Chemistry Commons^™

Gold Nanoparticle - Modified Zinc Oxide Nanoparticles As Novel Photocatalytic Materials, Nayane Udawatte

Dissertations

The current study entails the construction of a novel nano-composite catalyst based on ZnO and Au nanoparticles and demonstrates its distinctive photocatalytic characteristics. Monodisperse gold nanoparticles (GNPs) passivated with monolayers of tiopronin or glutathione were synthesized via facile methods, and they were assembled on ZnO nanoparticles to form the nanocatalyst.

Steady state and time resolved photoluminescent studies on the nanocomposite revealed interesting charge transfer characteristics within the nanocomposite. Enhanced photooxidation of rhodamine 6G was observed for the nano-composite over bare ZnO, and modulation of photoactivity with the extent of GNP loading was illustrated. Photoreduction of thionine over the nanocomposite was …

Structure-Property Correlation In Cyclopolymerization Of New Acrylate-Based Functional Monomers, Huseyin Tas

Dissertations

New ether dimer; (ED-Od) and (ED-Eh) and diester; (ODE) and (EHDE) derivatives of α-(hydroxymethyl)acrylate, each having two octadecyl and 2-ethylhexyl side chains respectively, and an amine-linked di(2-ethylhexyl)acrylate (AL-Eh), having three 2-ethylhexyl side chains, were synthesized and (co)polymerized to evaluate the effects of differences in the structures of the monomers on final (co)polymer properties, particularly glass transition temperature, Tg. The free radical polymerizations of these monomers yielded high molecular weight polymers. Cyclopolymer formation of ED-Od, ED-Eh and AL-Eh was confirmed by 13C NMR analysis and the cyclization efficiencies were found to be very high (~100%). Copolymers of ED-Od, ODE, ED-Eh, EHDE, …

Inhibition Studies Of Serine Hydrolases By Cyclic Phosphates And Phosphonates, Supratik Dutta

Dissertations

The serine hydrolase superfamily is one of the largest known enzyme families comprising approximately 1% of the predicted protein product in human genome. This family of enzymes contains a catalytic triad that is mainly consists of serine, aspartic acid/glutamic acid and histidine residues in their active sites. It has been proposed that the potential drug targets for Alzheimer’s disease and diabetes type 2 are enzymes that belong to this enzyme family. Acetylcholinesterase is an enzyme that catalyses the breakdown of acetylcholine, a neurotransmitter that helps transport information from one nerve cell to another. Breakdown of acetylcholine in Alzheimer’s disease patients …

The Nature Of The O-2/O-5 Cooperative Effect And Its Role In Chemical Glycosylation, Laurel Kathryn Mydock

Dissertations

Since carbohydrates were first discovered, understanding the structure, reactivity, and function of these bioorganic compounds has remained of great priority. However, as the appreciation for the biological roles of carbohydrates intensifies, a growing demand for efficient and scalable methods towards the synthesis of these challenging molecules has become even more imperative. While modern synthetic techniques have allowed us to readily achieve most glycosidic linkages, it is the inability to effectively predict and control the stereoselectivity of the glycosylation reaction that has remained the synthetic hurdle. Herein, much effort has been placed in the investigation of “mixed-patterned” glycosyl donors as they …

Effect Of Anions On The Iron Release Pathways Of Human Serum Transferrin, Rashmi Subhash Chander Sharma

Dissertations

Transferrin, the serum iron transport protein in humans, is used to transport 30-40 mg of iron per day through blood. The accessibility of transferrin makes it an attractive target for iron cheating therapeutic agents used in the treatment of iron overload. There is an ongoing search for ligands which can accelerate the rate of iron release, as the currently approved drug DFO has a very slow rate for iron removal. Previous studies have shown that anions can accelerate the rate of iron release. Studies on the effect of anions on the rates of iron release from C-terminal monoferric transferrin at …

Rational Design Of Self-Assembled Nanostructures Based On Polymers Synthesized Via Aqueous Reversible Addition-Fragmentation Chain Transfer Polymerization, Stacey Kirkland York

Dissertations

Recent advances in reversible addition-fragmentation chain transfer (RAFT) polymerization have allowed the rational, bottom-up design of biorelevant assemblies. Utilizing foresight, polymers can be tailored to self-assemble into nano-, micro-, and macroscopic structures. Given the size scale on which rationally-designed polymers can be tailored, they hold significant promise in the biomedical field. For example, nanoscale materials can be designed to carry small-molecule and gene therapeutics while macroscopic structures can be tailored for cell growth scaffolds. The design process begins by selecting monomers, chain transfer agents, and reaction conditions which will yield the desired polymer architecture and composition.

