Browsing by Subject "Chemistry"
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Item A feasibility study and design of a dual hot plate and ventilation system for use in a shielded hot cell(2021-12-09) McNair, Carson Rex; Haas, Derek Anderson, 1981-The objective of this thesis is to provide a feasibility study and design for a new dual hot plate and associated ventilation system for the Analytical Research Laboratory (ARL) located at the Materials and Fuels Complex (MFC) at Idaho National Laboratory (INL). This new system is to be installed inside the high radiation shielded hot cell #2. The hot plate and ventilation currently being used utilizes almost 50% of the hot cell floor space while only providing 200 in2 of heating surface during wet chemistry activities. The ARL plays a crucial role in most of the research activities that take place at INL. Samples collected during nuclear fuel cycle studies, whose radiation levels require a shielded hot cell for processing, are consistently required to schedule hot plate availability. Due to the precision of the results produced in the ARL, sample types are segregated and processed separately to prevent cross contamination between samples. In addition to sample dissolutions, the hot plate is also used for sample waste volume reduction. Sample waste volume reduction also competes for hot plate availability. A new dual hot plate and ventilation system, that continues to successfully address chemically hostile vapors and volatile radioactive isotopes produced during the dissolution of samples and sample waste processing, would allow multiple activities to be worked simultaneously. This increased efficiency and throughput will contribute to shortened turnaround times for the qualification of new nuclear materials and advanced nuclear fuels and speed up research that is being performed on the nuclear fuel cycle throughout INLItem Analysis of Citations to Books in Chemistry PhD Dissertations in an Era of Transition(ACRL Science and Technology Section, 2018) Flaxbart, DavidA citation analysis of chemistry PhD dissertations at the University of Texas at Austin yielded data on how often graduate students cite books in their bibliographies, and on the characteristics of the books cited, in terms of age and local ownership. The analysis examined samples of dissertations selected from five discrete years - 1988, 2006, 2009, 2012, and 2015 - in order to provide longitudinal data on how citation trends are changing during a transition period in libraries. Data indicated that chemistry graduate students cited low numbers of books relative to journal articles, confirming expectations from similar studies, and that the trend over the time period studied is downward, despite the increasing number and availability of e-books. The results could inform collection management decisions and strategies for promoting book content to graduate students in future.Item Bipolar electrodes for the screening of electrocatalyst candidates(2014-05) Fosdick, Stephen Edward; Crooks, Richard M. (Richard McConnell); Bard, Allen J; Manthiram, Arumugam; Mullins, Charles B; Stevenson, Keith JAdvances in the application of bipolar electrodes (BPEs) for screening of electrocatalysts, localized activation of a single conductive electrode, the optical tracking of single particles interacting with an active electrode, and the introduction of microwires in paper-based analytical devices are described. In an original proof of concept study arrays of BPEs were used to determine the relative activity of model nanoparticle systems for the oxygen reduction reaction (ORR) by a simple optical readout: the electrodissolution of Ag microbands. The number of bands that dissolved during the screening procedure determined the relative activity of the materials. These screening results for model nanoparticle systems were related to traditional electrochemical experiments and showed a strong correlation. Building on that initial study, the BPE platform for screening ORR electrocatalyst candidates was improved so that more materials could be evaluated simultaneously by increasing the density of electrodes in the array, controlled compositional variations were prepared with the implementation of piezodispensing, and a different reporter, Cr, replaced Ag at the BPE anodes which reduced the risk of contamination and improved reliability of screening experiments. Further studies into the versatility of the screening platform have been carried out using non-noble metal systems for the hydrogen evolution reaction (HER), which has a long history of interest for electrochemists. A single conductive electrode material can be made to act as an array of electrodes by confining it at the intersection of two orthogonal microfluidic channels. By manipulating the direction and magnitude of the electric field in the device, faradaic reactions can be selectively localized on the BPE. An approach for optically tracking individual, insulating microparticles interacting with an active UME has been achieved. This approach brings new insight and understanding of single particle electrochemical studies. Finally, a method for incorporating microwires and mesh electrodes into paper-based electroanalytical devices is reported. This has