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Sample records for applied electrochemistry prikladnaya

  1. Electrochemistry applied to biomass. Progress report, October 1980-September 1981

    SciTech Connect

    Chum, H. L.

    1982-04-01

    The electrochemical conversion of biomass-derived compounds, obtained through thermochemical pretreatments, into valuable organic chemicals, petrochemical substitutes, and energy-intensive chemicals is investigated. A hardwood-derived lignin obtained from ethanol extraction of the explosively depressurized aspen has been investigated. We have partially characterized this lignin material, and have also submitted it to electrolyses under controlled potential. The electrolytic conditions employed so far affect mainly the carbonyl groups of the ethanol-extracted steam-exploded aspen lignin. We have some evidence of demethoxylation and changed phenolic content after electrolysis. During product isolation, fractionation of the lignin occurs. The material with decreased methoxyl content may be suitable to replace phenol in phenol-formaldehyde-type resins. We are continuing these electrochemical and chemical investigations. Gel-permeation chromatography is being used to separate and characterize the several lignin fractions. In addition, we are carrying out electrolyses under more powerful reducing conditions which may lead to the cleavage of the main bonds in the lignin molecule (the ..beta..-0-4 ether linkages) producing monomeric and dimeric phenolic compounds. The electrochemistry and photoelectrochemistry of levulinic (4-oxo-pentanoic) acid, the major product of controlled degradation of cellulose by acids, have been investigated. This acid can be viewed as a major product of biomass thermochemical pretreatment or as a by-product of acid hydrolysis to fermentable sugars. Since this acid can be present in waste streams of biomass processing, we investigated the photoelectrochemical reactions of this acid on slurries composed of semiconductor/metal particles. The semiconductor investigated was undoped n-TiO/sub 2/, as anatase, anatase-rutile mixture, or rutile.

  2. Bipolar electrochemistry.

    PubMed

    Fosdick, Stephen E; Knust, Kyle N; Scida, Karen; Crooks, Richard M

    2013-09-27

    A bipolar electrode (BPE) is an electrically conductive material that promotes electrochemical reactions at its extremities (poles) even in the absence of a direct ohmic contact. More specifically, when sufficient voltage is applied to an electrolyte solution in which a BPE is immersed, the potential difference between the BPE and the solution drives oxidation and reduction reactions. Because no direct electrical connection is required to activate redox reactions, large arrays of electrodes can be controlled with just a single DC power supply or even a battery. The wireless aspect of BPEs also makes it possible to electrosynthesize and screen novel materials for a wide variety of applications. Finally, bipolar electrochemistry enables mobile electrodes, dubbed microswimmers, that are able to move freely in solution. PMID:23843205

  3. Electrochemistry, past and present

    SciTech Connect

    Stock, J.T. ); Orna, M.V. )

    1989-01-01

    This book is on electrochemistry. The authors discuss its history, development, and present status. Topics covered in this book are: foundations of electrochemistry, organic and biological electrochemistry, electroanalytical chemistry, and industrial electrochemistry.

  4. Supramolecular Electrochemistry

    NASA Astrophysics Data System (ADS)

    Kaifer, Angel E.; Gomez-Kaifer, Marielle

    1999-12-01

    This book describes the electrochemical behavior of supramolecular systems. Special emphasis will be given to the electrochemistry of host-guest complexes, monolayer and multilayer assemblies, dendrimers, and other supramolecular assemblies. A fundamental theme throughout the book is to explore the effects that supramolecular structure exerts on the thermodynamics and kinetics of electrochemical reactions. Conversely, attention will be placed to the various ways in which electrochemical or redox conversions can be utilized to control or affect the structure or properties of supramolecular systems. This first book on this topic will be of value for graduate students and advanced researchers in both electrochemistry and supramolecular chemistry.

  5. Scanning tunneling microscopy and electrochemistry

    NASA Astrophysics Data System (ADS)

    Arvía, A. J.

    1987-03-01

    The experimental gap existing between surface science and heterogeneous chemical kinetics applies also to electrochemistry. Difficulties for modelling the electrode surface topography under equilibrium and non-equilibrium conditions, particularly for solid electrodes, are presented. Attention is focussed on structural problems of metal/solution interfaces encountered in corrosion and passivation of metals and in electrocatalysis, although the analysis also extends to metal electrodeposition and to semiconductor/solution interfaces. STM has already provided important imaging of preferred oriented platinum electrode surfaces as well as large surface area platinum electrodes exhibiting practically no diffusional and ohmic polarization effects. Possible applications of STM to underpotential deposition of metals and to chemically modified electrodes are envisaged among others. Some future perspectives of STM for electrochemistry are advanced.

  6. Electrochemistry and Storage

    NASA Technical Reports Server (NTRS)

    Thaller, L. H.

    1984-01-01

    The term electrochemistry implies the use of devices that convert chemical energy into electrical energy and sometimes vice versa. These devices are usually composed of some number of individual cells that are connected together to form a battery. In the cases where these devices cannot be electrically recharged they are usually referred to as primary batteries, whereas if these batteries can be charged and recharged repeatedly, they are called secondary batteries. The past and present uses of primary and secondary batteries in aerospace applications are discussed.

  7. Electrochemistry in supercritical fluids.

    PubMed

    Branch, Jack A; Bartlett, Philip N

    2015-12-28

    A wide range of supercritical fluids (SCFs) have been studied as solvents for electrochemistry with carbon dioxide and hydrofluorocarbons (HFCs) being the most extensively studied. Recent advances have shown that it is possible to get well-resolved voltammetry in SCFs by suitable choice of the conditions and the electrolyte. In this review, we discuss the voltammetry obtained in these systems, studies of the double-layer capacitance, work on the electrodeposition of metals into high aspect ratio nanopores and the use of metallocenes as redox probes and standards in both supercritical carbon dioxide-acetonitrile and supercritical HFCs. PMID:26574527

  8. Electrochemistry in supercritical fluids

    PubMed Central

    Branch, Jack A.; Bartlett, Philip N.

    2015-01-01

    A wide range of supercritical fluids (SCFs) have been studied as solvents for electrochemistry with carbon dioxide and hydrofluorocarbons (HFCs) being the most extensively studied. Recent advances have shown that it is possible to get well-resolved voltammetry in SCFs by suitable choice of the conditions and the electrolyte. In this review, we discuss the voltammetry obtained in these systems, studies of the double-layer capacitance, work on the electrodeposition of metals into high aspect ratio nanopores and the use of metallocenes as redox probes and standards in both supercritical carbon dioxide–acetonitrile and supercritical HFCs. PMID:26574527

  9. Dynamic Electrochemistry: Methodology and Applications.

    ERIC Educational Resources Information Center

    Johnson, Dennis C.; And Others

    1984-01-01

    Reviews literature dealing with novel developments or important trends in electrochemistry. Areas examined include mass transfer, electrode kinetics, surface effects, chemically modified electrodes, coulostatic/galvanostatic methods, bioelectrochemistry, spectroelectrochemistry, and electrode instrumentation. Books, textbooks, and literature…

  10. LCEC: The Combination of Liquid Chromatography and Electrochemistry.

    ERIC Educational Resources Information Center

    Kissinger, Peter T.

    1983-01-01

    Use of combined liquid chromatography and finite-current electrochemistry (LCEC) procedures are discussed. Also discusses the relationship between electroactivity and molecular structure, selectivity in LCEC, and LCEC applications. Because of its selectivity and low detection limits, the procedures are most often applied in biomedical and…

  11. Fundamentals and applications of electrochemistry

    NASA Astrophysics Data System (ADS)

    McEvoy, A. J.

    2013-06-01

    The Voltaic pile, invented here on Lake Como 200 years ago, was a crucial step in the development of electrical engineering. For the first time a controlled and reliable source of electric current was available. The science of electrochemistry developed rapidly and is now a key contributor, not just to energy technology but also, for example, to metallurgy and industrial processes. The basic concepts of electrochemistry are presented, with the practical examples of its application in fuel cells, and with the perspective of the history of the subject.

  12. Photothermal deflection spectroscopy investigations of uranium electrochemistry

    SciTech Connect

    Rudnicki, J.D.; Russo, R.E.

    1993-12-31

    Photothermal Deflection Spectroscopy (PDS) has been successfully applied successfully applied to the study of uranium oxide electrochemistry. A brief description of PDS and preliminary results that demonstrate the technique are presented. Concentration gradients formed at the electrode surface are measured by this technique. The gradients give insight into the reaction mechanisms. There is some evidence of the initiation of non-electrochemical dissolution of the uranium oxide. Optical absorption by the uranium oxide is measured by PDS and the first results indicate that the absorption of the surface does not change during electrochemical experiments. This result is contrary to literature measurements of bulk samples that indicate that the optical absorption should be strongly changing.

  13. Factors that Prevent Learning in Electrochemistry

    ERIC Educational Resources Information Center

    Schmidt, Hans-Jurgen; Marohn, Annette; Harrison, Allan G.

    2007-01-01

    Electrochemistry plays an important role in curricula, textbooks, and in everyday life. The purpose of the present study was to identify and understand secondary-school students' problems in learning electrochemistry at an introductory chemistry level. The investigation covered four areas: (a) electrolytes, (b) transport of electric charges in…

  14. Semiconductor electrochemistry of coal pyrite

    SciTech Connect

    Osseo-Asare, K.

    1992-05-01

    This project seeks to advance the fundamental understanding of the physicochemical processes occurring at the pyrite/aqueous interface, in the context of coal cleaning, coal desulfurization, and acid mine drainage. A novel approach to the study of pyrite aqueous electrochemistry is proposed, based on the use of both synthetic and natural (i.e. coal-derived) pyrite specimens, the utilization of pyrite both in the form of micro (i.e. colloidal and subcolloidal) and macro (i.e. rotating ring disk)-electrodes, and the application of in-situ direct electroanalytical and spectroelectrochemical characterization techniques. Central to this research is the recognition that pyrite is a semiconductor material. (Photo)electrochemical experiments will be conducted to unravel the mechanisms of anodic and cathodic processes such as those associated with pyrite decomposition and the reduction of oxidants such as molecular oxygen and the ferric ion.

  15. An Effective Approach to Teaching Electrochemistry.

    ERIC Educational Resources Information Center

    Birss, Viola I.; Truax, D. Rodney

    1990-01-01

    An approach which may be useful for teaching electrochemistry in freshman college chemistry courses is presented. Discussed are the potential problems with teaching this subject and solutions provided by this approach. (CW)

  16. Ab-Initio Physics of Electrochemistry

    NASA Astrophysics Data System (ADS)

    Letchworth Weaver, Kendra; Arias, Tomás

    2010-03-01

    We present a Joint Density Functional Theory (JDFT)footnotetextS. A. Petrosyan, A. A. Rigos, and T. A. Arias, J. Phys. Chem. B, 109, 15436-15444 (2005).^,footnotetextJ. Lischner and T. A. Arias, Phys. Rev. Lett. 101, 216401 (2008). capturing the key electrostatic interactions between electronic systems and a fluid environment. This novel theory is relevant to the study of electrochemical systems and includes the dielectric properties of the fluid and charge screening due to the presence of ions in solution. We also demonstrate how DFT calculations can address the fundamental physical issues underlying electrochemistry, including the definition of a consistent reference potential, the treatment of charged surfaces under periodic boundary conditions, and the study of the solid-electrolyte interface as a function of the applied potential. Results for interfacial capacitances and potentials of zero charge calculated using these techniques will be compared to experimental values. Our theory allows simulation of a variety of materials, such as intermetallics and complex oxides, in contact with an ionic liquid environment. This method has a wide range of potential applications including catalysis in fuel cells, batteries, and photoelectrochemical cells.

  17. Electrochemistry at nanometer-sized electrodes.

    PubMed

    Chen, Shengli; Liu, Yuwen

    2014-01-14

    Electrodes of nanometer sizes provide a model approach to study the nanoscale electrochemical properties and processes, which are of fundamental and applied significance in a variety of areas including energy and environmental science, scanning probe microscopies, nanofabrication as well as electrochemistry itself. This Perspective reviews recent developments in conceptual understanding, theoretical modelling and simulation, and experimental observation of nanosize-induced properties and phenomena at interfaces between nanometer-sized electrodes and electrolytes. The aim is to provide a view on how the dimension comparability of nanoelectrodes with the electric double layer and the effective electron-tunnelling distance may raise distinct features in interfacial structure and reactivity. The strong coupling between the electrostatic field, the concentration field and the dielectric field of solvent at nanoelectrode/electrolyte interfaces is highlighted. The effects of this coupling on the voltammetric responses of nanoelectrodes are evaluated. Electron transfer kinetics at the nanoelectrode/electrolyte interface is discussed by emphasizing the inappropriateness of the Butler-Volmer (BV) and classic Marcus-Hush (MH) theories at potentials largely departing from the formal potential of the redox moieties and the importance of the long-distance electron tunnelling. The conditions for using the mathematically more straightforward BV and classic MH formalisms as an alternative to the physically more realistic but mathematically unfriendly Marcus-Hush-Chidsey model are analysed. PMID:24276332

  18. Electrochemistry "Discovery" Course for Undergraduates

    NASA Astrophysics Data System (ADS)

    May, Michael Alan; Gupta, Vijay K.

    1997-07-01

    We developed a chemistry selected topics course at Central State University, "Introduction to Laboratory Techniques in Electrochemistry" to: (1) give undergraduates hands-on experience with electrochemical measurements, (2) prepare students for summer research in Fuel Cell and Battery technology. Since students "learn by doing", the course is suitable for undergraduates from sophomore to senior levels. Students complete 6 laboratories, based on a "less is more" philosophy which emphasizes analytic and creative process rather than mandatory topical coverage. Eight electrochemical experiments are available: Construction of Zinc-Copper battery stacks, Lead Acid Battery discharge-charge cycles, Conductimetric titration of aspirin with Ammonium Hydroxide, Ion Selective Electrode determination of Fluoride in water, Cyclic Voltammetry of Potassium Ferricyanide solution, Cyclic Voltammetry of Sulfuric acid on Platinum working electrode, Anodic Stripping Voltammetry of Lead ion in solution, Differential Pulse Polarography of Lead ion in solution. Topics discussed in lecture include: chemical definitions, electrical definitions, Oxidation-Reduction reactions, Electrochemical series, Electrodes, Electrochemical Cells, direct Coulometry, electrolysis, electrochemical process efficiency, equilibrium Potentiometry, real Cell Voltages, Ion Selective Electrode types and designs, reference electrode designs, working electrode materials, pH buffers, Cyclic Voltammetry, Anodic Stripping Voltammetry, Polarography, differential pulse Polarography, and simple electrochemical instrumentation circuits.

  19. Semiconductor electrochemistry of coal pyrite

    SciTech Connect

    Osseo-Asare, K.; Wei, D.

    1993-02-01

    This project seeks to advance the fundamental understanding of the physics-chemical processes occurring at the pyrite/aqueous interface, in the context of coal cleaning, coal desulfurization, and acid minedrainage. A novel approach to the study of pyrite aqueous electrochemistry is proposed, based on the use of both synthetic and natural ( i.e. coal-derived) pyrite specimens, the utilization of.pyrite both in the form of micro (i.e. colloidal and subcolloidal) and macro (i.e. rotating ring disk) electrodes, and the application of in-situ direct electroanalytical and spectroelectrochemical characterization techniques. The kinetic study of the reaction between sulfide and ferrous ions in solution suggested that the black species formed initially is FeHS[sup +] intermediate. To farther confirm this mechanism, the experiments aimed at establishing the stoichiometry for the intermediate were carried out thermodynamically with a stopped-flow spectrophotometric technique. The results showed that the mole ratio of H[sup [minus

  20. Semiconductor electrochemistry of coal pyrite

    SciTech Connect

    Osseo-Asare, K.; Wei, D.

