Chemistry Commons^™

Quartz Crystal Microbalance Studies On Friction Modifiers For Lubricant Applications, Carey Lehner

Theses and Dissertations

Lubricants are used in numerous applications to control friction and protect moving parts from fatigue. These fluids consist of a variety of surface active chemistries competing for the surface to provide performance. In order to develop fluids that meet the ever-increasing requirements (from legislation and manufacturers), techniques that can provide insight into surface adsorption, in real time, and relate it back to performance are critical.

The objective of this work is to determine if Quartz Crystal Microbalance with Dissipation (QCM-D) is an effective technique to investigate surfactant adsorption in regimes that are common to the transportation lubricant industry. QCM-D is …

Icp-Oes Analysis Of The Chemical Composition Of Hypergolic Mixtures, Monique Jones

Undergraduate Research Posters

Hypergolic mixtures involve a chemical reaction between an oxidant and a fuel source. These reactions are self-igniting and can be performed using common household materials. The ease of access to the reactants, and delayed ignition have increased the occurrence of hypergolic mixtures in arson-related crimes and incendiary devices. Currently, few chemical signatures exist to link hypergolic residues to a perpetrator. This makes it difficult to obtain forensically relevant information from evidence during an investigation. A hypergolic reaction of interest to forensic laboratories involves combustion between a glycol-based fuel source and potassium permanganate. Past studies have determined that one can distinguish …

Light Controlled Drug Activation And Release, Jonathon Sheldon

Theses and Dissertations

Cancer constitutes a terrible burden on modern society. In the United States there are an estimated 1,658,370 new cancer diagnoses resulting in 589,430 deaths in 2015 alone.^[1] An estimated 41,170 of these cases will be diagnosed right here in Virginia. With new cancer patients comes the expanding demand for new treatments. As we all know, many modern chemotherapeutics cause adverse reactions to patients. This is because the toxic nature of these therapies often affects normal tissue alongside the tumors that are infesting the body. Therefore, researching novel ways to make chemotherapeutics selective for cancer, while leaving healthy tissue unscathed, …

Dispersant Effects On Zinc Dialkyldithiophosphate (Zddp) Tribofilm Structure And Composition, Makaye Tabibi

Theses and Dissertations

For decades, global regulations and government mandates have driven technological developments to improve vehicle fuel economy. Tribological components found in all automotive engines contain metal-on-metal contact zones that may result in increased friction and wear, reducing overall engine efficiency. Lubricant additives such as antiwear and friction modifying components are added to motor oils to prevent some of the damages that may occur at contact zones and improve friction. The effects of other additive components, such as dispersants, that are prevalent in a lubricant additive package on the anti-wear layer remain relatively unknown. Polyisobutenyl Succinimide (PIBSI) dispersants were evaluated for their …

Heteroatom-Doped Nanoporous Carbons: Synthesis, Characterization And Application To Gas Storage And Separation, Babak Ashourirad

Theses and Dissertations

Activated carbons as emerging classes of porous materials have gained tremendous attention because of their versatile applications such as gas storage/separations sorbents, oxygen reduction reaction (ORR) catalysts and supercapacitor electrodes. This diversity originates from fascinating features such as low-cost, lightweight, thermal, chemical and physical stability as well as adjustable textural properties. More interestingly, sole heteroatom or combinations of various elements can be doped into their framework to modify the surface chemistry. Among all dopants, nitrogen as the most frequently used element, induces basicity and charge delocalization into the carbon network and enhances selective adsorption of CO₂. Transformation of …

Physicochemical And Structural Analysis Of Polymers As Putative Drugs, Meghan L. Thompson

