Chemistry Commons^™

The Critical Role Of Water At The Gold-Titania Interface In Catalytic Co Oxidation, Johnny Saavedra, H. Doan, Christopher J. Pursell, L. C. Grabow, Bert D. Chandler

Chemistry Faculty Research

We provide direct evidence of a water-mediated reaction mechanism for room-temperature CO oxidation over Au/TiO2 catalysts. A hydrogen/deuterium kinetic isotope effect of nearly 2 implicates O-H(D) bond breaking in the rate-determining step. Kinetics and in situ infrared spectroscopy experiments showed that the coverage of weakly adsorbed water on TiO2 largely determines catalyst activity by changing the number of active sites. Density functional theory calculations indicated that proton transfer at the metal-support interface facilitates O2 binding and activation; the resulting Au-OOH species readily reacts with adsorbed Au-CO, yielding Au-COOH. Au-COOH decomposition involves proton transfer to water and was suggested to be …

Enhanced Adhesion Of Continuous Nanoporous Au Layers By Thermochemical Oxidation Of Glassy Carbon, Lori Ana Bromberg, Jiaxin Xia, Ryan Rooney, Nikolay Dimitrov

Chemistry Faculty Scholarship

The fabrication of a nanoporous gold (NPG)-based catalyst on a glassy carbon (GC) support results normally in large isolated and poorly adhering clusters that suffer considerable material loss upon durability testing. This work exploits thermochemical oxidation of GC, which, coupled with the utilization of some recent progress in fabricating continuous NPG layers using a Pd seed layer, aims to enhance the adhesion to the GC surface. Thermochemical oxidation causes interconnected pores within the GC structure to open and substantially improves the wettability of the GC surface, which are both beneficial toward the improvement of the overall quality of the NPG …

Palladium-Catalyzed Cross-Coupling Of 2-Aryl-1,3-Dithianes, Summer Baker Dockrey, Alicia K. Makepeace, Jason R. Schmink

Chemistry Faculty Research and Scholarship

Palladium-catalyzed cross-coupling of aryl bromides with 2-aryl-1,3-dithianes is described. This methodology takes advantage of the relatively acidic benzylic proton of the dithiane, allowing it to act as a competent, polarity-reversed transmetalation reagent. This unique approach affords the ability to employ an orthogonal deprotection strategy, and practical routes to both diaryl ketones and diarylmethanes are illustrated. Cross-coupling of a range of aryl dithianes with aryl bromides, including scope and current limitations, is presented.

Medicinal History Of North American Veratrum, Christopher M. Chandler, Owen M. Mcdougal

Chemistry and Biochemistry Faculty Publications and Presentations

Plants belonging to the genus Veratrum have been used throughout history for their medicinal properties. During the nineteenth and twentieth centuries, phytochemical investigations revealed a host of steroidal alkaloids in Veratrum species, some of which are potent bioactives. This review discusses Veratrum species that grow in North America with a focus on the medicinal history of these plants and the steroidal alkaloids they contain. While significant reviews have been devoted to singularly describing the plant species within the genus Veratrum (botany), the staggering breadth of alkaloids isolated from these and related plants (phytochemistry), and the intricacies of how the various …

High Valent Palladium Complexes And Their Role In C-C And C-X Bond Formation Chemistry., Fengrui Qu

All Theses and Dissertations (ETDs)

Energy is the currency of the universe. Without energy everything will come to a stall. According to the Energy Information Administration, in 2007 over 80 % of energy came from fossil fuel. When the fossil fuel will eventually run out at the current consumption rate, then what can we use for energy? While finding alternative energy sources is our ultimate goal, our research focus on the basic study of the role metal ions play in the catalysis of energy related process. Namely, the water oxidation catalysis and methane oligomerization process.

