Chemistry Commons^™

Macrocyclic Antibiotics As Separation Agents, Daniel W. Armstrong

Chemistry Faculty Research & Creative Works

Macrocyclic antibiotics having ring structures with at least 10 members act as separation agents in crystallization, precipitation, filtration, electrophoresis, and chromatography. The macrocyclic antibiotics include ansamacrolides, macrolides, macrocyclic peptides, polyenes and derivatives thereof. The process has been found to be especially advantageous for separation of optical isomers by electrophoresis and chromatography.

Self-Aligned Mechanical Attachment Of Carbon Nanotubes To Silicon Dioxide Structures By Selective Silicon Dioxide Chemical-Vapor Deposition, Jed D. Whittaker, Ghaleb A. Husseini, Matthew A. Linford, Robert C. Davis, Markus Brink

Faculty Publications

A self-aligned thin-film deposition technique was developed to mechanically attach carbon nanotubes to surfaces for the fabrication of structurally robust nanotube-based nanomechanical devices. Single-walled carbon nanotubes were grown by thermal chemical-vapor deposition (CVD) across 150-nm-wide SiO2 trenches. The nanotubes were mechanically attached to the trench tops by selective silicon tetraacetate-based SiO2 CVD. No film was deposited on the nanotubes where they were suspended across the trenches.

Seasonal Variation And Ecosystem Dependence Of Emission Factors For Selected Trace Gases And Pm2.5 For Southern African Savanna Fires, S. Korontzi, Darold E. Ward, Ronald A. Susott, Robert J. Yokelson, C. O. Justice, Peter V. Hobbs, E.A. H. Smithwick, Wei Min Hao

Chemistry and Biochemistry Faculty Publications

[1] In this paper we present the first early dry season (early June-early August) emission factor measurements for carbon dioxide (CO₂), carbon monoxide (CO), methane (CH₄), nonmethane hydrocarbons (NMHC), and particulates with a diameter less than 2.5 μm (PM_2.5) for southern African grassland and woodland fires. Seasonal emission factors for grassland fires correlate linearly with the proportion of green grass, used as a surrogate for the fuel moisture content, and are higher for products of incomplete combustion in the early part of the dry season compared with later in the dry season. Models of …

Dual Stage Microvalue And Method Of Use, Marc J. Madou, Sylvia Daunert

Chemistry Faculty Patents

A micro-machined drug delivery device and method of use for the delivery of labile drugs is disclosed. A micro-machined sensing device and method of use is also disclosed. A micro-machined drug delivery and sensing device and method of use is additionally disclosed. All three devices are intended to be inserted into a patient's body. The drug delivery devices allow for the mixing of drug components prior to the release of the mixture into the patient's body where the mixture is labile. The micro-machined sensing device is suitable for monitoring the concentration of a specific chemical in a patient's body fluids …

Investigation Of Nanodispersion In Polystyrene-Montmorillonite Nanocomposites By Solid State Nmr, Serge Bourbigot, David L. Vanderhart, Jeffery W. Gilman Sr., Walid Awad, Rick D. Davis, Alexander B. Morgan, Charles A. Wilkie

Chemistry Faculty Research and Publications

Nanocomposites result from combinations of materials with vastly different properties in the nanometer scale. These materials exhibit many unique properties such as improved thermal stability, reduced flammability, and improved mechanical properties. Many of the properties associated with polymer–clay nanocomposites are a function of the extent of exfoliation of the individual clay sheets or the quality of the nanodispersion. This work demonstrates that solid-state NMR can be used to characterize, quantitatively, the nanodispersion of variously modified montmorillonite (MMT) clays in polystyrene (PS) matrices. The direct influence of the paramagnetic Fe3, embedded in the aluminosilicate layers of MMT, on polymer protons within …

Comprehensive Laboratory Measurements Of Biomass-Burning Emissions: 1. Emissions From Indonesian, African, And Other Fuels, Ted J. Christian, B. Kleiss, Robert J. Yokelson, R. Holzinger, P. J. Crutzen, Wei Min Hao, B. H. Saharjo, Darold E. Ward