The work herein builds …

Investigation Of Novel Quasiliving Polyisobutylene Chain-End Functionalization (Quenching) Methods, David Lee Morgan

Dissertations

This volume recounts efforts toward the development and understanding of chain functionalization techniques involving the direct addition of nucleophiles to quasiliving polyisobutylene (PIB). Nucleophiles included in the study were sterically hindered organic bases, (di)sulfides, N-substituted pyrroles, and alkoxybenzenes. A kinetic investigation of the end-quenching of TiCl4-catalyzed quasiliving PIB with sterically hindered amines was used to determine the mode of interaction with TiCl4 and the active species responsible for -proton abstraction. 2,5-disubstituted-N-hydropyrroles formed pyrrole-TiCl3 adducts that were active in formation of exo-olefin chain ends; whereas, with other sterically hindered amines, only an equilibrium fraction of the amine that did not complex …

The Lipid Acyl-Chain Dynamics In Giant Liposomes And Characterization Of Domain 4 Of The Wilson Disease Protein, Wilson Okumu

Dissertations

Steady-state and nanosecond time-resolved fluorescence of the nitro-2, 1, 3- benzoxadiazol-4-yl (NBD) probe and line tension force were determined in phospholipids acyl-chain dynamics in giant liposomes made from a homologous series of phosphatidylcholines (PC). The fluorescence spectroscopy of a NBD probe attached to the headgroup (NBD PE) or the tail (NBD PC) of the phospholipid were used to determine the rate of dithionite quenching in a homologous series of phospholipids. Similar experiments were performed in the gel and the fluid phases of the l,2-dimyristoyl-s«-glycero-3-phosphocholine (DMPC ). Nanosecond time scale lifetimes and anisotropy measurements were obtained by a 470 nm LED …

Nanomaterials From Biologically Active Molecules: Self-Assembly And Molecular Recognition, Min Yu

Dissertations

This dissertation describes the development of molecular assemblies and molecular recognition of phospholipids (PLs) that exhibit potential applications in emerging nanotechnologies. It consists of two parts: (1) structural features of PLs responsible for recognition of synthetic copolymers, and (2) design, synthesis and analysis of magnetic nanotubes obtained from PLs with a common theme of colloidal synthesis served as a platform for film formation and nano-assemblies of nanotubes. Poly(methyl methacrylate/n-butyl acrylate) (p-MMA/nBA) colloidal particles that were stabilized by 1,2-dilauroyl-sn-glycero-3-phosphocholine (DLPC) PLs were synthesized, and upon the particle coalescence, PL stratification resulted in the formation of surface localized ionic clusters (SLICs). These …

Synthesis Of Functional Copolymers Via Aqueous Raft Polymerization For Bioconjugation And Targeted Delivery Of Small Interfering Rna, Adam Wesley York

Dissertations

The versatility of reversible addition-fragmentation chain transfer (RAFT) polymerization has moved this controlled radical technique to the forefront of copolymer construction for bioapplications including polymeric drug/gene delivery vehicles. Strengths of the RAFT process include the capacity to control the polymerization of a wide variety of vinyl monomers under mild conditions, its tolerance to numerous chemical groups that allow the preparation of functional copolymers for facile modification, and the range of copolymer architectures with predetermined end group functionalities which may be synthesized. Given these strengths, RAFT polymerization was utilized in this research to synthesize functional/reactive copolymers for bioconjugation and targeted delivery …