    1992-01-01

    Pyrite synthesis is of interest in many diverse fields, such as geology, fuel processing technology, chemistry, metallurgy, materials science, and so on. Based on fundamental studies of this process, the formation mechanisms of this important sulfide on the earth can be better understood. The studies can also help us to better understand the surface chemistry and electrochemistry of pyrite, thereby assisting in the development of more efficient processes for removal of the sulfide from coal. The work performed during this quarter focuses on the study of the reaction between aqueous sulfide ions and dissolved Fe(II) salts by using a stopped-flow spectrophotometric technique. At a wavelength of 500 mn, no absorption was observed with either aqueous sulfide or dissolved Fe(II) salt alone. However, when the two solutions were mixed, a strong absorbance appeared at the same wavelength. The absorbance-time curve showed that a black material formed at the first few seconds of the reaction, then this material decayed and changed gradually to a lighter dark material within the following several minutes. These processes were pH-dependent. It was more likely to form the black intermediate at the pH range from 7 to 8. This indicates that the reaction between Fe[sup 2+] and HS[sup [minus

  1. Computer-Animated Instruction and Students' Conceptual Change in Electrochemistry: Preliminary Qualitative Analysis

    ERIC Educational Resources Information Center

    Talib, Othman; Matthews, Robert; Secombe, Margaret

    2005-01-01

    This paper discusses the potential of applying computer-animated instruction (CAnI) as an effective conceptual change strategy in teaching electrochemistry in comparison to conventional lecture-based instruction (CLI). The core assumption in this study is that conceptual change in learners is an active, constructive process that is enhanced by the…

  2. An Audio-Tutorial Approach to the Teaching of Physical Chemistry and Electrochemistry.

    ERIC Educational Resources Information Center

    Lower, Stephen K.

    1981-01-01

    Demonstrates how audiotutorial techniques can be applied to the teaching of more advanced subjects (physical chemistry and electrochemistry), and how this can have significant affect on the overall quality of instruction and the mechanics of teaching the course. Includes a general description of audiotutorial instruction. (SK)

  3. High-speed electrochemistry using ultramicroelectrodes

    SciTech Connect

    Walsh, M.R.

    1989-01-01

    This research investigates the use of ultramicroelectrodes in performing electrochemistry on microsecond and nanosecond time scales. One purpose of this research was to look at new ways to apply ultramicroelectrodes to high speed experiments. Some of the aspects that are discussed in this thesis are: (a) A novel technique was developed for measuring currents on short time scales that involves conversion of the current to light using a light emitting diode and measuring the light intensity as a function of time using time correlated single photon counting (TCSPC). Computer processing of the light intensity data can convert this data back to current. The technique is capable of measurements on nanosecond time scales, but TCSPC requires tens or hundreds of millions of experiments to obtain a complete set of data and this frequently results in severe electrode fouling problems. (b) Potential step experiments were used instead of potential sweep experiments. Potential step experiments enable the separation in time of the faradaic and charging currents for chemical systems in which the faradaic impedance is greater than the uncompensated solution resistance. (c) For systems in which the faradaic impedance and uncompensated resistance are of the same order of magnitude, a computer simulation was developed which accounts for the interaction of the faradaic and double layer charging processes. (d) Application of short time scale experiments to the study of surface processes. Some processes studied in this work are the oxidation of clean platinum surfaces, electrode reactions of anthraquinone-2,6-disulfonic acid adsorbed on mercury, reductive hydrogen adsorption on platinum and double layer charging. (e) A study of the smallest available time constants was performed, taking into account non-idealities in the electrode such as stray capacitance and resistance of the electrode itself.

  4. A Tape-Lecture Course in Electrochemistry.

    ERIC Educational Resources Information Center

    Sheridan, P.

    1978-01-01

    Investigates the possibility of using audio-tapes for self-study courses in technical colleges. This article presents: (1) description of the electrochemistry course taught; (2) results of the assessment of student reaction to the course; and (3) conclusions. (HM)

  5. Electrochemistry in the General Chemistry Curriculum.

    ERIC Educational Resources Information Center

    Chambers, James Q.

    1983-01-01

    Outlines several ideas on introductory electrochemistry material suitable for college-level general chemistry. These include discussions of conductivity in solids and electrolytes, electrical quantities/properties, electrode potentials, and membrane potentials. Indicates that whatever strategy is used to present this material, the presentation…

  6. Seminal Publications in Electrochemistry and Electroanalysis

    NASA Astrophysics Data System (ADS)

    Scholz, Fritz; Inzelt, György; Stojek, Zbigniew

    This compilation of seminal publications in electrochemistry and electroanalysis is neither complete nor are all the listed contributions of the same importance. The authors feel that it might be of interest and very rewarding for people who use electroanalytical methods in the laboratory to go back to the roots and read some of the publications which later initiated strong developments of the science that is presented in this book. Many of the contributions to science cited here became an inherent part of textbooks and common knowledge so that the original work is usually not referred to and access to this information is difficult. The following web pages give access to much more information on the history of electrochemistry and electroanalysis:

  7. Bipolar electrochemistry for cargo-lifting in fluid channels.

    PubMed

    Loget, Gabriel; Kuhn, Alexander

    2012-05-01

    We report for the first time the vertical propulsion of conducting beads in liquid filled capillaries by bipolar electrochemistry. The beads, when exposed to an external electric field, act as bipolar electrodes showing hydroquinone oxidation on one side and proton reduction on the other side. The related asymmetric bubble generation occurring at the bottom part of the beads drives their motion. The characteristic features of the propulsion can be tuned by changing parameters such as the applied electric field or the capillary shape. Using a conical capillary, we show that a Yo-Yo type motion can be induced. The quite versatile concept can then be used for cargo-lifting and is of potential interest for microfluidic applications in LOC devices. PMID:22418898

  8. Development of an Electrochemistry Teaching Sequence Using a Phenomenographic Approach

    ERIC Educational Resources Information Center

    Rodriguez-Velazquez, Sorangel

    2013-01-01

    Electrochemistry is the area of chemistry that studies electron transfer reactions across an interface. Chemistry education researchers have acknowledged that difficulties in electrochemistry instruction arise due to the level of abstraction of the topic, lack of adequate explanations and representations found in textbooks, and a quantitative…

  9. Electrochemistry at carbon nanotubes: perspective and issues.

    PubMed

    Dumitrescu, Ioana; Unwin, Patrick R; Macpherson, Julie V

    2009-12-01

    Electrochemistry at carbon nanotubes (CNTs) is a large and growing field, but one in which there is still uncertainty about the fundamental activity of CNTs as electrode materials. On the one hand, there are many reports which focus on the favourable electrochemical properties of CNT electrodes, such as enhanced detection sensitivity, electrocatalytic effects and reduced fouling. On the other hand, other studies suggest that CNTs may be no more electroactive than graphitic powder. Furthermore, it has been proposed that the catalytic nanoparticles from which CNTs are formed may dominate the electrochemical characteristics in some instances. A considerable body of the literature presumes that the CNT sidewall is inert and that edge-plane-graphite-like open ends and defect sites are responsible for the electron transfer activity observed. In contrast, studies of well characterised single-walled nanotube (SWNT) electrodes, either as individual tubes or as two-dimensional networks, suggest sidewall activity. This review highlights how the various discrepancies in CNT electrochemistry may have arisen, by taking a historical view of the field and identifying crucial issues that still need to be solved. When assessing the behaviour of CNT electrodes, it is vitally important that careful consideration is given to the type of CNT used (SWNT or multi-walled), the quality of the material (presence of impurities), the effect of chemical processing steps in the fabrication of electrodes and the experimental arrangements adopted. Understanding these key features is an essential requirement to develop a fundamental understanding of CNT electrochemistry, to allow a wide range of electroanalytical applications, and to move the field forward rationally. As part of this process, high resolution electrochemical and electrical imaging techniques are expected to play a significant role in the future, as well as theoretical developments which examine the fundamentals of electron transfer

  10. NASA Glenn Research Center Electrochemistry Branch Overview

    NASA Technical Reports Server (NTRS)

    Manzo, Michelle A.; Hoberecht, Mark; Reid, Concha

    2010-01-01

    This presentation covers an overview of NASA Glenn's history and heritage in the development of electrochemical systems for aerospace applications. Current programs related to batteries and fuel cells are addressed. Specific areas of focus are Li-ion batteries and Polymer Electrolyte Membrane Fuel cells systems and their development for future Exploration missions. The presentation covers details of current component development efforts for high energy and ultra high energy Li-ion batteries and non-flow-through fuel cell stack and balance of plant development. Electrochemistry Branch capabilities and facilities are also addressed.

  11. Inquiry-Based Laboratory Activities in Electrochemistry: High School Students' Achievements and Attitudes

    NASA Astrophysics Data System (ADS)

    Acar Sesen, Burcin; Tarhan, Leman

    2013-02-01

    This study aimed to investigate the effects of inquiry-based laboratory activities on high school students' understanding of electrochemistry and attitudes towards chemistry and laboratory work. The participants were 62 high school students (average age 17 years) in an urban public high school in Turkey. Students were assigned to experimental ( N = 30) and control groups ( N = 32). The experimental group was taught using inquiry-based laboratory activities developed by the researchers and the control group was instructed using traditional laboratory activities. The results of the study indicated that instruction based on inquiry-based laboratory activities caused a significantly better acquisition of scientific concepts related to electrochemistry, and produced significantly higher positive attitudes towards chemistry and laboratory. In the light of the findings, it is suggested that inquiry-based laboratory activities should be developed and applied to promote students' understanding in chemistry subjects and to improve their positive attitudes.

  12. Graphene and its electrochemistry - an update.

    PubMed

    Ambrosi, Adriano; Chua, Chun Kiang; Latiff, Naziah Mohamad; Loo, Adeline Huiling; Wong, Colin Hong An; Eng, Alex Yong Sheng; Bonanni, Alessandra; Pumera, Martin

    2016-05-01

    The electrochemistry of graphene and its derivatives has been extensively researched in recent years. In the aspect of graphene preparation methods, the efficiencies of the top-down electrochemical exfoliation of graphite, the electrochemical reduction of graphene oxide and the electrochemical delamination of CVD grown graphene, are currently on par with conventional procedures. Electrochemical analysis of graphene oxide has revealed an unexpected inherent redox activity with, in some cases, an astonishing chemical reversibility. Furthermore, graphene modified with p-block elements has shown impressive electrocatalytic performances in processes which have been historically dominated by metal-based catalysts. Further progress has also been achieved in the practical usage of graphene in sensing and biosensing applications. This review is an update of our previous article in Chem. Soc. Rev. 2010, 39, 4146-4157, with special focus on the developments over the past two years. PMID:27052352

  13. Electrochemistry-based Battery Modeling for Prognostics

    NASA Technical Reports Server (NTRS)

    Daigle, Matthew J.; Kulkarni, Chetan Shrikant

    2013-01-01

    Batteries are used in a wide variety of applications. In recent years, they have become popular as a source of power for electric vehicles such as cars, unmanned aerial vehicles, and commericial passenger aircraft. In such application domains, it becomes crucial to both monitor battery health and performance and to predict end of discharge (EOD) and end of useful life (EOL) events. To implement such technologies, it is crucial to understand how batteries work and to capture that knowledge in the form of models that can be used by monitoring, diagnosis, and prognosis algorithms. In this work, we develop electrochemistry-based models of lithium-ion batteries that capture the significant electrochemical processes, are computationally efficient, capture the effects of aging, and are of suitable accuracy for reliable EOD prediction in a variety of usage profiles. This paper reports on the progress of such a model, with results demonstrating the model validity and accurate EOD predictions.

  14. Analytical Electrochemistry: Theory and Instrumentation of Dynamic Techniques.

    ERIC Educational Resources Information Center

    Johnson, Dennis C.

    1980-01-01

    Emphasizes trends in the development of six topics concerning analytical electrochemistry, including books and reviews (34 references cited), mass transfer (59), charge transfer (25), surface effects (33), homogeneous reactions (21), and instrumentation (31). (CS)

  15. Analytical Electrochemistry: Methodology and Applications of Dynamic Techniques.

    ERIC Educational Resources Information Center

    Heineman, William R.; Kissinger, Peter T.

    1980-01-01

    Reports developments involving the experimental aspects of finite and current analytical electrochemistry including electrode materials (97 cited references), hydrodynamic techniques (56), spectroelectrochemistry (62), stripping voltammetry (70), voltammetric techniques (27), polarographic techniques (59), and miscellany (12). (CS)

  16. Perspective on Electrospray Ionization and Its Relation to Electrochemistry

    NASA Astrophysics Data System (ADS)

    Pozniak, Boguslaw P.; Cole, Richard B.

    2015-03-01

    The phenomenon of electrospraying of liquids is presented from the perspective of the electrochemistry involved. Basics of current and liquid flow in the capillary and spray tip are discussed, followed by specifics of charging and discharging of the sprayed liquid surface. Fundamental theories and numerical modeling relating electrospray current to solution and spray parameters are described and then compared with our own experimentally obtained data. The method of mapping potentials and currents inside the electrospray capillary by using an inserted electrically-isolated small wire probe electrode is discussed in detail with illustrations from new and published data. Based on these experimentally obtained results, a new mathematical model is derived. The introduced "nonlinear resistor electrospray capillary model" divides the electrospray capillary into small sections, adds their contributions, and then, by transition to infinitely small section thickness, produces analytical formulas that relate current and potential maps to other properties of the electrospraying liquid: primarily conductivity and current density. The presentation of the model is undertaken from an elementary standpoint, and it offers the possibility to obtain quantitative information regarding operating parameters from typical analytical systems subjected to electrospray. The model stresses simplicity and ease of use; examples applying experimental data are shown and some predictions of the model are also presented. The developed nonlinear resistor electrospray capillary model is intended to provide a new quantitative basis for improving the understanding of electrochemical transformations occurring in the electrospray emitter. A supplemental material section gives full derivation of the model and discusses other consequences.

  17. The Mesoscopic Electrochemistry of Molecular Junctions

    NASA Astrophysics Data System (ADS)

    Bueno, Paulo R.; Benites, Tiago A.; Davis, Jason J.

    2016-01-01

    Within the context of an electron dynamic (time-dependent) perspective and a voltage driving force acting to redistribute electrons between metallic and addressable molecular states, we define here the associated electron admittance and conductance. We specifically present a mesoscopic approach to resolving the electron transfer rate associated with the electrochemistry of a redox active film tethered to metallic leads and immersed in electrolyte. The methodology is centred on aligning the lifetime of the process of electron exchange with associated resistance and capacitance quantities. Notably, however, these are no longer those empirically known as charge transfer resistance and pseudo-capacitance, but are those derived instead from a consideration of the quantum states contained in molecular films and their accessibility through a scattering region existing between them and the metallic probe. The averaged lifetime (τr) associated with the redox site occupancy is specifically dependent on scattering associated with the quantum channels linking them to the underlying metallic continuum and associated with both a quantum resistance (Rq) and an electrochemical (redox) capacitance (Cr). These are related to electron transfer rate through k = 1/τr = (RqCr)-1. The proposed mesoscopic approach is consistent with Marcus’s (electron transfer rate) theory and experimental measurements obtained by capacitance spectroscopy.

  18. The Mesoscopic Electrochemistry of Molecular Junctions

    PubMed Central

    Bueno, Paulo R.; Benites, Tiago A.; Davis, Jason J.