Chemistry and Biochemistry Faculty Publications

[1] Trace gas and particle emissions were measured from 47 laboratory fires burning 16 regionally to globally significant fuel types. Instrumentation included the following: open-path Fourier transform infrared spectroscopy; proton transfer reaction mass spectrometry; filter sampling with subsequent analysis of particles with diameter <2.5 μm for organic and elemental carbon and other elements; and canister sampling with subsequent analysis by gas chromatography (GC)/flame ionization detector, GC/electron capture detector, and GC/mass spectrometry. The emissions of 26 compounds are reported by fuel type. The results include the first detailed measurements of the emissions from Indonesian fuels. Carbon dioxide, CO, CH₄, NH₃, HCN, methanol, and acetic acid were the seven most abundant emissions (in order) from burning Indonesian peat. Acetol (hydroxyacetone) was a major, previously unobserved emission from burning rice straw (21–34 g/kg). The emission factors for our simulated African fires are consistent with field data for African fires for compounds measured in both …

“Design Of Molecular Mechanics Modeling Techniques For Exploring Molecular Recognition Using Cyclodextrins., Shannon Bradley Fox

Doctoral Dissertations

Molecular mechanics modeling techniques have been developed to study the behavior of cyclodextrins (CDs) in capillary electrophoresis (CE) separations. Using the commercial computational package, Sybyl, the mechanisms of molecular recognition between organic analytes and CDs are investigated.

Cyclodextrin-modified capillary electrochromatography (CDCE) experiments were conducted to separate neutral derivitized naphthalene solutes using carboxymethyl-beta-cyclodextrin (CM-b-CD). Grid conformation-searching programs were developed to explore the interaction space between CD and solute and to calculate their interaction energies using molecular mechanics. The interaction energies correlated remarkably well with the separation behavior. It was found that extensive minimization (more than 3000 iterations) was required at each …

Targeting Methanopterin Biosynthesis To Inhibit Methanogenesis, Razvan Dumitru, Hector Palencia, Scott D. Schroeder, Bree A. Demontigny, James M. Takacs, Madeline E. Rasche, Jess L. Miner, Stephen W. Ragsdale

James Takacs Publications

This paper describes the design, synthesis, and successful employment of inhibitors of 4-( β -D-ribofuranosyl) aminobenzene-5’-phosphate (RFA-P) synthase, which catalyzes the first committed step in the biosynthesis of methanopterin, to specifically halt the growth of methane-producing microbes. RFA-P synthase catalyzes the first step in the synthesis of tetrahydromethanopterin, a key cofactor required for methane formation and for one-carbon transformations in methanogens. A number of inhibitors, which are N-substituted derivatives of p-aminobenzoic acid (pABA), have been synthesized and their inhibition constants with RFA-P synthase have been determined. Based on comparisons of the inhibition constants among various inhibitors, we propose that the …

A Comparative Study Of Photomultiplier Tubes And Charge Coupled Devices In Glow Discharge-Optical Emission Spectrometry, Robert James Broadwater

Masters Theses

This Masters Thesis compared two glow discharge-optical emission spectrometers designed around two different types of detectors: the photomultiplier tube (PMT) and the charge-coupled device (CCD). The two instruments compared were the LECO SA2000 (PMT-based) and the LECO GDS500a (CCD-based). Detection limit, dynamic range, precision, accuracy, and drift were determined to compare the detection systems between 165 and 450nm.

The PMT-based system outperformed the CCD-based system in all five of the categories studied based on the initial protocol. However, it was shown that improvements could be made in four of the five categories studied by exploiting the CCDs ability to monitor …

Immobilization Of Fission Iodine By Reaction With A Fullerene Containing Carbon Compound And Insoluble Natural Organic Matrix: Quaterly Report September-December 2003, Spencer M. Steinberg

Separations Campaign (TRP)

The recovery of iodine released during the processing of used nuclear fuel poses a significant challenge to the transmutation of radioactive iodine. This proposal will develop and examine the use of Fullerene Containing Carbon (FCC) compounds as potential sorbents for iodine release from the reprocessing of nuclear fuel. This work will also include the development of bench-scale testing capabilities at UNLV to allow the testing of the FCC material in a simulated process off-gas environment. This experimental capability will also be used to test other potential sorption materials and processes, such as natural organic matter (NOM) and other promising alternatives. …

Afci Quarterly Input – Unlv October Through December, 2003, Harry Reid Center For Environmental Studies. Nuclear Science And Technology Division

Transmutation Research Program Reports (TRP)

Quarterly report highlighting research projects and objectives of the Transmutation Research Program at the Nuclear Science & Technology Division, Harry Reid Research Center.

The University of Nevada, Las Vegas supports the AFCI through research and development of technologies for economic and environmentally sound refinement of spent nuclear fuel. The UNLV program has four components: infrastructure, international collaboration, student-based research, and management and program support.

Inside Unlv, Gian Galassi, Katrina Hudak, Carol C. Harter, Eric Sandgren, Tom Hagge

Inside UNLV

No abstract provided.

