionization Energies From The Average Local Electron Energy Function, Amer Marwan El-Samman

Electronic Thesis and Dissertation Repository

It is a non-intuitive but well-established fact that the first and higher vertical ionization energies (VIE) of any N-electron system are encoded in the system's ground-state electronic wave function. This makes it possible to compute VIEs of any atom or molecule from its ground-state wave function directly, without performing calculations on the (N-1)-electron states. In practice, VIEs can be extracted from the wave function by using the (extended) Koopmans' theorem or by taking the asymptotic limit of certain wave-function-based quantities such as the ratio of kinetic energy density to the electron density. However, when the wave function is expanded in …

The Ghrelin Receptor And Its Appetite For Highly Potent Ghrelin Analogues, Tyler J. Lalonde

Electronic Thesis and Dissertation Repository

The growth hormone secretagogue receptor-1a (GHS-R1a) is expressed in many human tissues, most notably the hypothalamus, and causes an increase in appetite upon activation by its endogenous ligand, ghrelin. GHS-R1a is differentially expressed in malignant compared to benign tumours. Therefore, there is an interest in developing GHS-R1a-targeted peptides as novel drugs to modulate signaling for diseases such as cancer cachexia and obesity and to image the receptor for disease diagnosis and following progression.

Chapter 2 discusses a fluorescently labelled ghrelin analogue for imaging GHS-R1a in ex vivo biopsy analysis and in vivo distribution studies. The analogue was created through side-chain …

Shape-Controlled Nanoparticles As Effective Catalysts For Proton Exchange Membrane (Pem) Fuel Cells, Ali Feizabadi

Electronic Thesis and Dissertation Repository

Polymer electrolyte membrane fuel cell (PEMFC), is considered a promising candidate for the next generation power sources in transportation, stationary and portable applications. However, oxygen reduction reaction (ORR), one of the key reactions occurring on PEMFC is kinetically slow; this has limited performance and further advancement in this kind of fuel cells. Thus, improving the PEMFC efficiency requires a thorough understanding of the ORR mechanism on the desired catalyst. To address the above-mentioned demands, the scope of this thesis is focused on the fundamental understanding of facet-controlled nanoparticles, metal-support interactions, and bimetallic platinum catalysts, utilizing synchrotron-based X-ray absorption, X-ray photoelectron …

Synthesis Of Crosslinkable Poly(Ester Amide)S For Cell Encapsulation And Delivery, Yu Ting (Natalie) Liang

Electronic Thesis and Dissertation Repository

Tissue engineering using adipose-derived stromal cells (ASCs) shows promise for soft tissue regeneration. Biodegradable polymers are potential biomaterials as they support the growth and delivery of cells. Specifically, poly(ester amide)s (PEAs) are a class of biodegradable polymers with tunable structures that have been shown to exhibit low cytotoxicity and support the growth of various cell types. This thesis involved the development of new water soluble amino acid-based PEAs with crosslinkable moieties to enable formation of hydrogel scaffolds for ASC encapsulation. These hydrophilic phenylalanine-based and alanine-based PEAs were synthesized by solution polycondensation and photo-crosslinked into a series of hydrogels with and …

Synthesis And Characterization Of Peptide Nucleic Acids Incorporating Modified Nucleobases, Ali Heidari

Electronic Thesis and Dissertation Repository

Peptide Nucleic Acid (PNA), is a mimic of natural nucleic acids with exceptional binding properties. As such, numerous applications in biochemistry, medicine and biotechnology for PNA exist or have been proposed so far. Pseudo-complementary PNAs containing diaminopurine and thiouracil base pairs have been prepared and are shown to bind with high specificity and efficiency to complementary targets in double-stranded DNA by a mechanism termed ‘‘double duplex invasion’’ in which the duplex is unwound and both DNA strands are targeted simultaneously, each by one of the two pseudo-complementary PNAs. Chapter 2 describes a method for the preparation of modified nucleic acids …

The Reactivity Of Ditetrelenes Towards Organophosphorus Oxides, Maissa Belcina

Electronic Thesis and Dissertation Repository

The reactivity of tetramesityldisilene 4 and tetramesityldigermene 5 towards organophosphorus oxides was explored in this thesis. The reaction of dialkyl and diarylphosphine oxides and phosphites with ditetrelenes 4 and 5 resulted in a 1,3-addition to form diorganodisilyl and digermyl phosphinites 27, 28, 31, 32 and disilyl phosphites 35 and 36. The 1,3-addition resulted in a mild two electron reduction of the P(V) centre of the phosphine oxide and phosphite to a P(III) centre in the products, without the use of heat or a catalyst. The reaction of organophosphorus oxides provides another example of a main group …

Incorporation Of Fluorine Into Peptides And One-Bead One-Compound Libraries Through Copper-Free Click Chemistry For The Discovery Of Radiopharmaceuticals, Emily M. Murrell

Electronic Thesis and Dissertation Repository

Molecular imaging is making possible the understanding of intricate biological processes in real-time in both healthy and diseased tissues. The ability to non-invasively locate biomarkers of disease with good sensitivity and specificity affords the ability to provide accurate and early diagnoses, and patient stratification for therapy. The chemokine receptor CXCR4 is one biomarker of interest, as it is overexpressed in many cancers, yet has low expression elsewhere in normal physiology. This thesis will document a method of combinatorial chemistry to construct libraries of new potential peptide-based imaging agents for positron emission tomography (PET) imaging. It will also incorporate the study …

Synchrotron Radiation Analysis Of Daguerreotypes: Surface Characterization, Electrocleaning, And Preservation, Madalena S. Kozachuk

Electronic Thesis and Dissertation Repository

The first commercially viable photographic image, the daguerreotype, captured images from 1839 to 1860. While daguerreotypes provide a significant historical record of 19^th century individuals and events, deterioration now disfigures many of these images. This work describes the application of synchrotron radiation (SR) to the study of daguerreotypes.

