Physical Chemistry Commons^™

Recent Experimental Progresses On Electrochemical Atr-Seiras, Yao-Yue Yang, Han-Xuan Zhang, Wen-Bin Cai

Journal of Electrochemistry

Technical aspects on developing electrochemical ATR surface-enhanced infrared absorption spectroscopy are briefly accounted mainly based on our recent investigations, including wet-fabrication of metallic film electrodes on Si prism, design and construction of a wide-frequency combination optical window and a spectroelectrochemical cell switchable for external and internal reflection modes.

Applications Of Ellipsometry In The Investigations Of Electrode-Solution Interface, Jing-Lei Lei, Liang-Liu Wu, Ling-Jie Li, Sheng-Mao Wu, Sheng-Tao Zhang

Journal of Electrochemistry

Ellipsometry is an optical technique with high-sensitivity to quantitatively obtain surface/interface properties such as thickness andrefractive index by analyzing the changes in polarized light reflected from the surface/interface. Its noncontacting and nondestructivenature makes it possible to acquire thein situreal-time information of the change at the surface/interface. Therefore, ellipsometry has been used widely in the electrochemical investigations. In this paper, based on the brief introduction of the measurementprinciple of ellipsometry, the current progress and the future trends of ellipsometry in electrochemistry arediscussed. The applications of ellipsometry in the fields of conversion and storage of electrochemical energy, electrochemistry ofmaterials science,electroanalysisand bioelectrochemistry are …

Oxygen Reduction Reaction On Glycin Modified Pt(111) Electrode, Ming-Fang Li, Jing Kang, Ling-Wen Liao, Yan-Xia Chen, Shen Ye

Journal of Electrochemistry

O

xygen reduction reaction (ORR) on glycin (NH₂CH₂COOH) modified Pt(111) electrode has been investigated using hanging meniscus rotating disk electrode system (HMRD) in 0.05 mol•L^-1 H₂SO₄ and 0.1 mol•L^-1 HClO₄ solutions, respectively. Cyclic voltammograms of the glycin modified Pt (111) electrode measured in 0.05 mol•L^-1 H₂SO₄ solution similar to that of CN^- modified Pt(111) electrodes, demonstrating that sulfate adsorption is strongly inhibited at the glycin modified Pt(111). From the polarization curve of ORR recorded in 0.05 mol•L^-1 H₂SO₄ solution, it is …

Porous Electrodes With High Pt Utilization Obtained By Ion-Exchange/Electrodeposition, Si-Guo Chen, Wei Ding, Xue-Qiang Qi, Li Li, Zi-Hua Deng, Zi-Dong Wei

Journal of Electrochemistry

We report a novel method based on ion-exchange/electrodeposition (IEE) for constructing high Pt utilization porous electrodes. The electrode prepared using IEE was assessed by linear sweep voltammetry (LSV), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and single cell test. The preliminary results show that the undesired ion-exchange between Pt anion and surface functional group in carbon black can be eliminated through the electrode preparation process, and every Pt particle prepared by IEE is expected to be deposited on the three-phase reaction zone and thus can be fully utilized in fuel cell reactions. The Pt particle size, shape and distribution …

Effect Of Ti/Pbo2 Electrodes Doped With Different Elements On Electrocatalytic Oxidation Characteristics Of Phenol, Xiao-Lei Liu, Yuan-Yuan Dan, Hai-Yan Lu, Hai-Bo Lin, Ming-Li Ouyang, Chuan-Jun Yun

Journal of Electrochemistry

Three types of electrodes, namely, Ti/PbO₂, F-doped PbO₂ (Ti/PbO₂-F) and nano-Co₃O₄-doped PbO₂ (Ti/PbO₂+Nano-Co₃O₄) electrodes, were prepared by electro-deposition method on the Ti substrate with the interlayer of SnO₂-Sb₂O₅. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to study the compositions, structures and film morphologies of the electrodes. Electrocatalytic oxidation characteristics to phenol on the prepared electrodes were investigated by electrochemical method. The experimental results showed that compared with the Ti/PbO₂ electrode, the potentials of oxygen …