Synthesis Of Adenosine Derivatives As Transcription Initiators And Preparation Of 5 ' Fluorescein- And Biotin-Labeled Rna Through One-Step In Vitro Transcription, Faqing Huang, Guocan Wang, Tricia Coleman, Na Li

Faculty Publications

Expanding our previous finding of an adenosine-initiated transcription system, we now demonstrate that either the 5' site or the N6 site of adenosine nucleotides can be modified extensively without abolishing their ability to initiate transcription under the T7 phi2.5 promoter. Two series of amino derivatives of adenosine nucleotides were synthesized. Fluorescein and biotin groups were coupled to AMP derivatives through linkers of different sizes and hydrophobicities. Both fluorescein- and biotin-conjugated (at either the 5' or N6 site) adenosine nucleotides can act as efficient transcription initiators, producing fluorescein- and biotin-labeled RNA at the specific 5' end by a one-step transcription procedure, …

Mechanistic Studies Of The Oxidation Of Lignin And Cellulose Models, Oh-Kyu Lee

Electronic Theses and Dissertations

Oxygen delignification is an environmentally friendly pulp bleaching system. To develop a selective delignification process that results in high DP retention of carbohydrate with lignin being removed, obtaining better knowledge of reactions occurring during oxygen delignification is essential.

In this work, mixtures of guaiacol (model lignin) and methyl-ß-D-glucoside (model cellulose) were reacted in a pressurized oxygen reaction system (pH 12,65 psi O₂, and 95°C in a glass reaction vessel). In the results, methyl-ß-D-glucoside degraded only in the presence of lignin. This indicates that hydroxyl radicals, that subsequently react with methyl-ß-D-glucoside, are generated in the system. Unfortunately, we could …

Capillary Electrophoretic Separations Of Metal Ions, Elena Hofman

Masters Theses

Transition-metal (Zn(II), Co(II), Ni(II) and Cu(II)) ion separation was studied using 8-hydroxyquinoline-5-sulfonic acid and 2-methyl-8-hydroxyquinoline ligands with surfactants (cationic and anionic) by capillary electrophoresis under a variety of conditions (like pH, ionic strength, voltage and ion, ligand and surfactant amounts) and has debuted a clear separation mechanism. With cationic surfactants, ligands compete with capillary surface silanols for the metal ions; with anionic surfactants, ligands, silanols and micelles compete.

An empirical parameter, K_e, (electrophoretic-mobilities based) rationalizing the separation was proposed, experimentally analyzed and supported; it provides a silanol group per cm² value of the capillary surface, an equilibrium …

Quaternary Trialkyl(Polyfluoroalkyl)Ammonium Salts Including Liquid Iodides, Om D. Gupta, Douglas Armstrong, Jean'ne M. Shreeve

Faculty Scholarship – Chemistry

New quaternary ammonium salts that contain polyfluorinated alkyl substituents were prepared by the polyfluoroalkylation of tertiary amines with polyfluorinated alkyl iodides. Metathesis reactions of the iodide salts with fluorine-containing anions resulted in new low melting salts. The iodide salts of the tri(isooctyl)polyfluoroalkyl amines are also liquids at 25°C.

Evaluation Of 2,2'-Bipyridylpyridinetricarbonylrhenium (I) Triflate Complex As A Luminescent Probe For The Study Of Macromolecular Solution Dynamics, Richard Allen Allston

Seton Hall University Dissertations and Theses (ETDs)

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Non-Steady-State Approach #11;To Steady-State Kinetics: #11;Case Study Of H2s Oxidation By Oxygen, Andrey N. Zagoruiko, Vladimir V. Mokrinskii

Andrey N Zagoruiko

Non-steady-state kinetic models may be used for treatment of steady-state kinetic data in case when algebraic elaboration of steady-state kinetic equations is impossible or complicated. The proposed approach includes numerical integration of time-dependent differential equations until achievement of steady-state, resulting in possibility to numerically obtain the rate values for separate reaction stages for given composition of reaction mixture. The obtained non-steady-state model may be then applied in simulation of catalyst pellets and catalyst beds in research and engineering purposes. The case study demonstrates application of such approach for steady-state kinetic description of complicated reaction system of H2S oxidation by oxygen. …

Modeling Corrosion In Oxygen Controlled Lbe Systems With Coupling Of Chemical Kinetics And Hydrodynamics-Task V: Fourth Quarterly Report 09/01/2003-11/30/2003, Samir Moujaes, Yitung Chen