Three goals were addressed in this thesis: 1) to utilize SR to further elucidate the physics and chemistry of the daguerreotype and how the surface varies with time, 2) to study the effects of the electrocleaning system on the daguerreotype surface, and 3) to propose suggestions to improve their preservation and …

Synthesis, Characterization, And Applications Of Group 13 And 14 Complexes Of Chelating Formazanate Ligands, Ryan R. Maar

Electronic Thesis and Dissertation Repository

This thesis describes the synthesis and characterization of group 13 (boron and aluminum) and group 14 (silicon, germanium, and tin) complexes supported by chelating formazanate [R¹-N-N=C(R³)-N=N-R⁵]^‒ ligands. The resulting complexes are redox-active and often luminescent. Chapters two to four describe the synthesis and characterization of boron formazanate adducts. The work in these chapters demonstrates that through structural modification of the formazanate ligand, solid-state- and NIR photoluminescence can be achieved. Furthermore, the formation of an oxoborane (B=O) afforded a highly photoluminescent formazanate adduct due to the structural rigidity imposed by the B=O bond. These …

Development Of Bioorthogonal Molecular Tools On Gold Nanoparticles, Wilson Luo

Electronic Thesis and Dissertation Repository

This thesis describes the development of bioorthogonal chemical tools — originally designed to form bonds cleanly and selectively in living systems — on gold nanoparticles (AuNPs) as a model reactive nanomaterial template to showcase chemical modifications in a facile and robust manner. To achieve this goal, new methodologies to cleanly incorporate strained alkyne (SA) and cargo-bearing triarylphosphine derivatives onto AuNPs were developed. The protocols described herein provide well-defined reactive AuNP interfaces that undergo bioorthogonal bond-forming and breaking reactions cleanly, selectively, and rapidly to enable chemical tuning of their properties and function.

In order to circumvent the high reactivity of SAs, …

Non-Traditional Metallation Of Metallothioneins With Xenobiotic Therapeutic Metals, Daisy L. Wong

Electronic Thesis and Dissertation Repository

The rise of the Anthropocene has seen more global pollution than before in history. With the explosion of consumer electronics in the last half century, the rise of metal pollution from their extraction and disposal results in the unnatural introduction of heavy and rare metals into the ecosystem. Organisms have a metal defense protein, metallothionein, which has multiple roles in essential metal regulation and protection against minimal toxic metal exposure. However, these modern heavy metals prominent in electronics are not found biologically and their interactions in the body are generally unknown. Some of these metals are employed as therapeutic agents …

Investigating The Rotary Mechanism Of Atp Synthase Using Molecular Dynamics Simulations, Angela Marcela Murcia Rios

Electronic Thesis and Dissertation Repository

F₁-ATPase is a motor protein that can use ATP hydrolysis to drive rotation of the central subunit. The γ C-terminal helix constitutes of the rotor tip that is seated in an apical bearing formed by the α₃β₃ head. It remains uncertain to what extent the γ conformation during rotation differs from that seen in rigid crystal structures. Existing models assume that the entire γ subunit participates in every rotation. Here we develop a molecular dynamics (MD) strategy to model the off-axis forces acting on γ in F₁-ATPase. MD runs showed stalling of the …

Corrosion Studies On Lightweight Automotive Alloys: The Effect Of Microstructure And Fundamental Mechanisms, Wilfred J. Binns

Electronic Thesis and Dissertation Repository

Owing to their excellent strength-to-weight ratio and low density, magnesium alloys have the potential to significantly reduce the weight of automobiles leading to decreased emissions and greater range for electrical vehicles. However, the practicality of magnesium alloys for automotive and aerospace applications is severely hindered by their poor corrosion resistance in aqueous environments. Despite intensive research effort, the underlying mechanism(s) responsible for this poor corrosion resistance remains elusive. Further complicating the situation is the presence of secondary microstructures which are necessary for desirable physical properties but lead to microgalvanic coupling which exacerbates the poor corrosion resistance of magnesium alloys. This …

Development Of In Situ Forming Hydrogels For Intra-Articular Drug Delivery, Andy Prince

Electronic Thesis and Dissertation Repository

Hydrogels are 3-dimensional crosslinked polymer networks that can absorb significant amounts of water. The physical properties associated with hydrogels affords them resemblance to biological tissues making them good candidates for biomedical applications. Many pharmaceuticals, specifically non-steroidal anti-inflammatory drugs (NSAIDs), have poor aqueous solubility, which limits their bioavailability and efficacy. People suffering from chronic osteoarthritis (OA) are required to frequently take large doses to mitigate pain, which can lead to serious side effects. Hydrogels are good strategies to deliver NSAIDs via articular injection because they can form solid gels in situ. This thesis describes the synthesis, formulation, mechanical testing, in …

Protein Conformations In The Gas Phase Probed By Mass Spectrometry And Molecular Dynamics Simulations, Maryam Bakhtiari

Electronic Thesis and Dissertation Repository

Mass Spectrometry (MS) has been revolutionized by the ability to produce intact gaseous protein ions by electrospray ionization (ESI). The question to what extent these ions retain solution-like conformations under “native” ESI conditions remains a matter of debate. Traditional high-resolution structure determination techniques only report on proteins in the condensed phase. For this reason, MD simulations play an important role in exploring the behavior of gas phase proteins. In this research, mobile and non-mobile proton MD simulations along with mass spectrometry data at 300 K in both positive and negative ion mode indicated that native-like conformations were largely retained. Surface …