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Articles 1 - 27 of 27
Full-Text Articles in Physical Sciences and Mathematics
Synthesis, Structure And Magnetic Properties Of Oxy-Anion Based Magnetic Solids Containing Transition Metal Oxide Nanostructures, Kulugammana Gedera Ranmohotti
Synthesis, Structure And Magnetic Properties Of Oxy-Anion Based Magnetic Solids Containing Transition Metal Oxide Nanostructures, Kulugammana Gedera Ranmohotti
All Dissertations
Inline with the focus of our research, my goal for this dissertation study is to further explore new classes of magnetic insulators exhibiting novel properties. The scope of this work is twofold: 1) the exploratory synthesis of polyanion-based mixed-framework compounds containing transition metal oxide magnetic nanostructures, and 2) the investigation of the structure/property correlation with respect to the spin couplings in confined lattices. These studies are of fundamental and technological importance regarding the long-term development of low-dimensional magnetic solids for device applications in especially information storage and quantum computing. Several interesting and significant transition metal based silicate, phosphate arsenate and …
Synthesis, Characterization, And Application Of Ag Nanostructures, Stephen Hudson
Synthesis, Characterization, And Application Of Ag Nanostructures, Stephen Hudson
All Dissertations
Noble metal nanoparticles (NPs) have been used for many centuries; however their properties were not truly scrutinized until Michael Farady's investigations in the 1850's. Advances in the field of nanotechnology over the last three decades have enabled insights into the properties of materials as their dimensions are reduced to the nanoscale. The repercussions of these insights are seen in many modern applications.
In this dissertation, properties of novel nanostructures based on Ag NPs are presented and discussed. The exceptional optical properties of Ag NPs stem from the collective oscillations of the conduction electrons known as plasmon resonances. The excitation of …
Fabrication And Optical Properties Of Noble Metal Nanostructures, Mark Kinnan
Fabrication And Optical Properties Of Noble Metal Nanostructures, Mark Kinnan
All Dissertations
Experimental and theoretical results are presented in Chapters 2, 3, and 4 on the effects of dielectric medium, particle size, and interparticle distance, respectively, on plasmon coupling in two-dimensional arrays of silver nanoparticles. The arrays were fabricated via the self-assembly of single crystal particles from c.a. 46 nm to 287 nm on PVP-modified glass substrates. Spin-coated poly(methylmethacrylate) layers were used to immobilize the particles and prevent their surface aggregation. Varying the thickness of the PMMA layer made it possible to change the average dielectric medium between the particles. UV-Visible spectra of different arrays were compared to the corresponding electron microscope …
Fluorescent Conjugated Polymer Dots For Single Molecule Imaging And Sensing Applications, Changfeng Wu
Fluorescent Conjugated Polymer Dots For Single Molecule Imaging And Sensing Applications, Changfeng Wu
All Dissertations
While single molecule imaging and sensing hold the promise of providing unprecedented detail about cellular processes, many advanced applications are limited by the lack of appropriate fluorescence probes. In many cases, currently available fluorescent labels are not sufficiently bright and photostable to overcome the background associated with various autofluorescence and scattering processes. This dissertation describes research efforts focused on the development of a novel class of fluorescent nanoparticles called conjugated polymers dots (CPdots) for single molecule fluorescence detection. The CPdots contain highly fluorescent π-conjugated polymers that have been refined over the last decades as the active material in polymer light-emitting …
Novel Lactide Derived Polymers; Synthesis, Properties And Applications, Dahlia Haynes
Novel Lactide Derived Polymers; Synthesis, Properties And Applications, Dahlia Haynes
All Dissertations
This dissertation primarily encompasses the synthesis, characterization, properties and discussion of applications for lactide derived polymers. The methodology focuses on altering polylactide's (PLA's) dynamic and physical properties increasing its broad market utility in both traditional and non-traditional applications. The fundamentals of this work include understanding and enhancing the polymer chemistry and materials related processes through the use of copolymerization, fluorination, composite chemistry and materials science.