Water oxidation is a multi-electron process, which requires multiple single …

Ion Structure And Energetics In The Gas Phase Characterized Using Fourier Transfom Ion Cyclotron Resonance Mass Spectrometry, Chad A. Jones

Theses and Dissertations

In this dissertation, I use Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS) to study the structure and energetics of gas phase ions. Infrared multiphoton dissociation spectroscopy (IRMPD) is a technique for measuring the IR spectrum of gas phase ions in a Penning trap. I use this technique to investigate the conformation of cucurbituril complexes, terminal diamines, and protonated amino acids. Cross sectional areas by Fourier transform ion cyclotron resonance mass spectrometry (CRAFTI) is a technique developed by the Dearden lab to measure the cross section of gas phase ions. In this work, I further develop a fundamental understanding of …

Photocatalytic Activity And Stability Of Porous Polycrystalline Zno Thin-Films Grown Via A Two-Step Thermal Oxidation Process, James C. Moore, Robert Louder, Cody V. Thompson

Chemistry

The photocatalytic activity and stability of thin, polycrystalline ZnO films was studied. The oxidative degradation of organic compounds at the ZnO surface results from the ultraviolet (UV) photo-induced creation of highly oxidizing holes and reducing electrons, which combine with surface water to form hydroxyl radicals and reactive oxygen species. Therefore, the efficiency of the electron-hole pair formation is of critical importance for self-cleaning and antimicrobial applications with these metal-oxide catalyst systems. In this study, ZnO thin films were fabricated on sapphire substrates via direct current sputter deposition of Zn-metal films followed by thermal oxidation at several annealing temperatures (300-1200 °C). …

Small Molecule Tyrosine Kinase Inhibitors Of Erbb2/Her2/Neu In The Treatment Of Aggressive Breast Cancer., Richard L. Schroeder, Cheryl L. Stevens, Jayalakshmi Sridhar

Faculty and Staff Publications

he human epidermal growth factor receptor 2 (HER2) is a member of the erbB class of tyrosine kinase receptors. These proteins are normally expressed at the surface of healthy cells and play critical roles in the signal transduction cascade in a myriad of biochemical pathways responsible for cell growth and differentiation. However, it is widely known that amplification and subsequent overexpression of the HER2 encoding oncogene results in unregulated cell proliferation in an aggressive form of breast cancer known as HER2-positive breast cancer. Existing therapies such as trastuzumab (Herceptin^®) and lapatinib (Tyverb/Tykerb^®), a monoclonal antibody inhibitor …

Degradation Of Protective Glove Materials Exposed To Commercial Products: A Comparative Study Of Tensile Strength And Gravimetric Analyses, Todd B. Pelham

Electronic Theses, Projects, and Dissertations

ABSTRACT

Current glove guides attempt to assist in recommending which type of glove is appropriate for handling chemicals; however, they include information on less than 1% of the 89 million chemical products available today.

This study offers a solution by testing five durable polymer materials against 50 chemicals, using two rapid chemical degradation assessment techniques. The first technique involves gravimetric analysis of the weight change following constant immersion against the chemical mixture. The second method uses tensile strength to assess molecular changes in the polymer structure.

This study is focused on addressing three issues of concern. First, this study examines …

Crystal Structure Of 1-Methoxy-2,2,2-Tris(Pyrazol-1-Yl)Ethane, Ganna Lyubartseva, Sean Parkin, Morgan D. Coleman, Uma Prasad Mallik

Chemistry Faculty Publications

The title compound, C₁₂H₁₄N₆O, consists of three pyrazole rings bound via nitro­gen to the distal ethane carbon of meth­oxy ethane. The dihedral angles between the three pyrazole rings are 67.62 (14), 73.74 (14), and 78.92 (12)°. In the crystal, mol­ecules are linked by bifurcated C—H,H⋯N hydrogen bonds, forming double-stranded chains along [001]. The chains are linked via C—H⋯O hydrogen bonds, forming a three-dimensional framework structure. The crystal was refined as a perfect (0.5:0.5) inversion twin.