many advantages over traditional screen-printed carbon electrodes that are traditionally used in paper-based devices.Item A comparison of the effects of mobile device display size and orientation, and text segmentation on learning, cognitive load, and user perception in a higher education chemistry course(2015-05) Karam, Angela Marie; Resta, Paul E.; Liu, Min; Hughes, Joan E.; Riegle-Crumb, Catherine; Matthew, EastinThis study aimed to understand the relationship between mobile device screen display size (laptops and smartphones) and text segmentation (continuous text, medium text segments, and small text segments) on learning outcomes, cognitive load, and user perception. This quantitative study occurred during the spring semester of 2015. Seven hundred and seventy-one chemistry students from a higher education university completed one of nine treatments in this 3x3 research design. Data collection took place over four class periods. The study revealed that learning outcomes were not affected by the mobile screen display size or orientation, nor was working memory. However, user perception was affected by the screen display size of the device, and results indicated that participants in the sample felt laptop screens were more acceptable for accessing the digital chemistry text than smartphone screens by a small margin. The study also found that neither learning outcomes, nor working memory was affected by the text segmentation viewed. Though user perception was generally not affected by text segmentation, the study found that for perceived ease of use, participants felt medium text segments were easier to learn from than either continuous or small test segments by a small margin. No interaction affects were found between mobile devices and text segmentation. These findings challenge the findings of some earlier studies that laptops may be better for learning than smartphones because of screen size, landscape orientation is better for learning than portrait orientation in small screen mobile devices, and meaningful text segments may be better for learning than non-meaningful, non-segmented, or overly segmented text. The results of this study suggest that customizing the design to the smartphone screen (as opposed to a one-size-fits-all approach) improves learning from smartphones, making them equal to learning from laptops in terms of learning outcomes and cognitive load, and in some cases, user perspective.Item Cu-catalyzed three-component carboamination of 2-arylacrylates(2021-08) Popov, Andrei; Hull, KamiThere is an increasing demand for modern methods to construct one of the most ubiquitous bonds in biologically active molecules: a carbon-nitrogen bond. Transition metal catalysis represents a powerful tool to create new chemical bonds with great efficiency and selectivity. Thus, the development of novel catalytic techniques, based on transitions metals, for quick and effective assembly of nitrogen-containing organic molecules can be an advancement in synthetic routes to many drug molecules, agrochemicals, functional materials and many others. 1,2-carboamination of alkenes is the approach that unlocks the access to rapid assembly of complex organic nitrogen-containing frameworks from readily available feedstocks. In particular, the carboamination of acrylates can provide a synthetic access to various aminoacid derivatives. The present thesis is devoted to the development of the Cu-catalyzed carboamination of 2-arylacrylates. A wide substrate scope with good functional group tolerance is demonstrated. The mechanistic aspects of the reaction are discussed.Item Design, synthesis, and calorimetric studies on protein-ligand interactions : apolar surface area, conformational constraints, and cation-[pi] interactions(2013-05) Myslinski, James Michael; Martin, Stephen F.Because bimolecular interactions in water are poorly understood, three tactics commonly used to improve binding affinity in ligand design were investigated: (1) increasing apolar surface area, (2) introducing a conformational constraint, and (3) targeting a cation-[pi] interaction. Thermodynamic parameters of binding ligands to the Grb2 SH2 domain were determined by isothermal titration calorimetry (ITC), and structural data was obtained by X-ray crystallography. The apolar surface area of the pTyr+1 residue in Ac-pTyr-Acnc-Asn-NH₂ was varied by incrementally increasing the size of the cyclic Acnc residue from a 3-membered to a 7-membered ring. Increasing apolar surface area resulted in an increase in Ka due to a more favorable [delta]H⁰ that was dominated a less favorable [delta]S⁰. Structural analyses showed that all ligands bound in a similar mode, so differences in binding thermodynamics were attributed to the pTyr+1 residue. The thermodynamics of binding tripeptides wherein pTyr+1 was an n-alkyl group were studied. Ka increased when Ala was mutated to Abu, but additional methylene groups had no effect on Ka due to strong entropy-enthalpy compensation. While [delta]H⁰ was weakly correlated with buried surface area, there was no change in [delta]H⁰ between one methylene and two methylene groups, presumably because an enthalpic penalty is associated with a gauche interaction between C-[beta] and C-[gamma] of the Xaa side chain that