Chemistry Commons^™

Colloidal Synthesis And Photophysical Characterization Of Group Iv Alloy And Group Iv-V Semiconductors: Ge1-Xsnx And Sn-P Quantum Dots, Venkatesham Tallapally

Theses and Dissertations

Nanomaterials, typically less than 100 nm size in any direction have gained noteworthy interest from scientific community owing to their significantly different and often improved physical properties compared to their bulk counterparts. Semiconductor nanoparticles (NPs) are of great interest to study their tunable optical properties, primarily as a function of size and shape. Accordingly, there has been a lot of attention paid to synthesize discrete semiconducting nanoparticles, of where Group III-V and II-VI materials have been studied extensively. In contrast, Group IV and Group IV-V based nanocrystals as earth abundant and less-non-toxic semiconductors have not been studied thoroughly. From the …

Metal-Organic Frameworks And Graphene-Based Support Materials For Heterogeneous Catalysis, Andrew Lin

Theses and Dissertations

Nanoparticles are involved in a broad range of applications, including heterogeneous catalysis. Nanoparticles tend to quickly lose their well-defined shapes and facets due to aggregation under duress such as heat.

A series of highly studied materials are explored as support materials for nanoparticle supports. These supports include metal-organic frameworks (MOF), graphene oxide (GO), and a MOF-PRGO (partially reduced graphene oxide) hybrid. The inclusion of a support with the palladium increased lifespan of the catalyst by separation of nanoparticles. The choice of support material not only allowed for supporting of palladium nanoparticles, but allowed for rational catalyst synthesis in order to …

Heteroatom Doped Porous Carbon For Alternative Energy Conversion And Storage Systems, Fatema A. Choudhury

Theses and Dissertations

Abstract

The electrocatalysis of oxygen plays a significant role in several electrochemical energy storage and conversion systems including metal−air batteries, fuel cells, electrocatalytic and photocatalytic water splitting. The sluggish kinetics and complex reaction mechanism of this cathodic oxygen reduction reaction (ORR) affect the performance and practical application of such renewable energy technologies. To address this limiting factor, a suitable electrocatalyst is required for ORR. In general, platinum or highly dispersed Pt-based nanoparticles on carbon black are considered as the best ORR catalyst. But platinum being very scarce and expensive tends to increase the cost. Moreover, platinum-based catalysts are prone to …

Water Dynamics And The Effect Of Static And Alternating Electric Fields, Mohammadmahdi Shafiei Alavijeh

Theses and Dissertations

Having a net dipole moment, water molecules tend to align with an external electric field. The re-orientation of water molecules to align with the field direction can result in structural and dynamic changes in liquid water. Studying these changes can help us to understand the role of an E-field in many biological systems, chemical reactions, and many technological advancements.

In short, the application of static electric fields causes molecules to stay aligned with the field, so, fewer hydrogen bonds break, and molecules have slower dynamics. This type of field can be used when the mobility of water molecules needs to …

The Investigation Of Oxidative Addition Reactions Of Metal Complexes In Cross-Coupling Catalytic Cycles Based On A Unique Methodology Of Coupled Ion/Ion-Ion/Molecule Reactions, Mariah L. Parker

Theses and Dissertations

Popular catalytic cycles, such as the Heck, Suzuki, and Negishi, utilize metal centers that oscillate between two oxidation states (II/0) during the three main steps of catalysis: reductive elimination, oxidative addition, and transmetallation. There has been a push to use less toxic, cheaper metal centers in catalytic cycles, leading to interest in first-row transition metals, such as nickel and cobalt. With these metals, the cycles can potentially pass through the +1 oxidation state, which acts as reactive intermediates, undergoing oxidative additions to form products, potentially with radical characteristics. The oxidative addition steps of catalytic cycles are critical to determining overall …

Development Of Photocatalysts Supported On Graphitic Carbon Nitride For The Degradation Of Organic Water Pollutants, Atanu Giri

Theses and Dissertations

Graphitic carbon nitride (g-C₃N₄) heterojunction composites with the semiconducting metal oxides, CeO₂, ZnO and TiO₂ are prepared in situ by co-calcination of the precursor materials or by a solvothermal method. The structural, morphological and the optical properties of the prepared materials are studied using various microscopy and spectroscopy techniques. The synthesized composite materials, CeO₂/g-C₃N₄, ZnO/g-C₃N₄ and TiO₂/g-C₃N₄ are more efficient in the photocatalytic degradation of the water pollutants indigo carmine (IC) and atrazine than the pure metal oxide, g-C …