Theses and Dissertations

Sulfated low molecular weight lignins (LMWLs) have shown good activity as anticoagulants by allosterically inhibiting thrombin, as well as promising agents for treating emphysema through inhibition of elastolysis, oxidation, and inflammation. Sulfated LMWLs are chemo-enzymatically synthesized from starting monomers caffeic, ferulic, and sinapic acid into sulfated dehydropolymers known as CDS, FDS, and SDS. To further the LMWLs’ development as drugs, their structural composition and physicochemical characteristics were defined in this work. The molecular weight distribution profile of the sulfated LMWLs from size exclusion chromatography performed on a high pressure liquid chromatography system (SEC-HPLC) changed from bimodal when no surfactant is …

Gas-Phase Reactions And Mechanistic Details Of Gold, Silver, And Iridium Complexes, Christopher Swift

Theses and Dissertations

The ever increasing demand for more efficient and environmentally benign routes for synthesizing target compounds, has led to the use of organometallic catalysts. This demand has created the need to understand the mechanistic details that are at work in these organometallic catalytic cycles. Along with this, there is a demand for new organometallic catalysts that are tailored for specific transformations. This presents a myriad of challenges for organometallic chemists. Unfortunately, it is often difficult to gain an understanding of the reaction mechanisms at work when the intermediates are too short lived to be observed in the condensed phase. It is …

Electronic Principles Governing The Stability And Reactivity Of Ligated Metal And Silicon Encapsulated Transition Metal Clusters, Marissa B. Abreu

Theses and Dissertations

A thorough understanding of the underlying electronic principles guiding the stability and reactivity of clusters has direct implications for the identification of stable clusters for incorporation into clusters-assembled materials with tunable properties. This work explores the electronic principles governing the stability and reactivity of two types of clusters: ligated metal clusters and silicon encapsulated transition metal clusters. In the first case, the reactivity of iodine-protected aluminum clusters, Al₁₃I_x^- (x=0-4) and Al₁₄I_y^- (y-0-5), with the protic species methanol was studied. The symmetrical ground states of Al₁₃I_x^- showed no reactivity …

Synthesis Of Unnatural Amino Acids For Genetic Encoding By The Pyrrolysyl-Trna/Rna Synthetase System, William A. Knight

Theses and Dissertations

The complexity of all biomolecules in existence today can be attributed to the variation of the amino acid repertoire. In nature, 20 canonical amino acids are translated to form these biomolecules, however, many of these amino acids have revealed posttranslational modifications (i.e. acetylation, methylation) after incorporation. Amino acids that exhibit PTM are known for their involvement in cellular processes such as DNA repair and DNA replication; these PTMs are commonly found on histones within the chromatin complex. Utilization of in vivo site-specific incorporation has recently reported functionality of post-translationally modified amino acids.1 xii Here we report the synthesis and in …

A Continuous Process Towards The Synthesis Of Quinolones, Stevara N. Clinton

Theses and Dissertations

Abstract

The development of quinolones is described from the first quinolone to the latest fluoroquinolones. Quinolones have generated considerable interest since their discovery because of their antibacterial capabilities. Analogs incorporating the 4-quinolone ring system comprise a largely expanding group of synthetic compounds. The development of antibacterial resistance has created the need for an efficient synthesis of quinolones that can be easily adapted toward the assembly of quinolone based antibacterial drugs.

There are several reported approaches to the 4-quinolone ring system. Many of these methods use expensive starting materials, require the removal of high boiling solvents, or use high temperature conditions …

Colloidal Synthesis And Optical Characterizations Of Semiconductor Nanocrystals From Nontoxic Elements, Minh Q. Ho

Theses and Dissertations

To date, the search efforts have shifted from the toxic II-VI, III-V and IV-VI semiconductors to more environmentally friendly materials. Among Group II-V semiconductors, Zn₃P₂ has shown to be a more benign option, similar to Group IV (Ge, Si) materials, for future applications in photovoltaics and optoelectronics. This work is dedicated to the development of wet-chemical synthetic routes of (1) Zn₃P₂ and (2) Group IV (Ge, Si, Si_1-xGe_x) nanocrystals with precise control over composition, crystal structure, size and dispersity by adjusting different reaction parameters such as temperature, time and solvent …

