Chemistry Commons^™

Homogeneous Ligand-Centered Hydrogen Evolution And Hydrogen Oxidation : Exploiting Redox Non-Innocence To Drive Catalysis., Andrew Z. Haddad

Electronic Theses and Dissertations

Hydrogen is a promising carbon-free fuel / energy carrier and is an essential building block for many industrial and agricultural processes. Rising energy demands have ignited interest in the development of carbon-free and carbon neutral energy sources. In this context, hydrogen is an attractive candidate—being energy-dense, carbon-free—and easily accessible through a two-electron reduction of water. Accordingly, many electrochemical homogeneous catalyst systems have been studied, with a focus on understanding the mechanism of hydrogen evolution proceeding through metal-hydride intermediates. However, there has been a renaissance in hydrogen evolution reaction (HER) catalyst design, with many groups implicating ligand redox non-innocence as a …

Development Of Recyclable Gold Nanoparticles For Routine Benchtop Catalysis In Organic Transformations., Shengzong Liang

Electronic Theses and Dissertations

Homogeneous gold catalysis is a popular research area due to its high efficiency. Various gold catalysts have been utilized in organic synthesis and their reaction mechanisms are also well understood. However, most gold catalysis suffers from high catalyst loading or catalyst decay problems. In addition, homogeneous gold catalysts are not recyclable. These disadvantages have limited their application in large-scale synthesis and also caused a serious waste of this precious metal. A solution for these problems is to use a recyclable heterogeneous gold catalyst. So in this study, with the aim of making gold chemistry greener we successfully used heterogeneous gold …

Genetically Encoded Fluorescent Protein Biosensor For Nitric Oxide, Wenjia Zhai

Department of Chemistry: Dissertations, Theses, and Student Research

Nitric oxide (NO) is an important molecule in living cells for signaling, thus a specific sensor to detect its level in live cells is needed. Currently there are a few small molecule probes for the detection of NO. A common shortcoming of these probes is their unavoidable leakage from the target cells. In this project, I seek to develop a novel green fluorescent protein (GFP)-based biosensor to detect cellular NO. This GFP-based sensor is genetically encodable and can potentially avoid the possible false positive result due to the leakage. I synthesized an unnatural amino acid (unAA) and examined its incorporation …

An Investigation Of The Use Of Cerium And Polyhedral Oligomeric Silsesquioxanes For The Protection Of Polymeric Epoxy Compounds In The Low Earth Orbit Environment, Jessica Miriam Piness

Dissertations

Low Earth orbit presents many hazards for composites including atomic oxygen, UV radiation, thermal cycling, micrometeoroids, and high energy protons. Atomic oxygen and vacuum ultraviolet radiation are of concern for space-bound polymeric materials as they degrade the polymers used as matrices for carbon fiber composites, which are used in satellites and space vehicles due to their high strength to weight ratios. Epoxy-amine thermosets comprise a common class of matrix due to processability and good thermal attributes. Polyhedral oligomeric silsesquioxanes (POSS) have shown the ability to reduce erosion in polyimides, polyurethanes, and other polymers when exposed to atomic oxygen. The POSS …

Influence Of Multiwall Carbon Nanotubes On Corrosion Performance And Water Hydrogen Bonding Of Epoxy-Amine Thin Films, Greg William Curtzwiler

Dissertations

This dissertation research sought to provide a fundamental basis of understanding to commence the systematic investigation of developing economically viable fully formulated epoxy-amine coating systems containing multiwall carbon nanotubes (MWCNT). Namely, a facile and rapid method for multiwall carbon nanotube surface modification and molecular structure interpretation was developed to assist in designing MWCNT-polymer interactions and achieving high levels of dispersion. Additionally, a rapid and quantitative method was developed to investigate the dispersibility potential of MWCNTs possessing a given surface modification in combination with a dispersion protocol which can further be utilized as a quality control metric in commercial applications. It …

Formation Of Nanostructured Epoxy Networks Containing Polyhedral Oligomeric Silsesquioxane (Poss) And Silica Nanoparticles, Amit K. Sharma

Dissertations

This dissertation is focused on structure-property-processing relationship studies based on well-defined polyhedral oligomeric silsesquioxane (POSS) modified epoxy networks to present a comprehensive understanding of hybrid network behavior. In this research, a monoamine functional POSS molecule is incorporated into the epoxy monomer as pendant unit to mimic common epoxy structures and then crosslinked to form well-defined epoxy hybrid networks. The POSS cages behave as nanosized pendant unit in the epoxy matrices, while the mass fraction of POSS cages is varied and the effects on physical properties are examined with respect to changes in network architecture.