Experimental Evaluation Of Uranyl Transport Into Mesoporous Silica Gel Using Fluorescence, Brandon M. Dodd

Theses and Dissertations

This research investigated parameters that can affect the use of nanoporous silica gel as a media for accumulating a detectable amount of uranium. The unique fluorescence of the Uranyl (UO₂²⁺) ion was used to evaluate the transport kinetics and accumulation within silica gel in a static fluid and under pressure driven flow. The addition of fluid flow decreased the time constant from on the order of an hour to approximately 2s with a very low fluid velocity of 0.36cm/s. The 0.36cm/s fluid velocity was found to be the critical velocity above which there was no gain in …

Nitrogen Rich Porous Organic Frameworks: Proton Conduction Behavior Of 3d Benzimidazole And Azo-Linked Polymers, Michael J. Anhorn

Theses and Dissertations

Nitrogen-rich porous organic frameworks show great promise for use as acid-doped proton conducting membranes, due to their high porosity, excellent chemical and thermal stability, ease of synthesis, and high nitrogen content. Aided by very high surface area and pore volume, the material has the ability to adsorb high amounts of H₃PO₄ into its network, which creates a proton rich environment, capable of facile proton conduction. The morphology and chemical environment, doping behavior, and proton conduction of these materials were investigated. With such high acid-doping, ex-situ studies revealed that under anhydrous conditions, PA@BILP-16 (AC) produced a proton conductivity …

Dicarbon­Yl{[(E,E)-(2,3,4,5-Η)-6-Meth­­Oxy-6-Oxo-2,4-Hexa­Dien­Yl]Tri­Phenyl­Phospho­Nium}(Tri­Phenyl­Phosphane-ΚP)Iron(1+) Hexa­Fluorido­Phosphate, Yuzhi Ma, Sergey V. Lindeman, William A. Donaldson

Chemistry Faculty Research and Publications

In the title compound, [Fe(C₂₅H₂₄O₂P)(C₁₈H₁₅P)(CO)₂]PF₆, the Fe atom adopts a square-based pyramidal coordination geometry with the carbonyl groups and the two C=C bonds of the diene defining the basal sites and the phosphane ligand the apical position. The diene ligand has an E,E geometry, with the phospho­nium fragment pointed away from the Fe atom. The crystal structure displays C—H⋯F and C—H⋯O hydrogen bonding. The PF₆⁻ anion is rotationally disordered over four orientations.

A–C Estrogens As Potent And Selective Estrogen Receptor-Beta Agonists (Serbas) To Enhance Memory Consolidation Under Low-Estrogen Conditions, Alicia M. Hanson, K. L. Iresha Sampathi Perera, Jaekyoon Kim, Rajesh K. Pandey, Noreena Sweeney, Xingyun Lu, Andrea Imhoff, Alexander Craig Mackinnon, Adam J. Wargolet, Rochelle M. Van Hart, Karyn M. Frick, William A. Donaldson, Daniel S. Sem

Chemistry Faculty Research and Publications

Estrogen receptor-beta (ERβ) is a drug target for memory consolidation in postmenopausal women. Herein is reported a series of potent and selective ERβ agonists (SERBAs) with in vivo efficacy that are A–C estrogens, lacking the B and D estrogen rings. The most potent and selective A–C estrogen is selective for activating ER relative to seven other nuclear hormone receptors, with a surprising 750-fold selectivity for the β over α isoform and with EC₅₀s of 20–30 nM in cell-based and direct binding assays. Comparison of potency in different assays suggests that the ER isoform selectivity is related to the …

Recent Progress In The Synthesis Of Six-Membered Aminocyclitols (2008-2017), William A. Donaldson

Chemistry Faculty Research and Publications

Aminocyclitols are of interest as glucosidase inhibitors, as probes for the study of pseudoglycosyltransferases, and as potential therapeutics for the treatment of Gaucher’s disease. The synthesis of these targets was reviewed in early 2008, and the aim of this review is to cover material relevant to the synthesis of aminocyclitols since that time. While not a focus of this review, biological evaluation of compounds will be presented where it is recorded in the literature.