A Dft Calculation Screening Of Pt-Based Bimetallic Catalysts For Oxygen Reduction, Li-Hui Ou, Sheng-Li Chen

Journal of Electrochemistry

Developing Pt-lean catalysts for oxygen reduction reaction (ORR) is the key for large-scale application of proton exchange membrane fuel cell (PEMFC). In this paper, we have proposed a multiple-descriptor strategy for screening efficient and durable ORR alloy catalysts of low Pt content. We argue that an ideal Pt-based bimetallic alloy catalyst for ORR should possess simultaneously negative alloy formation energy, negative surface segregation energy of Pt and a lower oxygen binding ability than pure Pt. By performing detailed DFT calculations on the thermodynamics, surface chemistry and electronic properties of various Pt-M alloys (M refers to non-precious transition metals in the …

Sodium Carbonate Catalyzed Photoelectrochemical Water Splitting Over Tio2 Nanotubes Photoanode, De-Sheng Kong, Jing Wang, Xue-Di Zhang, Xi Zhao, Chao Wang, Yuan-Yuan Feng, Wen-Juan Li

Journal of Electrochemistry

Surface recombination of the photogenerated electron-hole pairs at semiconductor/electrolyte interface is one of the most essential reasons responsible for lowering photoconversion efficiency (Φ) of light to chemical energy for photoelectrochemical (PEC) water splitting reaction. In this paper, the catalytic effect of sodium carbonate on the oxygen evolution reaction (OER) over TiO₂ nanotubes photoanode during PEC water splitting was investigated by performing photocurrent and ac impedance measurements. It was demonstrated that the addiction of 1 mmol•L^-1 Na₂CO₃ in 0.5 mol•L^-1 NaClO₄ electrolyte can effectively improve the charge transfer properties for the photogenerated holes across …

Synthesis: What We Have Learned From The East Texas Radiocarbon Database, Robert Z. Selden Jr., Timothy K. Perttula

CRHR: Archaeology

This poster provides a short overview of what we have learned from the East Texas Radiocarbon Database since it became available on the Council of Texas Archeologists’ website in 2011. These successes are numerous and include the advancement of novel methodological approaches; an improvement in our comprehension of the temporal nuances within the East Texas Archaic; the division of the East Texas Woodland period into Early, Middle and Late; the refinement of Caddo temporal chronology – particularly from a geographic perspective -- and it has provided one line of evidence to use to argue for the fluorescence of corn-based agriculture …

Radiocarbon Trends And The East Texas Caddo Tradition (Ca. A.D. 800-1680), Robert Z. Selden Jr., Timothy K. Perttula

CRHR: Archaeology

Through the employment of radiocarbon (¹⁴C) dates as data, we use the date combination process to refine site-specific summed probability distributions for 555 dates from Caddo sites (n = 19) in East Texas with 10 or more ¹⁴C dates. Summed probability distributions are then contrasted across river basins and natural regions with the remainder of the East Texas Caddo Radiocarbon Database (n = 338 dates from 132 other Caddo sites), highlighting the temporal and spatial character of Caddo archaeological sites throughout East Texas.

X-Band Rapid-Scan Epr, Deborah Gale Mitchell

Electronic Theses and Dissertations

The advantages of rapid-scan EPR relative to CW and pulse techniques for samples with long longitudinal relaxation time T₁ (N_s⁰ defects in diamond, N@C₆₀, and amorphous hydrogenated silicon), heterogeneous samples (crystalline 1:1 α,γ-bisdiphenylene-β-phenylallyl (BDPA):benzene), lossy samples (aqueous nitroxyl radicals), and transient radicals (5-tert-butoxycarbonyl-5-methyl-1-pyrroline-N-oxide (BMPO)-superoxide adduct) were studied.