Diazaborole Linked Porous Polymers: Design, Synthesis, And Application To Gas Storage And Separation, Zafer Kahveci

Theses and Dissertations

The synthesis of highly porous organic polymers with predefined porosity has attracted considerable attention due to their potential in a wide range of applications. Porous organic polymers (POPs) offer novel properties such as permanent porosity, adjustable chemical nature, and noteworthy thermal and chemical stability. These remarkable properties of the POPs make them promising candidates for use in gas separation and storage. The emission of carbon dioxide (CO₂) from fossil fuel combustion is a major cause of global warming. Finding an efficient separation and/or storage material is essential for creating a cleaner environment. Therefore, the importance of the POPs …

Investigation Of The 4-Amino-Α,Α-Dihydroxy-3,5-Dichloroacetophenone Impurity In The Synthesis Of Clenbuterol Hydrochloride, Kerry Moore

Theses and Dissertations

Clenbuterol Hydrochloride is a bronchodilator marketed as Spirospent® for Human Pharmaceuticals and as Ventipulmin® for Veterinary Pharmaceuticals by Boehringer Ingelheim.1 This research investigates formation of the 4-amino-α,α-dihydroxy-3,5-dichloroacetophenone impurity (Dihydroxy Impurity) in the synthesis of Clenbuterol Hydrochloride. The Dihydroxy Impurity has increased three-fold since the process was transferred to Boehringer Ingelheim Chemicals, Inc. in 1999.1 The Dihydroxy Impurity is proposed to be produced during an amination/reduction step from a reaction of water with the starting material.2 Additionally, the Dihydroxy Impurity can be formed by the reaction of water with an impurity, 4-amino-α,α-didibromo-3,5-dichloroacetophenone (Dibromo Impurity), that is generated in the previous step.2 …

Determination Of The Factors That Affect The Gas-Phase Reactivity Of Metal-Centered Cyclopropanation Catalysts And Examination Of The Properties Of Their Reaction Products, Jamal Aldajaei

Theses and Dissertations

Gas phase studies of organometallic systems have provided deep insight into reaction mechanisms and reaction intermediates. In this thesis, several metal/ligand systems were examined in an effort to form metal carbenes in the gas phase. With cobalt and iron porphyrins, the carbene undergoes metal-ligand insertion. With copper bis-oxazolines, metal carbenes tend to undergo metal-ligand insertion and a Wolff rearrangement. To avoid insertions, we turned to a rigid ligand, 1, 10-phenanthroline. Under ESI conditions, a copper (I) complex with phenanthroline can be formed. When treated with diazoacetate esters, the dominant product results from addition with loss of nitrogen followed by loss …

Synthesis And Characterization Of Cobalt Carbide Based Nanomaterials, Zachary Huba

Theses and Dissertations

Permanent magnets are used heavily for multiple applications in industry and current electronic technologies. However, the current permanent landscape is muddled by high cost of materials and insufficient magnetic or thermal properties. The primary focus of this dissertation work is the synthesis and optimization of a new permanent magnetic material, in the form of cobalt carbide nanomaterials. The optimization revolved around controlling the crystal phase and particle shape of synthesized cobalt carbide particles; these parameters have significant impact on the observed magnetic properties of magnetic nanoparticles. Co₃C was identified to be the preferred crystal phase, leading to better …

Enhanced Magnetic Anisotropy In Cobalt-Carbide Nanoparticles, Ahmed A. El-Gendy, Meichun Qian, Zachary J. Huba, Shiv N. Khanna, Everett E. Carpenter

Chemistry Publications

An outstanding problem in nano-magnetism is to stabilize the magnetic order in nanoparticles at room temperatures. For ordinary ferromagnetic materials, reduction in size leads to a decrease in the magnetic anisotropy resulting in superparamagnetic relaxations at nanoscopic sizes. In this work, we demonstrate that using wet chemical synthesis, it is possible to stabilize cobalt carbide nanoparticles which have blocking temperatures exceeding 570 K even for particles with magnetic domains of 8 nm. First principles theoretical investigations show that the observed behavior is rooted in the giant magnetocrystalline anisotropies due to controlled mixing between C p- and Co d-states.

