Chemistry Commons^™

Size-Dependent Interactions Of Metal Nanoparticles With Fluorophores And Semiconductors, Liyana A. Wajira Ariyadasa

Dissertations

In recent years, nanoscale metallic particles have gained considerable interest due to their potential applications in advanced technology. Despite such interest, synthetic procedures that produce gram-scale, well-defined metallic nanoparticles with controlled size and shape, especially with diameters less than 5 nm remains a challenge. Our work has focused on developing synthetic procedures that produce well-defined platinum and palladium metal nanoparticles in the 1-5 nm size range. Thioether ligands were used as stabilizers and resulted in metal nanoparticles with controlled size. The nanoparticles were characterized using transmission electron microscopy (TEM), x-ray diffraction (XRD), selected area electron diffraction (SAED), x-ray photoelectron spectroscopy …

Fundamental Studies Of Protein Ionization For Improved Analysis By Electrospray Ionization Mass Spectrometry And Related Methods, Kevin A. Douglass

Dissertations

Mass spectrometry (MS) is an analytical technique in which a sample is converted to gas-phase ions that are subsequently separated and detected. It offers great speed, selectivity, and sensitivity during analysis, characteristics which have enabled it to become a leading method for the study of proteins. The applications of MS for these biologically significant macromolecules range from accurately determining identity and sequence to shedding light on post-translational modifications and protein-molecule interactions. As a first step towards analysis by MS, gas-phase protein ions must be formed. A common method for ionization is electrospray ionization (ESI), where a liquid sample including the …

Nanocarbons As Charge Carriers In Organic Solar Cells, Xinbo C. Lau

Dissertations

Organic photovoltaics (OPV) are an alternate to conventional silicon and thin film solar cells. They have several advantages such as simple fabrication, low material cost, light weight, and the ability to cover large areas. Typical OPV are based on bulk heterojunction structure consisting of a blend of an electron-donating semiconductor polymer and an electron-accepting molecule. Various approaches have been pursued to improve the performance of OPV: low bandgap polymers, new electron acceptors, processing additives, and tandem cell architecture.

Nanocarbons possess unique physical and chemical properties that can contribute to the enhancement of OPV performance, such as charge carrier mobility, thermal …

Investigation Of Chicago Air Pollution And Meteorological Influence On Pollution Development: Physical Measurements And Multivariate Statistical Analyses, Katrina Lyn Binaku

Dissertations

The goal of this project was to evaluate air pollutants and meteorology in Chicago, Illinois during summers 2010, 2011, and 2012. Sixty-six collection days of air pollutant and meteorological data were completed at the Loyola University Chicago sampling station atop Mertz Hall. Trace gases, nitrogen oxides and ozone, as well as the water-soluble fraction of aerosol material were the air pollutants of focus in this study. Data analysis showed that chloride, nitrate, sulfate, and oxalate were the most frequently quantified water-soluble ions in aerosol samples, followed by acetate, formate, potassium, phosphate, calcium, and magnesium ions. Ionic ratios showed that stationary …

Polyaminocarboxylic Acids As Potential Candidates For Trivalent Actinide/Lanthanide Separations, Daniel Stephen Kissel

Dissertations

Nuclear energy, which has historically been considered an alternative energy solution in the United States, is regaining support as an efficient means of energy production. The viability of nuclear energy for the future, however, will remain suspect until issues involving the waste created are fully addressed in the next generation of advanced nuclear fuel cycles. The TALSPEAK process, developed at Oak Ridge National Laboratory, is a classic solvent extraction technique that employs a series of analytical separations in an effort to remove radioactive contaminants from spent nuclear fuel (SNF) and recover uranium in high purity. This separation utilizes a polyaminocarboxylic …

Investigating The Biochemical And Catalytic Properties Of Nitrile Hydratases, Salette Martinez

Dissertations

Chemical and pharmaceutical industries make extensive use of amide compounds for the manufacture of commodity chemicals (e.g., acrylamide) and drug intermediates (e.g., nicotinamide). Production of amide compounds is typically achieved by the hydration of nitrile compounds under acidic or basic conditions, high temperatures, and copper catalysts. However, the use of such chemical methods leads to the generation of unwanted by-products and toxic wastes, in addition to low product yields and high production costs. An alternative route for amide production is the use of a natural catalyst, for example nitrile hydratases (NHase, E.C. 4.2.1.84). NHase is a metalloenzyme that efficiently converts …

Glycosyl Thiocarbamates As New Building Blocks For Chemical Glycosylation, Sneha Chandrashekhar Ranade