Development And Evaluation Of Carbon-Based Quantum Dots For Carbon Dioxide Photoconversion, Sushant Sahu

All Dissertations

World energy consumption has increasingly grown over the past several decades.Because of its potential in photochemical energy conversion, photocatalysis has been the subject of much recent research. Recently, carbon or graphene-based quantum dots have attracted growing attention in solar energy conversion applications, because of its unique optoelectronic properties, broad-band optical absorption, bright fluorescence emissions, favorable photoinduced electron transfer properties, reliable chemical inertness and stability, cost-effectiveness, and non-toxicity. While nanosized wide band gap semiconductor-based systems were largely at the center of attention in such studies, carbon-based quantum dots have recently emerged as a new class of semiconductor like photoactive materials, due …

Synthesis Of Homo- And Heterobimetallic NiIi–MIi (M = Fe, Co, Ni, Zn) Complexes Based On An Unsymmetric Ligand Framework: Structures, Spectroscopic Features, And Redox Properties, Denan Wang, Sergey V. Lindeman, Adam T. Fiedler

Chemistry Faculty Research and Publications

Several homo- and heterobimetallic Ni^II–M^II complexes (M^II = Fe, Co, Ni, Zn) supported by an unsymmetric polydentate ligand (L₁³⁻) are reported (L₁³⁻ is the trianion of 2-[bis(2-hydroxy-3,5-tert-butylphenyl)aminomethyl]-4-methyl-6-[(2-pyridylmethyl)iminomethyl]phenol). The L₁³⁻ chelate provides two distinct coordination environments: a planar tridentate {N₂O} site (A) and a tetradentate {NO₃} site (B). Reaction of L₁³⁻ with equimolar amounts of Ni^II and M^II salts provides bimetallic complexes in which the Ni^II ion exclusively occupies the tetragonal A-site and the M^II ion is found …

Synthesis Of (+)-Bovidic Acid, Geoffrey A. Phillips, Timothy B. Wright, Andrew C. Stevens, Brian Pagenkopf

Chemistry Publications

(+)-Bovidic acid is an 18-carbon hydroxyfuranoid acid isolated from the pelage of the gaur (Bosfrontalis) and displays potential as an insect repellant. Both a formal and total synthesis of (+)-bovidic acid was carried out with the core of the natural product being synthesized through Mukaiyama aerobic oxidative cyclization employing the second-generation Co(nmp)₂ catalyst.

Mechanistic Studies Of Salt Effects On Bimolecular Electron-Transfer Reactions Of Pentaamine Ruthenium Pyridyl Complexes Studied By 19f Nmr Line-Broadening And T2 Spin-Echo Techniques, Nicholas J. Magarian

Master's Theses

Kinetic salt effects on the bimolecular ET self-exchange reaction between pentaamineruthenium(II)(3-trifluoromethylpyridine)²⁺, (NH₃)₅Ru^IItfmp²⁺, and pentaamineruthenium(III)(3-trifluoromethylpyridine)³⁺, (NH₃)₅Ru^IIItfmp³⁺, have been measured using both ¹⁹F NMR line-broadening and CPMG T₂ spin-echo relaxation techniques in H₂O and D₂O. Over the equimolar reactants concentration range of 0.10 mM – 8.00 mM there was a definite “self-salting” rate increase arising from the increased solution ionic strengths due to the reactants and counterions themselves. The magnitude of this effect diverged significantly, however, …

100th Convocation 2014 Address - Amazing Mice Light Up The Liberal Arts, Marc Zimmer

Convocation Addresses

Connecticut College Professor of Chemistry Marc Zimmer states, "I like to think of our educational system as an intellectual maze. New students, you are standing at the entrance of this fantastic maze, a lush and verdant garden maze..."

He concludes: "We are all, faculty, students and staff tremendously privileged to be sitting here at the entrance of the amazing maze of learning."

High Resolution Electronic Spectroscopy Of The A 2 Σ − − X 2 Π 1/2 Transition Of Ptn, Kaitlin Womack, Sean Whittemore, James O'Brien, An Le, Timothy Steimle

Chemistry & Biochemistry Faculty Works

The (2,0) vibrational band of the A {sup 2}Σ{sup −} − X {sup 2}Π{sub 1/2} transition of platinum nitride, PtN, was recorded at Doppler-limited resolution using intracavity laser absorption spectroscopy (ILS) and at sub-Doppler resolution using molecular beam laser induced fluorescence (LIF) spectroscopy. Isotopologue structure for {sup 194}PtN, {sup 195}PtN, and {sup 196}PtN, magnetic hyperfine splitting due to {sup 195}Pt (I = ½), and nuclear quadrupole splitting due to {sup 14}N (I = 1) were observed in the spectrum. Molecular constants for the ground and excited states are derived. The hyperfine interactions are used to illuminate the nature of the …