A novel continuous reactor method is …

Bioinspired Design Of Wetting And Anti-Wetting Surfaces Via Thiol-Ene Photopolymerization, Li Xiong

Dissertations

Surface wettability is known to have a profound influence in both academic study and industrial application of materials. Superhydrophobic surfaces, with a static contact angle higher than 150° and a contact angle hysteresis lower than 10°, have received continued attention for their broad applications, such as self-cleaning, antifogging and frosting, and drag reduction. The continuous development of materials and approaches that used to create superhydrophobic surfaces has led to further exploration of coatings with other desirable properties such as superamphiphobicity, mechanical robustness and thermal stability.

In this work, coatings with super wetting and super anti-wetting properties were designed and fabricated …

Design And Synthesis Of Polymer Brush Surfaces With Complex Molecular Architectures And Morphologies, Wei Guo

Dissertations

The combination of surface-initiated polymerization (SIP) and postpolymerization modification (PPM) is a powerful technique for the fabrication of functional soft surfaces. Better understanding the influence of the aforementioned factors on the PPM effectiveness is valuable for fulfilling the potential of the PPM approach for the fabrication of functional soft surfaces. Specifically, by carefully balancing modification reactivity and limitation of mass transport, polymer brush with composition heterogeneity and gradient along the normal direction of the surface otherwise unattainable by methods of direct polymerization can be fabricated via the PPM approach which opens doors to new routes to polymer brush with complex …

Advancing Structure-Property Relationships In Functional Materials Via Thiol-Ene Photopolymerization, Brian Richard Donovan

Dissertations

Thiol-ene photopolymerizations provide a robust and versatile synthetic pathway to functional materials, and owing to the radical step-growth nature of polymerization and the resulting homogenous network structure, provide non-convoluted insight into how network chemistry influences and dictates macromolecular properties.

The first facet of this dissertation focuses on the design and synthesis of bio-inspired, thin film adhesives for dry and aqueous adhesion. Drawing inspiration from the intertidal marine mussel, Chapter II details the synthesis of adhesive networks containing a monofunctional catechol-based monomer. The inclusion of a catechol group resulted in significant improvements in adhesion on a variety of substrates. In Chapter …

Effect Of Chain Rigidity On Network Architecture And Deformation Behavior Of Glassy Polymer Networks, Kyler Reser Knowles

Dissertations

Processing carbon fiber composite laminates creates molecular-level strains in the thermoset matrix upon curing and cooling which can lead to failures such as geometry deformations, micro-cracking, and other issues. It is known strain creation is attributed to the significant volume and physical state changes undergone by the polymer matrix throughout the curing process, though storage and relaxation of cure-induced strains remain poorly understood. This dissertation establishes two approaches to address the issue. The first establishes testing methods to simultaneously measure key volumetric properties of a carbon fiber composite laminate and its polymer matrix. The second approach considers the rigidity of …

Polyisobutylene Telechelic Prepolymers By In Situ End-Quenching And Post-Polymerization Modifications, Bin Yang

Dissertations

This volume focuses on the development of telechelic polyisobutylene (PIB) prepolymers by combining end-capping of living carbocationic polymerization of isobutylene (IB) with suitable reactants and post-polymerization modifications. Alkylation kinetics of PIB tert-chloride with alkoxybenzenes using either TiCl₄ or AlCl₃ were investigated. Quantitative para-position end-capped products were only achieved if the alkoxybenzene/AlCl₃ molar ratio was greater than unity; while no such molar ratio is required for TiCl₄, but the alkylation rate was slower than AlCl₃ under the same conditions. Photopolymerization kinetics analysis of PIB triphenol tri(meth)acrylates with low and high M_ns, …

Parameterization Of Ar231453: A Potent Agonist Of The Gpr119 Receptor, A Target For Diabetes Treatment, John E. Hamilton

Theses and Dissertations

The first reported potent agonist for the GPR119 receptor, a potential target for the treatment of diabetes, is 2-fluoro-4-methanesulfonyl-phenyl-{6-[4-(3-isopropyl-[1,2,4]oxadiazol-5-yl)-piperidin-1-yl]-5-nitro-pyrimidin-4-yl}-amine (AR231453). The dynamic interactions of AR231453 with GPR119 using molecular dynamics simulation are of great interest. However, parameters for AR231453 that describe the behavior of the molecule in the CHARMM force field have not been determined. The following study produces parameters by creating model fragments and compares the produced parameters to quantum calculations. The produced parameters are then further refined within the Visual Molecular Dynamics (VMD) program’s plugin program, the Force Field Toolkit as well as Gaussian 09 and CHARMM. Molecular …