The first chapter discusses the important of this research with emphasis on current world issues that focuses on the feasibility of renewable resources and sustainability implementation. Modification of renewable resource materials like lactic acid is …
Hybrid Bond-Order Potential For Silicon, Suleiman Oloriegbe
Hybrid Bond-Order Potential For Silicon, Suleiman Oloriegbe
All Dissertations
ABSTRACT
A new hybrid bond-order potential for silicon is developed. The functional form of the potential is derived from hybrid of expressions from empirical bond-order formalism and first principles approximations. The total energy is expressed as the sum of attractive, repulsive and promotion energies. By introducing a screening function derived from approximations to first principles expressions, the potential is made long-ranged by allowing covalent interactions beyond the first nearest neighbor shell of atoms in agreement with quantum mechanical descriptions of the bonding in silicon. Environment-dependent promotion energy is introduced that accurately accounts for energetic interactions due to changes in hybridization …
Synthesis And Characterization Of Biodegradable Polyurethanes For Biomedical Application, Changhong Zhang
Synthesis And Characterization Of Biodegradable Polyurethanes For Biomedical Application, Changhong Zhang
All Dissertations
This dissertation constitutes the studies about the biomedical materials research of novel polyurethanes. These elastic and degradable polyurethanes exhibited the potential for drug delivery, scaffold fabrication by novel ink-jet printing technology or other biomedical applications. This dissertation includes two parts about two different types of polyurethanes.
In the first part of this dissertation, we studied a polyurethane that was synthesized from methylene di-p-phenyl-diisocyanate (MDI), polycaprolactone diol (PCL-diol) and N, N-bis (2-hydorxyethyl)-2-aminoethane-sulfonic acid (BES). MDI, PCL-diol and BES were polymerized into polyurethane and served as the hard segment, soft segment and chain extender respectively. The effects of the chain extender BES …
Multicolor Conjugated Polymer Dots For Biological Fluorescence Imaging, Changfeng Wu, Barbara Bull, Craig Szymanski, Kenneth Christensen, Jason Mcneill
Multicolor Conjugated Polymer Dots For Biological Fluorescence Imaging, Changfeng Wu, Barbara Bull, Craig Szymanski, Kenneth Christensen, Jason Mcneill
Publications
Highly fluorescent conjugated polymer dots were developed for demanding applications such as fluorescence imaging in live cells. These nanoparticles exhibit small particle diameters, extraordinary fluorescence brightness, and excellent photostability. Single particle fluorescence imaging and kinetic studies indicate much higher emission rates (∼108 s−1) and little or no blinking of the nanoparticles as compared to typical results for single dye molecules and quantum dots. Analysis of single particle photobleaching trajectories reveals excellent photostability—as many as 109 or more photons emitted per nanoparticle prior to irreversible photobleaching. The superior figures of merit of these new fluorescent probes, together …
Strategies For Expanding The Halogen Bonding Periodic Table And Desigining Complementary Halogen/Hydrogen Bonding Synthons, Hadi Arman
All Dissertations
Halogen bonding is the donation of electron density from an electron donor, such as N, O, S, Se atoms, to an electron acceptor such as a dihalogen or organohalogen. This interaction plays an important role in biological systems, such as the thyroid gland and is useful in many other fields such as drug design, crystal engineering, synthetic chemistry, material science and bioinorganic chemistry. However, currently there is a lack of information for this interaction in systems involving organoiodines with sulfur and selenium electron donors.