In-Situ Afm Force Curve Investigations On Layered Structures Of Au(111)-Ionic Liquid Interfaces And Temperature Dependence, Xiao Zhang, Yun-Xin Zhong, Jia-Wei Yan, Bing-Wei Mao

Journal of Electrochemistry

By utilizing in-situ AFM force curve measurements systematic investigations have been carried out on Au(111)-ionic liquid interface in BMIPF₆ and OMIPF₆ of imidazolium-based ionic liquids with different lengths of alkyl side chains. The temperature dependence of the number, thickness and stability of the layered structures of each system are studied by performing AFM force curve measurements at potentials far negative of the PZC. The layered structures at Au (111)/BMIPF₆ interface are composed of two charged interior layers and two neutral exterior layers at -1.0 V, while those at Au (111)/OMIPF₆ interface only one charged interior layer …

Electrochemical Catalysis: A Dft Study, Li Li, Zi-Dong Wei

Journal of Electrochemistry

In this review, we focus on achievements in electro-catalysis based on the density function theory study. The relationships among the electrode potential, electronic structure of catalysts and electro-catalytic activity are summarized in three parts: the adsorption and desorption of species, electron transfer, and stability of catalysts. The electrode potential and the electronic structure (d-band center or Fermi (HOMO) energy) of catalysts significantly influence the formation, adsorption and desorption of surface species on electrode. The electro-catalytic activity can be improved by modulating the electrode potential and electronic structure of catalysts.

Electrocatalytic Oxidation Of Formate On Pd-Cu/C - Effect Of Dealloying Pretreatment, Kun Jiang, Ye Wang, Tao Lin, Wen-Bin Cai

Journal of Electrochemistry

Carbon supported highly dispersed Pd-Cu nanoalloy catalyst toward formate electrooxidation is prepared via one-pot synthesis by using ethylene glycol as the reducing agent and sodium citrate as the stabilizer. The as-prepared catalyst is structurally characterized by TEM and XRD. The Cu dealloyment is carried out through repetitive potential cycling of the Pd-Cu/C catalyst in an acidic solution. The dealloying effect on the performance of the Pd-Cu/C is investigated by using cyclic voltammetry and chronoamperometry, and the surface structural change of Pd-Cu/C is probed by in situ ATR-IR measurement. The results show that the as-prepared Pd-Cu/C processes a better long-term stability …

Electrochemical And Surface Enhanced Raman Spectroscopic Studies Of Benzimidazole On Nickel Electrode, Ping-Jie Wei, Ya-Xian Yuan, Min-Min Xu, Jian-Lin Yao, Ren-Ao Gu

Journal of Electrochemistry

By measuring cyclic voltammograms and polarization curves, the inhibition effects of benzimidazole (BMIH) concentration in acetonitrile system on a nickel electrode were investigated. It was found that the oxidation and the corrosion potentials shifted positively, and the oxidation current decreased with the increase in the concentration of BIMH. Potential dependent adsorption and film formation behavior of BMIH on the nickel electrode were investigated by in situ SERS spectroscopy. With the potential moving from negative direction to positive direction, the complexes made of BIMH and nickel were formed, preventing the nickel electrode from corrosion. In addition, the 0.001 mol·L^-1 of …

Synthesis Of Silver Nanoparticles Supported On Graphene Quantum Dots For Oxygen Reduction Reaction, Jian Ju, Wei Chen

Journal of Electrochemistry

Silver-based catalysts have been extensively investigated as the platinum substituted catalysts due to their high catalytic efficiency, low cost and long-term durability. In this study, the surfactant-free silver nanoparticles supported on graphene quantum dots were synthesized through a facile approach without addition of any other protecting ligands and reducing agents. The “surface-clean” silver nanoparticles had remarkable electrocatalytic performance towards oxygen reduction reaction (ORR) with the most efficient four-electron transfer process. Compared with commercial Pt/C catalyst, the hybrid nanoparticles showed comparable catalytic performance for ORR but much higher tolerance to methanol. Such silver nanoparticles supported on graphene quantum dots may have …