    2016-01-01

    Within the context of an electron dynamic (time-dependent) perspective and a voltage driving force acting to redistribute electrons between metallic and addressable molecular states, we define here the associated electron admittance and conductance. We specifically present a mesoscopic approach to resolving the electron transfer rate associated with the electrochemistry of a redox active film tethered to metallic leads and immersed in electrolyte. The methodology is centred on aligning the lifetime of the process of electron exchange with associated resistance and capacitance quantities. Notably, however, these are no longer those empirically known as charge transfer resistance and pseudo-capacitance, but are those derived instead from a consideration of the quantum states contained in molecular films and their accessibility through a scattering region existing between them and the metallic probe. The averaged lifetime (τr) associated with the redox site occupancy is specifically dependent on scattering associated with the quantum channels linking them to the underlying metallic continuum and associated with both a quantum resistance (Rq) and an electrochemical (redox) capacitance (Cr). These are related to electron transfer rate through k = 1/τr = (RqCr)−1. The proposed mesoscopic approach is consistent with Marcus’s (electron transfer rate) theory and experimental measurements obtained by capacitance spectroscopy. PMID:26757677

  19. Tungsten Oxides for Photocatalysis, Electrochemistry, and Phototherapy.

    PubMed

    Huang, Zhen-Feng; Song, Jiajia; Pan, Lun; Zhang, Xiangwen; Wang, Li; Zou, Ji-Jun

    2015-09-23

    The conversion, storage, and utilization of renewable energy have all become more important than ever before as a response to ever-growing energy and environment concerns. The performance of energy-related technologies strongly relies on the structure and property of the material used. The earth-abundant family of tungsten oxides (WOx ≤3 ) receives considerable attention in photocatalysis, electrochemistry, and phototherapy due to their highly tunable structures and unique physicochemical properties. Great breakthroughs have been made in enhancing the optical absorption, charge separation, redox capability, and electrical conductivity of WOx ≤3 through control of the composition, crystal structure, morphology, and construction of composite structures with other materials, which significantly promotes the efficiency of processes and devices based on this material. Herein, the properties and synthesis of WOx ≤3 family are reviewed, and then their energy-related applications are highlighted, including solar-light-driven water splitting, CO2 reduction, and pollutant removal, electrochromism, supercapacitors, lithium batteries, solar and fuel cells, non-volatile memory devices, gas sensors, and cancer therapy, from the aspect of function-oriented structure design and control. PMID:26287959

  20. Exploiting plug-and-play electrochemistry for drug discovery.

    PubMed

    Gao, Lixia; Teng, Yong

    2016-04-01

    Electrochemistry has emerged as a powerful analytical technique for chemical analysis of living cells, biologically active molecules and metabolites. Electrochemical biosensor, microfluidics and mass spectrometry are the most frequently used methods for electrochemical detection and monitory, which comprise a collection of extremely useful measurement tools for various fields of biology and medicine. Most recently, electrochemistry has been shown to be coupled with nanotechnology and genetic engineering to generate new enabling technologies, providing rapid, selective, and sensitive detection and diagnosis platforms. The primary focus of this review is to highlight the utility of electrochemical strategies and their conjunction with other approaches for drug metabolism and discovery. Current challenges and possible future developments and applications of electrochemistry in drug studies are also discussed. PMID:27079543

  1. Chelating ionic liquids for reversible zinc electrochemistry.

    PubMed

    Kar, Mega; Winther-Jensen, Bjorn; Forsyth, Maria; MacFarlane, Douglas R

    2013-05-21

    Advanced, high energy-density, metal-air rechargeable batteries, such as zinc-air, are of intense international interest due to their important role in energy storage applications such as electric and hybrid vehicles, and to their ability to deal with the intermittency of renewable energy sources such as solar and wind. Ionic liquids offer a number of ideal thermal and physical properties as potential electrolytes in such large-scale energy storage applications. We describe here the synthesis and characterisation of a family of novel "chelating" ILs designed to chelate and solubilize the zinc ions to create electrolytes for this type of battery. These are based on quaternary alkoxy alkyl ammonium cations of varying oligo-ether side chains and anions such as p-toluene sulfonate, bis(trifluoromethylsulfonyl)amide and dicyanoamides. This work shows that increasing the ether chain length in the cation from two to four oxygens can increase the ionic conductivity and reduce the melting point from 67 °C to 15 °C for the tosylate system. Changing the anion also plays a significant role in the nature of the zinc deposition electrochemistry. We show that zinc can be reversibly deposited from [N(222(20201))][NTf2] and [N(222(202020201))][NTf2] beginning at -1.4 V and -1.7 V vs. SHE, respectively, but not in the case of tosylate based ILs. This indicates that the [NTf2] is a weaker coordinating anion with the zinc cation, compared to the tosylate anion, allowing the coordination of the ether chain to dominate the behavior of the deposition and stripping of zinc ions. PMID:23558696

  2. Electrochemistry, biosensors and microfluidics: a convergence of fields.

    PubMed

    Rackus, Darius G; Shamsi, Mohtashim H; Wheeler, Aaron R

    2015-08-01

    Electrochemistry, biosensors and microfluidics are popular research topics that have attracted widespread attention from chemists, biologists, physicists, and engineers. Here, we introduce the basic concepts and recent histories of electrochemistry, biosensors, and microfluidics, and describe how they are combining to form new application-areas, including so-called "point-of-care" systems in which measurements traditionally performed in a laboratory are moved into the field. We propose that this review can serve both as a useful starting-point for researchers who are new to these topics, as well as being a compendium of the current state-of-the art for experts in these evolving areas. PMID:25962356

  3. Development of an Electrochemistry Teaching Sequence using a Phenomenographic Approach

    NASA Astrophysics Data System (ADS)

    Rodriguez-Velazquez, Sorangel

    Electrochemistry is the area of chemistry that studies electron transfer reactions across an interface. Chemistry education researchers have acknowledged that difficulties in electrochemistry instruction arise due to the level of abstraction of the topic, lack of adequate explanations and representations found in textbooks, and a quantitative emphasis in the application of concepts. Studies have identified conceptions (also referred to as misconceptions, alternative conceptions, etc.) about the electrochemical process that transcends academic and preparation levels (e.g., students and instructors) as well as cultural and educational settings. Furthermore, conceptual understanding of the electrochemical process requires comprehension of concepts usually studied in physics such as electric current, resistance and potential and often neglected in introductory chemistry courses. The lack of understanding of physical concepts leads to students. conceptions with regards to the relation between the concepts of redox reactions and electric circuits. The need for instructional materials to promote conceptual understanding of the electrochemical process motivated the development of the electrochemistry teaching sequence presented in this dissertation. Teaching sequences are educational tools that aim to bridge the gap between student conceptions and the scientific acceptable conceptions that instructors expect students to learn. This teaching sequence explicitly addresses known conceptions in electrochemistry and departs from traditional instruction in electrochemistry to reinforce students. previous knowledge in thermodynamics providing the foundation for the explicit relation of redox reactions and electric circuits during electrochemistry instruction. The scientific foundations of the electrochemical process are explained based on the Gibbs free energy (G) involved rather than on the standard redox potential values (E° ox/red) of redox half-reactions. Representations of

  4. Humidity Effect on Nanoscale Electrochemistry in Solid Silver Ion Conductors and the Dual Nature of Its Locality

    SciTech Connect

    Yang, Sangmo; Strelcov, Evgheni; Paranthaman, Mariappan Parans; Tselev, Alexander; Noh, Tae Won; Kalinin, Sergei V.

    2015-01-07

    Scanning probe microscopy (SPM) is a powerful tool to investigate electrochemistry in nanoscale volumes. While most SPM-based studies have focused on reactions at the tip-surface junction, charge and mass conservation requires coupled and intrinsically non-local cathodic and anodic processes that can be significantly affected by ambient humidity. Here, we explore the role of water in both cathodic and anodic processes, associated charge transport, and topographic volume changes depending on the polarity of tip bias. The first-order reversal curve current-voltage technique combined with simultaneous detection of the sample topography, referred to as FORC-IVz, was applied to a silver solid ion conductor. We found that the protons generated from water affect silver ionic conduction, silver particle formation and dissolution, and mechanical integrity of the material. This work highlights the dual nature (simultaneously local and non-local) of electrochemical SPM studies, which should be considered for comprehensive understanding of nanoscale electrochemistry.

  5. Conceptual difficulties experienced by senior high school students of electrochemistry: Electrochemical (galvanic) and electrolytic cells

    NASA Astrophysics Data System (ADS)

    Garnett, Pamela J.; Treagust, David F.

    This research investigated students' understanding of electrochemistry following a 7-9-week course of instruction. A list of conceptual and propositional knowledge statements was formulated, and this provided the framework for semistructured interviews that were conducted with 32 students in their final year of high school chemistry, following instruction in electrochemistry. Three misconceptions identified in this study and five which have been reported earlier are incorporated into an alternative framework about electric current. The framework is grounded on the notion that a current always involves drifting electrons, even in solution. Another area where students' misconceptions were prevalent was in relation to the sign of the anode and cathode. Students who thought the anode was negatively charged believed cations would move toward it, and those who thought it was positively charged were unable to explain why electrons move away from it. Electrolytic cells also proved troublesome for students. Many students did not associate the positions of the anode and cathode with the polarity of the applied electromotive force (e.m.f.). Other students attempted to reverse features of electrochemical cells and apply the reversals to electrolytic cells. The implications of the research relate to students' interpretation of the language that is used to describe scientific phenomena and the tendency for students to overgeneralize, due to comments made by teachers or statements in textbooks.

  6. (The latest developments of the physical aspects of electrochemistry)

    SciTech Connect

    Liu, S.H.

    1990-09-24

    The author was one of 26 invited lecturers to discuss the latest developments of the physical aspects of electrochemistry. He interacted extensively with other lecturers and many participants from developing countries. He also visited with the Director of the Italian Synchrotron Radiation Source now under construction in Trieste, Italy.

  7. Facilitating Conceptual Change in Students' Understanding of Electrochemistry.

    ERIC Educational Resources Information Center

    Niaz, Mansoor

    2002-01-01

    Constructs a teaching strategy to facilitate conceptual change in freshman students' understanding of electrochemistry. Provides students with the correct response along with alternative responses (teaching experiments), producing a conflicting situation that is conducive to an equilibration of their cognitive structures. Concludes that the…

  8. Using a Teaching Model To Correct Known Misconceptions in Electrochemistry.

    ERIC Educational Resources Information Center

    Huddle, Penelope Ann; White, Margaret Dawn; Rogers, Fiona

    2000-01-01

    Describes a concrete teaching model designed to eliminate students' misconceptions about current flow in electrochemistry. The model uses a semi-permeable membrane rather than a salt bridge to complete the circuit and demonstrate the maintenance of cell neutrality. Concludes that use of the model led to improvement in students' understanding at…

  9. Understanding Electrochemistry Concepts Using the Predict-Observe-Explain Strategy

    ERIC Educational Resources Information Center

    Karamustafaoglu, Sevilay; Mamlok-Naaman, Rachel

    2015-01-01

    The current study deals with freshman students who study at the Department of Science at the Faculty of Education. The aim of the study was to investigate the effect of teaching electrochemistry concepts using Predict-Observe-Explain (POE) strategy. The study was quasi-experimental design using 20 students each in the experimental group (EG) and…

  10. Common Student Misconceptions in Electrochemistry: Galvanic, Electrolytic, and Concentration Cells.

    ERIC Educational Resources Information Center

    Sanger, Michael J.; Greenbowe, Thomas J.

    1997-01-01

    Investigates student (N=16) misconceptions concerning electrochemistry related to galvanic, electrolytic, and concentration cells. Findings indicate that most students demonstrating misconceptions were still able to calculate cell potentials correctly. Discusses common misconceptions and possible sources of these. Contains 33 references.…

  11. Alleviating the Common Confusion Caused by Polarity in Electrochemistry.

    ERIC Educational Resources Information Center

    Moran, P. J.; Gileadi, E.

    1989-01-01

    Discussed is some of the confusion encountered in electrochemistry due to misunderstandings of sign conventions and simple mathematical errors. Clarified are issues involving emf series, IUPAC sign conventions, calculation of cell potentials, reference electrodes, the polarity of electrodes in electrochemical devices, and overpotential. (CW)

  12. Scanning thermo-ionic microscopy for probing local electrochemistry at the nanoscale

    NASA Astrophysics Data System (ADS)

    Eshghinejad, Ahmadreza; Nasr Esfahani, Ehsan; Wang, Peiqi; Xie, Shuhong; Geary, Timothy C.; Adler, Stuart B.; Li, Jiangyu

    2016-05-01

    Conventional electrochemical characterization techniques based on voltage and current measurements only probe faradaic and capacitive rates in aggregate. In this work we develop a scanning thermo-ionic microscopy (STIM) to probe local electrochemistry at the nanoscale, based on imaging of Vegard strain induced by thermal oscillation. It is demonstrated from both theoretical analysis and experimental validation that the second harmonic response of thermally induced cantilever vibration, associated with thermal expansion, is present in all solids, whereas the fourth harmonic response, caused by local transport of mobile species, is only present in ionic materials. The origin of STIM response is further confirmed by its reduced amplitude with respect to increased contact force, due to the coupling of stress to concentration of ionic species and/or electronic defects. The technique has been applied to probe Sm-doped Ceria and LiFePO4, both of which exhibit higher concentrations of mobile species near grain boundaries. The STIM gives us a powerful method to study local electrochemistry with high sensitivity and spatial resolution for a wide range of ionic systems, as well as ability to map local thermomechanical response.

  13. Conceptual design and experiments of electrochemistry-flushing technology for the remediation of historically Cr(Ⅵ)-contaminated soil.

    PubMed

    Li, Dong; Sun, Delin; Hu, Siyang; Hu, Jing; Yuan, Xingzhong

    2016-02-01

    A conceptual design and experiments, electrochemistry-flushing (E-flushing), using electrochemistry to enhance flushing efficiency for the remediation of Cr(Ⅵ)-contaminated soil is presented. The rector contained three compartments vertically superposed. The upper was airtight cathode compartment containing an iron-cathode. The middle was soil layer. The bottom was anode compartment containing an iron-anode and connected to a container by circulation pumps. H2 and OH(-) ions were produced at cathode. H2 increased the gas pressure in cathode compartment and drove flushing solution into soil layer forming flushing process. OH(-) ions entered into soil layer by eletromigration and hydraulic flow to enhance the desorption of Cr(Ⅵ). High potential gradient was applied to accelerate the electromigration of desorbed Cr(Ⅵ) ions and produced joule heat to increase soil temperature to enhance Cr(Ⅵ) desorption. In anode compartment, Fe(2+) ions produced at iron-anode reduced the desorbed Cr(Ⅵ) into Cr(3+) ions, which reacted with OH(-) ions forming Cr(OH)3. Experimental results show that Cr(Ⅵ) removal efficiency of E-flushing experiments was more than double of flushing experiments and reached the maximum of removal efficiency determined by desorption kinetics. All electrochemistry processes were positively used in E-flushing technology. PMID:26539706

  14. Electrochemistry of dioxygen in lithium-air batteries

    NASA Astrophysics Data System (ADS)

    Hardwick, Laurence

    2014-03-01

    The non-aqueous lithium-oxygen battery is one of a host of emerging opportunities available for enhanced energy storage. Unlike a conventional battery where the reagents are contained within the cell, the lithium-oxygen cell uses dioxygen from the atmosphere to electrochemically form the discharge product lithium peroxide. Degrees of reversible oxidation and formation of lithium peroxide has been demonstrated in a number of non-aqueous electrolyte classes, mostly notably in dimethysulfoxide based electrolytes, thus making the lithium-oxygen cell a potential energy storage device. This talk will present our groups recent results of the electrochemistry of dioxygen in non-aqueous electrolytes, of which particular electrolytes could have practical application within a lithium-oxygen cell. Discussion will touch upon how the electrochemistry can be related to electrode substrate and will be presented with in situ spectroscopic studies that identify intermediate and surface species during the oxygen reduction reaction. Support from the EPSRC is gratefully acknowledged

  15. Strain Engineering to Modify the Electrochemistry of Energy Storage Electrodes.

    PubMed

    Muralidharan, Nitin; Carter, Rachel; Oakes, Landon; Cohn, Adam P; Pint, Cary L

    2016-01-01

    Strain engineering has been a critical aspect of device design in semiconductor manufacturing for the past decade, but remains relatively unexplored for other applications, such as energy storage. Using mechanical strain as an input parameter to modulate electrochemical potentials of metal oxides opens new opportunities intersecting fields of electrochemistry and mechanics. Here we demonstrate that less than 0.1% strain on a Ni-Ti-O based metal-oxide formed on superelastic shape memory NiTi alloys leads to anodic and cathodic peak potential shifts by up to ~30 mV in an electrochemical cell. Moreover, using the superelastic properties of NiTi to enable strain recovery also recovers the electrochemical potential of the metal oxide, providing mechanistic evidence of strain-modified electrochemistry. These results indicate that mechanical energy can be coupled with electrochemical systems to efficiently design and optimize a new class of strain-modulated energy storage materials. PMID:27283872

  16. Strain Engineering to Modify the Electrochemistry of Energy Storage Electrodes

    NASA Astrophysics Data System (ADS)

    Muralidharan, Nitin; Carter, Rachel; Oakes, Landon; Cohn, Adam P.; Pint, Cary L.