Self-Assembly And Gold Nanoparticle Cross-Linking Of Stimuliresponsive Block Copolymers Synthesized Bt Reversible Addition-Fragmentation Chain Transfer Polymerization, Adam Eugene Smith

Dissertations

The ability of amphiphilic block copolymers to self-assemble into various morphologies in aqueous solution in response to specific stimuli has attracted widespread interest for potential applications as targeted drug delivery and diagnostic vehicles. Stimuli-responsive block copolymers afford a facile method for tuning the hydrophilic mass fraction to provide access to various solution morphologies. Reversible additionfragmentation chain transfer (RAFT) polymerization provides the ability to prepare stimuli-responsive block copolymers while maintaining precise control over the macromolecular characteristics (molecular weight, copolymer composition, functionality, etc.) that dictate nanostructure morphology.

This work may be divided into four sections. In the first section the synthesis and …

Polyisobutylene Chain End Transformations: Block Copolymer Synthesis And Click Chemistry Functionalizations, Andrew Jackson David Magenau

Dissertations

The primary objectives of this research were twofold: (1) development of synthetic procedures for combining quasiliving carbocationic polymerization (QLCCP) of isobutylene (IB) and reversible addition fragmentation chain transfer (RAFT) polymerization for block copolymer synthesis; (2) utilization of efficient, robust, and modular chemistries for facile functionalization of polyisobutylene (PIB). Two site transformation strategies were employed to create block copolymers effectively linking PIB with either poly(methylmethacrylate) (PMMA), polystyrene (PS), and poly(Nisopropylacrylamide) (PNIPAM) block segments. Functionalization of PIB was accomplished by utilizing two click chemistries, the azide-alkyne 1,3-dipolar cyclo addition and the thiol-ene hydrothiolation reaction, and by efficient transformation of the thiol functional …

Molecular Design And Patterning Of Biosurfaces On Poly(Tetrafluoroethylene) (Ptfe), Nattharika Aumsuwan

Dissertations

This dissertation describes the design, synthesis, and development of biocompatible poly(tetrafluoroethylene) (PTFE) surfaces that exhibit anti-microbial, anticoagulant, and dual functional surface properties. It consists of two parts: (1) design, synthesis, and analysis of antimicrobial and anti-coagulant PTFE surfaces, and (2) controllable micropatterning of anti-microbial and anti-coagulant species on the surface. PTFE was modified by Ar microwave plasma reactions in the presence of maleic anhydride, which upon hydrolysis creating COOH groups. These COOH primers were utilized as a platform for further surface reactions to attach polyethylene glycol (PEG) spacers, and penicillin (PEN) or ampicillin (AM) onto the PTFE surfaces. The use …

Towards Multiplexed Electrogenerated Chemiluminescent Detection, Shijun Wang

Dissertations

The main objective of this dissertation is to understand and study the principle of electrogenerated chemiluminescence (ECL) and its applications to detect biomolecules simultaneously. Four aspects of ECL were studied. In order to carry out multiplexed ECL detection, both classical and several novel ECL systems have been investigated.

In the first aspect, significant effect of chloride ions on the ECL behavior of the tris(2,2′-bipyridyl) ruthenium(II) (Ru(bpy)3 2+)/tri-n-propylamine (TPrA) system at Au electrode was investigated. At low concentrations (e.g., [Cl-] < 5 mM), the ECL was enhanced; at relatively high concentrations, however, the ECL intensity decreased with the increase of the [Cl-]. At [Cl-] = 90 mM, ~ 50% and 100% ECL inhibition was observed for the first and the second ECL wave, respectively. The electrogenerated chloroaurate anions (AuCl2 - and AuCl4 -) which were verified using an electrochemical quartz-crystal microbalance (EQCM) method were found to be responsible for the ECL inhibition. This study suggests that care must be taken when Au working electrode is used for ECL studies in chloride-containing buffer solutions (widely used in DNA probes) and/or with the commonly used chloride-containing reference electrodes since in these cases the ECL behavior may significantly disagree with that obtained using other electrodes and reaction media.