Preparation And Lithium Storage Performance Of Sn-Snsb Nanoparticles, Yao Xiao, Jiao-Hong Wu, Qi Wang, Ling Huang, Jun-Tao Li, Shi-Gang Sun

Journal of Electrochemistry

Tin was widely studied as alternative anode material to carbon for lithium-ion batteries thanks to its much higher theoretical capacity. However, a pure tin electrode suffers severely from its poor cycleability due to mechanical fatigue caused by volume change during lithium insertion and extraction processes. Tin-based alloy may improve the cycleability property of tin electrode. In this article, we report facile synthesis of spherical Sn-SnSb nanopartciles using a simple solvent-thermal approach. It is amazing to find that the spherical Sn-SnSb nanoparticles can circumvent volume changes effectively during charge-discharge process. Electrochemical discharge/charge results show that the spherical Sn-SnSb nanoparticles electrode exhibits …

Electrochemical Fabrication Of Two-Dimensional Flower-Like Pt Nanostructures For Methanol Electrocatalytic Oxidation, Xia Wang, Jun Hu, Yong-Jun Li

Journal of Electrochemistry

Two-dimensional flower-like Pt nanostructures (2D FPNs) were fabricated on glassy carbon substrates by galvanostatical electrochemical technique. The electrolyte was the HAuCl₄ + HClO₄ aqueous solution without addition of any structure-directing organic reagent, which made as-prepared Pt nanostructures cleaner, exhibiting much higher reactivity. Scanning electron microscopic images revealed that 2D FPNs were spherical Pt nano-flowers constructed by the smallest building blocks, nano-leaves. The number density of spherical Pt nano-flowers can be tuned by controlling the electrodeposition time. High resolution transmission electron microscopic images indicated that each nano-leaf was formed by growing along Pt(111) direction. Electrocatalytic activities of as-prepared 2D …

High Sensitive Detection Of Cd(Ii) And Pb(Ii) Based On Antimony-Film Covered Pencil Core Electrodes, Shan Chen, Zhao-Yan Zheng, Yi-Min Fang, Li-Qing Zheng, Jian-Jun Sun

Journal of Electrochemistry

In this paper, a pencil core was used as the substrate for an antimony-film electrode for simultaneous detection of Cd(II) and Pb(II) by square-wave anodic stripping voltammetry (SWASV). With the deposition time of 180 s, the low limit of detection (LOD) for the electrode was determined to be 0.075·g?L-1 for Cd(II), while 0.13·g·L-1 for Pb(II) with good reproducibility in low pH solutions (pH = 2). The results show a much lower LOD than that of bismuth-film pencil core electrode. Finally, this antimony-film electrode was successfully applied to determine Cd(II) and Pb(II) in tap water.

A Sensitive And Label-Free Electrochemical Aptasensor Based On Signal Amplification Of Carbon Nanotubes, Chun-Yan Deng, Hui-Min Fan, Juan Xiang, Yuan-Jian Li

Journal of Electrochemistry

A label-free electrochemical sensing electrode for highly sensitive detection of adenosine was constructed based on the signal amplification of carbon nanotubes (CNTs). The change in the interfacial feature of the modified electrode was characterized by electrochemical impedance spectroscopy. Using [Ru(NH₃)₆]³⁺ as the signaling moiety, adenosine with concentrations as low as 0.027 nmol·L^-1 can be selectively detected. Additionally, the fabrication of this present aptasensor was simple, time-saving and cost-effective. Compared with other reported aptasensors, the proposed aptasensor had advantages of excellent sensitivity, selectivity and simplicity, which plays a potential role in development of aptasensor.