    2016-06-01

    Strain engineering has been a critical aspect of device design in semiconductor manufacturing for the past decade, but remains relatively unexplored for other applications, such as energy storage. Using mechanical strain as an input parameter to modulate electrochemical potentials of metal oxides opens new opportunities intersecting fields of electrochemistry and mechanics. Here we demonstrate that less than 0.1% strain on a Ni-Ti-O based metal-oxide formed on superelastic shape memory NiTi alloys leads to anodic and cathodic peak potential shifts by up to ~30 mV in an electrochemical cell. Moreover, using the superelastic properties of NiTi to enable strain recovery also recovers the electrochemical potential of the metal oxide, providing mechanistic evidence of strain-modified electrochemistry. These results indicate that mechanical energy can be coupled with electrochemical systems to efficiently design and optimize a new class of strain-modulated energy storage materials.

  17. Strain Engineering to Modify the Electrochemistry of Energy Storage Electrodes

    PubMed Central

    Muralidharan, Nitin; Carter, Rachel; Oakes, Landon; Cohn, Adam P.; Pint, Cary L.

    2016-01-01

    Strain engineering has been a critical aspect of device design in semiconductor manufacturing for the past decade, but remains relatively unexplored for other applications, such as energy storage. Using mechanical strain as an input parameter to modulate electrochemical potentials of metal oxides opens new opportunities intersecting fields of electrochemistry and mechanics. Here we demonstrate that less than 0.1% strain on a Ni-Ti-O based metal-oxide formed on superelastic shape memory NiTi alloys leads to anodic and cathodic peak potential shifts by up to ~30 mV in an electrochemical cell. Moreover, using the superelastic properties of NiTi to enable strain recovery also recovers the electrochemical potential of the metal oxide, providing mechanistic evidence of strain-modified electrochemistry. These results indicate that mechanical energy can be coupled with electrochemical systems to efficiently design and optimize a new class of strain-modulated energy storage materials. PMID:27283872

  18. Synthesis, Electrochemistry, and Photophysics of Aza-BODIPY Porphyrin Dyes.

    PubMed

    Pascal, Simon; Bucher, Léo; Desbois, Nicolas; Bucher, Christophe; Andraud, Chantal; Gros, Claude P

    2016-03-24

    The synthesis of dyad and triad aza-BODIPY-porphyrin systems in two steps starting from an aryl-substituted aza-BODIPY chromophore is described. The properties of the resulting aza-BODIPY-porphyrin conjugates have been extensively investigated by means of electrochemistry, spectroelectrochemistry, and absorption/emission spectroscopy. Fluorescence measurements have revealed a dramatic loss of luminescence intensity, mainly due to competitive energy transfer and photoinduced electron transfer involving charge separation followed by recombination. PMID:26938146

  19. Solvolysis, Electrochemistry, and Development of Synthetic Building Blocks from Sawdust.

    PubMed

    Nguyen, Bichlien H; Perkins, Robert J; Smith, Jake A; Moeller, Kevin D

    2015-12-18

    Either aldehyde or cinnamyl ether products can be selectively extracted from raw sawdust by controlling the temperature and pressure of a solvolysis reaction. These materials have been used as platform chemicals for the synthesis of 15 different synthetic substrates. The conversion of the initial sawdust-derived materials into electron-rich aryl substrates often requires the use of oxidation and reduction chemistry, and the role electrochemistry can play as a sustainable method for these transformations has been defined. PMID:26544912

  20. Solvents' Critical Role in Nonaqueous Lithium-Oxygen Battery Electrochemistry.

    PubMed

    McCloskey, B D; Bethune, D S; Shelby, R M; Girishkumar, G; Luntz, A C

    2011-05-19

    Among the many important challenges facing the development of Li-air batteries, understanding the electrolyte's role in producing the appropriate reversible electrochemistry (i.e., 2Li(+) + O2 + 2e(-) ↔ Li2O2) is critical. Quantitative differential electrochemical mass spectrometry (DEMS), coupled with isotopic labeling of oxygen gas, was used to study Li-O2 electrochemistry in various solvents, including carbonates (typical Li ion battery solvents) and dimethoxyethane (DME). In conjunction with the gas-phase DEMS analysis, electrodeposits formed during discharge on Li-O2 cell cathodes were characterized using ex situ analytical techniques, such as X-ray diffraction and Raman spectroscopy. Carbonate-based solvents were found to irreversibly decompose upon cell discharge. DME-based cells, however, produced mainly lithium peroxide on discharge. Upon cell charge, the lithium peroxide both decomposed to evolve oxygen and oxidized DME at high potentials. Our results lead to two conclusions; (1) coulometry has to be coupled with quantitative gas consumption and evolution data to properly characterize the rechargeability of Li-air batteries, and (2) chemical and electrochemical electrolyte stability in the presence of lithium peroxide and its intermediates is essential to produce a truly reversible Li-O2 electrochemistry. PMID:26295320

  1. Environmental management/pollution prevention/environmental electrochemistry opportunities

    SciTech Connect

    Nosenchuck, N.H.

    1994-12-31

    Thank you for inviting me to be your keynoter. I`m impressed by what you`ve accomplished through the years and the program that you`ve put together for this International Forum on Environmental Electrochemistry. Above all, we must remember what has brought us together. We must be aware of the challenge, the need, the opportunity we have before us. Sustainable economic development that is responsive to environmental concerns is vital to continued national prosperity. Coincidentally, there are boundless environmental electrochemistry opportunities in environmental management and pollution prevention. The basic approach to environmental protection in this country, for far too many years, has been, for the most part, reactive. As a society, we react to crisis; and in the environmental business, we react to environmental crisis. We react to problems that already were posing substantial ecological and human health risks and problems that already were causing significant public concern. We need both a quality and results-oriented national environmental electrochemistry program.

  2. Development of an Electrochemistry Teaching Sequence using a Phenomenographic Approach

    NASA Astrophysics Data System (ADS)

    Rodriguez-Velazquez, Sorangel

    Electrochemistry is the area of chemistry that studies electron transfer reactions across an interface. Chemistry education researchers have acknowledged that difficulties in electrochemistry instruction arise due to the level of abstraction of the topic, lack of adequate explanations and representations found in textbooks, and a quantitative emphasis in the application of concepts. Studies have identified conceptions (also referred to as misconceptions, alternative conceptions, etc.) about the electrochemical process that transcends academic and preparation levels (e.g., students and instructors) as well as cultural and educational settings. Furthermore, conceptual understanding of the electrochemical process requires comprehension of concepts usually studied in physics such as electric current, resistance and potential and often neglected in introductory chemistry courses. The lack of understanding of physical concepts leads to students. conceptions with regards to the relation between the concepts of redox reactions and electric circuits. The need for instructional materials to promote conceptual understanding of the electrochemical process motivated the development of the electrochemistry teaching sequence presented in this dissertation. Teaching sequences are educational tools that aim to bridge the gap between student conceptions and the scientific acceptable conceptions that instructors expect students to learn. This teaching sequence explicitly addresses known conceptions in electrochemistry and departs from traditional instruction in electrochemistry to reinforce students. previous knowledge in thermodynamics providing the foundation for the explicit relation of redox reactions and electric circuits during electrochemistry instruction. The scientific foundations of the electrochemical process are explained based on the Gibbs free energy (G) involved rather than on the standard redox potential values (E° ox/red) of redox half-reactions. Representations of

  3. 2010 ELECTROCHEMISTRY GRC, JANUARY 9-15, 2010, VENTURA, CA

    SciTech Connect

    Stephen Creager

    2010-12-31

    Electrochemical science plays a crucial role in many important technologies and is intimately involved in many natural phenomena. Several new Gordon Research Conferences have appeared recently that are dedicated to electrochemical technologies, however electrochemistry as a discipline continues to thrive and provide the underpinnings of these technologies. The 2010 Electrochemistry GRC will focus on a wide range of fundamental electrochemical phenomena and materials and on their application in areas involving energy storage, information storage, chemical analysis, and motion actuation. The meeting will include sessions dedicated to the following specific topics: electrochemical energy storage (e.g. batteries; at least two sessions); electrochemical motion actuation (e.g. electrokinesis); electrocatalysis; electrochemistry in digital information storage; and bioelectrochemistry (including bioanalysis). An Open Session devoted to highlighting the activities of {approx}10 young investigators and non-North American visitors via brief 10-minute talks, and two open poster sessions highlighting the contributions of approximately 60 conference participants including graduate students, will be held. Altogether the conference is expected to include approximately 90 presentations. As has been the case in the recent past, the meeting will bring together participants from academia, national labs, and the private sector, including senior and junior-level scientists, postdoctoral scientists, and graduate students for informal interactions and exchange of ideas. An affiliated Gordon-Kenan Research Seminar (GRS) will also be held with the conference. Special efforts will be made to invite participation from members of underrepresented groups.

  4. A Conceptual Change Teaching Strategy To Facilitate High School Students' Understanding of Electrochemistry.

    ERIC Educational Resources Information Center

    Niaz, Mansoor; Chacon, Eleazar

    2003-01-01

    Describes a study that used a teaching strategy based on two teaching experiments which could facilitate students' conceptual understanding of electrochemistry. Involves two sections (n=29 and n=28) of 10th grade high school students in Venezuela. Concludes that the teaching experiments facilitated student understanding of electrochemistry.…

  5. Electrospray ion source with reduced analyte electrochemistry

    DOEpatents

    Kertesz, Vilmos; Van Berkel, Gary J

    2013-07-30

    An electrospray ion (ESI) source and method capable of ionizing an analyte molecule without oxidizing or reducing the analyte of interest. The ESI source can include an emitter having a liquid conduit, a working electrode having a liquid contacting surface, a spray tip, a secondary working electrode, and a charge storage coating covering partially or fully the liquid contacting surface of the working electrode. The liquid conduit, the working electrode and the secondary working electrode can be in liquid communication. The electrospray ion source can also include a counter electrode proximate to, but separated from, said spray tip. The electrospray ion source can also include a power system for applying a voltage difference between the working electrodes and a counter-electrode. The power system can deliver pulsed voltage changes to the working electrodes during operation of said electrospray ion source to minimize the surface potential of the charge storage coating.

  6. Electrochemistry of Graphene Edge Embedded Nanopores

    NASA Astrophysics Data System (ADS)

    Banerjee, Shouvik; Shim, Jiwook; Rivera, Jose; Jin, Xiaozhong; Estrada, David; Solovyeva, Vita; You, Xiuque; Pak, James; Pop, Eric; Aluru, Narayana; Bashir, Rashid

    2013-03-01

    We demonstrate a stacked graphene- Al2O3 dielectric nanopore architecture to investigate electrochemical activity at graphene edges. It has proven to be difficult to isolate electrochemical activity at the graphene edges from those at the basal planes. We use 24 nm of Al2O3 to isolate the graphene basal planes from an ionic fluid environment. Nanopores ranging from 5 to 20 nm are formed by an electron beam sculpting process to expose graphene edges. Electrochemical measurements at isolated graphene edges show current densities as high as 1.2 x 104 A/cm2, 300x greater than those reported for carbon nanotubes. Additionally, we modulate nanopore conductance by tuning the graphene edge electrochemical current as a function of the applied bias on the embedded graphene electrode. Our results indicate that electrochemical devices based on graphene nanopores have promising applications as sensitive chemical and biological sensors, energy storage devices, and DNA sequencing.

  7. Electrospray ion source with reduced analyte electrochemistry

    DOEpatents

    Kertesz, Vilmos [Knoxville, TN; Van Berkel, Gary [Clinton, TN

    2011-08-23

    An electrospray ion (ESI) source and method capable of ionizing an analyte molecule without oxidizing or reducing the analyte of interest. The ESI source can include an emitter having a liquid conduit, a working electrode having a liquid contacting surface, a spray tip, a secondary working electrode, and a charge storage coating covering partially or fully the liquid contacting surface of the working electrode. The liquid conduit, the working electrode and the secondary working electrode can be in liquid communication. The electrospray ion source can also include a counter electrode proximate to, but separated from, said spray tip. The electrospray ion source can also include a power system for applying a voltage difference between the working electrodes and a counter-electrode. The power system can deliver pulsed voltage changes to the working electrodes during operation of said electrospray ion source to minimize the surface potential of the charge storage coating.

  8. Mesomorphism and electrochemistry of thienoviologen liquid crystals.

    PubMed

    Cospito, S; Beneduci, A; Veltri, L; Salamonczyk, M; Chidichimo, G

    2015-07-21

    The thienoviologen series 4,4'-(2,2'-bithiophene-5,5'-diyl)bis(1-alkylpridinium)X2, with = counterion is a new class of electron acceptor materials which show very interesting electrochromic and electrofluorescence properties. Depending on the length, m, of the promesogenic alkyl chains, and on the counterion, thienoviologens might become liquid crystals. Here, we present the mesomorphic behaviour, and the electrochemical and spectroelectrochemical properties in solution of new thienoviologens of the series and (I = iodide; NTf2(-) = bis(tri-fuoromethylsulfonyl)imide) with m = 8, 12. Interestingly, we found that only the compounds are liquid crystals, exhibiting a calamitic behaviour in contrast to the homologous compounds of the series with m = 9-11 and X = NTf2(-), which showed columnar rectangular mesophases. The electrochemical study here reported allowed us to explain for the first time the anomalous behaviour of these thienoviologens already observed in cyclic voltammetry, where two apparently irreversible redox processes occur. This can be explained by a comproportionation reaction in which the neutral species rapidly reduces the dication to the radical-cation, due to its strong reducing power. Electrochemical reduction of the thienoviologens causes electrochromism since a new absorption band, occurring at 660 nm in the electronic spectra, appears with the negative potential bias applied. With a LUMO level of 3.64 eV, similar to those of the C60 and of other n-type materials, these compounds can find applications in several electronics devices, where their liquid crystalline properties can be used to control film morphology and geometry, provided they have good electron mobility. PMID:26082287

  9. Construction and direct electrochemistry of orientation controlled laccase electrode

    SciTech Connect

    Li, Ying; Zhang, Jiwei; Huang, Xirong; Wang, Tianhong

    2014-03-28

    Highlights: • A recombinant laccase with Cys-6×His tag at the N or C terminus was generated. • Orientation controlled laccase electrodes were constructed via self assembly. • The electrochemical behavior of laccase electrodes was orientation dependent. • The C terminus tagged laccase was better for bioelectrocatalytic reduction of O{sub 2}. - Abstract: A laccase has multiple redox centres. Chemisorption of laccases on a gold electrode through a polypeptide tag introduced at the protein surface provides an isotropic orientation of laccases on the Au surface, which allows the orientation dependent study of the direct electrochemistry of laccase. In this paper, using genetic engineering technology, two forms of recombinant laccase which has Cys-6×His tag at the N or C terminus were generated. Via the Au-S linkage, the recombinant laccase was assembled orientationally on gold electrode. A direct electron transfer and a bioelectrocatalytic activity toward oxygen reduction were observed on the two orientation controlled laccase electrodes, but their electrochemical behaviors were found to be quite different. The orientation of laccase on the gold electrode affects both the electron transfer pathway and the electron transfer efficiency of O{sub 2} reduction. The present study is helpful not only to the in-depth understanding of the direct electrochemistry of laccase, but also to the development of laccase-based biofuel cells.