A variety of sulfur and selenium Lewis base donors were investigated with various organoiodines. The main …
Synthesis And Pharmacology Of N-Alkyl-3-(Halo-Naphthoyl)Indoles, Valerie Smith
Synthesis And Pharmacology Of N-Alkyl-3-(Halo-Naphthoyl)Indoles, Valerie Smith
All Dissertations
The medicinal values of marijuana have often been overshadowed due to the psychotropic, 'recreational' effects it brings about in a user. For hundreds of years the therapeutic uses of cannabis sativa were appreciated, but the inability to control the dosage of the main constituent, and therefore the psychotropic effects, rendered the drug a liability. The elucidation of the structure of this main psychoactive constituent, ∆9-tetrahydrocannabinol (∆9-THC) by Gaoni and Mechoulam in 1964 opened the door to the discovery of a vast array of knowledge about cannabinoids. From the multiple classes of cannabinoids and the ways these compounds interact with the …
The Role Of Metal Coordnation In The Inhibition Of Iron(Ii)- And Copper(I)-Mediated Dna Damage By Organoselenium And Organosulfur Compounds, Erin Battin
All Dissertations
Copper and iron are two widely-studied transition metals associated with hydroxyl radical (OH) generation: Fe2+/Cu+ + H2O2 = Fe3+/Cu2+ + OH + OH-. Metal-mediated oxidative damage is a major cause of cellular DNA damage and death, and has been implicated in cancer, neurodegenerative, and cardiovascular diseases. Because sulfur and selenium antioxidants ameliorate oxidative damage, the ability of twenty biological sulfur- and selenium-containing compounds to inhibit metal-mediated DNA damage caused by hydroxyl radical has been quantified. In the Cu+/H2O2 system, six sulfur compounds and three selenium compounds inhibited DNA damage with IC50 values ranging from 3.3 to 25.5 μM. Several sulfur …
Functionalized Carbon Nanotubes For Biological Applications, Lingrong Gu
Functionalized Carbon Nanotubes For Biological Applications, Lingrong Gu
All Dissertations
Carbon nanotubes with their unique pseudo-one-dimensional nanostructures and related electronic, optical, and mechanical properties have been attracting much attention for potential biological applications, such as biosensors, bio-delivery, bioimaging and so on. In this dissertation, recent studies and advances toward bioapplications of carbon nanotubes are critically reviewed, followed by detailed reports on my research projects concerning the use of carbon nanotubes as unique scaffolds for multivalent display of sugars and the relevant results from bio-evaluation of these novel nanomaterials.
Single-walled (SWNTs) and multiple-walled carbon nanotubes (MWNTs) were functionalized with amine-derivatived monosaccharides (galactoses and mannoses) and their dendritic constructs. These sugar-functionalized carbon …
Structure And Transport Characteristics Of Highly Rigid Ionomers, Lilin He
Structure And Transport Characteristics Of Highly Rigid Ionomers, Lilin He
All Dissertations
The structure and transport characteristics in a novel family of ionomers consisting of a hydrophobic polyphenylene backbone substituted by sulfonic acid functionalized phenyl side chains (sPPs) have been investigated. These polymers have potential applications in electrochemistry as well as separation both as membranes and thin films. The bulk structure as a function of hydration has been explored by X-ray and neutron scattering. Interfacial structure was studied by AFM and neutron reflectometry. The characteristics of water in the bulk were studied by NMR and FTIR and that in thin films by neutron reflectometry.
The sPPs exhibit characteristic structure due to their …
Electrochemical Synthesis And Characterization Of Polymers From Bis(3,4-Ethylenedioxythiophene)-Thiophenes (Bedot-Ts) And Bis(3,4-Ethylenedioxythiophene)-Benzenes (Bedot-Bs) As Optoelectronic Materials, Kalya Eaiprasertsak
All Dissertations
ABSTRACT
A series of bis(3,4-ethylenedioxythiophene)-thiophene derivatives (BEDOT-Ts) and bis(3,4-ethylenedioxythiophene)-benzene derivatives (BEDOT-Bs) monomers were electrochemically polymerized onto glassy carbon or ITO-coated glass electrodes. Cyclic voltammetry (CV), infrared (IR), UV-vis-NIR and photoluminescence (PL) spectroscopy were employed to investigate and characterize properties of resulting polymers. dc-conductivities of these polymers were measured by the four-point probe method.