Low-Temperature Phase Transitions In A Soluble Oligoacene And Their Effect On Device Performance And Stability, J. W. Ward, K. P. Goetz, A. Obaid, Marcia M. Payne, P. J. Diemer, C. S. Day, John E. Anthony, O. D. Jurchescu

Chemistry Faculty Publications

The use of organic semiconductors in high-performance organic field-effect transistors requires a thorough understanding of the effects that processing conditions, thermal, and bias-stress history have on device operation. Here, we evaluate the temperature dependence of the electrical properties of transistors fabricated with 2,8-difluoro-5,11-bis(triethylsilylethynyl)anthradithiophene, a material that has attracted much attention recently due to its exceptional electrical properties. We have discovered a phase transition at T = 205 K and discuss its implications on device performance and stability. We examined the impact of this low-temperature phase transition on the thermodynamic, electrical, and structural properties of both single crystals and thin films …

Cyclic Voltammetric Studies In Adsorption Of Cetyltrimethylammonium Bromide (Ctab) On Au(111) Electrode, Ling Chen, Chang-Deng Xu, Jin-Yu Ye, Chun-Hua Zhen, Shi-Gang Sun

Journal of Electrochemistry

Adsorption of cetyltrimethylammonium bromide (CTAB) on Au(111) electrode was investigated by cyclic voltammetry (CV). The results demonstrate that the adsorption of CTAB on Au(111) yields particular CV features. Both the adsorption of CTA⁺ and the phase change of the surfactant film are surface structure selective. Two pairs of stable sharp peaks that depend on halide species appear upon the adsorption of cationic surfactant on Au(111) electrode. The relationship between the peak current density and the scan rate indicates that the electron transfer reaction was controlled by diffusion process. These CV features are observed for the first time, and reflect …

Investigation Of The Dynamics Of Photocarriers During Photoelectrochemical Water Splitting By Combination Of Photoelectrochemistry And Transient Absorption Spectroscopy, Wen-Hua Leng

Journal of Electrochemistry

Semiconductor photoelectrochemical hydrogen production is an important and promising technology for utilizing solar energy. The efficiency of hydrogen production depends on the efficiencies of separation and transport of photo-generated carriers. A deep understanding of the behavior of these processes has guiding significance for designing efficient solar hydrogen device. photoelectrochemical and transient absorption spectroscopy methods are powerful tool for studying the microscopic dynamics and mechanism of photocatalytic reaction. This review describes the part of the latest results of the author regarding the semiconductor photoelectrochemical hydrogen production obtained by these methods,and the problems and future research priorities in this field are proposed.

Effecting Of Dissolved Oxygen On Microbial Fuel Cells Based On Pseudomonas Aeruginosa, Chang-Li Cao, Li-Xiang Chen, Ran-Ran Wu, Ken-Lin Chang, Feng Zhao

Journal of Electrochemistry

In this work, the reaction between the electron shuttle secreted by Pseudomonas aeruginosa and anode was studied by measuring cyclic voltammogram and open circuit potential. The effect of dissolved oxygen on the oxidation reaction of anode was explored. It was demonstrated that the reaction was a diffusion-controlled and reversible process. The anode was a little affected when the dissolved oxygen of inocula was low (0 ~ 1.6 mg·L^-1). The polarization curves showed that the current output of microbial fuel cells decreased 7% with the impact of dissolved oxygen.

Room Temperature Ionic Liquid Templated Meso-Macroporous Material By Self-Assembled Giant Gold Nanoparticles And Its Enhancement On The Direct Electrochemistry Of Cytochrome C, Pei Li, Dong-Ping Zhan, Yuan-Hua Shao

Journal of Electrochemistry

Room temperature ionic liquid (RTIL) is used as a soft-template to organize a meso-macroporous material constructed by self-assembled giant gold nanoparticles which are capped by L-cysteine. First, L-cysteine capped gold nanoparticles can self-assembly to form nanowires and sub-micrometer spherical giant particles due to the static interaction and/or the condensation reaction between the carboxyl and amino groups at the outer terminal of the ligand. Second, the spherical assembled particles can form a quasi-solid gel when grinding with a hydrophobic RTIL, 1-octyl-3-metyllimidazolium hexafluorophosphate. Finally, when the composite gel is coated on a glassy carbon electrode and then polarized by using cyclic voltammetry …