In the second aspect, the electrochemical behavior of a trinuclear ruthenium(II)- containing complex, [((phen)2Ru(dpp))2RhCl2]5+ (where phen = 1,10-phenanthroline, dpp = 2,3-bis-2-pyridylpyrazine), …

Aqueous Raft Synthesis Of Stimuli-Responsive, Amphiphilic Block Copolymers And Self-Assembly Behavior In Solution And Incorporation Into Lbl Films, Matthew Grady Kellum

Dissertations

Of all the living radical polymerization techniques, reversible addition– fragmentation chain transfer (RAFT) polymerization is arguably the most versatile in terms of the reaction conditions (e.g. temperature and solvent selection), monomer selection (e.g. neutral, anionic, cationic, and zwitterionic), and purification. Since the introduction of RAFT in 1998, the McCormick research group and others including the Lowe, Sumerlin, and Davis research groups have synthesized a wide range of (co)polymers with predetermined molecular weights, low polydispersities, and advanced architectures utilizing aqueous RAFT (ARAFT) polymerization. These research groups have also studied how various block copolymers exhibit stimuli-responsive behavior due to a change in …

Multi Stimuli-Responsive Copolymers Obtained From Colloidal Dispersions, Fang Liu

Dissertations

This dissertation describes the design, synthesis, and development of multi stimuli-responsive random copolymers that exhibit collective responsiveness to temperature, pH or electromagnetic radiation. New colloidal particles of poly(N-(DL)-(1- Hydroxyymethyl) propylmethacrylamide/n-butyl acrylate) (p(DL-HMPMA/nBA) and poly(2-(N,N′-dimethylamino)ethyl methacrylate/n-butyl acrylate) (p(DMAEMA/nBA)) were synthesized, which upon coalesce to form solid continuous films. The presence of lower glass transition (Tg) nBA components not only facilitate film formation, but also provide sufficient free volume for polymer chain rearrangements. These studies showed that coalesced films exhibit 3D dimensional changes upon external stimuli, which are attributed to the collapse and conformational changes of stimuli-responsive components as well as buckling …

Developing A Biosensor For The Detection Of Bacteria: A Comparison Of Methods For Isolating Bacteria-Specific Antibodies, Scott Allen Walper

Dissertations

The antigen-antibody interaction is known to be a high affinity and highly specific interaction that can readily be used for the detection and identification of biological and chemical agents. These studies were conducted to develop an efficient and cost-effective method of obtaining bacteria-specific antibody molecules for integration into a fielddeployable biosensor. Antigen-binding molecules were obtained both as full-length IgG molecules from a hybridoma cell line and as recombinant single-chain Fv (scFv) antibodies isolated from naïve and immunize libraries. Monoclonal and recombinant antibody systems were compared on the effectiveness of producing new, target-specific molecules; the efficiency of production and purification of …

Synthesis, Characterization, And Deuterium Labeling Of Polyamides Studied By Nuclear Magnetic Resonance Spectroscopy, Christopher Allen Lange

Dissertations

The synthesis, characterization, and deuterium labeling of polyamides have been investigated. In Chapter II, selective deuterium labeling of various polyamides was demonstrated via a facile method which does not require organic solvent or catalyst. Quantitative solution-state NMR analysis showed deuterium incorporation at the carbon alpha to the carbonyl ranged from 20-75%. Incorporation in ε-caprolactam increased with repeated treatments. Isotopic shift effects for the deuterated materials were additive for all sites within experimental error.

In Chapter III, the effect of stoichiometric imbalances on the polymerization of poly(dodecamethylene terephthalamide)was investigated. Molecular weight was varied by polymerizing the monomer salt with excess diaminododecane, …

Structure-Property Relationships In The Formation Of Polyphenylsulfone Molecular Composites And Nanocomposites, Paul Joseph Jones

Dissertations

As the constituent phases in a polymer composite approach the molecular level, specific phenomena occur that can lead to significant changes in material properties when only minimal quantities of the additive are incorporated into the polymer matrix. Molecular composite and nanocomposites are state-of-the-art polymeric materials that contain nanostructured additives effectively dispersed within polymer matrices. The properties of molecular composites and nanocomposites are directly related to the interactions of the nanostructured additive and the polymer matrix. Subtle changes to the nanostructured additive can have profound effects on the ultimate properties of the composite material. Therefore, understanding the structure-property relationships in these …