Quantum Dynamics Of Isolated Molecules: General Discussion, Dmitri Babikov, David Benoit, Joel Bowman, Timothy Burd, David Clary, Robert Donovan, Ingo Fischer, Francesco Gianturco, Majdi Hochlaf, Susmita Kar, Adam Kirrander, Stephen Leone, Thomas Malcomson, Uwe Manthe, Anne B. Mccoy, Jens Petersen, Jeremy Richardson, Petr Slavíček, Thierry Stoecklin, Krzysztof Szalewicz, Ad Van Der Avoird, Roland Wester, Graham Worth, Anne Zehnacker-Rentien

Chemistry Faculty Research and Publications

No abstract provided.

Teaching Chemistry In A Spiral Progression Approach: Lessons From Science Teachers In The Philippines, Joymie R. Orbe, Allen A. Espinosa, Janir T. Datukan

Australian Journal of Teacher Education

As the Philippines moves towards implementing the K-12 curriculum, there has been a mismatch in teacher preparation in science. The present teacher education curriculum prepares science teachers to specialise in a specific field (e.g. integrated science, biology, chemistry, and physics). However, in the K-12 curriculum, they are required to teach all the sciences in a spiral progression approach. Hence, this study analysed the experiences of science teachers in teaching chemistry in the K-12 curriculum in order to identify their challenges and how they are overcoming them. Findings suggest that the teacher’s content, pedagogy, and assessment in chemistry are problematic; specifically, …

Human P450 Cyp17a1: Control Of Substrate Preference By Asparagine 202, Michael C. Gregory, Piotr J. Mak, Yogan Khatri, James R. Kincaid, Stephen G. Sligar

Chemistry Faculty Research and Publications

CYP17A1 is a key steroidogenic enzyme known to conduct several distinct chemical transformations on multiple substrates. In its hydroxylase activity, this enzyme adds a hydroxyl group at the 17α position of both pregnenolone and progesterone at approximately equal rates. However, the subsequent 17,20 carbon–carbon scission reaction displays variable substrate specificity in the numerous CYP17A1 isozymes operating in vertebrates, manifesting as different K_d and k_cat values when presented with 17α-hydroxypregnenlone (OHPREG) versus 17α-hydroxyprogesterone (OHPROG). Here we show that the identity of the residue at position 202 in human CYP17A1, thought to form a hydrogen bond with the A-ring alcohol …

Fhbc, A Hexa‐Peri‐Hexabenzocoronene–Fluorene Hybrid: A Platform For Highly Soluble, Easily Functionalizable Hbcs With An Expanded Graphitic Core, Tushar S. Navale, Maxim V. Ivanov, Mohammad M. Hossain, Rajendra Rathore

Chemistry Faculty Research and Publications

Materials based upon hexa‐peri‐hexabenzocoronenes (HBCs) show significant promise in a variety of photovoltaic applications. There remains the need, however, for a soluble, versatile, HBC‐based platform, which can be tailored by incorporation of electroactive groups or groups that can prompt self‐assembly. The synthesis of a HBC–fluorene hybrid is presented that contains an expanded graphitic core that is highly soluble, resists aggregation, and can be readily functionalized at its vertices. This new HBC platform can be tailored to incorporate six electroactive groups at its vertices, as exemplified by a facile synthesis of a representative hexaaryl derivative of FHBC. Synthesis of …

Structural Evidence Of A Major Conformational Change Triggered By Substrate Binding In Dape Enzymes: Impact On The Catalytic Mechanism, Boguslaw P. Nocek, Cory Reidl, Anna Starus, Tahirah Heath, David L. Bienvenue, Jerzy Osipiuk, Robert Jedrzejczak, Andzrej Joachimiak, Daniel P. Becker, Richard C. Holz

Chemistry Faculty Research and Publications

The X-ray crystal structure of the dapE-encoded N-succinyl-l,l-diaminopimelic acid desuccinylase from Haemophilus influenzae (HiDapE) bound by the products of hydrolysis, succinic acid and l,l-DAP, was determined at 1.95 Å. Surprisingly, the structure bound to the products revealed that HiDapE undergoes a significant conformational change in which the catalytic domain rotates ∼50° and shifts ∼10.1 Å (as measured at the position of the Zn atoms) relative to the dimerization domain. This heretofore unobserved closed conformation revealed significant movements within the catalytic domain compared to that of wild-type HiDapE, which results in effectively closing off access to …

Development And Evaluation Of Post-Production Oxygenation Techniques For The Augmentation Of Biochar, Matthew David Huff