Dissertations

Having multiple functions in biological systems e.g. fertilization, blood group determination, cell growth; carbohydrates have remained attractive subjects for the study. They are also involved in various life threatening biological processes, such as viral and bacterial infections, tumor development, etc. Understanding of these involvements/interactions of carbohydrates in such critical processes is essential for the development of carbohydrate based vaccines and therapeutics. Although carbohydrates are present abundantly in nature, their isolation is cumbersome and low yielding, which is why, the synthesis of carbohydrate units has been of interest to many scientists. Efforts have been made to make these synthetic methods more …

Design And Synthesis Of Flexible And Functional Polybenzoxazine Thin Films, Austin David Baranek

Dissertations

Polybenzoxazines offer the unique ability to incorporate a variety of properties and functionality into a single polymer network through simple synthetic techniques. However, within benzoxazine materials exist certain drawbacks of which brittleness is the primary issue when exploring thin film applications. This brittleness leads to poor mechanical stability and would reduce the lifetime of any device sought after. It is, however, through the simplistic nature of the benzoxazine monomer synthesis that the mechanical stability could be addressed chemically, avoiding the complications of using rubber toughening agents or plasticizers. The monomer synthesis offers tailorability of both the phenol and amine to …

An Insight Into Asymmetric Synthesis And Bioorganic Applications Of Novel Cα- Methyl-Lysine, - Proline, - Nipocotic Acid Analogues, Souvik Banerjee

Dissertations

Prochiral malonic diesters consisting of a quaternary carbon center have been successfully converted into a different set of tBoc-Fmoc-α2,2-methyllysine-OH analogues through chiral malonic half-ester intermediates achieved via enzymatic (Pig Liver Esterase, PLE) hydrolysis. The selection of chiral half-ester intermediates, which vary from 1 to 6 methylene units in the side chain, are achieved in high optical purity (92% - 97% ee) and in good yields (65% - 72%). The PLE hydrolysis of malonic diesters with a variety of side chain lengths observed to obey the Jones’s PLE model as evidenced from the stereochemical configurations of the resulting chiral half-esters. The …

Application Of Iron Complexes As Catalysts In C-O And C-C Bond Forming Reactions, Pushkar Sudhakar Shejwalkar

Dissertations

‘Green Chemistry’ is a philosophy that encourages chemists in research and industry to reduce toxic waste for cleaner and safer chemical production. Oxidation reactions are commonly used in industry and are traditionally achieved by methods that involve toxic metals (such as chromium) and solvents, generating considerable waste compared to the value of the final product. The Mukaiyama Aldol reaction is another organic reaction that utilizes metals as Lewis acid catalysts. The principles of Green Chemistry suggest that chemical reactions should be performed with a maximum of efficiency and with a minimum of side product formation, accompanied by a minimal use …

Siloles Bearing Coordination-Active 2,5-Substituents: Synthesis, Reactivity, Structural And Spectral Properties., James Bryan Carroll

Dissertations

Siloles, or silacyclopentadienes and other group 14 metalloles are structurally analogous to their all-carbon analogue, cyclopentadiene, except for the heavy group 14 element (i.e., Si, Ge, Sn, and Pb) in the 1-position. The placement of the heavy element in this position allows for unique properties, such as high electron affinity, mobility, and bathochromically shifted optical spectra, as compared to cyclopentadienes, and the relatively low-lying lowest-unoccupied molecular orbital (LUMO) helps to account for these properties. The substituents about the silole have a significant impact on the electronics and properties observed, with 2,5-substituents inducing the most substantive changes. Even as many 2,5-substituents …

In Situ Quenching And Post-Polymerization Modification Of Telechelic Polyisobutylene, Todd Raymond Hartlage

Dissertations

Polyisobutylene (PIB) is a saturated hydrocarbon elastomer that can only be produced by cationic polymerization. The water-initiated, chain transfer controlled synthesis conducted on an industrial scale produces monofunctional PIB with mixed olefin end groups. Living cationic techniques produce mono- and di-functional telechelic PIB. In situ quenching is the process of adding functional molecules to the polymerization reactor after all monomer is consumed. These quencher species bond to the chain ends, installing their latent functionality onto the polymer chain. To date, all quenchers utilized have been soft π-nucleophiles.