was noted in the crystal structure. An olefin was installed in an attempt to alleviate the energetic penalty incurred from the gauche interaction, but the introduction of the constraint resulted in equipotent ligands. A putative cation-[pi] interaction between Arg67 and various aromatic groups was probed by varying the [pi]-donating capability of groups attached to a tripeptide scaffold. Although crystal structures demonstrated that three of the aryl groups were close enough to Arg67 to form a cation-[pi] interaction, only a modest increase in Ka was observed relative to analogues having only an N-acetyl group. Furthermore, a simple cyclohexyl group in place of aryl groups resulted in ligands that were equipotent with indolyl- and phenyl- derived analogues, so any cation-[pi] interaction is not significant.Item Effects of using presentation formats that accommodate the learner's multiple intelligences on the learning of freshman college chemistry concepts(2004-12) Brown Wright, Gloria Aileen; Lagowski, J. J.Howard Gardner's Theory of Multiple Intelligences identifies linguistic, spatial and logical-mathematical intelligences as necessary for learning in the physical sciences. He has identified nine intelligences which all persons possess to varying degrees, and says that learning is most effective when learners receive information in formats that correspond to their intelligence strengths. This research investigated the importance of the multiple intelligences of students in first-year college chemistry to the learning of chemistry concepts. At three pre-selected intervals during the first-semester course each participant received a tutorial on a chemistry topic, each time in a format corresponding to a different one of the three intelligences, just before the concept was introduced by the class lecturer. At the end of the experiment all subjects had experienced each of the three topics once and each format once, after which they were administered a validated instrument to measure their relative strengths in these three intelligences. The difference between a pre- and post-tutorial quiz administered on each occasion was used as a measure of learning. Most subjects were found to have similar strengths in the three intelligences and to benefit from the tutorials regardless of format. Where a difference in the extent of benefit occurred the difference was related to the chemistry concept. Data which indicate that students' preferences support these findings are also included and recommendations for extending this research to other intelligences are made.Item Electrochemical materials for the production and storage of renewable energy(2020-06-23) Wygant, Bryan Russell; Mullins, C. B.; Crooks, Richard M; Roberts, Sean T; Eberlin, Livia S; Yu, Edward TThe production of electricity from renewable sources, including solar power, is increasingly important as our society seeks to move to cleaner energy sources. Organolead halide perovskites, a class of thin film photovoltaic (PV) materials, are an exciting competitor to traditional Si devices, but suffer from poor material stability. Further, PV power is intermittent, creating a need for efficient energy storage during times when solar power is unavailable. H₂ gas, produced via electrochemical water electrolysis, is a promising way to store this energy in chemical bonds but efficient electrocatalysts are required to drive the reaction. This need for electrocatalysts is particularly acute for the complementary oxygen evolution reaction (OER), the rate-limiting half reaction of electrolysis. Here, we address both halves of the renewable energy problem above, production and storage, and study how the chemistry of PV and OER electrocatalyst materials impacts electrochemical performance and material stability. In regard to production, we studied the performance and stability of quasi-2D Ruddlesden-Popper phase (RPP) perovskites under humid conditions. We found that RPP perovskites are more stable than typical 3D perovskites due to a unique moisture-driven disproportionation mechanism that passivates and protects the surface of the RPP perovskite. This process can also result in the formation of discrete RPP crystallites within the bulk of a perovskite film or device. We also found that changing the composition of the RPP perovskite enables control of the halide diffusion barrier, further impacting material stability. We next investigated energy storage, and studied how elemental composition affected the performance of two transition metal-based OER electrocatalyts. We found that for a Co-containing oxide perovskite, changes in the crystal structure of the catalyst from hexagonal to orthorhombic had little effect on OER performance, while adding small amounts of Fe improved catalytic behavior. Likewise, we found that the addition of Se to a nickel sulfoselenide material improved OER performance, even though the sulfoselenide material itself oxidizes during electrocatalysis to produce a catalytically-active nickel (oxy)hydroxide surface. Altogether, our work highlights the importance chemical composition when studying the material stability and electrochemical performance of both PV and electrocatalytic materials for renewable energy applications.Item Insights