For samples with long relaxation times, CW (continuous wave) EPR is challenging due to power saturation and distortions from passage effects. In rapid-scan EPR, the field is swept through resonance in a time that is short relative to T₂. In rapid-scan EPR, the magnetic field is …

Metastable Nanostructured Metallized Fluoropolymer Composites For Energetics, Hannah A. Miller, Bradley S. Kusel, Seth T. Danielson, James W. Neat, Eryn K. Avjian, Scott N. Pierson, Stephen M. Budy, David W. Ball, Scott T. Iacono, Sharon C. Kettwich

Chemistry Faculty Publications

Fluoropolymers have long served as potent oxidizers for metal-based pyrolant designs for the preparation of energetic materials. Commercial perfluoropolyethers (PFPEs), specifically known as Fomblins®, are well-known to undergo accelerated thermal degradation in the presence of native metals and Lewis acids producing energetically favorable metal fluoride species. This study employs the use of PFPEs to coat nano-aluminum (n-Al) and under optimized stoichiometric formulations, harness optimized energy output. The PFPEs serve as ideal oxidizers of n-Al because they are non-volatile, viscous liquids that coat the particles thereby maximizing surface interactions. The n-Al/PFPE blended combination is required to interface with an epoxy-based matrix …

Exploring Molecular Systems From Chemical Physics To Biochemistry Using Classical And Quantum Mechanics, Brian Thomas Psciuk

Wayne State University Dissertations

Six topic are considered in this dissertation. Chapter 2 is an investigation into the role of ultra-fast hydrogen dynamics in determining fragmentation products of C3H4 following exposure to intense laser fields. Classical dynamics simulations were performed starting from C3H4 isomers with 190 - 240 kcal/mol excess energy distributed randomly as nuclear momenta. Deprotonation events were seen in ca. 50 - 75 % of all trajectories. Roughly one third of all trajectories showed fragmentation involving internal isomerization prior to dissociation. Chapter 3 is a survey of currently popular density functional methods and their ability to calculate accurate excitation energies and intensities …

Fundamental Studies And Applications Of Strong Field Ionization, Lu Yan

Wayne State University Dissertations

In an intense laser field, atoms and molecules experience tunneling ionization directly to the continuum. We used this method to study several aspects and applications of strong field ionization (SFI) in atoms and molecules. One study used SFI to probe the photofragments produced by photodissociation using DC sliced imaging. The photodissociation mechanism of two polyatomic molecules (sulfur dioxide and nitromethane) were investigated. In a second study, we show the strong field ionization rate depends on the sign of the magnetic number distribution. We detect the signal of sequential double ionization of argon dications by a pump-probe method to investigate the …

Preparation Of Phosphonoterephthalic Acids Via Palladium-Catalyzed Coupling Of Aromatic Iodoesters, Nathaniel Ivan, Vladimir Benin, Alexander Morgan

Chemistry Faculty Publications

The current article reports in detail the preparation of two phosphonoterephthalic acids: 2-phosphonoterephthalic acid (1) and 2,5-diphosphonoterephthalic acid (2). Efficient, scalable syntheses have been developed for both compounds based on Pd-catalyzed coupling reactions of iodinated terephthalate esters. Phosphonoterephthalic acids are potentially useful as flame-retardant additives or as monomers for the construction of acid-pendant polymer chains.

The Bench Synthesis Of Silver Nanostructures Of Variable Size And An Introductory Analysis Of Their Optical Properties, Aoife Power, Tony Betts, John Cassidy

Articles

A laboratory practical was designed for use by both undergraduate and second level students to demonstrate the synthesis and characterisation of tuneable silver colloids. It clearly illustrates the novel optical properties of silver nanoparticles compared to the bulk metal. The synthesis is both rapid and repeatable, and can be conducted on the laboratory bench at room temperature.