  10. Bipolar electrochemistry: from materials science to motion and beyond.

    PubMed

    Loget, Gabriel; Zigah, Dodzi; Bouffier, Laurent; Sojic, Neso; Kuhn, Alexander

    2013-11-19

    Bipolar electrochemistry, a phenomenon which generates an asymmetric reactivity on the surface of conductive objects in a wireless manner, is an important concept for many purposes, from analysis to materials science as well as for the generation of motion. Chemists have known the basic concept for a long time, but it has recently attracted additional attention, especially in the context of micro- and nanoscience. In this Account, we introduce the fundamentals of bipolar electrochemistry and illustrate its recent applications, with a particular focus on the fields of materials science and dynamic systems. Janus particles, named after the Roman god depicted with two faces, are currently in the heart of many original investigations. These objects exhibit different physicochemical properties on two opposite sides. This makes them a unique class of materials, showing interesting features. They have received increasing attention from the materials science community, since they can be used for a large variety of applications, ranging from sensing to photosplitting of water. So far the great majority of methods developed for the generation of Janus particles breaks the symmetry by using interfaces or surfaces. The consequence is often a low time-space yield, which limits their large scale production. In this context, chemists have successfully used bipolar electrodeposition to break the symmetry. This provides a single-step technique for the bulk production of Janus particles with a high control over the deposit structure and morphology, as well as a significantly improved yield. In this context, researchers have used the bipolar electrodeposition of molecular layers, metals, semiconductors, and insulators at one or both reactive poles of bipolar electrodes to generate a wide range of Janus particles with different size, composition and shape. In using bipolar electrochemistry as a driving force for generating motion, its intrinsic asymmetric reactivity is again the

  11. Humidity Effect on Nanoscale Electrochemistry in Solid Silver Ion Conductors and the Dual Nature of Its Locality

    DOE PAGESBeta

    Yang, Sangmo; Strelcov, Evgheni; Paranthaman, Mariappan Parans; Tselev, Alexander; Noh, Tae Won; Kalinin, Sergei V.

    2015-01-07

    Scanning probe microscopy (SPM) is a powerful tool to investigate electrochemistry in nanoscale volumes. While most SPM-based studies have focused on reactions at the tip-surface junction, charge and mass conservation requires coupled and intrinsically non-local cathodic and anodic processes that can be significantly affected by ambient humidity. Here, we explore the role of water in both cathodic and anodic processes, associated charge transport, and topographic volume changes depending on the polarity of tip bias. The first-order reversal curve current-voltage technique combined with simultaneous detection of the sample topography, referred to as FORC-IVz, was applied to a silver solid ion conductor.more » We found that the protons generated from water affect silver ionic conduction, silver particle formation and dissolution, and mechanical integrity of the material. This work highlights the dual nature (simultaneously local and non-local) of electrochemical SPM studies, which should be considered for comprehensive understanding of nanoscale electrochemistry.« less

  12. Single-crystal-like NiO colloidal nanocrystal-aggregated microspheres with mesoporous structure: Synthesis and enhanced electrochemistry, photocatalysis and water treatment properties

    SciTech Connect

    Suo, Zhirong; Dong, Xiaonan; Liu, Hui

    2013-10-15

    A new microwave-assisted hydrothermal synthetic route based on the self-assembly and subsequently controlled thermal decomposition process is proposed to fabricate nickel oxide colloidal nanocrystal aggregated microspheres (CNAMs) with mesoporous structure. XRD, EDS, SEM, TEM. FTIR, and N{sub 2} adsorption and desorption isotherm techniques are employed for morphology and structure characterizations. The as-prepared nickel oxide CNAMs, which has a high surface area (234 m{sup 2}/g) with narrow pore distribution at around 3.25 nm, are composed of numerous hexagonal mesoporous nanocrystals of approximately 50–60 nm in size, and present a single-crystal-like characteristic. The experimental results also demonstrated that the CNAMs showed outstanding performance in electrochemistry, photocatalysis and waste water treatment due to their special hierarchical and mesoporous structure, presenting the promising candidate for catalysis and catalysis support materials. - Graphical abstract: CNAMs with mesoporous structure synthesized via a simple microwave-assisted hydrothermal method was applied in electrochemistry and catalysis and exhibited enhanced performance. Display Omitted - Highlights: • CNAMs with mesoporous structure are achieved via a simple microwave-assisted hydrothermal method. • Morphology, structure and pore distribution of sample particles is specifically controlled. • The samples show enhanced properties in electrochemistry and catalysis due to hierarchical structure.

  13. Electrochemistry at Edge of Single Graphene Layer in a Nanopore

    PubMed Central

    Banerjee, Shouvik; Shim, Jiwook; Rivera, Jose; Jin, Xiaozhong; Estrada, David; Solovyeva, Vita; You, Xiuque; Pak, James; Pop, Eric; Aluru, Narayana; Bashir, Rashid

    2013-01-01

    We study the electrochemistry of single layer graphene edges using a nanopore-based structure consisting of stacked graphene and Al2O3 dielectric layers. Nanopores, with diameters ranging from 5 to 20 nm, are formed by an electron beam sculpting process on the stacked layers. This leads to unique edge structure which, along with the atomically thin nature of the embedded graphene electrode, demonstrates electrochemical current densities as high as 1.2 × 104 A/cm2. The graphene edge embedded structure offers a unique capability to study the electrochemical exchange at an individual graphene edge, isolated from the basal plane electrochemical activity. We also report ionic current modulation in the nanopore by biasing the embedded graphene terminal with respect to the electrodes in the fluid. The high electrochemical specific current density for a graphene nanopore-based device can have many applications in sensitive chemical and biological sensing, and energy storage devices. PMID:23249127

  14. Electrochemistry Corrosion Properties of Pulsed Laser Welding Hastelloy C-276

    NASA Astrophysics Data System (ADS)

    Ma, G.; Niu, F.; Wu, D.; Qu, Y.

    Based on the welding quality requirement of Hastelloy C276 in the extreme environment, the electrochemistry corrosion property of laser welding Hastelloy C276 was evaluated in the neutral, acid and alkaline solutions, and the corroded surface was observed by the co-focal laser scanning microscope to confirm the corrosion mechanism. The results indicated, the corrosion trend of the weld was weaker than that of base metal in the neutral and acid solutions, but in the alkaline solutions, the corrosion trend of the base metal was weaker. However, the corrosion rate of the weld was much slower than that of base metal in all solutions. At the point of corrosion mechanism, in the acid and alkaline solutions, the base metal and weld showed the uniform corrosion. However, in the neutral solution, the selective corrosion and intergranular corrosion occurred in the base metal and the weld, respectively.

  15. Electrochemistry of orthosilicate-based lithium battery cathodes: a perspective.

    PubMed

    Ferrari, Stefania; Capsoni, Doretta; Casino, Simone; Destro, Matteo; Gerbaldi, Claudio; Bini, Marcella

    2014-06-14

    Lithium metal orthosilicates are attracting a lot of attention owing to their promising prospects as potential high capacity cathode materials for Li-ion batteries. Currently, great efforts are being made in order to achieve the full theoretical specific capacity of 330 mA h g(-1), but many issues remain unsolved (e.g., poor structural and cycling stability), which limit their practical application. The present perspective highlights the importance of assessing the electrochemical behaviour of Li2(Fe,Mn)SiO4 by combining an arsenal of characterization techniques both spectroscopic and structural, in and ex situ. Here, we review the most recent achievements in the investigation of the electrochemical performance of lithium metal orthosilicate cathodes and, through some of our recent results, we attempt to clarify the relationship between the structure and electrochemistry of these compounds. PMID:24764049

  16. Electrochemistry of Silicon: Instrumentation, Science, Materials and Applications

    NASA Astrophysics Data System (ADS)

    Lehmann, Volker

    2002-04-01

    Silicon has been and will most probably continue to be the dominant material in semiconductor technology. Although the defect-free silicon single crystal is one of the best understood systems in materails science, its electrochemistry to many people is still a kind of "alchemy". This view is partly due to the interdisciplinary aspects of the topic: Physics meets chemistry at the silicon-electrolyte interface. This book gives a comprehensive overview of this important aspect of silicon technology as well as examples of applications ranging from photonic crystals to biochips. It will serve materials scientists as well as engineers involved in silicon technology as a quick reference with its more than 150 technical tables and diagrams and ca. 1000 references cited for easy access of the original literature.

  17. Facile synthesis of cuprous oxide nanoparticles by plasma electrochemistry

    NASA Astrophysics Data System (ADS)

    Liu, Jiandi; Chen, Qiang; Li, Junshuai; Xiong, Qing; Yue, Guanghui; Zhang, Xianhui; Yang, Size; Huo Liu, Qing

    2016-07-01

    We report on a simple plasma electrochemistry method for synthesizing cuprous oxide (Cu2O) nanoparticles in the presence of glucose. In this system, Ar plasma in contact with a NaCl solution was used as one electrode, and a Cu plate was immersed in the solution as the counter electrode. The plasma-solution interaction produced many reducing and oxidizing species which can react with the Cu ions released from the Cu electrode. Cu2O nanoparticles, with an average diameter of 22 +/- 6 nm, were formed under the competition of reducing and oxidizing reactions in the solution. The results show that the glucose added in the electrolyte strongly influences the properties of the products. Corresponding to high, medium, and low concentrations of glucose, the products were nanoparticles from amorphous Cu2O, polycrystalline Cu2O, and a mixture of polycrystalline Cu2O and Cu2Cl(OH)3, respectively.

  18. Oxygen electrochemistry as a cornerstone for sustainable energy conversion.

    PubMed

    Katsounaros, Ioannis; Cherevko, Serhiy; Zeradjanin, Aleksandar R; Mayrhofer, Karl J J

    2014-01-01

    Electrochemistry will play a vital role in creating sustainable energy solutions in the future, particularly for the conversion and storage of electrical into chemical energy in electrolysis cells, and the reverse conversion and utilization of the stored energy in galvanic cells. The common challenge in both processes is the development of-preferably abundant-nanostructured materials that can catalyze the electrochemical reactions of interest with a high rate over a sufficiently long period of time. An overall understanding of the related processes and mechanisms occurring under the operation conditions is a necessity for the rational design of materials that meet these requirements. A promising strategy to develop such an understanding is the investigation of the impact of material properties on reaction activity/selectivity and on catalyst stability under the conditions of operation, as well as the application of complementary in situ techniques for the investigation of catalyst structure and composition. PMID:24339359

  19. Solid-state electrochemistry on the nanometer and atomic scales: the scanning probe microscopy approach

    DOE PAGESBeta

    Strelcov, Evgheni; Yang, Sang Mo; Jesse, Stephen; Balke, Nina; Vasudevan, Rama K.; Kalinin, Sergei V.

    2016-04-21

    Energy technologies of the 21st century require an understanding and precise control over ion transport and electrochemistry at all length scales – from single atoms to macroscopic devices. Our short review provides a summary of recent studies dedicated to methods of advanced scanning probe microscopy for probing electrochemical transformations in solids at the meso-, nano- and atomic scales. In this discussion we present the advantages and limitations of several techniques and a wealth of examples highlighting peculiarities of nanoscale electrochemistry.

  20. Solid-state electrochemistry on the nanometer and atomic scales: the scanning probe microscopy approach.

    PubMed

    Strelcov, Evgheni; Yang, Sang Mo; Jesse, Stephen; Balke, Nina; Vasudevan, Rama K; Kalinin, Sergei V

    2016-08-01

    Energy technologies of the 21(st) century require an understanding and precise control over ion transport and electrochemistry at all length scales - from single atoms to macroscopic devices. This short review provides a summary of recent studies dedicated to methods of advanced scanning probe microscopy for probing electrochemical transformations in solids at the meso-, nano- and atomic scales. The discussion presents the advantages and limitations of several techniques and a wealth of examples highlighting peculiarities of nanoscale electrochemistry. PMID:27146961

  1. Solid-state electrochemistry on the nanometer and atomic scales: the scanning probe microscopy approach

    NASA Astrophysics Data System (ADS)

    Strelcov, Evgheni; Yang, Sang Mo; Jesse, Stephen; Balke, Nina; Vasudevan, Rama K.; Kalinin, Sergei V.

    2016-07-01

    Energy technologies of the 21st century require an understanding and precise control over ion transport and electrochemistry at all length scales - from single atoms to macroscopic devices. This short review provides a summary of recent studies dedicated to methods of advanced scanning probe microscopy for probing electrochemical transformations in solids at the meso-, nano- and atomic scales. The discussion presents the advantages and limitations of several techniques and a wealth of examples highlighting peculiarities of nanoscale electrochemistry.

  2. Pore-Scale Investigation of Mass Transport and Electrochemistry in a Solid Oxide Fuel Cell Anode

    SciTech Connect

    Grew, Kyle N.; Joshi, Abhijit S.; Peracchio, Aldo A.; Chiu, Wilson K. S.

    2009-10-31

    The development and validation of a model for the study of pore-scale transport phenomena and electrochemistry in a Solid Oxide Fuel Cell (SOFC) anode are presented in this work. This model couples mass transport processes with a detailed reaction mechanism, which is used to model the electrochemical oxidation kinetics. Detailed electrochemical oxidation reaction kinetics, which is known to occur in the vicinity of the three-phase boundary (TPB) interfaces, is discretely considered in this work. The TPB regions connect percolating regions of electronic and ionic conducting phases of the anode, nickel (Ni) and yttria-stabilized zirconia (YSZ), respectively; with porous regions supporting mass transport of the fuel and product. A two-dimensional (2D), multi-species lattice Boltzmann method (LBM) is used to describe the diffusion process in complex pore structures that are representative of the SOFC anode. This diffusion model is discretely coupled to a kinetic electrochemical oxidation mechanism using localized flux boundary conditions. The details of the oxidation kinetics are prescribed as a function of applied activation overpotential and the localized hydrogen and water mole fractions. This development effort is aimed at understanding the effects of the anode microstructure within TPB regions. This work describes the methods used so that future studies can consider the details of SOFC anode microstructure.

  3. Using the Electrochemistry of the Electrospray Ion Source

    SciTech Connect

    Van Berkel, Gary J; Kertesz, Vilmos

    2007-01-01

    Electrospray mass spectrometry (ES-MS) is one of the more widely used analysis methods in science today, impacting fields as diverse as conventional chemistry to biotechnology and materials science. , Even 20 years after bursting onto the mass spectrometry scene, the underlying processes in ES ionization continue to be better understood exposing new opportunities for the technique. , , , , Such is the case for the improved understanding related to the electrochemical processes inherent to the operation of this ion source, , , which is the topic of this report. Electrospray ionization involves three main steps prior to mass analysis: the generation and charging of the ES droplets; droplet evaporation and the production of gas-phase ions; and secondary processes that modify the gas-phase ions in the atmosphere and the sub-atmospheric pressure sampling regions of the mass spectrometer. Integral to the generation and charging of the ES droplets are electrochemical reactions that occur at the conductive contact/solution interface within or near the ES emitter to maintain the quasi-continuous production of charged droplets and ultimately gas-phase ions. The basic electrochemical phenomena concerning the ES ion source were first brought to wide attention in the mass spectrometry community by Kebarle and co-workers in the early 1990's,8 but the electrochemistry of electrostatic spray devices and possible analytical consequences resulting from this phenomenon were realized and discussed in the literature at least as far back as the mid-1970's. When asked to intercede in a debate on the significance of electrochemistry in the ES ionization (ESI) process, 2002 Nobel Laureate in Chemistry John Fenn noted that to him " the idea that electrochemical reactions might be taking place in an ES ion source was too obvious to mention. That products of such reactions are of vital significance in the overall ESI process was much less obvious. Indeed, it seems fair to say that with few

  4. Electrochemistry of lithium-oxygen batteries using microelectrode voltammetry

    NASA Astrophysics Data System (ADS)

    Nemanick, E. Joseph

    2014-02-01

    The electrochemistry of non-aqueous lithium-oxygen (Li-O2) batteries on both reduction and oxidation was investigated using carbon black and single-walled nanotube (SWNT) microcavity electrodes. Two oxidative peaks were observed on oxidation (charge). The first peak at 3.0-3.7 V vs. Li/Li+ was limited in storable charge (∼8 × 103 C cm-3). The oxidation potential of this first peak was independent of Li2O2 thickness (as measured by total charge on reduction) and assigned to interfacial Li2O2, lying between the bulk of the Li2O2 and the carbon surface. A second peak between 4.0 and 4.6+ V showed significant discharge product thickness dependence on oxidation potential and was assigned to bulk Li2O2, away from the carbon surface. On reduction (discharge), deposition of the interfacial Li2O2 showed a significant overpotential indicated by the ratio of interfacial/bulk Li2O2 formed at varying reduction potentials. SWNT were shown to effectively decrease the Li-O2 average charge overpotential for a given charge by increasing the electrode surface area available for formation of interfacial discharge products.