Transmutation Sciences Materials (TRP)

The Lead-Bismuth eutectic (LBE) has been determined from previous experimental studies by the Russians and the European scientific community to be a potential material that can be used as a spallation target and coolant for the TRP proposed application. Properly controlling the oxygen content in LBE can drastically reduce the LBE corrosion to structural steels. However, existing knowledge of material corrosion performance was obtained from point-wise testing with only very sparse experimental data. Scientists have noticed that the concentration of oxygen dissolved in the liquid alloy could control the corrosion rate of steels exposed to Pb or Pb-Bi. At high …

Preparation And Characterization Of Y-Type Carbon Nanotubes By Using Anodized Alumina Oxide (Aao) Template, Jing Zhang, Quan-Yong Gao, Yong Yang

Journal of Electrochemistry

In this work, potential_modulation method was used in two_step anodization process to make an AAO template with Y_type nanochannels. Then Y_type carbon nanotubes with controlled length and branch angle were prepared in the template based on chemical vapor decomposion (CVD) method with Co particles as catalyst and C2H2 as carbon source. The Y_type nanotube branches exhibit the angle distribution ranging from 20° to 120°. The results demonstrated that the oxidation potential should be responsible for the angles and length of the branches. Short pulse and high oxidation potential will result in the short and dense nanotube branches.

Effect Of Dspp Al_2o_3 On Electrical Properties Of Polymer Electrolyte, Hai-Fen Xie, Xiao-Xiang Sun, Yi-Pin Wang, Guang-Yuan Li

Journal of Electrochemistry

The PEO_NaSCN polymer solid electrolytes by adding dispersed second phase particles (DSPP) of Al2O3 were studied. The characteristics of solid electrolytes and conductivity values are dependent on DSPP Al2O3 sizes and its contents. It was found that when the Al2O3 sizes are less than 1 μm, which is a criticle size, the sample conductivities were larger than those of the pure PEO_NaSCN samples and when the Al2O3 sizes are larger than 1 μm then the sample conductivities are less then those of the pure samples. The maximum conductivity appears when the content of Al2O3 is 25% .Low frequency and high …

The Current Fluctuations Of Carbon Steel In Nano_2-Nacl Solutions, Yu-Ming Tang, Yu Zuo

Journal of Electrochemistry

The characteristics of current fluctuations of A3 carbon steel in NaNO2_NaCl solutions were studied with potentiostatic and potentiodynamic polarization methods. The steel remained stable passivation in 0.1 mol/L NaNO2 solution without Cl-. After NaCl was added in to the solution, current fluctuations with a characteristic of quick increase and slow decrease occurred, indicating quick dissolution and slow re_passivation of the metastable pits. The metastable pitting may cause accumulated corrosion damage around certain area and result in observable pits. With the increase of chloride concentration, the occurring potential for metastable pits Em rised, and peak values and frequency of current fluctuations …

Adsorption And Oxidation Of Phenol Electrode Processes, Bao-Cheng Wang, Yan-Ping Sun, Jin-Hua Zhu

Journal of Electrochemistry

The electrochemical behaviors of platinum electrode were studied by cyclic voltammetry in 1mol/L sulfuric acid solution and 1mol/L sulfuric acid solution contained phenol. The adsorption characteristics of phenol and the intermediat on electrode surface have been discussed. The reactive reversibility and oxidation mechanism of phenol on electrode process have been investigated.The potential of characteristic adsorption was suggested. The various products woud be formed when the electrode potential was greater than the one of characteristic adsorption.

Optimizing Catalyst Layer Composition Of Pemfc By Orthogonal Method, Ming-Hua Wang, Xin-Jian Zhu, Guang-Yi Cao, Sheng Sui, Qing-Chun Yu, Ming-Ruo Hu, Zheng-Yu Fan

Journal of Electrochemistry

The optimal composition of catalyst layer in a PEMFC electrode was studied through orthogonal method. It was showed that the performance of hydrophilic electrodes, in which there is no PTFE in the catalyst layer, were more favorable than that of hydrophobic electrodes. According to this condition, the power density of PEMFC attained 0.37 w·cm-2 when the Nafion loading was 1.4 mg·cm-2, and the Pt loading was 0.4 mg·cm-2 in the catalyst layer, using H2 as fuel and air as oxidant both at atmospheric pressure. Additionally, the results showed that increasing Pt loading in Pt/C catalyst was a reasonable way to …

Electronic Structures And Geometries Of Lial, Liang-Gen Wu, Rong-Qin Wu, Li-Juan Chen, Zi-Zhong Zhu, Yong Yang

Journal of Electrochemistry

LiAl is an important anode material for lithium batteries. Based on the plane_wave method and first_principles pseudopotentials, the electronic and geometric properties of LiAl have been studied. The cohesive energies versus volumes of unit cell, energy band structures, electronic density of states and charge density distributions of LiAl under some important structures are presented. The reason of B32_structure as the ground_state of LiAl crystal has also been elucidated, which is owing to Al_Al atoms in B32_structure form strong diamond_type covalent bonds. The present theoretical ground state structure of LiAl is consistent with the experimental and other theoretical results.

