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) …

Development Of Fertilizer Coatings From Polyglyoxylate-Polyester Blends Responsive To Root-Driven Ph Change., Spencer M Heuchan, Bo Fan, Jessica J Kowalski, Elizabeth R Gillies, Hugh A L Henry

Chemistry Publications

Many current controlled-release fertilizers (CRFs) are coated with nonbiodegradable polymers that can contribute to microplastic pollution. Here, coatings of self-immolative poly(ethyl glyoxylate) (PEtG) capped with a carbamate and blended with polycaprolactone (PCL) or poly(l-lactic acid) (PLA) were evaluated. They were designed to depolymerize and release fertilizers in the vicinity of plant roots, where the pH is lower than that in the surrounding environment. PEtG/PCL coatings exhibited significant temperature and pH effects, requiring 18 days at pH 5 and 30 °C, compared to 77 days at pH 7 and 22 °C, to reach 15% mass loss. Plant roots were also effective …

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 …

Charging And Supercharging Of Proteins For Mass Spectrometry: Recent Insights Into The Mechanisms Of Electrospray Ionization., Lars Konermann, Haidy Metwally, Quentin Duez, Insa Peters

Chemistry Publications

Electrospray ionization (ESI) is an essential technique for transferring proteins from solution into the gas phase for mass spectrometry and ion mobility spectrometry. The mechanisms whereby [M + zH]^z+ protein ions are released from charged nanodroplets during ESI have been controversial for many years. Here we discuss recent computational and experimental studies that have shed light on many of the mysteries in this area. Four types of protein ESI experiments can be distinguished, each of which appears to be associated with a specific mechanism. (i) Native ESI proceeds according to the charged residue model (CRM) that entails droplet evaporation …

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, …

Altering The Optoelectronic Properties Of Boron Difluoride Formazanate Dyes Via Conjugation With Platinum(Ii)-Acetylides, Jasveer S. Dhindsa, Adyn Melenbacher, Stephanie M. Barbon, Martin J. Stillman, Joe Gilroy

Chemistry Publications

The combination of π-conjugated organic compounds and Pt(II)-acetylides is a powerful strategy for the production of functional optoelectronic materials. The presence of the heavy element, Pt, in these compounds enhances electronic delocalization generally resulting in low-energy absorption and emission maxima and often leads to intersystem crossing, resulting in phosphorescence. When boron complexes of N-donor ligands, such as boron dipyrromethenes (BODIPYs), are involved the molecular and polymeric materials produced have properties that are advantageous for their use as oxygen-sensors, in triplet–triplet annihilation, and as the functional components of photovoltaics. Based on these exciting results, we endeavored to thoroughly examine the effect …

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 …

In Search Of The Hot Spot., Danielle M Mcrae, François Lagugné-Labarthet

Chemistry Publications

Tip-enhanced spectroscopy and its Raman variant, tip-enhanced Raman spectroscopy (TERS), provide the possibility to spatially resolve the vibrations of a single molecule when combined with ultra-high vacuum technology, but this technique suffers from poor time resolution2,3. On the other hand, surface-enhanced Raman spectroscopy (SERS) is a more common technique, and is used for many imaging and bioanalytical applications, still with single molecule sensitivity but, unlike TERS, without spatially resolved molecular imaging capabilities4. In SERS, the roughness and geometric characteristics of metallic surfaces (in general Al, Ag or Au) are exploited to enable high spatial …

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 …

Carving Plasmon Modes In Silver Sierpiński Fractals, Isobel C. Bicket, Edson P. Bellido, Danielle M. Mcrae, Francois Lagugne-Labarthet, Gianluigi A. Botton

Chemistry Publications

The surface plasmon resonance (SPR) modes of the first three generations of a Sierpiński fractal triangle are investigated using electron energy loss spectroscopy (EELS) complemented with finite difference time domain simulations. The Sierpiński fractal geometry is created in a subtractive manner, by carving triangular apertures into the triangular prism of the previous fractal generation. The ability of the fractal antenna to efficiently utilize space in coupling to long wavelength excitations is confirmed on the single nanostructure level via redshifting of the primary dipole mode as the fractal generation is increased. Through application of the Babinet principle, it is demonstrated that …

Synthesis Of Functionalized Tetrahydropyridines By Sncl4-Mediated [4+2] Cycloaddition Between Donor–Acceptor Cyclobutanes And Nitriles, David Tong, Jackie Wu, Nathan Bazinski, Donghyun Koo, Naresh Vemula, Brian Pagenkopf

Chemistry Publications

Cycloadditions of strained carbocycles promoted by Lewis acids are powerful methods to construct heterocyclic frameworks. In fact, the formal [3+2] cycloadditions of donor-acceptor (DA) cyclopropanes with nitriles has seen particular success in synthesis. In this work, we report on the first [4+2] cycloaddition of nitriles with DA cyclobutanes via Lewis acid activation. Tetrahydropyridine derivatives were obtained in up to 91% yield from various aryl activated cyclobutane diesters and aliphatic or aromatic nitriles.

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 …

Testing The Robustness Of Solution Force Fields For Md Simulations On Gaseous Protein Ions., Justin H Lee, Katja Pollert, Lars Konermann

Chemistry Publications

It is believed that electrosprayed proteins and protein complexes can retain solution-like conformations in the gas phase. However, the lack of high-resolution structure determination methods for gaseous protein ions implies that their properties remain poorly understood. Many practitioners tackle this difficulty by complementing mass spectrometry-based experiments with molecular dynamics (MD) simulations. It is a potential problem that the standard MD force fields used for this purpose (such as OPLS-AA/L and CHARMM) were optimized for solution conditions. The question whether these force fields produce meaningful gas-phase data has received surprisingly little attention. Standard force fields are overpolarized to account for an …

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 …

What Is The Accuracy Limit Of Adiabatic Linear-Response Tddft Using Exact Exchange–Correlation Potentials And Approximate Kernels?, Jaspreet Kaur, Egor Ospadov, Viktor N. Staroverov

Chemistry Publications

Calculation of vertical excitation energies by the adiabatic linear-response time-dependent density-functional theory (TDDFT) requires static Kohn–Sham potentials and exchange–correlation kernels. When these quantities are derived from standard density-functional approximations (DFA), mean absolute errors (MAE) of the method are known to range from 0.2 eV to over 1 eV, depending on the functional and type of excitation. We investigate how the performance of TDDFT varies when increasingly accurate exchange–correlation potentials derived from Hartree–Fock (HF) and post-HF wavefunctions are combined with different approximate kernels. The lowest MAEs obtained in this manner for valence excitations are about 0.15–0.2 eV, which appears to be …