Cyclic voltammetry studies show that the redox half potentials of PBEDOT-3BT, PBEDOT-3OT, PBEDOT-3TBS and PBEDOT-3MPT are -290, -297, -325 and -284 mV versus Ag/Ag+, respectively. The redox half potentials of PBEDOT-TOL, PBEDOT-BOB and PBEDOT-FB are -130, -147 and -327 mV vs. Ag/Ag+, respectively, and a bit higher …
Effects Of Polyphenol Compounds On Iron-And Copper-Mediated Dna Damage: Mechanisms And Predictive Models, Nathan Perron
Effects Of Polyphenol Compounds On Iron-And Copper-Mediated Dna Damage: Mechanisms And Predictive Models, Nathan Perron
All Dissertations
Polyphenol compounds are widely recognized for their antioxidant activity; however, under some conditions these compounds can also exhibit prooxidant activity. This work examined the interactions of polyphenols with iron and copper to improve understanding of both their antioxidant and prooxidant effects. Polyphenols with catechol and gallol groups effectively inhibit iron-mediated oxidative DNA damage by chelating iron, with IC50 values ranging from 1-59 µM. Gallate compounds are more potent than their catecholate analogues in every instance, and their antioxidant potencies correlate to pKa values for the most acidic phenolic hydrogen. This correlation represents the first predictive model of …
Exploratory Synthesis Of New Open-Framework Iron (Ii,Iii)-Containing Polyanion Systems Targeted For Lithium-Ion Battery Applications, Gregory Becht
Exploratory Synthesis Of New Open-Framework Iron (Ii,Iii)-Containing Polyanion Systems Targeted For Lithium-Ion Battery Applications, Gregory Becht
All Dissertations
The chemistry demonstrated in this dissertation is concerned with the synthesis, structure, properties and applications of inorganic solids containing iron(II,II) redox centers. The endeavor in exploratory synthesis is due largely to the employment of molten salt fluxes such as alkali metal chloride. These halide-fluxes act in two parts; 1) as a solvent to lower the reaction temperature and 2) as an in situ source of unavailable alkali oxides through metathesis reactions. Using these halide fluxes has allowed for the discovery of several new transition metal-containing phosphates, arsenates, and vanadates for a structure/property correlation study. From this study the selected compounds …
Design And Validation Of A Multimethod Assessment Of Metacognition And Study Of The Effectiveness Of Metacognitive Interventions, Guillermo Sandi-Urena
Design And Validation Of A Multimethod Assessment Of Metacognition And Study Of The Effectiveness Of Metacognitive Interventions, Guillermo Sandi-Urena
All Dissertations
The central role of metacognition in learning and problem solving, in general and in chemistry in specific, has been substantially demonstrated and has raised pronounced interest in its study. However, the intrinsic difficulties associated with the inner processes of such a non-overt behavior have delayed the development of appropriate assessment instruments. The first research question addressed in this work originates from this observation: Is it possible to reliably assess metacognition use in chemistry problem solving? This study presents the development, validation, and application of a multimethod instrument for the assessment of metacognition use in chemistry problem solving. This multimethod is …
Synthesis, Electronic Structure, And Reactivity Of Endohedral Metallofullerenes And Other Endohedral Carbon Nanostructures, Bevan Elliott
Synthesis, Electronic Structure, And Reactivity Of Endohedral Metallofullerenes And Other Endohedral Carbon Nanostructures, Bevan Elliott
All Dissertations
The discovery in 1985 of fullerenes combined with the development of STM beginning in 1981 is credited as the starting point of the current nanoscience revolution. Endohedral fullerenes, discovered shortly after, have drastically different electronic properties when compared with the empty fullerenes. This dissertation has as its central focus the synthesis and electronic properties of endohedral metallofullerenes and other endohedral nanostructures.