Specific Salt Effects On The Formation And Thermal Transitions Among Β-Lactoglobulin And Pectin Electrostatic Complexes, Stacey Ann Hirt

Open Access Theses

Factors of ion specificity and ionic strength (I~0-100) were studied in the electrostatic complex formation and protein particle formation by thermal treatment for a β-lactoglobulin and pectin system. ζ-potential showed β-lactoglobulin and pectin began to interact near pH 5.50 and interactions were strengthened with decrease in pH. Visible light turbidimetry and light scattering at 90° revealed a trend in critical pH transitions for electrostatic complex formation based on both the ionic strength and the anion of the salt species, while effects of the monovalent cation was insignificant. Critical pH values for complex formation and separation (pHc and pHΦ) decreased with …

Pickering Stabilization Of Oil-Water Interfaces By Heated B-Lactoglobulin/Pectin Particles, Laura Kathryn Zimmerer

Open Access Theses

The use of natural biopolymer particles as Pickering stabilizers for oil-in-water emulsions was investigated. B-lactoglobulin microgels and B-lactoglobulin/pectin complexes were created by heating appropriate biopolymer solutions at pH 5.8 and 4.75, respectively. Resultant particles exhibited spherical morphology with diameters of 100-300 nm and possessed significant negative surface charge. Particles were first homogenized with 1% corn oil at 0.05%, 0.1% or 0.25% (wt/ wt) particle concentrations. All emulsions appeared stable over seven days with only a thin, creamed ring forming after several hours. Corn oil emulsions were most stable with 0.25% heated complexes, with volume-weighted mean droplet diameter remaining around 480 …

The Critical Role Of Mechanism-Based Models For Understanding And Predicting Liposomal Drug Loading, Binding And Release Kinetics, Sweta Modi

Theses and Dissertations--Pharmacy

Liposomal delivery systems hold considerable promise for improvement of cancer therapy provided that critical formulation design criteria can be met. The main objective of the current project was to enable quality by design in the formulation of liposomal delivery systems by developing comprehensive, mechanism-based mathematical models of drug loading, binding and release kinetics that take into account not only the therapeutic requirement but the physicochemical properties of the drug, the bilayer membrane, and the intraliposomal microenvironment.

Membrane binding of the drug affects both drug loading and release from liposomes. The influence of bilayer composition and phase structure on the partitioning …

Reaction Between Polyol-Esters And Phosphate Esters In The Presence Of Metal Carbides, David W. Johnson, Carolyn Iacullo, John E. Hils

Chemistry Faculty Publications

The reaction of metal carbides with polyol esters found in aerospace lubricants and phosphate esters commonly used as additives was investigated. Carbides were of particular interest since modern materials under consideration at high temperature bearings have surfaces that are primarily metal carbides. Vanadium and chromium carbide were found to react with the ester and phosphate ester by a transesterification reaction, producing an alkyl phosphate which is less stable than the aromatic phosphate esters. In the process, the metal carbide is converted to the metal phosphate and metal polyphosphate, evidenced by the infrared and Raman spectra of the solid residue and …

Brust-Schiffrin Synthesis Of Catalytic Bipodal Pdpt Nanoparticles With Some Mechanistic Insights, Sangbum Han, Vara P. Sheela, Wei Cao, Balasubramanian Ramjee

Applied Research Center Publications

Brust–Schiffrin reduction of Pd and Pt precursors in the presence of resorcinarene amine surfactant led to the formation of substantially Pt rich, PdPt bimetallic nanoparticles of a V-shape or variants on the V-shape. New insights into this reaction are provided on the basis of reversed Brust–Schiffrin syntheses, DLS, UV-vis, and NMR analysis. Based on our experiments we conclude that the resorcinarene amine surfactant is part of the inverse micelle formed from TOABr and it also selectively complexes with the Pd salts prior to their reduction. Remarkably, the composition of the bipodal nanoparticles could be varied substantially by varying the reaction …

Properties And Structures Of Li-N Based Hydrogen Storage Materials, Junqing Zhang

Dissertations, Master's Theses and Master's Reports - Open

Traditional transportation fuel, petroleum, is limited and nonrenewable, and it also causes pollutions. Hydrogen is considered one of the best alternative fuels for transportation. The key issue for using hydrogen as fuel for transportation is hydrogen storage. Lithium nitride (Li3N) is an important material which can be used for hydrogen storage. The decompositions of lithium amide (LiNH2) and lithium imide (Li2NH) are important steps for hydrogen storage in Li3N. The effect of anions (e.g. Cl-) on the decomposition of LiNH2 has never been studied. Li3N can react with LiBr to form lithium nitride bromide Li13N4Br which has been proposed as …