  5. Electrochemistry of magnesium electrolytes in ionic liquids for secondary batteries.

    PubMed

    Vardar, Gulin; Sleightholme, Alice E S; Naruse, Junichi; Hiramatsu, Hidehiko; Siegel, Donald J; Monroe, Charles W

    2014-10-22

    The electrochemistry of Mg salts in room-temperature ionic liquids (ILs) was studied using plating/stripping voltammetry to assess the viability of IL solvents for applications in secondary Mg batteries. Borohydride (BH4(-)), trifluoromethanesulfonate (TfO(-)), and bis(trifluoromethanesulfonyl)imide (Tf2N(-)) salts of Mg were investigated. Three ILs were considered: l-n-butyl-3-methylimidazolium (BMIM)-Tf2N, N-methyl-N-propylpiperidinium (PP13)-Tf2N, and N,N-diethyl-N-methyl(2-methoxyethyl)ammonium (DEME(+)) tetrafluoroborate (BF4(-)). Salts and ILs were combined to produce binary solutions in which the anions were structurally similar or identical, if possible. Contrary to some prior reports, no salt/IL combination appeared to facilitate reversible Mg plating. In solutions containing BMIM(+), oxidative activity near 0.8 V vs Mg/Mg(2+) is likely associated with the BMIM cation, rather than Mg stripping. The absence of voltammetric signatures of Mg plating from ILs with Tf2N(-) and BF4(-) suggests that strong Mg/anion Coulombic attraction inhibits electrodeposition. Cosolvent additions to Mg(Tf2N)2/PP13-Tf2N were explored but did not result in enhanced plating/stripping activity. The results highlight the need for IL solvents or cosolvent systems that promote Mg(2+) dissociation. PMID:25248147

  6. Mechanics and electrochemistry of ionic polymer metal composites

    NASA Astrophysics Data System (ADS)

    Cha, Youngsu; Porfiri, Maurizio

    2014-11-01

    Ionic polymer metal composites (IPMCs) are electroactive materials composed of a hydrated ionomeric membrane that is sandwiched between noble metal electrodes. Here, we propose a modeling framework to study quasi-static large deformations and electrochemistry of IPMCs. Specifically, IPMC kinematics is described in terms of its mechanical deformation, the concentration of mobile counterions neutralizing the ionomer, and the electric potential. The chemoelectromechanical constitutive behavior is obtained from a Helmholtz free energy density, which accounts for mechanical stretching, ion mixing, and electric polarization. The three-dimensional framework is specialized to plane bending of thin IPMCs. Hence, we propose a structural model, where the moment and the charge stored along the IPMC are computed from the solution of a modified Poisson-Nernst-Planck system, in terms of the through-the-thickness coordinate. For small static deformations, we present a semianalytical solution based on the method of matched asymptotic expansions, which is ultimately used to study IPMC sensing and actuation. We demonstrate that the linearity of IPMC actuation in a broad voltage range could be attributed to the interplay of two competing nonlinear phenomena, associated with Maxwell stress and osmotic pressure. In agreement with experimental observations, our model confirms the possibility of tailoring IPMC actuation by varying the counterion size and the concentration of fixed ions. Finally, the model is successful in predicting the significantly different voltage levels displayed by IPMC sensors and actuators, which are associated with remarkable variations in the ion mixing and polarization energies.

  7. Direct electrochemistry of nitrate reductase from the fungus Neurospora crassa.

    PubMed

    Kalimuthu, Palraj; Ringel, Phillip; Kruse, Tobias; Bernhardt, Paul V

    2016-09-01

    We report the first direct (unmediated) catalytic electrochemistry of a eukaryotic nitrate reductase (NR). NR from the filamentous fungus Neurospora crassa, is a member of the mononuclear molybdenum enzyme family and contains a Mo, heme and FAD cofactor which are involved in electron transfer from NAD(P)H to the (Mo) active site where reduction of nitrate to nitrite takes place. NR was adsorbed on an edge plane pyrolytic graphite (EPG) working electrode. Non-turnover redox responses were observed in the absence of nitrate from holo NR and three variants lacking the FAD, heme or Mo cofactor. The FAD response is due to dissociated cofactor in all cases. In the presence of nitrate, NR shows a pronounced cathodic catalytic wave with an apparent Michaelis constant (KM) of 39μM (pH7). The catalytic cathodic current increases with temperature from 5 to 35°C and an activation enthalpy of 26kJmol(-1) was determined. In spite of dissociation of the FAD cofactor, catalytically activity is maintained. PMID:27060250

  8. Realtime structural electrochemistry of platinum clusters using dispersive XAFS

    SciTech Connect

    Allen, P.G.; Conradson, S.D.; Wilson, M.S.; Gottesfeld, S.; Raistrick, I.D.

    1993-12-31

    Chemical reference tables state that the standard potential for the reaction of Pt with water, Pt + 2H{sub 2}O {r_arrow} Pt(OH){sub 2} + 2H{sup +} + 2e{sup {minus}}, is 0.98 V, and electrochemical studies propose that this reaction may occur at potentials as low as 0.8 V. Using dispersive x-ray absorption fine-structure (XAFS) spectroscopy, the authors have directly probed the structural evolution of a Pt catalyst operating in-situ in a polymer electrolyte fuel cell during cyclic voltammetry. The changes in the number of Pt and O nearest-neighbors and the Pt charge demonstrate a close correspondence with features in the voltammogram. Because dispersive XAFS is very sensitive to detecting structural changes, they have been able to detect the presence of chemisorbed oxygen at potentials of 0.6--0.9 V in the anodic sweep. Since double-layer charging is regarded as the only process in this region for bulk Pt, these results may reflect a limitation of previous (indirect) studies on Pt electrochemistry, or they may indicate that these clusters are different from their bulk metal counterparts. Exploiting the time-resolving capability of dispersive XAFS, they also monitored changes in the Pt charge and the number of O and Pt nearest-neighbors during the electrochemical oxidation and reduction of the Pt clusters in real-time. The results are inconsistent with those expected from the place-exchange mechanism for the formation of the surface oxide on bulk Pt electrodes in aqueous solution; Pt{sub red} (k{sub 1}) {yields} Pt (submonolayer O)(k{sub 2}) {yields} PtO{sub x} (place exchanged Pt and O atoms: k{sub 1} >> k{sub 2}). Their current model for understanding these behaviors is that, relative to bulk Pt, unusual types of surface sites play a major role in determining the reactivity of these clusters.

  9. Martian Dust Devil Electron Avalanche Process and Associated Electrochemistry

    NASA Technical Reports Server (NTRS)

    Jackson, Telana L.; Farrell, William M.; Delory, Gregory T.; Nithianandam, Jeyasingh

    2010-01-01

    Mars' dynamic atmosphere displays localized dust devils and larger, global dust storms. Based on terrestrial analog studies, electrostatic modeling, and laboratory work these features will contain large electrostatic fields formed via triboelectric processes. In the low-pressure Martian atmosphere, these fields may create an electron avalanche and collisional plasma due to an increase in electron density driven by the internal electrical forces. To test the hypothesis that an electron avalanche is sustained under these conditions, a self-consistent atmospheric process model is created including electron impact ionization sources and electron losses via dust absorption, electron dissociation attachment, and electron/ion recombination. This new model is called the Dust Devil Electron Avalanche Model (DDEAM). This model solves simultaneously nine continuity equations describing the evolution of the primary gaseous chemical species involved in the electrochemistry. DDEAM monitors the evolution of the electrons and primary gas constituents, including electron/water interactions. We especially focus on electron dynamics and follow the electrons as they evolve in the E field driven collisional gas. When sources and losses are self-consistently included in the electron continuity equation, the electron density grows exponentially with increasing electric field, reaching an equilibrium that forms a sustained time-stable collisional plasma. However, the character of this plasma differs depending upon the assumed growth rate saturation process (chemical saturation versus space charge). DDEAM also shows the possibility of the loss of atmospheric methane as a function of electric field due to electron dissociative attachment of the hydrocarbon. The methane destruction rates are presented and can be included in other larger atmospheric models.

  10. Direct Electrochemistry and Electrocatalysis of Myoglobin Immobilized on Graphene-CTAB-Ionic Liquid Nanocomposite Film

    SciTech Connect

    Liao, Honggang; Wu, Hong; Wang, Jun; Liu, Jun; Jiang, Yanxia; Sun, Shigang; Lin, Yuehe

    2010-10-01

    We have investigated direct electrochemistry and electrocatalysis of myoglobin immobilized on graphene-cetylramethylammonium bromide (CTAB)-ionic liquid nanocomposite film on a glassy carbon electrode. The nanocomposite was characterized by TEM, SEM, XPS, and electrochemistry. It was found that the high surface area of graphene was helpful for immobilizing more proteins and the nanocomposite film can provide a favorable microenvironment for MB to retain its native structure and activity and to achieve reversible direct electron transfer reaction at an electrode. The nanocomposite films also exhibit good stability and catalytic activities for the electrocatalytic reduction of H2O2.

  11. LIGA-based microsystem manufacturing:the electrochemistry of through-mold depostion and material properties.

    SciTech Connect

    Kelly, James J. (Sandia National Laboratories, Livermore, CA); Goods, Steven Howard (Sandia National Laboratories, Livermore, CA)

    2005-06-01

    The report presented below is to appear in ''Electrochemistry at the Nanoscale'', Patrik Schmuki, Ed. Springer-Verlag, (ca. 2005). The history of the LIGA process, used for fabricating dimensional precise structures for microsystem applications, is briefly reviewed, as are the basic elements of the technology. The principal focus however, is on the unique aspects of the electrochemistry of LIGA through-mask metal deposition and the generation of the fine and uniform microstructures necessary to ensure proper functionality of LIGA components. We draw from both previously published work by external researchers in the field as well as from published and unpublished studies from within Sandia.

  12. Royal Society, Discussion on Prospects for Industrial Electrochemistry, London, England, December 10, 11, 1980

    NASA Astrophysics Data System (ADS)

    1981-09-01

    Among the topics dicussed are electrode kinetics, organic reactions via electrochemically generated intermediaries, speculations on industrial electrochemistry, classically modified electrodes for electrocatalysis, and bioelectrocatalysis. Also covered are industrially useful electrochemical cell designs and meaningful optimization procedures, the industrialization of electrochemical reations, electrochemistry in the service of engineering, pulse voltametric methods of analysis, and on-line sensors in industrial water analysis. Attention is in addition given to sodium-sulphur batteries, the nickel-zinc battery for electric vehicles, and novel materials for advanced batteries.

  13. Electrochemically modulated liquid chromatography: Theoretical investigations and applications from the perspectives of chromatography and interfacial electrochemistry

    SciTech Connect

    Keller, David W.

    2005-05-01

    Electrochemically modulated liquid chromatography (EMLC) employs a conductive material as both a stationary phase for chromatographic separations and as a working electrode for performing electrochemistry experiments. This dual functionality gives EMLC the capacity to manipulate chromatographic separations by changing the potential applied (E{sub app}) to the stationary phase with respect to an external reference. The ability to monitor retention as a function of E{sub app} provides a means to chromatographically monitor electrosorption processes at solid-liquid interfaces. In this dissertation, the retention mechanism for EMLC is examined from the perspective of electrical double layer theory and interfacial thermodynamics. From the chromatographic data, it is possible to determine the interfacial excess ({Lambda}) of a solute and changes in interfacial tension (d{gamma}) as a function of both E{sub app} and the supporting electrolyte concentration. Taken together, these two experimentally manipulated parameters can be examined within the context of the Gibbs adsorption equation to delineate the contribution of a variety of interfacial properties, including the charge of solute on the stationary phase and the potential of zero charge (PZC), to the mechanism behind EMLC-based retention. The chromatographic probing of interfacial phenomena is complemented by electroanalytical experiments that exploit the ability to monitor the electronic current flowing through an EMLC column. Cyclic voltammetry and chronoamperometry of an EMLC column are used to determine the electronic performance characteristics of an EMLC column. An electrochemical flow injection analysis of a column is provided in which the current required to maintain a constant E{sub app} is monitored and provides a way to examine the influence that acetonitrile and supporting electrolyte composition, flow rate, column backpressure, and ionic strength have on the structure of electrified interfaces.

  14. SOME RECENT STUDIES IN RUGHENIUM ELECTROCHEMISTRY AND ELECTROCATALYSIS.

    SciTech Connect

    MARINKOVIC, N.S.; VUKMIROVIC, M.B.; ADZIC, R.R.

    2006-08-01

    Ruthenium is a metal of a considerable importance in electrochemical science and technology. It is a catalyst or co-catalyst material in Pt-Ru alloys for methanol- and reformate hydrogen-oxidation in fuel cells, while ruthenium oxide, a component in chlorine-evolution catalysts, represents an attractive material for electrochemical supercapacitors. Its facile surface oxidation generates an oxygen-containing species that provides active oxygen in some reactions. Ru sites in Pt-Ru catalysts increase the ''CO tolerance'' of Pt in the catalytic oxidation-reaction in direct methanol fuel cells (DMFC) and in reformate hydrogen-oxidation in proton exchange membrane fuel cells (PEMFC). The mechanism of Ru action is not completely understood, although current consensus revolves around the so-called ''bifunctional mechanism'' wherein Ru provides oxygenated species to oxidize CO that blocks Pt sites, and has an electronic effect on Pt-CO interaction. While various studies of polycrystalline Ru go back several decades those involving single crystal surfaces and the structural sensitivity of reactions on Ru surfaces emerged only recently. Using well-ordered single crystalline surfaces brings useful information as the processes on realistic catalysts are far too complex to allow identification of the microscopic reaction steps. In this article, we focus on progress in model systems and conditions, such as electrochemistry and electrocatalysis on bare and Pt-modified well-ordered Ru(0001) and Ru(10{bar 1}0) single-crystal surfaces. We also review current understanding of the mechanistic principles of Pt-Ru systems and a new development of a Pt submonolayer on Ru support electrocatalyst. Ruthenium crystallizes in a hexagonal close-packed structure, (hcp). Figure 1.1 shows the two single crystal surfaces of Ru. The Ru(0001) surface possesses the densest, i.e. hexagonal arrangement of atoms, Fig. 1.1a. The other plane, Ru(10{bar 1}0), can have one of the two terminations of the

  15. A Historical Analysis of the Daniell Cell and Electrochemistry Teaching in French and Tunisian Textbooks

    ERIC Educational Resources Information Center

    Boulabiar, Ahlem; Bouraoui, Kamel; Chastrette, Maurice; Abderrabba, Manef

    2004-01-01

    The condition in which the Daniell Cell was historically constructed is examined and the evolution of its presentation in French and Tunisian chemistry textbooks is analyzed. Based on the studies, several innovations to facilitate the teaching of the cell, and more generally, the teaching of electrochemistry and of ionic conduction are proposed.

  16. Conceptual Difficulties Experienced by Senior High School Students of Electrochemistry: Electrochemical (Galvanic) and Electrolytic Cells.

    ERIC Educational Resources Information Center

    Garnett, Pamela J.; Treagust, David F.

