Chemistry Commons^™

Synthesis Of (+)-Decarestrictine L, Julie Lukesh, William A. Donaldson

Chemistry Faculty Research and Publications

A synthesis of (+)-decarestrictine L 1, a cholesterol biosynthesis inhibitory metabolite isolated from Penicillium simplicissimum, is described. Beginning from tri-O-acetyl- -glucal, alkylation with trimethylaluminum introduced the axial methyl group at C-2 in a stereoselective fashion. Chain extension at the C-6 carbon was accomplished by generation of the primary tosylate, followed by displacement with cyanide anion. The synthesis of (+)-1 was completed in 13 steps and 6.3% overall yield.

Density Of States Simulations Of Proteins, Nitin Rathore, Thomas A. Knotts Iv, Juan J. De Pablo

Faculty Publications

A modified version of a recently introduced algorithm that calculates density of states by performing a random walk in energy space has been proposed and implemented to study protein folding in a continuum. A united atom representation and the CHARMM19 [B. R. Brooks, R. E. Bruccoleri, B. D. Olafson, D. J. States, S. Swaminathan, and M. Karplus, J. Comput. Chem. 4, 187 (1983)] force field are employed for these simulations. This method permits estimation of the density of states of a protein via a random walk in the energy space, thereby allowing the system to escape from local free-energy minima …

Magnetic Resonance Studies On Lithium Intercalation Into Carbons, Xiao-Rong Zhou, Zhen-Ming Du, Lin Zhuang, Jun-Tao Lu

Journal of Electrochemistry

The electron spin resonance(ESR) and 7Li-NMR magnetic resonance (7Li-NMR) studies on lithium intercalation into carbons were reviewed based on recently published papers, including those by the authors of this review. Two kinds of electronic spins were found in ESR studies. One corresponds to the charge carrier electrons and is called the Pauli spin. From the ESR intensity of Pauli spins, the curve of the density of electronic states can be deduced for the carbon material studied and, in turn, the contribution of the band model mechanism to the lithium intercalation can be calculated for the given carbon sample. The other …

The Study On The Synthesis And Electrochemical Property Of K2Feo4, Yong-Long Wang, Ning Zhou, Shi-Hai Ye, Xue-Ping Gao, Feng Wu, Zuo-Xiang Zhou, De-Ying Song

Journal of Electrochemistry

The synthesis,characterization and electrochemical property of K₂FeO₄ for positive materal of lithium ion battery were studied. K₂FeO₄ with low purity was gained through the reaction of KCIO and Fe(NO₃)₃ in KOH solution and after recrystalization the purity of K₂FeO₄ reached 97%～98%. The methods of XRD and FTIR were used to measure the structure of K₂FeO₄ and its initial discharge performance was tested.

Study Of Electrochemical Lithium Intercalation Performance Of Ni0.67Mg0.33O, Zhen-Cai Huang, Mao-Hui Chen, Guo-Tao Wu, Jin-Kua You, Zu-Geng Lin

Journal of Electrochemistry

In the present work, Ni_0.67Mg_0.33O and NiO were produced by sol-gel method, and characterized by XRD, a rietveld refinement and the discharge/charge test.It was found that the magnesium-doping restrained the reduction of Ni and decreased the reversible capacity for the sample of Ni_0.67Mg_0.33O. But the formation of the solid solution after the magnesium-doping facilitated the high dispersion of NiO, and accordingly improved the electrochemical performance.

Application Of Biphenyl Electroploymerization For Overcharge Protection In Li-Ion Batteries, Li-Fen Xiao, Xin-Ping Ai, Yu-Liang Cao, Han-Xi Yang

Journal of Electrochemistry

The electropolymerization of biphenyl at overcharged positive electrode was investigated for overcharge protection of Li-ion batteries. Biphenyl in electrolyte as an additive can electrochemically polymerize at 4.5～4.75 V(vs. Li/Li⁺) to form a layer of conductive film on cathode surface. The surface film increases the internal resistance and the gases released during the electropolymerization also increases the internal pressure of the batteries, which therefore enhance the sensitivities of the electrical disconnecting devices. During prolonged overcharge, the growth of the conductive polymer film can create short circuit between the positive and negative electrodes and cause self-discharge of the batteries to …

In Situ Measurements Of Solution Conductivity In Microwave Field, Yong-Qing Su, Chun-Peng Liu