A Study Of The Effective Interfacial Tension Between Miscible Fluids By Spinning Drop Tensiometer And Microfluidics, Gloria Dollie Viner

Dissertations

A miscible system is a system in which two fluids can completely dissolve in one another. A sharp concentration gradient can be observed in miscible systems. We studied the concentration gradient or miscible interface between IBA (isobutyric acid) and water, a miscible system near a consulate point (close to the system’s upper critical solution temperature [UCST]). The original hypothesis was that the sharp concentration gradient of IBA/water was due to barodiffusion, a diffusion effect driven by pressure. We tested this hypothesis by studying IBA/water at five different rotation rates and three different temperatures. At 20 oC, increasing rotation acceleration from …

Designing Molecular And Nanoscale Materials For Environmental Chemistry Processes, Wen Guo

Dissertations

This dissertation focuses on fundamental studies to identify materials that detect and degrade common organic environmental pollutants. Chapter 1 represents the overview of two widespread ground water contaminants: organohalides and organophosphorous compounds. Due to continuous usage of these compounds as well as their toxicity, reliable and sensitive methods for their detection and degradation are urgently needed. In Chapter 2 a description of molecular sensors designed with high sensitivity and selectivity to detect and distinguish between three organophosphorus (OP) pesticides are described. These sensors provide dual optical and electrochemical signals for detection, which minimizes false-positives. The signal transduction occurs in real …

The In-Situ Removal Of Menthofuran From Peppermint Oil And Subsequent Reactions Of The Solid-Supported Adduct, Robert Joseph Justice Ii

Dissertations

Menthofuran is an aromatic heterocyclic compound found naturally in the essential oil of Mentha piperita L. or peppermint. Natural peppermint oil may contain between approximately 2 to 8% menthofuran.

Peppermint oil is a complex mixture of over 350 identified chemical compounds; market demands dictate the extent of processing the oil undergoes prior to being introduced into consumer goods. Menthofuran has long been known to readily autoxidize, either alone or within the peppermint oil matrix, leading to a discolored oil with negative organoleptic consequences that adversely affects its commercial viability. Therefore, a facile method for selective removal of menthofuran was developed …

Characterization Of The N-Terminal Domains And Disease-Causing Mutations Of The Human Wilson Protein, Joshua Mutambuki Muia

Dissertations

The Wilson protein (ATP7B) is a copper transporting ATPase that is involved in copper trafficking and homeostasis. Unlike the other known P-type ATPases, it possesses six homologous metal binding domains at the N-terminal end. Several mutations in the gene coding for this protein lead to Wilson disease, a hepatic disorder characterized by impaired excretion of copper in the bile, and accumulation of copper in body organs such as the liver, brain, kidney, and eye cornea. Characterization of various regions of expressed and purified ATP7B has been hampered by its low stability, aggregation and degradation.

In this research, novel methods were …

Investigation Of Network Architecture Development And Properties In Thermoset Matrices, Jeremy Owen Swanson

Dissertations

Matrices employed in composite materials directly influence overall composite properties. In all thermoset materials, molecular level interactions and transformations during cure result in heterogeneous architecture. Variability in connectivity results from the often dramatic spatial and topological changes that occur during the crosslinking process. Compatibility (fillers, pigments, additives), temperature gradients and reactivity differences in the precursors only serve to increase the complexity of network formation. The objective of the research herein is to characterize and understand the relationships between cure conditions, conversion, connectivity, network architecture and properties in glassy thermosetting matrix resins.