Desorption Electrospray Ionization (Desi) Mass Spectrometric Imaging Of Spatially Regulated In Vivo Metabolic Rates, Charlotte Reininger Lewis

Theses and Dissertations

Desorption electrospray ionization (DESI) is an ambient ionization technique used for mass spectrometric imaging of biological samples. When coupled with isotopic ratio measurements of deuterium-labeled tissues, DESI provides a means of measuring metabolic rates on a spatially resolved basis. In vivo metabolic rates are desired to better understand diseases such as Alzheimer's, Parkinson's, Huntington's, and various forms of cancer that negatively impact metabolic rates within different organs of the human body. Although DESI has been used to image lipids and metabolites of a variety of tissues and other imaging techniques, such as NIMS, have been used to study kinetic turnover …

The Direct Dissociation Of Methanol On V(100) Surfaces, John Allred

Master of Science in Chemical Sciences Theses

The study of dissociating methanol on vanadium surfaces was investigated in order to provide insight into reaction pathways for methane dissociation and partial oxidation into other feedstock chemicals. The construction of a custom-designed ultrahigh vacuum chamber was done to permit surface analysis to a greater extent than was previously available in the lab. Prior to experimentation, the clean vanadium surface was characterized through use of X-ray photoelectron spectroscopy, scanning electron microscopy, and energy dispersive X-ray spectroscopy. This surface characterization revealed significant oxidation of the vanadium surface from atmospheric oxygen, water and carbon dioxide. The direct dissociation and partial oxidation of …

Formation Of Lifepo4-Pan Submicron Fibers Via Forcespinning ® For Battery Cathode Applications, Ashlee L. Lopez

Theses and Dissertations

LiFePO4/C composite nanofibers were prepared by utilizing Forcespinning® technology and calcination approaches. Polyacrylonitrile (PAN) was dissolved in N, N-dimethylformamide (DMF) to produce the media that allotted nanofiber formation via Forcespinning® and also served as the carbon source. A LiFePO4 solution was synthesized separately in DMF, which served as the precursor. The separately prepared PAN/DMF and LiFePO4/DMF solutions were then mixed at different weight percent’s (wt.%) prior to being subjected to Forcespinning ®. Elemental analysis of the LiFePO4/PAN nanofibers was characterized by energy dispersive spectroscopy (EDS) and x-ray photoelectron spectroscopy (XPS). The study of the surface morphology was conducted by scanning …

Ab Initio And Semi-Empirical Calculations Of Cyanoligated Rhodium Dimer Complexs, Yazeed Asiri

Electronic Theses and Dissertations

Molecular modeling, using both ab initio and semi-empirical methods has been undertaken for a series of dirhodium complexes in order to improve the understanding of the nature of the chemical bonding in this class of homogeneous catalysts. These complexes, with carboxylamidate and carboxylate ligands, are extremely functional metal catalysts used in the synthesis of pharmaceuticals and agrochemicals. The X-ray crystallography shows anomalies in the bond angles that have potential impact on understanding the catalysis. To resolve these issues, minimum energy structures of several examples (e.g. Rh₂(NHCOCH₃)₄, Rh₂(NHCOCH₃)₄NC, Rh …

Functionalized Silica Gel For Adsorption Of Cesium From Solution, Kenneth Marshall Seaton Iii

Electronic Theses and Dissertations

Mesoporous silica gel containing embedded phosphotungstic acid (PTA) was synthesized by sol-gel co-condensation of tetraethyl orthosilicate with PTA in acidic media. The obtained material had high Brunauer-Emmett-Teller Theory (BET) surface area and pore volume. A characteristic band of the Keggin structure of PTA was present in its FT-IR spectrum while its X-ray diffraction patterns were absent. This proved the embedding of PTA on a sub-molecular level and not as a second phase. Acidic sites were determined by neutralization with base in aprotic solvent, followed by titration of the remaining base with an acid. The material demonstrated high adsorption capacity of …

In Situ Electron Microscopy Of Plasmon-Mediated Nanocrystal Synthesis, Peter Sutter, Ying Li, Christos Argyropoulos, Eli A. Sutter

Department of Electrical and Computer Engineering: Faculty Publications

Chemical processes driven by nonthermal energy (e.g., visible light) are attractive for future approaches to energy conversion, synthesis, photocatalysis, and so forth. The growth of anisotropic metal nanostructures mediated by excitation of a localized surface plasmon resonance (LSPR) is a prototype example of such a reaction. Important aspects, notably the growth mechanism and a possible role of plasmonic “hot spots” within the metal nanostructures, remain poorly understood. Here, we use in situ electron microscopy to stimulate and image the plasmon-mediated growth of triangular Ag nanoprisms in solution. The quantification of the time-dependent evolution of the lateral size and thickness of …