In the first project, free thiols, both aromatic and aliphatic, are shown to …

Biophysical Understanding Of Novel Synthetic Amyloid-Β (Aβ) Prions In Alzheimer's Disease, Amit Kumar

Dissertations

Oligomers of amyloid-β (Aβ) peptide are the primary toxic agents that play a pivotal role in the pathogenesis of Alzheimer’s disease (AD). Oligomers are the intermediates formed during the Aβ aggregation process leading up to insoluble fibrils. It is important to know that oligomers can also be formed via pathways that do not lead to fibril formation. Such ‘off-pathway’ oligomers would have significantly longer half-lives than the ‘on-pathway’ ones, which may result in prolonged toxicity to neuronal cells. Furthermore, neither the mechanism of neurotoxicity nor the potential mechanisms of propagation and proliferation to neighboring cells are well understood. Moreover, recent …

Relation Between The Adsorption Behavior And Bulk Complexation In Oppositely Charged Polyelectrolyte-Surfactant Systems: Effect Of Polyelectrolyte Concentration, Molecular Weight, Charge Localization And Backbone Rigidity/Hydrophobicity, Vipul Suhas Padman

Dissertations

Due to a wide range of applications, much emphasis has been placed on understanding the physicochemical behavior of polyelectrolyte/surfactant complexes, both at air-water interface and in the bulk. However, the correlation between the adsorption behavior and complexation in the bulk is less explored. In this research, this correlation is investigated and its dependence on polyelectrolyte concentration, molecular weight, charge localization and backbone rigidity and hydrophobicity is studied. The polyelectrolyte concentration is normalized with respect to it critical overlap concentration in order to compare the polymer in same concentration regime. Different polyelectrolyte systems were used to analyze the polyelectrolyte structural effect: …

Synthesis And Characterization Of Polyisobutylene-Block-Polyamides As Novel Thermoplastic Elastomers, Lauren Renee Kucera

Dissertations

Academic research has focused on two main areas of the living carbocationic polymerization (LCP) of isobutylene (IB): (1) the in-depth study and understanding of mechanistic features of the polymerization, and (2) the utilization and manipulation of the unique aspects of PIB in order to produce practically useful polymeric materials. The research included in this dissertation focuses mainly on the latter objective. This work details three main areas of research: (1) the copolymerization of PIB and polyamides (PA) to form novel thermoplastic elastsomers (TPEs), (2) the mechanical, physical and thermal properties of the novel PIB-PA materials, and (3) the use of …

Ultrafast Dynamics And Two-Photon Absorption Properties Of Chromophores At Interfaces, Semere Ghebru Bairu

Dissertations

Materials with large two-photon absorption (2PA) cross-sections found applications in several areas such as sensor protection, 3D micro/nano fabrication, photodynamic therapy, optical data-storage, multi-photon sensing, multi-photon microscopy and imaging. Several successful research strategies were developed in literature to achieve 2PA materials with enhanced cross-sections. However, the obtained cross-sections are far from adequate and there is a need to develop new strategies. In a parallel development, numerous research efforts were focused on studying the dynamics of interfacial charge-transfer (ICT) across chromophoresemiconductor interfaces, especially in the context of dye-sensitized solar cells. While investigating the fundamentals of ICT, it was found that these …

Stability And Precipitation Of Diverse Nanoparticles, Chintal Desai

Dissertations

Nanotechnology is a rapidly growing industry that is exploiting the novel characteristics of materials manufactured at the nanoscale. Carbon based nanomaterials such as Carbon Nanotubes (CNTs) and Detonation Nanodiamond (DND) possess unique properties and find a wide range of industrial applications. With the advent of mass production of such materials, there is a possibility of contamination of water resources. Depending on the surface properties and structures, they might aggregate and settle down, or be dispersed and transported by the water. Therefore, there is a need to develop an understanding of the fate of such materials in aqueous media. The understanding …

Application Of Hydrogen Peroxide As Brown Tide Bloom Control Agent, Varunpreet Randhawa

Dissertations

Harmful algal blooms (HABs) are growing problem across the globe. One such HAB that’s recurring in the coastal waters of New York and New Jersey since mid-1980s, and has been reported in other countries recently, is brown tide bloom. The causal organism is a minute pel agophyte (cell diameter ~- 2µ m) Aureococcus anophagefferens. The brown tide bloom has been responsible for the severe ecological damage and economic loss (e.g. shellfishery) in the affected areas. This research focuses on finding a method to control brown tide blooms and explores the potential of natural chemical biocide hydrogen peroxide (H_{2 …}

Study Of Elementary Reactions Of Combustion Importance At Elevated Temperatures And Pressures, Manuvesh Sangwan