Chemistry & Biochemistry Theses & Dissertations

Biochar is the carbon rich solid by-product of biomass pyrolysis. Interest in biochar can be broken down to several main categories: use as a carbon sequestration agent, use as a medium for the removal via adsorption of unwanted materials in wastewater, and as a soil amendment for the increase of cation exchange capacity (CEC). In order to generate a biochar which is stable enough for carbon sequestration, higher temperature pyrolysis must be used in order to ensure a lower O:C ratio in order to increase the half-life of biochar in soil. This dissertation addresses the evaluation of biochars made from …

Computational Investigation Of Energetic Materials: Influence Of Intramolecular And Intermolecular Interactions On Sensitivity, Ashley Lauren Shoaf

Chemistry & Biochemistry Theses & Dissertations

The development of novel high energy density materials (HEDMs) with superior energetic properties depends on characterizing how and why detonation occurs. Detonation is highly energetic and a nearly instantaneous process, making experimental studies challenging; thus, computational modeling through density functional theory (DFT) and molecular dynamics (MD) can be used to propose weakened, or activated, bonds that break to initiate explosive decomposition, termed trigger bonds. Bond activation is characterized by the Wiberg bond index (WBI), a measure of interatomic electron density. Trigger bonds in HEDMs are commonly found in explosophores, functional groups that contribute to energetic potential such as X-NO_{2 …}

Synthesis And Characterization Of Glycolipids, Glycoclusters And Glycomacrocycles, Anji Chen

Chemistry & Biochemistry Theses & Dissertations

Low molecular-weight gelators (LMWGs) are a fascinating and interesting class of compounds that can self-assemble and form supramolecular structures in appropriate solvents. The gelators form fibrous networks which entrap the solvent and result in a supramolecular gel. Carbohydrate-derived LMWGs are especially useful since they are more likely to be biocompatible and biodegradable. Dendritic gelators are branch-shaped molecules with precise molecular weight that are between small molecules and polymer gelators. Glycoclusters with sugar moieties at the periphery of the molecules are important classes of bioactive compounds due to the multivalency effect. Lower generation glycoclusters are relatively small branched systems that have …

Structure Of The Picornavirus Replication Platform: A Potential Drug Target For Inhibiting Virus Replication, Meghan Suzanne Warden

Chemistry & Biochemistry Theses & Dissertations

Picornaviruses are small, positive-stranded RNA viruses, divided into twelve different genera. Members of the Picornaviridae family cause a wide range of human and animal diseases including the common cold, poliomyelitis, foot and mouth disease, and dilated cardiomyopathy. The picornavirus genome is replicated via a highly conserved mechanism involving a presumed cloverleaf structure located at the 5’ noncoding region of the virus genome. The 5’ cloverleaf consists of three stem loops (B, C, and D) and one stem (A), which interact with a variety of virus and host cell proteins during replication. In this dissertation, human rhinovirus serotype 14 (HRV-14) SLB …

Physicochemical, Spectroscopic Properties, And Diffusion Mechanisms Of Small Hydrocarbon Molecules In Mof-74-Mg/Zn: A Quantum Chemical Investigation, Gemechis Degaga

Dissertations, Master's Theses and Master's Reports

In petroleum refining industries, the fracturing process allows for the cracking of long-chain hydrocarbons into a mixture of small olefin and paraffin molecules that are then separated via the energetically and monetarily demanding cryogenic distillation process. In an attempt to mitigate both energetic and capital consumptions, selective sorption of light hydrocarbons by tunable sorbents, such as metal-organic frameworks (MOFs), appears to be the most promising alternative for a more efficient gas separation process. MOFs are novel porous materials assembled from inorganic bricks connected by organic linkers. From a crystal engineering stand point, MOFs are advantageous in creating a range …

Direct Measurement Of Rupture Force Of Single Triazole Molecule By Atomic Force Microscope And Solid Phase Synthesis Of Monodisperse Polyethylene Glycols, Ashok Khanal

Dissertations, Master's Theses and Master's Reports

This dissertation includes two topics, which are related to each other: (1) Rupture force measurement of single triazole molecule by atomic force microscope (AFM) and (2) Solid phase stepwise synthesis of polyethylene glycols (PEGs).

The reaction of an alkyne and an azide to form a 1,2,3- triazole has found wide applications. However, the stability of triazole under mechanical stress is unclear. We investigated the cycloreversion at the single molecular level using atomic force microscopy. A mica surface functionalized with a molecule containing a 1,2,3-triazole moiety in the middle and an activated ester at the end was prepared. An AFM tip …