Ultrasensitive Analysis Of Binding Affinity Of Hiv Receptor And Neutralizing Antibodies Using Solution-Phase Electrochemiluminescence Assay, Xiao-Hong Nancy Xu, Zhaoyang Wen, William J. Brownlow

Chemistry & Biochemistry Faculty Publications

Binding of a few ligand molecules with its receptors on cell surface can initiate cellular signaling transduction pathways, and trigger viral infection of host cells. HIV-1 infects host T-cells by binding its viral envelope protein (gp120) with its receptor (a glycoprotein, CD4) on T cells. Primary strategies to prevent and treat HIV infection is to develop therapies (e.g., neutralizing antibodies) that can block specific binding of CD4 with gp120. The infection often leads to the lower counts of CD4 cells, which makes it an effective biomarker to monitor the AIDS progression and treatment. Despite research over decades, quantitative assays for …

Broadband Fourier Transform Rotational Spectroscopy For Structure Determination: The Water Heptamer, Cristóbal Pérez, Simon Lobsiger, Nathan A. Seifert, Daniel P. Zaleski, Berhane Temelso, George C. Shields, Zbigniew Kisiel, Brooks H. Pate

Faculty Journal Articles

Over the recent years chirped-pulse, Fourier-transform microwave (CP-FTMW) spectrometers have chan- ged the scope of rotational spectroscopy. The broad frequency and large dynamic range make possible structural determinations in molecular systems of increasingly larger size from measurements of heavy atom (¹³C, ¹⁵N, ¹⁸O) isotopes recorded in natural abundance in the same spectrum as that of the parent isotopic species. The design of a broadband spectrometer operating in the 2–8 GHz frequency range with further improvements in sensitivity is presented. The current CP-FTMW spectrometer performance is benchmarked in the analyses of the rotational spectrum of the water …

The Relation Between Atmospheric Humidity And Temperature Trends For Stratospheric Water, S. Fueglistaler, Y. S. Liu, T. J. Flannaghan, P. H. Haynes, D. P. Dee, W. J. Read, E. E. Remsberg, L. W. Thomason, D. F. Hurst, J. R. Lanzante, P. F. Bernath

Chemistry & Biochemistry Faculty Publications

We analyze the relation between atmospheric temperature and water vapor-a fundamental component of the global climate system-for stratospheric water vapor (SWV). We compare measurements of SWV (and methane where available) over the period 1980-2011 from NOAA balloon-borne frostpoint hygrometer (NOAA-FPH), SAGE II, Halogen Occultation Experiment (HALOE), Microwave Limb Sounder (MLS)/Aura, and Atmospheric Chemistry Experiment Fourier Transform Spectrometer (ACE-FTS) to model predictions based on troposphere-to-stratosphere transport from ERA-Interim, and temperatures from ERA-Interim, Modern Era Retrospective- Analysis (MERRA), Climate Forecast System Reanalysis (CFSR), Radiosonde Atmospheric Temperature Products for Assessing Climate (RATPAC), HadAT2, and RICHv1.5. All model predictions are dry biased. The interannual …

Hydrocarbons In The Upper Troposphere And Lower Stratosphere Observed From Ace-Fts And Comparisons With Waccm, Mijeong Park, William J. Randel, Douglas E. Kinnison, Louisa K. Emmons, Peter F. Bernath, Kaley A. Walker, Chris D. Boone, Nathaniel J. Livesey

Chemistry & Biochemistry Faculty Publications

Satellite measurements from the Atmospheric Chemistry Experiment Fourier Transform Spectrometer (ACE-FTS) are used to examine the global, seasonal variations of several hydrocarbons, including carbon monoxide (CO), ethane (C₂H₆), acetylene (C₂H₂), and hydrogen cyanide (HCN). We focus on quantifying large-scale seasonal behavior from the middle troposphere to the stratosphere, particularly in the tropics, and furthermore make detailed comparisons with the Whole Atmosphere Community Climate Model (WACCM) chemistry climate model (incorporating tropospheric photochemistry, time-varying hydrocarbon emissions, and meteorological fields nudged from reanalysis). Comparisons with Microwave Limb Sounder (MLS) measurements of CO are also included …