Journal of Electrochemistry

The curves of the conductivity as a function of temperature for 24 kinds of solutions have been in situ measured both in the microwave field and in absence of microwave field. The results indicated that the relationship between the conductivity in microwave field (L_w) and temperature (T) can be expressed by an equation L_w=a′+b′T+c′T² , similar to the one that is valid in absence of the microwave field L_n=a+bT+cT². Conductivity in the absence and presence of microwave field can be linked by the equation lnL_w=A+BL_n+CL²_{n …}

An Eqcm Study Of Water Adsorption And Oxidation On Pt Electrodes In Sulfate Acid Sulotions, Heng Lin, Sheng-Pei Chen, Jin-Mei Lin, Ai-Lan Lin, Guo-Liang Chen

Journal of Electrochemistry

Simultaneous frequency and current responses during potential cycling of Pt electrode were measured in 0.1 mol·L^-1 H₂SO₄ solution by using EQCM. Quantitative analysis of the mass change revealed that the increase of mass in the hydrogen and double-layer regions in a positive-going potential scan was due to water adsorption on the Pt electrode, further calculation indicated that water molecules adsorbed on Pt electrode in the double-layer regions through a low discharge quomodo .The EQCM studies provided quantitative results of surface mass variation during water adsorption and oxidation,and have thrown new light in elucidating the structure of …

Behaviors Of Fe-Cr Alloys During Cavitation Damage, Xia Bai, Dong-Bai Sun, Hong-Ying Yu, Hui-Ming Meng, Hui-Qin Li, Zi-Shuang Fan

Journal of Electrochemistry

The influence of the surface galvanic effect on the behaviors of three Fe-Cr alloys during cavitation damage in NaCl solutions have been investigated. The results showed that the galvanic effect caused by the inhomogeneity between the undamaged surface of the alloy and the damaged one will be enhanced by the area ratio of the undamaged and the damaged. The behaviors of alloys during cavitation are closely related to both their mechanical performance and anti-corrosion capabilities.

Study For The Cathodic Behavior Of Active Chlorine On 316l Ss Electrode Surface, Hui Yu, Ming-Xian Sun, Yan Ma, Xiao-Bin Wang

Journal of Electrochemistry

The cathodic reducing reactions of active chlorine on 316 L SS electrode surface have been investigated by electrochemical techniques. The open circuit potential shifted positively and the limited diffusion current density increased significantly with the increasing content of active chlorine in the 3.5% sodium chloride solution. The two cathodic reduction processes of HClO and ClO^- exhibited on the surface of electrode with the active chlorine added to the 3.5%sodium chloride solution and the corresponding potentials of the two reducing reactions were confirmed. The linear relationship of the mass transport-limited Faradaic current, Id vs. the square root of the angular …

Development And Study Of The (Ag)-Ni/Cr Composite Plating With Antibacterial Properties And Corrosion Resistance, Ya-Ping Zhao, Jin-Hua Wang, Ren-He Yin, Jin Zheng, Le-Shu Yu

Journal of Electrochemistry

The 3-factor and 3-level orthogonal experiment was designed and through the comparison of the different films' antibacterial properties measured by bacterial colony counting and the corrosion resistance studied with the AC impedance method. The optimal plating conditions of the (Ag)-Ni/Cr composite plating, a novel functional plating, were determined. The results have indicated that the (Ag)-Ni/Cr composite plating is characterized by both antibacterial and corrosion resisting properties and has its wide applied prospect.

Investigations Of Smooth Function Of Polyethylene Glycol Surfactants On The Electrolessly Deposited Silver Film, Hao Tong, Zhi-Qing Qiao, Fen-Ning Jing, Meng-Ke Li, Chun-Ming Wang

Journal of Electrochemistry

Some non-ionic surfactants of Polyethylene Glycol 2000, 6000 and 20000 were used to estimate the smooth affection on the electrolessly deposited silver film. The adsorption state of the surfactants about Si/solution interface was investigated by using open circuit potential-time technology (Opt). As comparative experiments, the atomic force microscopy (AFM) was also performed to study the surface smooth effection of the surfactants. It was found that with the increasing of the carbon chain in the surfactants, the smooth effection is getting great. PEG 20000 showed the best smooth function.

Fenton Reagent Produced In Electrolysis Cell And Its Using In Degradation And Decolourization Of Dye, Xi Zheng, Ri-Yao Chen, Rui-Fang Lan, Xiao Chen, Zhen Chen

Journal of Electrochemistry

The electro-chemical processing to produce Fenton reagent has been described. Fenton reagent having a high redox potential has been used as an oxidant in treatment of dye wastewater. Results show that both of the degradation and decolourization of dyes are efficient. The decolourization of dye wastewater reaches 100%.The COD removing rate is about 80%.