Dissertations

The aim of the present study is to study the kinetics of elementary reactions of combustion importance at elevated temperatures and pressures. High pressure is encountered in many systems of practical importance such as internal combustion engines and rocket combustion chambers. Several reactions of OH, CH₃ and HO₂ radicals are studied. The pressure range covered in this study is 1 - 100 bar and the temperature range is 292 - 834 K. The experimental approach used is laser photolysis coupled to UV transient absorption spectroscopy. A unique high pressure heatable flow reactor is employed and a novel approach …

Escherichia Coli 2-Oxoglutarate Dehydrogenase Multienzyme Complex: E1 And E2 Substrate Specificty, E1 Carboligase Activity, And E2 Interchain Succinyl Transfer, Da Jeong Shim

Dissertations

Escherichia coli (E. coli) 2-oxoglutarate dehydrogenase multienzyme complex (OGDHc) contains three components: a thiamin di phosphate (ThD P) dependent 2-oxogl utarate dehydrogenase (E1 o), a di hydrol i poylsucci nyl transferase (E2o), and a di hydrol i poyl dehydrogenase (E3). The first two components carry out the principal reactions for succinyl CoA formation while the third one reoxidizes dihydrolipoamide to lipoamide. This mechanism is similar to other 2-oxoacid dehydrogenase complexes, including pyruvate dehydrogenases (PDHc) and branched-chain dehydrogenases.

E1o of the E. coli OGDHc was engineered to accept unnatural substrates. The natural substrate for E1 o is 2-oxogl utarate …

Computational Thermochemistry Of Hydrocarbons, Oxygenates, Cyclic Alkanes, And Furans, Jason Michael Hudzik

Dissertations

Fundamental thermochemical properties including enthalpies (ΔH°_{f 298}), entropies (S° (T)), heat capacities (C_p(T)), and bond dissociation energies (BDEs) for several common and complex hydrocarbon fuel species are determined using computational chemical methods. ΔH° _{f 298} values are calculated using work reactions with the B3LY P (6-31 G(d,p) and 6-311G(2d,2p) basis sets), CBS-QB3, and G3MP2B3 calculation methods. Structures, moments of inertia, vibrational frequencies, and internal rotor potentials are calculated for contributions to entropies and heat capacities. Kinetic rate parameters are calculated for hydrogen abstraction and chemical activation reactions.

Recommended ΔH° …

Synthesis And Characterization Of Luminescent Cyclic Germanium Compounds, Teresa Lynn Bandrowsky

Dissertations

The vision in the field of organic electronics is the realization of flexible, easily manufactured, low cost optoelectronics for use in organic light emitting diodes (OLEDs) for large area displays and lighting applications, organic photovoltaic cells, and organic field-effect transistors. The active layers within such devices are composed of semiconducting small molecules or polymers. The rich chemistry of new π-conjugated materials holds the key to continued progress by allowing the material properties of organic semiconductors to be readily tuned towards application specific demands. At the core of this subject matter is how to modify the electronic structures of π-conjugated molecules …

The Investigation Of Iron(Ii) Complexes And Their Catalytic Applications, Matthew Joseph Lenze

Dissertations

Several new η5-indenyl (Ind) complexes of iron featuring phosphinooxazoline (PHOX) ligands were synthesized and spectroscopically characterized and in a few cases structurally. The complexes were synthesized using phosphinooxazoline ligands and the corresponding iron precursor [Fe(η5-Ind) I(CO)2], yielding novel piano-stool iron complexes of the general formula [Fe(η5-Ind)(CO)(PHOX)]+ in 73% to 81% isolated yields. The complexes were tested for their efficacy in a carbon-carbon bond formation known as the Mukaiyama aldol reaction. The [Fe(η5-Ind)(CO)(PHOX)]+ complexes were capable of activating the carbonyl of aromatic aldehydes towards by attack 1-(tertbutyldimethylsilyloxy)-1-methoxyethene to form the expected silyl protected β-hydroxyesters. In these complexes, the η5-η3 haptotropic shift …

Microglial Activation By Amyloid-Beta, Geeta Subhash Paranjape

Dissertations

Paranjape, Geeta S.,Ph.D.,University of Missouri-Saint Louis, May 2012. Aβ(1-42) Protofibrils But Not Fibrils Activate Microglia. Major Professor: Michael R. Nichols. One of the hallmark features of the Alzheimer’s disease (AD) brain is the extracellular deposition of amyloid-β protein (Aβ) in both fibrillar (senile plaques) and diffuse forms. Significant proinflammatory markers including activated microglia and cytokines have been detected surrounding the plaques but are absent in diffuse areas suggesting that microglial activation is sensitive to Aβ structure. Since Aβ displays structural polymorphism in vitro, we sought to determine the relationship between Aβ aggregation state and microglial proinflammatory response. Size exclusion chromatography …