    1992-01-01

    This research used semistructured interviews to investigate students' (n=32) understanding of electrochemistry following a 7-9 week course of instruction. Three misconceptions were identified and incorporated with five previously reported into an alternative framework about electric current involving drifting electrons. Also noted was the tendency…

  17. Effect of Cooperative Learning Strategies on Students' Understanding of Concepts in Electrochemistry

    ERIC Educational Resources Information Center

    Acar, Burcin; Tarhan, Leman

    2007-01-01

    The present study was conducted to investigate the degree of effectiveness of cooperative learning instruction over a traditional approach on 11th grade students' understanding of electrochemistry. The study involved forty-one 11th grade students from two science classes with the same teacher. To determine students' misconceptions concerning…

  18. Semiconductor electrochemistry of coal pyrite. Final technical report, September 1990--September 1995

    SciTech Connect

    Osseo-Asare, K.; Wei, D.

    1996-01-01

    This project is concerned with the physiochemical processes occuring at the pyrite/aqueous interface, in the context of coal cleaning, desulfurization, and acid mine drainage. The use of synthetic particles of pyrite as model electrodes to investigate the semiconductor electrochemistry of pyrite is employed.

  19. Effects of Jigsaw and Animation Techniques on Students' Understanding of Concepts and Subjects in Electrochemistry

    ERIC Educational Resources Information Center

    Doymus, Kemal; Karacop, Ataman; Simsek, Umit

    2010-01-01

    This study investigated the effect of jigsaw cooperative learning and animation versus traditional teaching methods on students' understanding of electrochemistry in a first-year general chemistry course. This study was carried out in three different classes in the department of primary science education during the 2007-2008 academic year. The…

  20. Inquiry-Based Laboratory Activities in Electrochemistry: High School Students' Achievements and Attitudes

    ERIC Educational Resources Information Center

    Sesen, Burcin Acar; Tarhan, Leman

    2013-01-01

    This study aimed to investigate the effects of inquiry-based laboratory activities on high school students' understanding of electrochemistry and attitudes towards chemistry and laboratory work. The participants were 62 high school students (average age 17 years) in an urban public high school in Turkey. Students were assigned to experimental (N =…

  1. Microbial Electrochemistry and its Application to Energy and Environmental Issues

    NASA Astrophysics Data System (ADS)

    Hastings, Jason Thomas

    Microbial electrochemistry forms the basis of a wide range of topics from microbial fuel cells to fermentation of carbon food sources. The ability to harness microbial electron transfer processes can lead to a greener and cleaner future. This study focuses on microbial electron transfer for liquid fuel production, novel electrode materials, subsurface environments and removal of unwanted byproducts. In the first chapter, exocellular electron transfer through direct contact utilizing passive electrodes for the enhancement of bio-fuel production was tested. Through the application of microbial growth in a 2-cell apparatus on an electrode surface ethanol production was enhanced by 22.7% over traditional fermentation. Ethanol production efficiencies of close to 95% were achieved in a fraction of the time required by traditional fermentation. Also, in this chapter, the effect of exogenous electron shuttles, electrode material selection and resistance was investigated. Power generation was observed using the 2-cell passive electrode system. An encapsulation method, which would also utilize exocellular transfer of electrons through direct contact, was hypothesized for the suspension of viable cells in a conductive polymer substrate. This conductive polymer substrate could have applications in bio-fuel production. Carbon black was added to a polymer solution to test electrospun polymer conductivity and cell viability. Polymer morphology and cell viability were imaged using electron and optical microscopy. Through proper encapsulation, higher fuel production efficiencies would be achievable. Electron transfer through endogenous exocellular protein shuttles was observed in this study. Secretion of a soluble redox active exocellular protein by Clostridium sp. have been shown utilizing a 2-cell apparatus. Cyclic voltammetry and gel electrophoresis were used to show the presence of the protein. The exocellular protein is capable of reducing ferrous iron in a

  2. Bipolar Electrochemistry for Concurrently Evaluating the Stability of Anode and Cathode Electrocatalysts and the Overall Cell Performance during Long-Term Water Electrolysis.

    PubMed

    Eßmann, Vera; Barwe, Stefan; Masa, Justus; Schuhmann, Wolfgang

    2016-09-01

    Electrochemical efficiency and stability are among the most important characteristics of electrocatalysts. These parameters are usually evaluated separately for the anodic and cathodic half-cell reactions in a three-electrode system or by measuring the overall cell voltage between the anode and cathode as a function of current or time. Here, we demonstrate how bipolar electrochemistry can be exploited to evaluate the efficiency of electrocatalysts for full electrochemical water splitting while simultaneously and independently monitoring the individual performance and stability of the half-cell electrocatalysts. Using a closed bipolar electrochemistry setup, all important parameters such as overvoltage, half-cell potential, and catalyst stability can be derived from a single galvanostatic experiment. In the proposed experiment, none of the half-reactions is limiting on the other, making it possible to precisely monitor the contribution of the individual half-cell reactions on the durability of the cell performance. The proposed approach was successfully employed to investigate the long-term performance of a bifunctional water splitting catalyst, specifically amorphous cobalt boride (Co2B), and the durability of the electrocatalyst at the anode and cathode during water electrolysis. Additionally, by periodically alternating the polarization applied to the bipolar electrode (BE) modified with a bifunctional oxygen electrocatalyst, it was possible to explicitly follow the contributions of the oxygen reduction (ORR) and the oxygen evolution (OER) half-reactions on the overall long-term durability of the bifunctional OER/ORR electrocatalyst. PMID:27469162

  3. Serendipity: Genesis of the Electrochemical Instrumentation at Princeton Applied Research Corporation

    ERIC Educational Resources Information Center

    Flato, J. B.

    2007-01-01

    Princeton Applied Research Corporation (PAR) was a small electronic instrument company in early 1960s but once they entered electrochemistry they were very successful. Since then they have developed and designed successful instruments with their tremendous knowledge and have made great contribution to the field of analytical chemistry.

  4. Direct electrochemistry and electrocatalysis of a glucose oxidase-functionalized bioconjugate as a trace label for ultrasensitive detection of thrombin.

    PubMed

    Bai, Lijuan; Yuan, Ruo; Chai, Yaqin; Yuan, Yali; Wang, Yan; Xie, Shunbi

    2012-11-18

    For the first time, a glucose oxidase-functionalized bioconjugate was prepared and served as a new trace label through its direct electrochemistry and electrocatalysis in a sandwich-type electrochemical aptasensor for ultrasensitive detection of thrombin. PMID:23032443

  5. A Preliminary Study of Some of the Learning and Assessment Difficulties in Connection with O-Level Electrochemistry.

    ERIC Educational Resources Information Center

    Hillman, R. A. H.; And Others

    1981-01-01

    Describes a study which explored some difficulties related to technical and nontechnical vocabulary and the structure of the examination questions in electrochemistry. Includes results from a sample of 1,500 students in the fourth forms. (DS)

  6. The electrochemistry of SIMFUEL in dilute alkaline hydrogen peroxide solutions

    NASA Astrophysics Data System (ADS)

    Goldik, Jon

    The work described in this thesis is a study of the electrochemistry of SIMFUEL (SIMulated nuclear FUEL) in dilute, alkaline hydrogen peroxide solutions. In the first set of experiments, the reaction of H2O 2 on SIMFUEL electrodes was studied electrochemically and under open circuit conditions in 0.1 mol L-1 NaCl solutions at pH 9.8. The composition of the oxidized UO2 surface was determined by X-ray photoelectron spectroscopy. Hydrogen peroxide reduction was found to be catalyzed by the formation of a mixed UIV/UV (UO 2+x) surface layer, but to be blocked by the accumulation of UVI species (UO3· yH2O or adsorbed (UO2)2+) on the electrode surface. The formation of this UVI layer blocks both H2O2 reduction and oxidation, thereby inhibiting the potentially rapid H2O2 decomposition reaction to H2O and O2. Decomposition is found to proceed at a rate controlled by the desorption of the adsorbed (UO2)2+ or reduction of adsorbed O2 species. Reduction of (O2) ads is coupled to the slow oxidative dissolution of UO2 and formation of a corrosion product deposit of UO3· yH2O. In the second series of experiments, the electrochemical reduction of hydrogen peroxide on SIMFUEL was studied using the steady-state polarization technique. Kinetic parameters for the reaction, such as Tafel slopes and reaction orders, were determined. The results were interpreted in terms of a chemical-electrochemical mechanism involving UIV/UV donor-acceptor reduction sites. The large values of the Tafel slopes and the fractional reaction orders with respect to H2O2 can be understood in terms of the potential-dependent surface coverage of active sites, similar to that observed in the reduction of hydrogen peroxide on oxidized copper surfaces. The effects of pH over the range 10-13 were also investigated. The H2O 2 reduction currents were nearly independent of pH in the range 10-11, but were slowed at more alkaline values. The change in pH dependence appears to be related to the acid-base properties

  7. Proceedings of the conference on electrochemistry of carbon allotropes: Graphite, fullerenes and diamond

    SciTech Connect

    Kinoshita, K.; Scherson, D.

    1998-02-01

    This conference provided an opportunity for electrochemists, physicists, materials scientists and engineers to meet and exchange information on different carbon allotropes. The presentations and discussion among the participants provided a forum to develop recommendations on research and development which are relevant to the electrochemistry of carbon allotropes. The following topics which are relevant to the electrochemistry of carbon allotropes were addressed: Graphitized and disordered carbons, as Li-ion intercalation anodes for high-energy-density, high-power-density Li-based secondary batteries; Carbons as substrate materials for catalysis and electrocatalysis; Boron-doped diamond film electrodes; and Electrochemical characterization and electrosynthesis of fullerenes and fullerene-type materials. Abstracts of the presentations are presented.

  8. Nanoplasmonic biosensor: coupling electrochemistry to localized surface plasmon resonance spectroscopy on nanocup arrays.

    PubMed

    Zhang, Diming; Lu, Yanli; Jiang, Jing; Zhang, Qian; Yao, Yao; Wang, Ping; Chen, Bilian; Cheng, Qiaoyuan; Liu, Gang Logan; Liu, Qingjun

    2015-05-15

    The nanoscale Lycurgus cup arrays were hybrid structures of nanocups and nanoparticles with ultrasensitivity to refractive index change. In this study, an electrochemical localized surface plasmon resonance (LSPR) sensor was developed by coupling electrochemistry to LSPR spectroscopy measurement on the nanoscale cup arrays (nanoCA). Based on the combination of electrochemistry and LSPR measurement, the electrochemical LSPR on nanoCA was observed with significant resonance wavelength shifts in electrochemical modulation. The synchronous implementation of cyclic voltammetry and optical transmission spectrum can be used to obtain multiply sensing information and investigate the enhancement for LSPR from electrochemical scanning. The electrochemical enhanced LSPR was utilized as biosensor to detect biomolecules. The electrochemical LSPR biosensor with synchronous electrochemical and optical implement showed higher sensitivity than that of conventional optical LSPR measurement. Detecting with multi-transducer parameters and high sensitivity, the electrochemical LSPR provided a promising approach for chemical and biological detection. PMID:25172029

  9. A Distributed Electrochemistry Modeling Tool for Simulating SOFC Performance and Degradation

    SciTech Connect

    Recknagle, Kurtis P.; Ryan, Emily M.; Khaleel, Mohammad A.

    2011-10-13

    This report presents a distributed electrochemistry (DEC) model capable of investigating the electrochemistry and local conditions with the SOFC MEA based on the local microstructure and multi-physics. The DEC model can calculate the global current-voltage (I-V) performance of the cell as determined by the spatially varying local conditions through the thickness of the electrodes and electrolyte. The simulation tool is able to investigate the electrochemical performance based on characteristics of the electrode microstructure, such as particle size, pore size, electrolyte and electrode phase volume fractions, and triple-phase-boundary length. It can also investigate performance as affected by fuel and oxidant gas flow distributions and other environmental/experimental conditions such as temperature and fuel gas composition. The long-term objective for the DEC modeling tool is to investigate factors that cause electrode degradation and the decay of SOFC performance which decrease longevity.

  10. Modeling the Electrochemistry of an SOFC through the Electrodes and Electrolyte

    SciTech Connect

    Ryan, Emily M.; Recknagle, Kurtis P.; Khaleel, Mohammad A.

    2011-12-01

    This paper describes a distributed electrochemistry model of the solid oxide fuel cell (SOFC) electrodes and electrolyte. The distributed electrochemistry (DEC) model solves the transport, reactions, and electric potential through the thickness of the SOFC electrodes. The DEC model allows the local conditions within the electrodes to be studied and allows for a better understanding of how electrochemical and microstructural parameters affect the electrodes. In this paper the governing equations and implementation of the DEC model are presented along with several case studies which are used to investigate the sensitivity of the cathode to the microstructural and electrochemical parameters of the model and to explore methods of improving the electrochemical performance of the SOFC cathode.

  11. Effect of experimental conditions on size control of Au nanoparticles synthesized by atmospheric microplasma electrochemistry.

    PubMed

    Huang, Xunzhi; Li, Yongsheng; Zhong, Xiaoxia

    2014-01-01

    Atmospheric microplasma electrochemistry was utilized to synthesize Au nanoparticles (NPs). The synthesized Au NPs were investigated as a function of reduction current, solution temperature, and stirring (or not) by using ultraviolet-visible (UV-Vis) absorbance and transmission electron microscopy (TEM). It was illustrated that high current promoted the growth of Au NPs with small size, and more Au NPs with large size were synthesized as a rise of temperature. The Au NPs often with small size were synthesized as a result of stirring. The production rate, the electrostatic repulsion, and the residence time of the Au NPs at the interfacial region play an important role in the growth of Au NPs. The results shed light upon the roadmap to control the size and particle size distribution (PSD) of Au NPs synthesized by atmospheric microplasma electrochemistry. PMID:25364315

  12. Application of Nuclear Microprobes towards Understanding Complex Ore Geo-electrochemistry

    NASA Astrophysics Data System (ADS)

    Laird, J. S.; Szymanski, R.; Large, R.; Ryan, C. G.

    2012-10-01

    We report on recent development on the CSIRO Nuclear Microprobe (NMP) towards catering for long exposure mapping required for large area scanning. A new data collection system based on Labview FPGA highly co-ordinated with beam transport sits at the heart of the upgrade. These upgrades are discussed and an example of the systems use for μ-Particle Induced X-ray Emission (PIXE) analysis in the area of complex ore geo-electrochemistry is briefly described.

  13. Proton-coupled electron transfer in solution, proteins, and electrochemistry.

    PubMed

    Hammes-Schiffer, Sharon; Soudackov, Alexander V

    2008-11-13

    Recent advances in the theoretical treatment of proton-coupled electron transfer (PCET) reactions are reviewed. These reactions play an important role in a wide range of biological processes, as well as in fuel cells, solar cells, chemical sensors, and electrochemical devices. A unified theoretical framework has been developed to describe both sequential and concerted PCET, as well as hydrogen atom transfer (HAT). A quantitative diagnostic has been proposed to differentiate between HAT and PCET in terms of the degree of electronic nonadiabaticity, where HAT corresponds to electronically adiabatic proton transfer and PCET corresponds to electronically nonadiabatic proton transfer. In both cases, the overall reaction is typically vibronically nonadiabatic. A series of rate constant expressions have been derived in various limits by describing the PCET reactions in terms of nonadiabatic transitions between electron-proton vibronic states. These expressions account for the solvent response to both electron and proton transfer and the effects of the proton donor-acceptor vibrational motion. The solvent and protein environment can be represented by a dielectric continuum or described with explicit molecular dynamics. These theoretical treatments have been applied to numerous PCET reactions in solution and proteins. Expressions for heterogeneous rate constants and current densities for electrochemical PCET have also been derived and applied to model systems. PMID:18842015

  14. Hollow spherical nanostructured polydiphenylamine for direct electrochemistry and glucose biosensor.

    PubMed

    Santhosh, P; Manesh, K M; Uthayakumar, S; Gopalan, A I; Lee, K-P

    2009-03-15

    Nanostructured, hollow spheres of polydiphenylamine (HS-PDPA) are prepared through a "soft template assisted self-assembly" approach. An enzymatic glucose biosensor is fabricated through immobilizing glucose oxidase (GOx) into HS-PDPA matrix. The HS-PDPA-GOx electrode exhibits a pair of well-defined reversible redox peaks with a fast heterogeneous electron transfer rate. At an applied potential of +0.65V, HS-PDPA-GOx electrode possesses high sensitivity (1.77 microAmM(-1)cm(-2)), stability and reproducibility towards glucose. The amperometric current response of HS-PDPA-GOx to glucose is linear in the concentration range between 1 and 28 mM with a detection limit of 0.05 mM (S/N=3). Also, HS-PDPA-GOx electrode shows high selectivity towards glucose in the presence of ascorbic acid, uric acid and acetaminophen at their maximum physiological concentrations. PMID:19041234

  15. Improvement of capabilities of the Distributed Electrochemistry Modeling Tool for investigating SOFC long term performance

    SciTech Connect

    Gonzalez Galdamez, Rinaldo A.; Recknagle, Kurtis P.