into computational methods for surface science and catalysis(2021-12-06) Ciufo, Ryan Anthony; Henkelman, Graeme; Humphrey, Simon M; Hwang, Gyeong S.; Webb, Lauren J.The fundamental understanding of both the reactions at catalytic surfaces and the ways in which these surfaces change throughout a catalytic cycle and lifetime are important for both academic and industrial disciplines. To develop these understandings on complex catalytic systems, ultra-high vacuum techniques such as molecular beam studies, temperature programmed desorption, reflection-absorption infrared spectroscopy and Auger electron spectroscopy can be used to study the simplest interactions between gas molecules and surfaces. These interactions can be studied from a bottom-up approach to learn about the system in question, upon which additional complexities can be added. To parallel these experimental techniques, a number of computational methods can be used to support findings and guide new experiments. Ab-initio electronic structure calculations allow for a better understanding of adsorbate-surface interactions, while long timescale dynamic simulations provide insight into the time evolution and kinetics of catalysts and catalytic surfaces. Empirical and machine-learning guided potentials can be developed to lessen computational cost while retaining accuracies comparable to ab-initio calculations. Fitting such potentials ultimately allows for larger calculations to be performed and longer timescales to be simulated. The above methods will be applied to a number of industrially and academically relevant catalytic systems, including studying the interaction of H₂ and CO with Cobalt based Fischer-Tropsch catalysts and the interaction between hydrogen and palladium surfaces. Additionally, the development of a machine learning package to fit and use interatomic potentials will be discussed.Item Investigation of the mitigation of charged impurity and defect scattering effects by polar molecules on graphene(2016-08) Worley, Barrett C.; Dodabalapur, Ananth, 1953-; Akinwande, Deji; Vanden Bout, David; Crooks, Richard; Henkelman, GraemeGraphene is a promising material for use in microelectronics, due to its high mobility, operating frequency, and good stability. These characteristics are governed by charge carrier transport and charged impurity scattering effects, the latter of which are caused by adventitious doping from both the ambient and semiconductor fabrication processes. A variety of chemical interactions between graphene and both its defects and charged impurities influence the electrical properties. This dissertation focuses on the chemical interactions between polar molecules and the impurities and defects on graphene. The monatomic thickness of the graphene monolayer renders interfacial charged impurities located at the graphene/substrate interface susceptible to the dielectric environment surrounding graphene. Our group has shown that the electrical properties of graphene devices are improved upon coating with fluoropolymers or exposure to gas-phase polar organic vapors. These improvements include reduction of the Dirac voltage, increased mobility, and decreased residual carrier density. We attribute these changes to screening by polar molecules of fields induced by charged impurities/defects in or near the active layer. The magnitude of the changes produced in the graphene device parameters scales well with the dipole moment of the delivered vapor molecules. These effects are reversible, a unique advantage of working in the vapor phase. The changes observed upon polar molecule delivery are analogous to those produced by depositing and annealing fluoropolymer coatings on graphene. We attribute these changes to similar charge screening phenomena. Quantum mechanical modeling showed that polar molecules interacted more strongly with impure or defective graphene than with pristine graphene. Molecular mechanics simulations revealed more insight into how polar molecules interact with two types of charged impurities atop graphene. Polar molecules both displace and electrostatically screen charged impurities to reduce the electrostatic potential profile in the plane of graphene. These computational observations correlate well with our experimental results to support our hypothesis that polar molecules can act to screen charged impurities on or near monolayer graphene. Such screening favorably mitigates charge scattering, improving graphene transistor performance. Our understanding of charged impurity screening methods can further be applied to graphene nanoribbons and other 2D materials.Item Measuring electrostatics in complex protein systems using vibrational Stark effect spectroscopy(2019-06-21) Novelli, Elisa Talcott; Webb, Lauren J.; Brodbelt, Jennifer S; Maynard, Jennifer A; Baiz, Carlos R; Crooks, Richard MThe non-covalent interactions between and within proteins are important because of their specificity and their ability to control protein structure and function. The measurement of electric fields, which describe these complex interactions, is crucial to understanding the physical properties of proteins such as folding, catalysis, and multimolecular interactions. Our goal is to understand and ultimately exploit these complex