Electroreduction Of Cd(Ⅱ) In Dmso And Complexation Of Cd(Ⅱ) With Coumarin Derivates, Ji-Guo Song, Hua-Can Song, Qi-Qin Yang, Yi-Wen Chen, Zun-Le Xu

Journal of Electrochemistry

Cadmium p-toluenesulfonate was synthesized and tested electrochemically for the first time. This salt can lose all the hydrated water easily and the dehydrated salt do not deliquesce in the air.Hence,the cadmium p-toluenesulfonate is suitable for the electrochemical studies in organic solvents.When the Cd(Ⅱ) reduced on Pt electrode in Cd(p-CH₃C₆H₄SO₃)₂+TBAP+DMSO, underpotential deposition of cadmium occurred at first, and then cadmium deposited. 4-Methyl-7-hydroxylcoumarin and 3-aminocoumarin coordinate with Cd(Ⅱ) respectively, as a result the reductive potentials of Cd(Ⅱ) moved to the negative direction.

Environment-Induced Degradation And Crack-Growth Studies Of Candidate Target Materials, Ajit K. Roy, Brendan O'Toole

Transmutation Sciences Materials (TRP)

During the past two years (2001-2002) of this project, the primary effort was focused on evaluating the effect of hydrogen on the cracking behavior of candidate target materials namely, Alloys EP-823, HT-9 and 422 in aqueous environments of different pH values at ambient and elevated temperatures. More recently, emphasis is being placed to evaluate the cracking behavior of these materials in molten lead-bismuth eutectic (LBE) environment at much higher testing temperatures so as to compare the cracking susceptibility in environments containing molten metals and aqueous solutions, respectively. The most recent tests to evaluate the cracking susceptibility were primarily based on …

Modeling Corrosion In Oxygen Controlled Lbe Systems With Coupling Of Chemical Kinetics And Hydrodynamics: Quarterly Progress Report 12/1/02- 2/28/03, 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 AAA 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 very limited density. The transport of oxygen and corrosion products, their interaction and variation of corrosion/precipitation along the flow are not well understood.

The first subtask of this project involves using a …

Enhanced Magnetic Quantum Oscillations In The Mixed State Of A Two-Dimensional Organic Superconductor, J. Wosnitza, J. Hagel, P. J. Meeson, D. Bintley, J. A. Schlueter, Javid Mohtasham, Rolf Walter Winter, Gary L. Gard

Chemistry Faculty Publications and Presentations

We report on de Haas–van Alphen (dHvA) oscillations observed in the mixed state of the organic superconductor β″–(BEDT-TTF)₂SF₅CH₂CF₂SO₃ (BEDT-TTF stands for bisethylenedithio-tetrathiafulvalene) utilizing the field-modulation technique and torque magnetometry. At low temperatures (30 mK), the dHvA signal persists down to 1.4 T well below the upper critical field Bc2≈3.6T. Contrary to most theoretical predictions and previous experimental findings, no additional damping of the dHvA-oscillation amplitude, but a reduced damping of the dHvA signal is found. This highly unusual effect might indicate a reduced quasiparticle scattering rate or an additional oscillatory contribution in the superconducting state.

The Electrochemical Performance Studies On Novel Lifepo4 Cathode Materials For Li-Ion Batteries, Zhi-Cong Shi, Chen Li, Yong Yang

Journal of Electrochemistry

The cathode materials of LiFePO₄ and  LiFePO₄ coated with carbon were synthesized by means of solid state reaction and ballmilling. The samples were characterized by X-ray diffraction, scanning electron microscopy, gas-phase element analysis and titration analysis methods. Electrochemical tests of two kinds of materials showed that both of them exhibit a 3.4V discharge voltage plateau, however, the coated samples demonstrated the improved performance in terms of discharge capacity and cyclic stability.

The Preparation And Characterization Of Zno-Pani Composite Film, Yan-Yan Xi, Huai-Guo Huang, Zhi-Xin Zheng, Ping Dong, Jian-Zhang Zhou, Ling-Ling Wu, Zhong-Hua Lin

Journal of Electrochemistry

ZnO nanoparticle films were prepared on the Au film, PANI film and ITO by sol-gel method, and their morphological optical and photoelectrochemical properties were also studied. The results showed that the porous structure of PANI can suppress the aggregation of ZnO particles, resulting in the blue shift of on-set in the UV-Vis spectra and fluorescence spectra of ZnO-PANI composite film compared with that of ZnO-Au film. It was suggested that the ZnO-PANI composite film can be used in photoelectric coversion.