The opening two chapters give a brief background of the discovery of fullerenes. A comprehensive literature list is given for the various families of trimetallic nitride endohedral fullerenes as well as other large endohedral metallic cluster fullerenes. Finally, a …
Becoming A Chemist: Graduate Students' Perspectives On Chemists And Chemistry, Bethany Walls
Becoming A Chemist: Graduate Students' Perspectives On Chemists And Chemistry, Bethany Walls
All Theses
In order to better understand the development of chemistry graduate students throughout the research phase of their Ph.D. degrees, we conducted a study on graduate students' self-concept of being chemists. This research is motivated by our previous results that forming identities as chemists is a key step in the transformation of organic chemistry graduate students from laboratory technicians into practicing chemists. In this research study, analytical, inorganic, and physical chemistry graduate students participated in a single, semi-structured interview designed to probe how their beliefs on what it means to know and practice chemistry affect their graduate training. Results from these …
Semifluorinated Polymers Via Cycloaddition And Nucleophilic Addition Reactions Of Aromatic Trifluorovinylethers, Scott Iacono
Semifluorinated Polymers Via Cycloaddition And Nucleophilic Addition Reactions Of Aromatic Trifluorovinylethers, Scott Iacono
All Dissertations
This dissertation encompasses the synthesis, characterization, and properties of semifluorinated polymers derived from thermal polymerization of aryl trifluorovinyl ether (TFVE) monomers. This work is divided into two parts based on the methodology of thermal polymerization using aryl TFVE monomers. The first part of this work involves the thermal [2 + 2]cyclodimerization of aryl TFVE monomers affording perfluorocyclobutyl (PFCB) aryl ether polymers. Chapter 1 provides an overview of PFCB aryl ether polymers as a next-generation class of high performance fluoropolymers that have been successfully employed for a myriad of technologies. PFCB aryl ether polymers are highly desired because of their high …
Synthesis And Electrochemical Studies In Microstructured Media, Jamie Norton
Synthesis And Electrochemical Studies In Microstructured Media, Jamie Norton
All Dissertations
In-situ electrochemical methods involving both oxidative and reductive mediators were employed to modify the oxidation state (doping level) of PEDOT polymers in colloidal PEDOT-coated silica core-shell particles that were prepared as a dispersion encapsulated in a hydrogel matrix. The modifications of the redox states of the PEDOT coating induced a change in the absorbance characteristics. A mediated electron transfer system was employed to ferry charge from the electrodes of the cell to the isolated particles. The mediator diffuses between the electrode surface and the PEDOT-coated particles to accomplish (de)doping. The developed system was a fully self-contained and electrically driven device. …
Carbon Nanotubes And Nanocomposites For Thermal And Electrical Applications, Wei Wang
Carbon Nanotubes And Nanocomposites For Thermal And Electrical Applications, Wei Wang
All Dissertations
The known electrical and thermal properties of carbon nanotubes have prompted many predictions on their extraordinary potentials for ultimately performing polymeric nanocomposites. In this dissertation, chemical modification and functionalization of carbon nanotubes have been demonstrated as being effective for high-quality polymeric carbon nanotube composites, especially with our approach of using polymers that are structurally identical or maximally similar to the matrix polymers in the nanotube functionalization. For example, a poly(N-vinyl carbazole) (PVK) copolymer containing pendant hydroxyl groups was synthesized for the functionalization of single-walled carbon nanotubes (SWNTs). The shared solubility of the functionalized nanotube samples with PVK matrix polymer enabled …
Preparation And Characterization Of Macroporous Electrodes For Electrochemical Bioassays, Ashwin Rao
Preparation And Characterization Of Macroporous Electrodes For Electrochemical Bioassays, Ashwin Rao
All Dissertations