Photopolymerization And Characterization Of Modified Thiol-Ene Networks, Bradley James Sparks

Dissertations

Photopolymerization provides a unique ability to control variables typically uncontrollable using traditional thermally initiated polymerization, thus leading to its use in a broad range of commercial operations. Many of the traditional photopolymers suffer from several setbacks, including oxygen inhibition, unwanted stress buildup which leads to bulk shrinkage, etc., which ultimately lead to diminished polymer performance. The photopolymerization of multifunctional thiols and alkenes has been shown to provide a means to improve upon the weaknesses of traditional photoinitiated polymerizations. The free radical polymerization of thiol and –ene monomers occurs via a series of free radical chain transfer events, as a result, …

Dynamic Bioactive Stimuli-Responsive Polymeric Surfaces, Heather Marie Pearson

Dissertations

This dissertation focuses on the design, synthesis, and development of antimicrobial and anticoagulant surfaces of polyethylene (PE), polypropylene (PP), and poly(tetrafluoroethylene) (PTFE) polymers. Aliphatic polymeric surfaces of PE and PP polymers functionalized using click chemistry reactions by the attachment of –COOH groups via microwave plasma reactions followed by functionalization with alkyne moieties. Azide containing ampicillin (AMP) was synthesized and subsequently clicked into the alkyne prepared PE and PP surfaces. Compared to non-functionalized PP and PE surfaces, the AMP clicked surfaces exhibited substantially enhanced antimicrobial activity against Staphylococcus aureus bacteria. To expand the biocompatibility of polymeric surface …

Biological And Biologically Inspired Polymers For Interface Modification, Lea Clayton Paslay

Dissertations

Naturally occurring macromolecules are produced for a specific function and have the selectivity to accomplish objectives with little waste in energy. The scientific community strives to develop smart, efficient molecules on an economical scale, thus lessons can be learned from nature and applied to cost effective synthetic systems. First, the mimicry of naturally occurring antimicrobial peptides (AMPs) will be described. AMPs show great potential as alternatives to conventional antibiotics as they can selectively bind and eliminate pathogenic bacteria without harming eukaryotic tissues. Aqueous reversible addition–fragmentation chain transfer (RAFT) polymerization was utilized to prepare primary and tertiary amine containing AMP polymer …

Investigations Toward Tunability Of Mechanical, Thermal, And Impact Properties Of Thiol-Ene Networks For Novel High Energy Absorbing Materials, Olivia Devon Mcnair

Dissertations

The UV polymerization of thiols with electron rich alkenes is a highly resourceful reaction that has been utilized by scientists within various disciplines to produce an even more versatile display of applications. This dissertation focuses on a newer application, thiol-ene network (TEN) materials for energy absorption devices. TEN networks display a host of positive polymer properties such as low stress, high optical clarity and uniformity, but they also suffer from unfavorable mechanical properties such as low toughness and elongation at break. The poor mechanical properties demonstrated by TENs prohibit them as choice materials for applications requiring thicker material forms, including …

Synthesis Of Polyhedral Oligomeric Silsesquioxane (Poss) Functionalized Carbon Nanotubes For Improved Dispersion In Polyurethane Films, Xiaonan Kou

Dissertations

Carbon nanotube (CNT) polymer nanocomposites are promising advanced materials. These materials exhibit the advantages of traditional polymeric materials, such as being light weight and easy to process, combined with the potential to exhibit enhanced mechanical, thermal and electrical properties compared to pure polymers. To achieve substantial improvement of composite properties at low CNT loading, uniform dispersion of CNTs in the polymer matrix and strong CNT-polymer interfacial interaction are needed. However, it is difficult to achieve adequate dispersion and interfacial interactions due to the inert nature of CNTs. In this project, polyhedral oligomeric silsequioxane (POSS) will be used as a dispersing …

Nanoparticle Filled Polymeric Systems For Gas Barrier And Flame Retardant Properties, Yingji Wu

Dissertations

Polymer composite gas barrier and fire retardant properties were studied in this investigation. An increase in the gas barrier property was observed by adding silicate nanotubes or clay nanoparticles into polymeric systems. Oxygen permeability, diffusivity, solubility and water vapor permeability were determined for polyimide/silicate nanocomposites with 0 to 9.99% (vol/vol) filler loading. Both oxygen and water vapor permeability for the system gradually decreased when adding increasing amounts of nanofiller up to 4.50% (vol/vol) and increase again after that. The permeability decrease was caused by both the diffusivity and solubility coefficient changes, although diffusivity (the tortuous factor) is the main reason …