The Electrochemical Behavior Of Amorphous Ni-P And Ni-B Alloys In 0.5 Mol/L H2So4, Xu-Cheng Wang, Wei-Jiang Wang, Hou-Tian Liu, Zu-Zhan Yu

Journal of Electrochemistry

Polarization curves and impedance spectra were used to investigate the electrochemical behavior of amorphous Ni-P and Ni-B alloys in 0.5 mol/L H₂SO₄ solutions. The possible reason about the remarkable difference in the electrochemical behavior between amorphous Ni-P and Ni-B alloys was discussed.

Study On The Corrosion & Electrochemical Properties Of Alloy Aa5083 And The Effect Of Active Chlorine In Seawater, Hong-Ren Wang, Jian-Hua Wu, Jun-Tao Wang, Hong-Bin Wang, Zhi-Gang Fang

Journal of Electrochemistry

In this paper potentiodynamic technique, cyclic polarization technique and immersion corrosion method were used to study the corrosion and electrochemical properties of AA5083 alloy in quiescent seawater, the effect of active chlorine on its properties was also studied. The results obtained indicate that the active chlorine has no remarkable impact on the corrosion and electrochemical properties of AA5083 alloy in area of design concentration which range from 0.2 to 0.5 mg/L, and it has favorable influence on the improvement of pitting corrosion resistance. While the pH value of seawater has evident influence on the corrosion resistance of AA5083 alloy.

Synthesis By Complexation Processes And Characterization Of Lini0.8Co0.2O2 Cathode Materials, Jing Liu, Zhao-Yin Wen, Zhong-Hua Gu, Xiu-Jian Zhu, Zu-Xiang Lin

Journal of Electrochemistry

The layered LiNi_0.8Co_0.2O₂ compound, which has been of great interest for lithium ion batteries, was prepared at low temperatures by calcining a complex precursor at different temperatures. The physical properties of the synthesized cathode materials were discussed in the light of structural (XRD). The charge and discharge cycling of the cells containing the synthesized oxide as the positive electrode in conjunction with lithium metals and employing a non-aqueous electrolyte showed that LiNi_0.8Co_0.2O₂ treated at 900 ℃ exhibited excellent performances. The first discharge capacity of LLiNi_0.8Co_0.2O_{2 …}

Fabrication Of SncuX/Cms Composite Materials For Lithium-Ion Batteries, Yu Liu, Jing-Ying Xie, Jun Yang, Ke Wang, Bao-Feng Wang

Journal of Electrochemistry

The composite material were prepared by sub-ctrochemical cycling tests showed that coulombic efficiency of the electrodes prepared by the composite materials was near 100 % after second cycle and the capacity dropped less than 5% after the 30th cycle, versus 390 mAh⋅g^-1 special capacity, improving 26% special capacity of pure CMS electrode. The electrochemical performance of the composite materials is depended strongly on the alloy content in the composite, the addhesive strength between alloy particles and CMS matrix, the distribution of particles on the surface of CMS and the particle size of alloy. The composite material can be applied …

Pure Iron Electrolyzed From Scrap Iron Chips And Its Corrosion Characteristics, Wei-Min Cao, Ren-He Yin, Hui-Ceng Yan, Zhi-Qiang Ye

Journal of Electrochemistry

The high purity electrolytic iron was made from scrap iron chips. Electrolytic conditions of pure iron were determined in chloride baths and the highest purity was 99.983% by chemical analysis. Pure iron had very compact texture and high mechanical strength by SEM figures of cross section. In deaerated 0.5 kmol·m^-3 H₂SO₄ and 0.5 kmol·m^-3 NaCl solutions, the corrosion rate of iron decreased with increasing purity.

Microscopic Theory Of Network Glasses, Randall W. Hall, Peter G. Wolynes

Collected Faculty Scholarship

A theory of the glass transition of network liquids is developed using self-consistent phonon and liquid state approaches. The dynamical transition and entropy crisis characteristic of random first-order transitions are mapped as a function of the degree of bonding and density. Using a scaling relation for a soft-core model to crudely translate the densities into temperatures, theory predicts that the ratio of the dynamical transition temperature to the laboratory transition temperature rises as the degree of bonding increases, while the Kauzmann temperature falls explaining why highly coordinated liquids are “strong” while van der Waals liquids without coordination are “fragile.”