Characterization Of Dust On Solar Devices In Southern Nevada, Jason Sylva

UNLV Theses, Dissertations, Professional Papers, and Capstones

Dust can impact the efficiency of solar energy collection devices, and in some arid environments, dust can reduce solar energy efficiency up to 30%. Reducing the impact of dust is therefore critical in the expansion of solar technology throughout regions where solar energy is utilized. Characterization of suspended and settled particulate matter can assist in developing strategies for dust mitigation. With the characterization of suspended and settled particulate in remote, rural, and urban environments, more informed decisions can be made regarding the selection of coating material on solar panels as well as developing cleaning and maintenance procedures. Particulate matter that …

Spectroscopic Signatures Of Uranium Speciation For Forensics, Nicholas Wozniak

UNLV Theses, Dissertations, Professional Papers, and Capstones

Chemical speciation offers opportunities for development of signatures that arise from the production, conversion, and aging processes of nuclear materials. This information has been useful for environmental science and remediation and the ability to measure chemical signatures, from processed materials may be of great use to nuclear forensics. Many nuclear forensics analyses deal with radiochronometry and isotopic analysis, but because processing is chemical in nature, there are opportunities for chemical signatures from the bulk products, reagents, or reaction intermediates to be measured.

Many spectroscopic techniques can be utilized in a remote setting outside of the laboratory, with minimal or no …

Influence Of Histidine Residues, Ph And Charge Interactions On Membrane-Spanning Peptides, Ashley N. Henderson

Graduate Theses and Dissertations

Designed transmembrane peptides were employed for investigations of histidine residues within the hydrophobic environment of the lipid bilayer by means of oriented solid-state deuterium NMR spectroscopy. Using the model peptide GWALP23 sequence (GGALW(LA)6LWLAGA) as a host framework, the effects of single and double histidine mutations were explored. Replacement of leucine residue 12 to polar neutral histidine had little influence on the peptide average orientation, however under strongly acidic pH conditions in DOPC bilayers, the histidine becomes positively charged (pKa 2.5) and the GWALP23-H12 peptide exits the membrane and adopts a surface-bound orientation. Conversely, mutation of leucine 14 to neutral histidine …

Morphology Controlled Synthesis Of Copper Based Multimetallic Nanostructures And Their Electrocatalytic Properties For Methanol Oxidation Reaction, Leanne Elizabeth Mathurin

Graduate Theses and Dissertations

This research focuses on the development of shape-controlled synthesis of Cu NM, Cu-based bimetallic and trimetallic nanostructures, and their electrocatalytic properties for methanol oxidation reaction (MOR). Copper nanomaterials (Cu NM) with specific surface facets can tailor their catalytic activity. Understanding reagents responsible for Cu NM growth is important for morphology-controlled synthesis of the nanostructures. This research studies the halide influence on Cu NM growth and morphology in an oil-based synthesis. The morphology of the Cu NM varies with the halide type (i.e., Cl-, Br-, I-), and the halide concentration. Additionally, the type of Cu precursor also influenced the morphology of …

Electrochemical Time Of Flight For Rapid And Direct Measurement Of Diffusion Coefficients, Jonathan C. Moldenhauer

Graduate Theses and Dissertations

The determination of diffusion coefficients is of fundamental importance to the understanding of electrochemistry and sensors. Developing a method by which diffusion coefficients of Red/ox active analytes can be determined quickly and elegantly, would be a great advancement over presently accepted methods. This dissertation reports the reviving electrochemical time of flight (ETOF), and developing a method that allows for empirical determination of diffusion coefficients from a single measurement. ETOF is a generate and detect experiment where the time an electrochemically generated species takes to transit a known distance is measured and related to the diffusion coefficient of the species. The …

Caffeine And Acetaminophen Concentration And Other Water Quality Parameters Along The Middle To Lower Bear River, Autumn Slade

Undergraduate Honors Capstone Projects

Various water quality parameters were measured at seven sites along the Middle to Lower Bear River and compared across the sites, to past data and to set standards in Utah and Idaho. Much of the data was comparable to past data with most state standards being met. However, nitrate was above indicator level for half of the sites, and turbidity is a problem at the last two sites. Also, chloride and unionized ammonia are at high levels by the last site. Overall, the river tended to decrease in water quality as it moved downstream, with dams like at Cutler Reservoir …