interactions for therapeutic value. In particular, our group has been interested in small GTPase signaling proteins, such as Ras, because of their known oncogenic properties, complex network of binding partner proteins, and their difficulty as a drug target. In particular the highly specific protein-protein interactions inherent in the signaling role of Ras and other GTPase proteins are interesting potential drug targets that could avoid the toxicity of competitive inhibition at the GTP binding site. To this end, we have made use of vibrational Stark effect spectroscopy, a technique that directly reports on electrostatic environment, to measure the electric fields in Ras and other GTPases by site-specifically incorporating small nitrile vibrational probes into proteins. We have related the quantitative field measurements to protein activity to elucidate the role of electric fields in the intrinsic hydrolysis mechanism of oncogenic Ras mutants. We also designed experiments to investigate the role of electrostatics in driving specific protein-protein interactions and their inhibition by the small molecule Brefeldin A in the GTPase protein Arf. Finally, we developed the Staphylococcus aureus protein staphylococcal nuclease as a robust model system for experiments aimed at better understanding how pK [subscript a] and nitrile probes respond to their local electrostatic environment. Together, this work demonstrates the importance of electrostatic forces in protein function and highlights how vibrational Stark effect spectroscopy can be applied effectively to interesting and relevant protein systems to observe and exploit the physical properties of proteins for therapeutic benefit.Item Modeling reactive rarefied systems using a novel quasi-particle Boltzmann solver(2020-12-04) Poondla, Yasvanth Kumar; Varghese, Philip L.; Goldstein, David Benjamin, doctor of aeronautics; Raja, Laxminarayan; Liechty, Derek; Moore, ChristopherThe goal of this work is to build up the capability of Quasi-Particle Simulation (QuiPS), a novel flow solver, such that it can adequately model the rarefied portion of an atmospheric reentry trajectory. Direct Simulation Monte Carlo (DSMC) is the conventional solver for such conditions, but struggles to resolve transient flows, trace species, and high level internal energy states due to stochastic noise. Quasi-Particle Simulation (QuiPS) is a novel Boltzmann solver that describes a system with a discretized, truncated velocity distribution function. The resulting fixed-velocity, variable weight quasi-particles enable smooth variation of macroscopic properties. The distribution function description enables use of a variance reduced collision model, greatly minimizing expense near equilibrium. Improvements made to the method in this work include parallelization of the collision integral routine, modification of the velocity space definition to improve performance and resolution of the distribution function, and the addition of a neutral chemistry model. Chemistry's dependence on the tail of a distribution function necessitates accurate resolution of said tail, a computationally challenging proposition. The effects of these additions are verified and studied through a number of 0D calculations, including simulations for which analytic solutions exist and model simulations intended to capture relevant physics present in more complicated problems. The explicit representation of internal distributions in QuiPS reveals some of the flaws in existing physics models. Variance reduction, a key feature of QuiPS can greatly reduce expense of multi-dimensional calculations, but is only cheaper when the gas composition is near chemical equilibrium.Item On the role of invariant objects in applications of dynamical systems(2012-05) Blazevski, Daniel, 1984-; Llave, Rafael de la; Chen, Thomas (Ph. D. in mechanical engineering and Ph. D. in mathematical physics); Koch, Hans; Morrison, Phil; Ocampo, Cesar; Pavlovic, Natasa; Vasseur, AlexisIn this dissertation, we demonstrate the importance of invariant objects in many areas of applied research. The areas of application we consider are chemistry, celestial mechanics and aerospace engineering, plasma physics, and coupled map lattices. In the context of chemical reactions, stable and unstable manifolds of fixed points separate regions of phase space that lead to a certain outcome of the reaction. We study how these regions change under the influence of exposing the molecules to a laser. In celestial mechanics and aerospace engineering, we compute periodic orbits and their stable and unstable manifolds for a object of negligible mass (e.g. a satellite or spacecraft) under the presence of Jupiter and two of its moons, Europa and Ganymede. The periodic orbits serve as convenient spot to place a satellite for observation purposes, and computing their stable and unstable manifolds have been used in constructing low-energy transfers between the two moons. In plasma physics, an important and practical problem is to study barriers for heat transport in magnetically confined plasma undergoing fusion. We compute barriers for which heat cannot pass through. However, such barriers break down and lead to robust partial barriers. In this latter case, heat can flow across