Measurement Of The Anti-Cancer Agent Gemcitabine In Human Plasma By High-Performance Liquid Chromatography, Bruce Keith, Yan Xu, Jean L. Grem

Chemistry Faculty Publications

A reversed-phase HPLC assay has been developed to determine the concentration of the anti-metabolite 2′,2′-difluorodeoxycytidine (gemcitabine, dFdC) in human plasma over the concentration range of 0.5–150 μM (0.13–39.44 μg/ml), and 2′,2′-difluorodeoxyuridine (dFdU), the deaminated, inactive metabolite, over the range of 1.0–227 μM (0.26–60 μg/ml). After the addition of 20 nmol 2′-fluorodeoxycytidine (FdC) as an internal standard, 0.5-ml samples of plasma were subjected to acetonitrile precipitation, followed by analysis using a gradient reversed-phase HPLC assay with UV detection. A Phenomenex Columbus™ C18 column, 5 μm, 150×4.6 mm, and a Waters C18, 4 μm, Nova-Pak Sentry guard column were used to achieve …

Experimental Investigation Of Steel Corrosion In Lead Bismuth Eutectic (Lbe): Characterization, Species Identification, And Chemical Reactions, John Farley, Dale L. Perry, Allen L. Johnson

Transmutation Sciences Materials (TRP)

The goal of the present research is to achieve a basic understanding of corrosion of steels by Lead Bismuth Eutectic (LBE). Liquid LBE is under consideration in the transmuter as both a spallation target and as a blanket coolant. There have been previous studies of LBE, especially by the Russians, who have over 80 reactor-years experience with LBE coolant in their Alpha-class submarine reactors. The Russians found that the presence of small amounts (ppm) of oxygen in the LBE significantly reduced corrosion. However, a fundamental understanding and verification of its role in the corrosion of steels is still very incomplete. …

Cooperative Effects In One-Dimensional Chains Of Three-Center Hydrogen Bonding Interactions, Ruben D. Parra, Satya S. Bulusu, Xiao Cheng Zeng

Xiao Cheng Zeng Publications

Cooperative effects in a one-dimensional network of intermolecular bifurcated hydrogen bonding interactions are investigated by means of ab initio calculations. The trans–trans conformation of the diformamide molecule is used as a basic motif to model a chain of bifurcated H bonds. In this model system, the two proton–acceptor atoms belong to the same molecule. The one-dimensional network is modeled then by periodically stacking up to 12 molecules of the unit motif. Different indicators of H-bond strength such as energetic, structural, dielectric, vibrational frequencies, and isotropic chemicals shifts consistently show significant cooperative effects in the chains. The dissociation energy in the …

Structures And Stabilities Of Small Silicon Clusters: Ab Initio Molecular-Orbital Calculations Of Si7–Si11, Xiaolei Zhu, Xiao Cheng Zeng

Xiao Cheng Zeng Publications

Ab initio all-electron molecular-orbital calculations have been carried out to study the structure and relative stability of small silicon clusters (Si_n , n=7 – 11). A number of low-energy geometric isomers are optimized at the second-order Møller–Plesset (MP2) MP2/6-31G(d) level. Harmonic vibrational analysis has been performed to assure that the optimized geometries are stable. The total energies of stable isomers are computed at the coupled-cluster single and double substitutions (including triple excitations) [CCSD(T)] CCSD(T)/6-31G(d) level. The calculated binding energies per atom at both the MP2/6-31G(d) and CCSD(T)/6-31G(d) levels agree with …

Particle Growth In Urban And Industrial Plumes In Texas, Charles A. Brock, Michael Trainer, Thomas B. Ryerson, J. Andrew Neuman, David D. Parrish, John S. Holloway, Dennis K. Nicks, Gregory J. Frost, Gerhard Hübler, Fred C. Fehsenfeld, J. Charles Wilson, J. Michael Reeves, Bernard G. Lafleur, Henrike Hilbert, Elliot L. Atlas, Stephen G. Donnelly Ph.D., Sue M. Schauffler, Verity R. Stroud, Christine Wiedinmyer

Chemistry Faculty Publications

Particle size distributions and gas-phase particle precursors and tracer species were measured aboard an aircraft in the plumes downwind from industrial and urban sources in the vicinity of Houston, TX during the daytime in late August and early September 2000. Plumes originating from the Parish gas-fired and coal-fired power plant, petrochemical industries along the Houston ship channel, the petrochemical facilities near the Gulf coast, and the urban center of Houston were studied. Most of the particle mass flux advected downwind of Houston came from the industries and electrical utilities at the periphery of the city rather than from sources in …