Role Of Nanoparticles In Voltammetric Signal Enhancement Exhibited By Layer-By-Layer (Lbl) Gold Nanoparticle-Modified Screen-Printed Carbon Electrodes (Spces), Ben K. Ahiadu

Electronic Theses and Dissertations

Screen-printed electrodes (SPEs) have found wide use as sensing platforms due to their simple fabrication, customizability in terms of geometry and composition, and relatively low cost of production. Nanoparticles have been incorporated in or interfaced with SPEs in order to improve sensor response or provide electrocatalytic capabilities. Though nanomaterial-modified SPEs are becoming increasingly common sensing platforms, the benefits provided by nanomaterials are often determined through voltammetric studies with common redox probes, such as ferricyanide. However, recent reports have documented the ferri-/ferrocyanide redox couple to be an unreliable system for characterizing some carbon-based electrodes due to the dependence of its electrochemical …

Fourier Transform Spectroscopy Of The A3Π–X3Σ− Transition Of Oh+, James N. Hodges, Peter F. Bernath

Chemistry & Biochemistry Faculty Publications

The OH⁺ ion is of critical importance to the chemistry in the interstellar medium and is a prerequisite for the generation of more complex chemical species. Submillimeter and ultraviolet observations rely on high quality laboratory spectra. Recent measurements of the fundamental vibrational band and previously unanalyzed Fourier transform spectra of the near-ultraviolet A³Π-X 3Σ^- electronic spectrum, acquired at the National Solar Observatory at Kitt Peak in 1989, provide an excellent opportunity to perform a global fit of the available data. These new optical data are approximately four times more precise as compared to the previous values. …

Characterization Of Sufs And Sufe Of Suf Pathway For Fe-S Cluster Assembly In Escherichia Coli, Guangchao Dong

Theses and Dissertations

Fe-S clusters are one major type of the sulfur-containing cofactors, which conduct essential functions in organisms. The Suf pathway is one of the three main pathways for the biosynthesis of Fe-S clusters. In E. coli, the Suf pathway is utilized under iron limitation and oxidative stress. This ability is important for pathogens to survive. Also, the Suf pathway is found to be exclusive in bacteria, so it is a good target for novel antibiotic design. SufS is a cysteine desulfurase in the Suf pathway to extract sulfur from L-cysteine. It needs the enhancement of SufE. To better understand the catalytic …

Advances In Chemistry, Part I: Noise, Calibration, And Educational Advances In Analytical Chemistry. Part Ii: Safety Oversight In Chemical Journals, Lauren E. Grabowski

Theses and Dissertations

Part I:

The accuracy and precision of the results of any chemical analysis depends on the calibration graph and its associated systematic and random errors. Least squares regression generally treats all data with equal weights. A weighted least-squares fit is an improvement but requires knowledge of the imprecision in each point of the calibration graph. The imprecision is not easy to estimate with high confidence because of the large number of replicates needed.

The imprecision depends on the types and magnitudes of the sources of noise. We characterized the noise sources in ICP-OES and UV/Vis and developed a model that …

Antimicrobial Biomaterials And Sustainable Polymers From Renewable Biomass, Mitra Shiran Ganewatta

Theses and Dissertations

In this dissertation, development of antimicrobial biomaterials and sustainable polymers from renewable biomass is described. In Chapter 1, an overview and recent development about sustainable polymers from renewable biomass, antimicrobial biomaterials and polymerization methods are given. Afterwards, the major research objectives of this doctoral research work are described.

Innovative cationic polymers containing pine resin sourced abietic acid is discussed in Chapter 2. The preparation of cationic compounds is conversed via a combination of Diels-Alder, catalytic esterification, quaternization and subsequent decoration of polycaprolactone that was prepared via ring-opening polymerization (ROP). Furthermore, the antimicrobial activity against a range of bacteria, biocompatibility with …

Shaping Metallic Nanoparticles Toward Integrated Plasmonics And Catalysis, Qingfeng Zhang

Theses and Dissertations

Noble metal nanoparticles have been of tremendous interest because of their intriguing size- and shape-dependent plasmonic and catalytic properties. The combination of tunable plasmon resonances with superior catalytic activities on the same nanoparticle, however, has long been challenging because plasmonics and catalysis require nanoparticles in two drastically different size regimes. Tunable plasmon resonances is a unique feature of sub-wavelength metallic nanoparticles, whereas heterogeneous catalysis requires the use of sub-5 nm nanoparticles as the catalysts. In this dissertation, I firstly found a unique way to bridge this size gap between nanoplasmonics and nanocatalysis. I demonstrated that desired plasmonic and catalytic properties …