Wetting Transparency Of Graphene In Water, J. Driskill, D. Vanzo, D. Bratko, A. Luzar

Chemistry Publications

Measurements of contact angle on graphene sheets show a notable dependence on the nature of the underlying substrate, a phenomenon termed wetting transparency. Our molecular modeling studies reveal analogous transparency in case of submerged graphene fragments in water. A combined effect of attractive dispersion forces, angle correlations between aqueous dipoles, and repulsion due to the hydrogen-bond-induced orientation bias in polarized hydration layers acting across graphene sheet, enhances apparent adhesion of water to graphene. We show wetting free energy of a fully wetted graphene platelet to be about 8 mNm−1 lower than for graphene wetted only on one side, which gives …

Astroecology, Cosmo-Ecology, And The Future Of Life, Michael Noah Mautner

Chemistry Publications

Astroecology concerns the relations between life and space resources, and cosmo-ecology extrapolates these relations to cosmological scales. Experimental astroecology can quantify the amounts of life that can be derived from space resources. For this purpose, soluble carbon and electrolyte nutrients were measured in asteroid/meteorite materials. Microorganisms and plant cultures were observed to grow on these materials, whose fertilities are similar to productive agricultural soils. Based on measured nutrient contents, the 10²² kg carbonaceous asteroids can yield 10¹⁸ kg biomass with N and P as limiting nutrients (compared with the estimated 10¹⁵ kg biomass on Earth). These data …

A Novel Two-Laser Interface For Coupling Capillary Electrochromatography With Ion-Trap Time-Of-Flight Mass Spectrometry, David C. Simpson, Alexander J. Yates, John H. Knox, Pat R.R. Langridge-Smith

Chemistry Publications

An interface has been developed for the hyphenation of capillary electrochromatography (CEC) with mass spectrometry (MS). Chromatographic eluate vaporization and selective analyte ionization occur within a quadrupole ion-trap, which permits significant instrument simplification when compared with the atmospheric pressure interfaces typically used for CEC-MS. Vaporization is achieved using laser desorption at 1064 nm while ionization is accomplished through UV photoionization. This two-step approach, through ionization laser wavelength selection, can provide ultratrace analysis with high selectivity. The mass spectrometer is a hybrid ion-trap time-of-flight (TOF) instrument in which the ion-trap is used in radio frequency-only mode, with DC-pulse ejection, to provide …

Direct Observation Of Metal Nanoparticles As Heterogeneous Nuclei For The Condensation Of Supersaturated Organic Vapors: Nucleation Of Size-Selected Aluminum Nanoparticles In Acetonitrile And N-Hexane Vapors, Victor Abdelsayed, M. Samy El-Shall

Chemistry Publications

This work reports the direct observation and separation of size-selected aluminum nanoparticlesacting as heterogeneous nuclei for the condensation of supersaturated vapors of both polar and nonpolar molecules. In the experiment, we study the condensation of supersaturated acetonitrile and n-hexane vapors on charged and neutral Al nanoparticles by activation of the metalnanoparticles to act as heterogeneous nuclei for the condensation of the organic vapor.Aluminum seed nanoparticles with diameters of 1 and 2 nm are capable of acting as heterogeneous nuclei for the condensation of supersaturated acetonitrile and hexane vapors. The comparison between the Kelvin and Fletcher diameters indicates that for theheterogeneous …

Nanoconfined Water Under Electric Field At Constant Chemical Potential Undergoes Electrostriction, Davide Vanzo, D. Bratko, Alenka Luzar