Organic Photovoltaics: A Charge Transfer Perspective In The Study Of Donor-Acceptor Systems, Marco Olguin

Open Access Theses & Dissertations

The present research involves the study of donor-acceptor (D/A) dyad complexes from a charge transfer energy perspective. The aim is to provide insight and predictive understanding into the charge transfer processes of the molecular-level components in donor-acceptor based organic solar cells using computational methods to describe photochemical processes at the quantum mechanical level within the Density Functional Theory (DFT) approximation. Predictive understanding is anchored in reproducing experimental results, wherein the present work a perturbative excited-state DFT method is described in detail and shown to give Charge Transfer (CT) energies in excellent agreement with benchmark experimental data. With an accurate excited …

Self-Assembling Of Gold Nanoparticles Array For Electro-Sensing Applications, Islam M. Al-Akraa Dr, Ahmad M. Mohammad Prof, Mohamed S. El-Deab Prof, Bahgat E. El-Anadouli Prof

Chemical Engineering

A colloidal solution of citrate-stabilized gold nanoparticles (AuNPs) with an average size of ca. 2.6 nm has been prepared, characterized and further implemented in electro-sensing applications. This colloidal solution of AuNPs has been prepared via the reduction of NaAuCl4 with sodium tetrahydroborate (NaBH4) using trisodium citrate as a stabilizer. The optical properties of this solution have been studied with UV–Vis spectroscopy. Next, these AuNPs have been immobilized onto a polycrystalline Au (poly-Au) electrode with the assistance of benzenedimethanethiol (BDMT), which served as a binder. Attention has been taken to ensure the formation of a compact impermeable layer of BDMT on …

Homogeneous Connectivity Of Potential Energy Network In A Solidlike State Of Water Cluster, Takuma Akimoto, Toshihiro Kaneko, Kenji Yasuoka, Xiao Cheng Zeng

Xiao Cheng Zeng Publications

A novel route to the exponential trapping-time distribution within a solidlike state in water clusters is described. We propose a simple homogeneous network (SHN) model to investigate dynamics on the potential energy networks of water clusters. In this model, it is shown that the trappingtime distribution in a solidlike state follows the exponential distribution, whereas the trapping-time distribution in local potential minima within the solidlike state is not exponential. To confirm the exponential trapping-time distribution in a solidlike state, we investigate water clusters, (H₂O)₆ and (H₂O)12, by molecular dynamics simulations. These clusters change dynamically from …

Structure And Thermodynamics Of H3o+(H2o)8 Clusters: A Combined Molecular Dynamics And Quantum Mechanics Approach, Berhane Temelso, Thorsten Koddermann, Karl K. Kirschner, Katurah L. Klein, George C. Shields

Faculty Journal Articles

We have studied the structure and stability of (H₃O⁺)(H₂O)₈ clusters using a combination of molecular dynamics sampling and high-level ab initio calculations. 20 distinct oxygen frameworks are found within 2 kcal/mol of the electronic or standard Gibbs free energy minimum. The impact of quantum zero-point vibrational corrections on the relative stability of these isomers is quite significant. The box-like isomers are favored in terms of electronic energy, but with the inclusion of zero-point vibrational corrections and entropic effects tree-like isomers are favored at higher temperatures. Under conditions from 0 to 298.15 K, the …

Structures And Reactions Of Biomolecules At Interfaces, Xiaoning Zhang

Theses and Dissertations--Chemistry

This dissertation serves to study a protein's conformation-function relationship since immobilized proteins often behave differently from their solution-state counterparts. Therefore, this study is important to the application of protein-based biodevices. Another aim of this dissertation is to explore a new approach to realize low voltage electrowetting without the help of oil bath. Utilizing this approach, a protein micro-separation was realized. Additionally, the interfacial properties of ionic liquid (IL) solid-like layer, which played a key role in electrowetting, was studied for further developments of IL-based applications.

Atomic Force Microscopy (AFM) was utilized in the study and played multiple roles in this …