Study On Electrochemical Behavior Of Sus316l Stainless Steel After Surface Modification, Cheng-Hao Liang, Liang Guo, Wan Chen, Jing-Xiao Liu

Journal of Electrochemistry

The surface modification for SUS316L stainless steel was carried out by electroplating Rh, ion beam assisted deposition Ta2O5 and sol_gel_derived TiO2. In Tyrode's stimulated body fluid, the surface modified samples had been investigated with electrochemical techniques. The results indicated that the electrochemical stability and dissolution were improved significantly after surface modification.Moreover, as to ion beam assisted deposition Ta2O5 and Sol_gel_derived TiO2 film, the metal's d orbit electron holes filled up by the oxygen electrons made against the adsorption of hydrogen. Thus the cathode process, which is controlled by the hydrogen reduction,was held back. X_ray diffraction analysis of SUS316L stainless steel …

Application Of Hydrogen-Storage Alloy Electrode In Electrochemical Reduction Of Glucose, Hui Chen, You-Gen Tang, Zheng Tang

Journal of Electrochemistry

Electrolysis of glucose was performed at constant potential using hydrogen_storage alloy as catalytic reduction electrode. It was found that the superficial treatment and activation of hydrogen_storage alloy powder had obvious effects on improving the current efficiency of sorbitol. Under the optimums, current efficiency of sorbitol by electrolyzing glucose was over 94%. The yield of sorbitol was over 80%, the lifespan of electrode was tested and analyzed, the ways of regeneration were discussed.

The Study Of Green Corrosion Inhibitors For Mild Steel 907 In Natural Seawater Environment, Ping Gong, Min Du, Qing-Zhang Wang, Zhen-Jun Mu

Journal of Electrochemistry

Nine green compounds,including calcium gluconate,zinc gluconate,zinc sulfate,garlic,ACUSOL 445N,OS_15,APG,OCTA and STPP were selected according to the methods of molecule design and function groups prune. The functions of combined corrosion inhibitors mixed by the compounds mentioned above for mild steel in seawater were studied in this work using the methods of polarization curve and weight_loss.The best weight ratio and distinct synergistic effect of calcium gluconate,zinc sulfate and OCTA were studied by Latin experiment. The afgereffects of the best weight ratio corrosoin inhibitor were studied by subsection experiment. In this way, a kind of high effect green corrosion inhibitor was obtained.

The Study On Carbon Nanotube-Loaded Pt Catalysts For Proton Exchange Membrane Fuel Cells, Hong Zhu, Feng-Juan Ge, Xiao-Hong Kang, Yu-Guo Yang, Yun-Hua Xu

Journal of Electrochemistry

Carbon nanotube_supported_platinum (Pt/CNTs) and carbon_supported_platinum (Pt/C) catalysts were synthesized by in_situ chemical reduction. They were analyzed using TEM and XRD, then made into electrodes to be part of assemable PEMFC for the performence tests. The resulted show that Pt clusters in both catalysts are of small particle size (about 4nm), and Pt/CNTs exhibits a higher catalytic activity than Pt/C.

Study On The Gas Generation In Different Charging Voltage During Formation Process In Polymer Lithium-Ion Battery, Li Huang, Ming-Gang Jin, Hui-Qun Cai, Ming-Sen Zheng, Quan-Feng Dong, Jin-Kua You, Zu-Geng Lin

Journal of Electrochemistry

The gases of polymer lithium_ion battery(PLI) generated under different voltages during the first charging process were examined by means of gas chromatography (GC), and the mechanism of the gas generation was discussed. The electrolyte used in batteries was 1 mol/L LiPF6_EC～DMC～EMC=1∶1∶1(in volume). The results showed that when the charging voltage is less than 2.5 V, the main component of generated gases are H2 and CO2, and when the charging voltage is 2.5 V, EC begins to decompose. Due to the decomposition of EC, the main generated gas is C2H4 when the charge voltages between 3.0 V and 3.5 V. As …