the barrier, but at a very slow rate. Finally, infinite dimensional coupled map lattice systems are considered in a wide variety of areas, most notably in statistical mechanics, neuroscience, and in the discretization of PDEs. We assume that the interaction amont the lattice sites decays with the distance of the sites, and assume the existence of an invariant whiskered torus that is localized near a collection of lattice sites. We prove that the torus has invariant stable and unstable manifolds that are also localized near the torus. This is an important step in understanding the global dynamics of such systems and opens the door to new possible results, most notably studying the problem of energy transfer between the sites.Item Presentation: How I Learned to Love Chemistry (Or Watch Dr. Laude Blow Stuff Up)(Environmental Science Institute, 2014-09-12) Environmental Science Institute; Laude, DavidItem Synthesis and Characterization of Luminescent Lanthanide Nano-Rings(2016) Bard, Alexander; Jones, RichardIt is not uncommon for inorganic chemistry classes to gloss over the chemistry of the lanthanides. Because most inorganic chemists work closely with the d -electrons of the transition metals, the shielded and inert f -electrons of the lanthanides may at first glance seem monotone or even boring. However, to truly appreciate the lanthanides and the complexes they produce, one must come to embrace their chemical simplicity and understand their much more interesting electronic properties that lead to extremely interesting luminescent and magnetic molecules. Furthermore, though the lanthanides generally only form 3+ ions, it is important to consider that their high coordination number can lead to some very large and unusual molecular structures. Additionally, lanthanide complexes are known for their photophysical properties, specifi cally their sharp emission peaks. This, along with the fact that they don't photobleach and are relatively nontoxic, make them ideal for biological probes. If the ligand in the complex can be functionalized to couple with an antibody, the complex should then be able to follow the antibody wherever it goes, for example, to a cancerous tumor, and the probes would then aggregate in the area, causing localized luminescence, aiding in early detection of cancer. This thesis reports the synthesis of a 42-nuclear lanthanide nano-ring: likely the highest nuclearity lanthanide complex ever produced. This complex, referred to as Ln 42, is produced by reacting an ortho-vanillin based ligand with lanthanide acetate, the suitable lanthanides being gadolinium, terbium, dysprosium, and holmium. The complex self-assembles, interestingly, fi rst hydrolyzing the ligand such that the only portion that remains in the final complex is deprotonated ortho-vanillin. Acetate and hydroxyl groups also remain in the final complex, in addition to the lanthanide centers. The structure in the crystalline solid state was determined using single crystal X-ray diffraction.Item Synthesis of homoaporphine-type alkaloids via intramolecular phenol alkylation, design and synthesis of a new class of Trypanosoma brucei growth inhibitors, and neurons that matter : using light to tag neuronal ensembles based on function(2017-05-03) Meis, Alan Ronald; Martin, Stephen F.; Sessler, Johnathon L; Anslyn, Eric V; Keatinge-Clay, Adrian T; Zemelman, Boris VThe synthesis of a homoaporphine-type alkaloid was accomplished in 10-steps. The synthesis featured a synthetic strategy to establish the key quaternary center through an early Suzuki cross coupling and a late-stage p-phenolic C-alkylation reaction, which proceeded in high yields. A medicinal chemistry and rational drug design approach was undertaken to design and synthesize a new class of Trypanosoma brucei growth inhibitors. This hit-to-lead strategy resulted in compounds with up to a 25-fold increase in efficacy towards T. brucei growth inhibition, with respect to the initial hit compound, and a single compound with activity in sub-micromolar concentrations. A collaborative effort has begun to develop a function based method to label or tag neurons. We have developed a photocaged derivative of erythromycin A in order to control gene expression within neurons using light. The photochemical properties of the photocaged-erythromycin derivative were studied and in vitro proof of principle assays are currently underway.Item Tandem mass spectrometry approaches to characterizing challenging biomolecules : stapled and cyclic peptides and variants of lipid A from gram-negative bacteria(2016-08) Crittenden, Christopher Martin; Brodbelt, Jennifer S.; Mullins, Charles BMass spectrometry has emerged as a leading tool in the field of chemistry as an analytical method for the characterization of small molecules, proteins, and other complex biomolecules. Specifically, cyclic and stapled peptides have become an intriguing class of biomolecules in drug research afforded to them because of their biological stability and resistance to proteolytic digestions. However, challenges are presented in regards to the characterization of these molecules as traditional methods are ineffective in determining a ring-opening site on the peptidic backbone. Additionally, lipid A, the hydrophobic domain