Chemistry Publications

Electric control of nanopore permeation by water and solutions enables gating in membrane ion channels and can be exploited for transient surface tuning of rugged substrates, to regulate capillary permeability in nanofluidics, and to facilitate energy absorption in porous hydrophobic media. Studies of capillary effects, enhanced by miniaturization, present experimental challenges in the nanoscale regime thus making molecular simulations an important complement to direct measurement. In a molecular dynamics (MD) simulation, exchange ofwater between the pores and environment requires modeling of coexisting confined and bulk phases, with confined water under the field maintaining equilibrium with the unperturbed environment. In the …

Proton-Bound Dimers Of Nitrogen Heterocyclic Molecules: Substituent Effects On The Structures And Binding Energies Of Homodimers Of Diazine, Triazine, And Fluoropyridine, Isaac K. Attah, Sean P. Platt, Michael Mautner, M. S. El-Shall, Saadullah G. Aziz, Abdulrahman O. Alyoubi

Chemistry Publications

The bonding energies of proton-bound homodimers BH⁺B were measured by ion mobilityequilibrium studies and calculated at the DFT B3LYP/6-311++G^{* *} level, for a series of nitrogen heterocyclic molecules (B) with electron-withdrawing in-ring N and on-ring F substituents. The binding energies (ΔH°dissoc) of the proton-bound dimers (BH⁺B) vary significantly, from 29.7 to 18.1 kcal/mol, decreasing linearly with decreasing the proton affinity of the monomer (B). This trend differs significantly from the constant binding energies of most homodimers of other organic nitrogen and oxygen bases. The experimentally measured ΔH°dissoc for (1,3-diazine)2H⁺, i.e., (pyrimidine)2H⁺ and …

Unconventional Hydrogen Bonding To Organic Ions In The Gas Phase: Stepwise Association Of Hydrogen Cyanide With The Pyridine And Pyrimidine Radical Cations And Protonated Pyridine, Ahmed M. Hamid, M. Samy El-Shall, Rifaat Hilal, Shaaban Elroby, Saadullah G. Aziz

Chemistry Publications

Equilibrium thermochemical measurements using the ion mobility drift cell technique have been utilized to investigate the binding energies and entropy changes for the stepwise association of HCN molecules with the pyridine and pyrimidine radical cations forming the C5H5N^+· (HCN)nand C4H4N2 ^+· (HCN)n clusters, respectively, with n = 1–4. For comparison, the binding of 1–4 HCN molecules to the protonated pyridine C5H5NH⁺(HCN)n has also been investigated. The binding energies of HCN to the pyridine and pyrimidine radical cations are nearly equal (11.4 and 12.0 kcal/mol, respectively) but weaker than the HCN binding to the protonated pyridine (14.0 kcal/mol). …

Quantitative Mass Spectrometric Investigations Of Protein Biomarkers: Serum Thymidine Kinase 1 And Human Osteopontin, Morse Faria

Theses and Dissertations

Mass spectrometry is being increasingly used in biomarker research mainly due to its ability to achieve high selectivity coupled with high sensitivity. This dissertation focuses on quantitative mass spectrometric investigations of two protein biomarkers i.e. serum thymidine kinase 1 (TK1) and human osteopontin (OPN).

First part of this research was focused on developing a liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS) method for measuring the activity of TK1 in serum by monitoring the conversion of a TK1 specific exogenous substrate, 3’-deoxy-3’-fluorothymidine (FLT), to its mono-phosphorylated form 3’-deoxy-3’-fluorothymidine monophosphate (FLT-MP). A method to quantify FLT-MP on LC-MS/MS was developed and …

Exploring The Asymmetric Environment Of Various Chiral Catalysts Using A Modified Ion-Trap Mass Spectrometer: Towards The Development Of A Rapid Chiral Catalyst Screening Method, Cary M. Davis

Theses and Dissertations

Since the tragedy of the drug Thalidomide® in the late 1950 to early 1960’s, chirality has been recognized as an important aspect that must be controlled in the drug development process in the pharmaceutical industry. Since then, there has been a considerable movement towards single enantiomer drugs. This demand has presented many challenges for the synthetic organic chemist. Chiral catalysts offer one solution to this problem, as they afford the unique ability to preferentially synthesize one enantiomer. Unfortunately, the design of new chiral catalysts is often empirical, with luck and trial and error necessary due to factors that govern enantioselectivity. …