In this research, epoxy and vinyl ester resins (VERs) …

Investigating Fabrication Methods For Micro Single-Chamber Solid Oxide Fuel Cells, Man Yang

Dissertations

A Solid Oxide Fuel Cell (SOFC) is a green energy technology that offers a cleaner and efficient alternative to fossil fuels. The efficiency and utility of SOFCs can be enhanced by fabricating miniaturized component structures within the fuel cell footprint. This research focuses on the microfabrication of parallel-connected inter-digitized design of micro single chamber SOFC (µ-SC-SOFCs). In this dissertation, candidate micro/nano fabrication techniques to precisely fabricate micro patterns on planar substrates have been studied. These include EBL, soft lithography, photolithography, and direct-writing. After analyzing preliminary results, two combinational approaches were further investigated. The first method involves the combination of the …

Modulation Of Restriction Enzyme Pvuii Activity By Metal Ion Cofactors, Charulata Bhaskaran Prasannan

Dissertations

Metal ions like Ca2+, Mn2+, Tb3+, Eu3+ etc., can bind at the active site and have varying effects on the enzymatic activity. In a crystal structure with DNA, two Ca2+ ions were bound to the active site of each PvuII monomer, and the metals share the ligands. Ca2+ ions promote DNA binding and not cleavage in many nucleases. We explored the role of Mg2+ and Ca2+ binding at the metal binding sites of PvuII to elucidate the role of each metal site. We monitored the cleavage kinetics of PvuII in presence of mixed metals. The cleavage kinetics data for Ca2+ …

Replacing Hydrogen Bonds With Coordinate Covalent Bonds In Coordination Networks, Colin Stewart Rodger

Dissertations

The overall theme of the dissertation is that metal ions such as silver(I) can replace H+ in hydrogen bonded organic frameworks. Because organic solids have been extensively studied, we can insert metal ions into the supramolecular assemblies, thus creating predictable coordination solids of varying dimensions. One example of an organic solid tested involves the organic compounds terephthalic and isophthalic acids. These dicarboxylic acids have previously been shown to self-assemble into tape-like structures via hydrogen bonding, with neighboring dicarboxylic acids located at angles of 180° and 120° respectively. By substituting the hydrogen bonds with coordination metal-ligand bonds similar assemblies are formed. …

Investigation Of Novel Thiol "Click" Reactions, Justin William Chan

Dissertations

The thio-Michael addition reaction is traditionally considered a base catalyzed reaction which involves high catalyst concentrations and long reaction times. This reaction utilizes potent, simple nucleophiles to catalyze the reaction, decreases the catalyst concentration and greatly increases the reaction times. The free radical mediated thiol-ene click reaction uses light or heat and an initiator to catalyze the rapid and quantitative addition of thiols to most electron rich enes without the formation of side products and in the absence of solvent. Recently, the thiol-ene click reaction has been exploited for these reasons in materials science and organic synthesis. The research herein …

Investigation Of The Relationship Between Polymer Structures And Thermal, Mechanical, Viscoelastic Properties, Ethem Kaya

Dissertations

The research presented in this dissertation involves four distinct areas: physical crosslinking systems, UV curable coatings for enhanced oxygen and carbon dioxide barrier properties, synthesis, and investigation of melting behavior/crystallinity relations of linear polyamides with long alkyl chains, and synthesis and characterization of cyclic diamides as precursors to linear polyamides 6 4.

The physical crosslinking section involves synthesis of monomers and polymers bearing cyclodextrin and adamantane pendent groups, and investigation of non-covalent interactions between these polymers (Chapter II). Two methacrylate monomers bearing cyclodextrin and adamantane were synthesized, and copolymerized with poly(ethylene glycol) methyl ether methacrylate. The specific interaction between copolymers …

Random And Block Copolymers Of Poly(Dodecamethyleneterephthalamide), Theodore Frank Novitsky Jr.

Dissertations

The following dissertation focuses on the synthesis and characterization of poly(dodecamethylene terephthalamide) (PA-12,T) and novel copolymers. Chapter I details the synthesis of PA-12,T homopolymer by melt condensation polymerization. A series of homopolymers with different molecular weights were obtained by adjusting the stoichiometry of the polymerization using 1,12-diaminododecane, terephthalic acid and benzoic acid. End group 13C NMR spectroscopy resonances were obtained by correlating peak intensities with intrinsic viscosity values. From the NMR data, total end group concentrations and molecular weights were determined for each sample. The data exhibited a linear trend when plotting log (IV) versus log (Mn), and previously unknown …