Applications such as point-of-care medical diagnosis and in-the-field biological warfare agent detection require portable bioassays which are less laborious yet cost effective. Conventional sandwich bioassays see limited use for such applications as it involves time consuming steps of reagent treatment and washings, and are restricted to use inside laboratories. We explore new platforms for sandwich bioassays required by such applications. The platform we have developed is based on electrochemical methods of detection. Flow-through three-dimensional electrodes suitable for use in electrochemical sandwich bioassays were fabricated. A composite of superporous agarose and reticulated vitreous carbon (SPA-RVC) material was used for the fabrication …
Perfluorocyclobutyl Aryl Ether Polymers: A Modular Approach To Tailored Emission, Andrew Neilson
Perfluorocyclobutyl Aryl Ether Polymers: A Modular Approach To Tailored Emission, Andrew Neilson
All Dissertations
Aryl trifluorovinyl ethers (TFVE) are versatile precursors to perfluorocyclobutyl aryl ether (PFCB) polymers. TFVE functionalized chromophores of a variety of colors have been synthesized for copolymerization to form PFCB polymers with tunable emissive properties. TFVE small molecule chromophores containing fluorene, benzothiadiazole, and bisthiophene show superb emissive properties and prove that the TFVE and PFCB structures have no effect on chromophore emission. Copolymerization of these chromophores with commercial TFVE monomers produced high molecular weight, thermally stable, emissive materials. With the use of trifunctional TFVE monomers these materials can be made into optical glasses. PFCB-phenylene vinylenes were prepared by Wittig polymerization and …
Exploratory Synthesis Of Plyanion-Based Open-Framework Solids As Potential Candidates For Cathode Material Applications, Adam Siegfried
Exploratory Synthesis Of Plyanion-Based Open-Framework Solids As Potential Candidates For Cathode Material Applications, Adam Siegfried
All Theses
This thesis is concerned with exploratory synthesis of polyanion based open-framework solids that can potentially be used as cathode materials in lithium batteries. Two silver manganese vanadates were discovered, Ag3Mn(VO4)2 and AgMn2V3O10, which show different possibilities as cathode materials for primary battery applications; the former contains a higher (Ag+Mn)/V ratio, which is sought for high capacity devices, while the latter may prove better for lower power devices. The structures of the two materials differ in that Ag3Mn(VO4)2 is a layered material where as AgMn …
Structure And Dynamics Of Poly (Para-Phenyleneethynylene)S In Solutions And Thin Films, Yunfei Jiang
Structure And Dynamics Of Poly (Para-Phenyleneethynylene)S In Solutions And Thin Films, Yunfei Jiang
All Dissertations
This research focuses on the structure and dynamics of a family of rigid polymers, poly(para-phenyleneethynylene)s (PPEs) in solutions and thin films using small angle neutron scattering, neutron spin echo, nuclear magnetic resonance, X-ray scattering, atomic force microscopy and fluorescence spectroscopy. The effects of the solvent and the side chain on the molecular conformation and the association of PPEs have been investigated.
In dilute solutions, the phase diagram of dinonyl PPE in toluene and cyclohexane exhibits three distinct phases. At higher temperatures, PPEs form molecular solutions with extended conformations in toluene and worm-like chains in cyclohexane. With decreasing temperatures, PPEs associate …
Perfluorocyclobutyl Aryl Ether Polymers For Proton Exchange Membranes, Raul Hernandez
Perfluorocyclobutyl Aryl Ether Polymers For Proton Exchange Membranes, Raul Hernandez
All Theses
Over the last decades Nafion¨ has emerged as the polymer of choice for the fabrication of Proton Exchange Membranes (PEM)s, due to its excellent proton conductivity and long-term stability. However, high temperatures and low relative humidity decrease fuel cell efficiency, due to the highly hydrated conditions required for proton conductivity. To overcome these issues, different types of sulfonated polymers have been proposed as promising substitutes for Nafion ¨, these include; Poly(arylene ether sulfones) (PAES) and Perfluorocyclobutyl (PFCB) aryl ether polymers among others.
Chapter 2 of this thesis describes the synthesis of a new class of sulfonated PAESs containing the perfluorocyclobutyl …