of lipopolysaccharide (LPS), consists of a diglucosamine backbone and is responsible for fastening LPS to a membrane surface. Lipid A becomes a biologically relevant molecule to study as its function within LPS is directly related to the infectious and toxic properties of gram-negative bacteria, but the molecule is structurally complex and offers many challenges in terms of traditional mass spectrometry characterization. Presented in the thesis are methods to further comprehend structural motifs related to the aforementioned biomolecules. The “ornithine effect”, which describes the conversion of an arginine residue to an ornithine residue via reaction with hydrazine and subsequent preferential cyclization via nucleophilic attack of the ornithine side-chain to the neighboring carbonyl group, inducing heterolytic cleavage of the adjacent amide bond under gentle activation, is used to preferentially open cyclic and stapled rings to linearize these challenging biomolecules. Ramped collisional and photon based activation (in terms of energy and laser pulses) of lipid A molecules that contain differences in acyl-chain length and connectivity reveal general trends about the lability of certain bonds on the lipid A molecules themselves and paints a picture of the overall fragmentation trends associated with variations in lipid A structural motifs.Item The development and study of materials for optoelectronic devices and sensors(2018-06-15) Moore, Matthew Darren; Sessler, Jonathan L.; Humphrey, Simon M; Que, Emily; Anslyn, Eric V; Slinker, Jason DLuminescence is a property of materials that allows for the emission of photons when a given amount of energy is applied. The luminescent properties of both polymeric and small molecule materials can generally be controlled through rational design, allowing for the development of materials that can be used in a variety of applications (e.g. sensing, light emissive devices, photovoltaics, photochemistry, etc…). Several families of small molecule emissive materials were designed for use in light emitting electrochemical cells (LEECs). A set of iridium complexes was designed to promote rapid turn-on time in devices, as well as raise the LEEC’s external quantum efficiency (EQE). By systematically substituting mesityl groups onto a base iridium complex, the turn-on times were lowered from minutes to seconds for systems containing the new substituents. Furthermore, the EQE was raised from 0.45% to 1.38% for one material. The study of platinum-based emitters in LEEC devices has not been previously reported, thus it is of interest to determine if this subset of highly efficient emitters may behave in devices similarly to iridium complexes. A family of platinum complexes was synthesized and studies are ongoing to establish device behavior. Moreover, an all organic, ionic set of emissive small molecules was synthesized. Studies are similarly ongoing to determine device behavior. Sensing is also an important capability of some emissive materials. The sensitivity of particular materials to their environment is an attribute that can be utilized to design a sensor. By using a mixed lanthanide metal-organic-framework (MOF), the sensing of trace (<0.5%) water in organics was accomplished. How the systems are able to show such sensitivity was also examined to determine how to further improve upon the MOF’s sensing abilities. This same material was further used in a fingerprinting system that permits the rapid identification of unknown solvents.Item Towards a better understanding of bitumen chemistry, microstructure, and rheology(2018-11-27) Sakib, Nazmus; Bhasin, Amit; Baumgardner, Gaylon; Saleh, Navid; Juenger, Maria; Faxina, AdalbertoBitumen is the residua of fractional distillation of crude oil. It generally consists of complex and a diverse variety of organic molecules and other heteroatoms. The nature and interactions between these molecules dictate the engineering properties of the bitumen. One of the attributes used to classify and examine these diverse constituent molecules is based on their relative polarities. Typically a bitumen is classified into four polarity based fractions, namely saturates, aromatics, resins and asphaltenes (SARA) using physical separation by precipitation and chromatography. Such separations require specialized equipment and expertise. In this study, two new fast and repeatable techniques of chromatography using disposable and inexpensive parts were developed. One of these methods was then used to fractionate a large set of bitumens in order to compare the constitution of the bitumens based on these fractions to their rheological, mechanical, and microstructural properties. Results show that parameters based on bitumen stiffness and tensile strength correlate well with these fractions. Similar relationship with more time dependent parameters was not conclusive. Microscopic observation of surface microstructures indicates similarity among bitumens from the same producer. There was also a good correlation between SARA parameters and surface microstructure for bitumens from the same producer. However, this relationship was unique for each producer and not global suggesting that other factors related to the crude source need to be considered as well