Catalytic Activity Of Heteropoly Tungstophosphoric Acid Supported On Partially Reduced Graphene Oxide Prepared By Laser And Microwave Irradiation, Mark Paul Jimena Dailo

Theses and Dissertations

The solid acid catalyst of the Keggin-type 12-tungstophosphoric acid (H₃PW₁₂O₄₀, HPW) is supported on partially reduced graphene oxide (PRGO) nanosheets for acid-catalyzed reactions. HPW is a new class of catalyst with a good thermal stability and high Bronsted acidity in order to replace common mineral acids. However, it has low specific surface area (1-5 m²/g). Therefore, the possibility of PRGO as a catalytic support for HPW is investigated due to its high surface area (2630 m²/g) and good thermal stability. The synthesis of HPW-GO catalyst is prepared using microwave and …

The Study Of Au(Iii) Compounds And Their Interaction With Zinc Finger Proteins, Sarah Spell

Theses and Dissertations

Gold compounds have been used in medicine dating back as early as 2500 BC. Over the years gold(I) and gold(III) compounds have been used and designed to target rheumatoid arthritis, cancer, and viral diseases. New drug targets have been found for gold compounds that give insight into their mechanisms of action. Here we focus on the synthesis of Au(III) compounds designed to selectively target zinc finger (ZF) proteins. ZF proteins exhibit a variety of functions, including transcription, DNA repair, and apoptosis. Displacement of the central zinc ion, along with mutation of coordinated amino acids can result in a loss of …

Modified Seed Growth Of Iron Oxide Nanoparticles In Benzyl Alcohol: Magnetic Nanoparticles For Radio Frequency Hyperthermia Treatment Of Cancer, Stanley E. Gilliland Iii

Theses and Dissertations

Iron oxide nanoparticles have received sustained interest for biomedical applications as synthetic approaches are continually developed for precise control of nanoparticle properties. This thesis presents an investigation of parameters in the benzyl alcohol synthesis of iron oxide nanoparticles. A modified seed growth method was designed for obtaining optimal nanoparticle properties for magnetic fluid hyperthermia. With a one or two addition process, iron oxide nanoparticles were produced with crystallite sizes ranging from 5-20 nm using only benzyl alcohol and iron precursor. The effects of reaction environment, temperature, concentration, and modified seed growth parameters were investigated to obtain precise control over properties …

Fabrication And Characterization Of High Surface Area Gold Electrodes, Madhura S. Damle

Theses and Dissertations

High surface area gold electrodes are very good substrates for biosensors, catalysis and drug delivery. Their performance is characterized by good sensitivity, low detection limit and high signal. As a result, extensive research is being carried out in this field using different approaches of fabrication to generate high surface area porous electrodes of different morphology, pore size and structure. The morphology of the electrodes can be changed based on whether the approach involves a template or not, types of metal deposition, method and time of dealloying etc. The deposition of metal can be carried out using various approaches such as …

New Synthetic Strategies For Improved Gas Separation By Nanoporous Organic Polymers, Suha Altarawneh

Theses and Dissertations

Abstract NEW SYNTHETIC STRATEGIES FOR IMPROVED GAS SEPARATION BY NANOPOROUS ORGANIC POLYMERS Suha S. Altarawneh, Ph.D. The emission of carbon dioxide (CO2) from fossil fuel combustion is a major cause of climate change. Therefore, the efficient separation of CO2 from mixtures of gases such as flue gas and impure sources of CH4 (e.g. natural gas and landfill gas) is an essential step in meeting the ever increasing demands on natural gas and creating a cleaner environment. Carbon capture and storage technology (CCS) is one of the methods employed for gas separation using chemisorption and/or physisorption processes. Several materials such as …