    2012-04-30

    This report provides an overview of the work performed for Solid Oxide Fuel Cell (SOFC) modeling during the 2012 Winter/Spring Science Undergraduate Laboratory Internship at Pacific Northwest National Laboratory (PNNL). A brief introduction on the concept, operation basics and applications of fuel cells is given for the general audience. Further details are given regarding the modifications and improvements of the Distributed Electrochemistry (DEC) Modeling tool developed by PNNL engineers to model SOFC long term performance. Within this analysis, a literature review on anode degradation mechanisms is explained and future plans of implementing these into the DEC modeling tool are also proposed.

  16. Atomic-scale electrochemistry on the surface of a manganite

    DOE PAGESBeta

    Vasudevan, Rama K.; Tselev, Alexander; Baddorf, Arthur P.; Kalinin, Sergei V.

    2015-04-09

    The doped manganese oxides (manganites) have been widely studied for their colossal magnetoresistive effects, for potential applications in oxide spintronics, electroforming in resistive switching devices, and are materials of choice as cathodes in modern solid oxide fuel cells. However, little experimental knowledge of the dynamics of the surfaces of perovskite manganites at the atomic scale exists. Here, through in-situ scanning tunnelling microscopy (STM), we demonstrate atomic resolution on samples of La0.625Ca0.375MnO3 grown on (001) SrTiO3 by pulsed laser deposition (PLD). Furthermore, by applying triangular DC waveforms of increasing amplitude to the STM tip, and measuring the tunnelling current, we demonstratemore » the ability to both perform and monitor surface electrochemical processes at the atomic level, including, for the first time in a manganite, formation of single and multiple oxygen vacancies, disruption of the overlying manganite layers, and removal and deposition of individual atomic units or clusters. Our work paves the way for better understanding of surface oxygen reactions in these systems.« less

  17. Atomic-scale electrochemistry on the surface of a manganite

    SciTech Connect

    Vasudevan, Rama K.; Tselev, Alexander; Baddorf, Arthur P.; Kalinin, Sergei V.

    2015-04-09

    The doped manganese oxides (manganites) have been widely studied for their colossal magnetoresistive effects, for potential applications in oxide spintronics, electroforming in resistive switching devices, and are materials of choice as cathodes in modern solid oxide fuel cells. However, little experimental knowledge of the dynamics of the surfaces of perovskite manganites at the atomic scale exists. Here, through in-situ scanning tunnelling microscopy (STM), we demonstrate atomic resolution on samples of La0.625Ca0.375MnO3 grown on (001) SrTiO3 by pulsed laser deposition (PLD). Furthermore, by applying triangular DC waveforms of increasing amplitude to the STM tip, and measuring the tunnelling current, we demonstrate the ability to both perform and monitor surface electrochemical processes at the atomic level, including, for the first time in a manganite, formation of single and multiple oxygen vacancies, disruption of the overlying manganite layers, and removal and deposition of individual atomic units or clusters. Our work paves the way for better understanding of surface oxygen reactions in these systems.

  18. Assessment of insulated conductive cantilevers for biology and electrochemistry

    NASA Astrophysics Data System (ADS)

    Frederix, Patrick L. T. M.; Gullo, Maurizio R.; Akiyama, Terunobu; Tonin, Andreas; de Rooij, Nicolaas F.; Staufer, Urs; Engel, Andreas

    2005-08-01

    This paper describes the characterization and application of electrically insulated conductive tips mounted on a cantilever for use in an atomic force microscope and operated in liquid. These multifunctional probes were microfabricated and designed for measurements on biological samples in buffer solution, but they can also be employed for electrochemical applications, in particular scanning electrochemical microscopy. The silicon nitride based cantilevers had a spring constant <=0.1 N m-1 and a conductive tip, which was insulated except at the apex. The conductive core of the tip consisted of a metal, e.g. platinum silicide, and exhibited a typical radius of 15 nm. The mechanical and electrical characterization of the probe is presented and discussed. First measurements on the hexagonally packed intermediate layer of Deinococcus radiodurans demonstrated the possibility to adjust the image contrast by applying a voltage between a support and the conductive tip and to measure variations of less than 1 pA in faradaic current with a lateral resolution of 7.8 nm.

  19. Bioconjugation of zirconium uridine monophosphate: application to myoglobin direct electrochemistry.

    PubMed

    Qiao, Yuanbiao; Jian, Fangfang; Bai, Qian

    2008-03-14

    Porous nano-granule of zirconium uridine monophosphate, Zr(UMP)2.H2O is, for the first time, synthesized under mild experimental conditions and applied to the bioconjugation of myoglobin (Mb) to realize its direct electron transfer. UV-vis and resonance Raman spectroscopies prove that Mb in the Zr(UMP)2.H2O film maintains its secondary structure similar to the native state. The conjugation film of the Mb-Zr(UMP)2.H2O on the glassy carbon (GC) electrode gives a well-defined and quasi-reversible cyclic voltammogram, which reflects the direct electron transfer of the heme Fe III/Fe II couple of Mb. On the basis of the satisfying bioelectrocatalysis of the nano-conjugation of Mb and genetic substrate, a kind of mediator-free biosensor for H2O2 is developed. The linear range for H2O2 detection is estimated to be 3.92-180.14 microM. The apparent Michaelis-Menten constant (Km) and the detection limit based on the signal-to-noise ratio of 3 are found to be 196.1 microM and 1.52 microM, respectively. Both the apparent Michaelis-Menten constant and the detection limit herein are much lower than currently reported values from other Mb films. This kind of sensor possesses excellent stability, long-term life (more than 20 days) and good reproducibility. PMID:18180152

  20. Direct electrochemistry of Penicillium chrysogenum catalase adsorbed on spectroscopic graphite.

    PubMed

    Dimcheva, Nina; Horozova, Elena

    2013-04-01

    The voltammetric studies of Penicillium chrysogenum catalase (PcCAT) adsorbed on spectroscopic graphite, showed direct electron transfer (DET) between its active site and the electrode surface. Analogous tests performed with the commercially available bovine catalase revealed that mammalian enzyme is much less efficient in the DET process. Both catalases were found capable to catalyse the electrooxidation of phenol, but differed in the specifics of catalytic action. At an applied potential of 0.45V the non-linear regression showed the kinetics of the bioelectrochemical oxidation catalysed by the PcCAT obeyed the Hill equation with a binding constant K=0.034±0.002 M(2) (Hill's coefficient n=2.097±0.083, R(2)=0.997), whilst the catalytic action of the bovine catalase was described by the Michaelis-Menten kinetic model with the following parameters: V(max,app)=7.780±0.509 μA, and K(M,app)=0.068±0.070 mol L(-1). The performance of the electrode reaction was affected by the electrode potential, the pH, and temperature. Based on the effect of pH and temperature on the electrode response in presence of phenol a tentative reaction pathway of its bioelectrocatalytic oxidation has been hypothesised. The possible application of these findings in biosensing phenol up to concentration 30 mM at pHs below 7 and in absence of oxidising agents (oxygen or H(2)O(2)) was considered. PMID:23103554

  1. The application of electrochemistry to pharmaceutical stability testing--comparison with in silico prediction and chemical forced degradation approaches.

    PubMed

    Torres, Susana; Brown, Roland; Szucs, Roman; Hawkins, Joel M; Zelesky, Todd; Scrivens, Garry; Pettman, Alan; Taylor, Mark R

    2015-11-10

    The aim of this study was to evaluate the use of electrochemistry to generate oxidative degradation products of a model pharmaceutical compound. The compound was oxidized at different potentials using an electrochemical flow-cell fitted with a glassy carbon working electrode, a Pd/H2 reference electrode and a titanium auxiliary electrode. The oxidative products formed were identified and structurally characterized by LC-ESI-MS/MS using a high resolution Q-TOF mass spectrometer. Results from electrochemical oxidation using electrolytes of different pH were compared to those from chemical oxidation and from accelerated stability studies. Additionally, oxidative degradation products predicted using an in silico commercially available software were compared to those obtained from the various experimental methods. The electrochemical approach proved to be useful as an oxidative stress test as all of the final oxidation products observed under accelerated stability studies could be generated; previously reported reactive intermediate species were not observed most likely because the electrochemical mechanism differs from the oxidative pathway followed under accelerated stability conditions. In comparison to chemical degradation tests electrochemical degradation has the advantage of being much faster and does not require the use of strong oxidizing agents. Moreover, it enables the study of different operating parameters in short periods of time and optimisation of the reaction conditions (pH and applied potential) to achieve different oxidative products mixtures. This technique may prove useful as a stress test condition for the generation of oxidative degradation products and may help accelerate structure elucidation and development of stability indicating analytical methods. PMID:26299525

  2. Nanoflake-like SnS₂ matrix for glucose biosensing based on direct electrochemistry of glucose oxidase.

    PubMed

    Yang, Zhanjun; Ren, Yanyan; Zhang, Yongcai; Li, Juan; Li, Hongbo; Hu, Xiaochun Huang Xiaoya; Xu, Qin

    2011-07-15

    A novel biosensor is developed based on immobilization of proteins on nanoflake-like SnS₂ modified glass carbon electrode (GCE). With glucose oxidase (GOD) as a model, direct electrochemistry of the GOD/nanoflake-like SnS₂ is studied. The prepared SnS₂ has large surface area and can offer favorable microenvironment for facilitating the electron transfer between protein and electrode surface. The properties of GOD/SnS₂ are characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), UV-vis spectroscopy, Fourier transform infrared spectroscopy (FTIR) and cyclic voltammetry (CV), respectively. The immobilized enzyme on nanoflake-like SnS₂ retains its native structure and bioactivity and exhibits a surface-controlled, reversible two-proton and two-electron transfer reaction with the apparent electron transfer rate constant (k(s)) of 3.68 s⁻¹. The proposed biosensor shows fast amperometric response (8s) to glucose with a wide linear range from 2.5 × 10⁻⁵ M to 1.1 × 10⁻³ M, a low detection limit of 1.0 × 10⁻⁵ M at signal-to-noise of 3 and good sensitivity (7.6 ± 0.5 mA M⁻¹ cm⁻²). The resulting biosensor has acceptable operational stability, good reproducibility and excellent selectivity and can be successfully applied in the reagentless glucose sensing at -0.45 V. It should be worthwhile noting that it opens a new avenue for fabricating excellent electrochemical biosensor. PMID:21592767

  3. Carbon nanotubes-nanoflake-like SnS2 nanocomposite for direct electrochemistry of glucose oxidase and glucose sensing.

    PubMed

    Li, Juan; Yang, Zhanjun; Tang, Yan; Zhang, Yongcai; Hu, Xiaoya

    2013-03-15

    Multi-walled carbon nanotubes (MWCNTs)-nanoflake-like SnS(2) nanocomposite were designed for immobilization of glucose oxidase (GOx). The direct electrochemistry of GOx and glucose sensing at MWCNTs-SnS(2) modified glassy carbon electrode were studied. Compared with single MWCNTs or SnS(2), the MWCNTs-SnS(2) film has larger surface area and provides a more favorable microenvironment for facilitating the electron transfer between enzyme and electrode surface. The properties of GOx/MWCNTs-SnS(2) were examined by scanning electron microscopy, UV-vis spectroscopy, Fourier transform infrared spectroscopy and cyclic voltammetry. The immobilized enzyme on MWCNTs-SnS(2) composite film retained its native structure and bioactivity and showed a surface controlled, reversible two-proton and two-electron transfer reaction with a apparent electron transfer rate constant of 3.96 s(-1). The constructed glucose biosensor exhibits wider linear range from 2.0×10(-5) M to 1.95×10(-3) M, much lower detection limit of 4.0×10(-6) M at signal-to-noise of 3 and higher sensitivity of 21.65 mA M(-1) cm(-2) than our previous nanoflake-like SnS(2)-based glucose sensor. The proposed biosensor has excellent selectivity, good reproducibility, and acceptable operational stability and can be successfully applied in the reagentless glucose sensing at -0.43 V. This MWCNTs-SnS(2) composite provides a new avenue for immobilizing proteins and fabricating excellent biosensors. PMID:23083908

  4. Integration of electrochemistry in micro-total analysis systems for biochemical assays: recent developments.

    PubMed

    Xu, Xiaoli; Zhang, Song; Chen, Hui; Kong, Jilie

    2009-11-15

    Micro-total analysis systems (microTAS) integrate different analytical operations like sample preparation, separation and detection into a single microfabricated device. With the outstanding advantages of low cost, satisfactory analytical efficiency and flexibility in design, highly integrated and miniaturized devices from the concept of microTAS have gained widespread applications, especially in biochemical assays. Electrochemistry is shown to be quite compatible with microanalytical systems for biochemical assays, because of its attractive merits such as simplicity, rapidity, high sensitivity, reduced power consumption, and sample/reagent economy. This review presents recent developments in the integration of electrochemistry in microdevices for biochemical assays. Ingenious microelectrode design and fabrication methods, and versatility of electrochemical techniques are involved. Practical applications of such integrated microsystem in biochemical assays are focused on in situ analysis, point-of-care testing and portable devices. Electrochemical techniques are apparently suited to microsystems, since easy microfabrication of electrochemical elements and a high degree of integration with multi-analytical functions can be achieved at low cost. Such integrated microsystems will play an increasingly important role for analysis of small volume biochemical samples. Work is in progress toward new microdevice design and applications. PMID:19782186

  5. Merits of online electrochemistry liquid sample desorption electrospray ionization mass spectrometry (EC/LS DESI MS).

    PubMed

    Looi, Wen Donq; Brown, Blake; Chamand, Laura; Brajter-Toth, Anna

    2016-03-01

    A new online electrochemistry/liquid sample desorption electrospray ionization mass spectrometry (EC/LS DESI MS) system with a simple electrochemical thin-layer flow-through cell was developed and tested using N,N-dimethyl-p-phenylenediamine (DMPA) as a model probe. Although oxidation of DMPA is observed as a result of ionization of LS in positive ion mode LS DESI, application of voltage to the online electrochemical (EC) cell in EC/LS DESI MS increases yields of oxidation products. An advantage of LS DESI MS is its sensitivity in aqueous electrolyte solutions, which improves efficiency of electrochemical reactions in EC/LS DESI MS. In highly conductive low pH aqueous buffer solutions, oxidation efficiency is close to 100 %. EC/ESI MS typically requires mixed aqueous/organic solvents and low electrolyte concentrations for efficient ionization in MS, limiting efficiency of electrochemistry online with MS. Independently, the results verify higher electrochemical oxidation efficiency during positive mode ESI than during LS DESI. Graphical abstract Detection of DMPA oxidation in online electrochemical cell with EC/LS DESI MS. PMID:26886744

  6. Metal-air batteries: from oxygen reduction electrochemistry to cathode catalysts.

    PubMed

    Cheng, Fangyi; Chen, Jun

    2012-03-21

    Because of the remarkably high theoretical energy output, metal-air batteries represent one class of promising power sources for applications in next-generation electronics, electrified transportation and energy storage of smart grids. The most prominent feature of a metal-air battery is the combination of a metal anode with high energy density and an air electrode with open structure to draw cathode active materials (i.e., oxygen) from air. In this critical review, we present the fundamentals and recent advances related to the fields of metal-air batteries, with a focus on the electrochemistry and materials chemistry of air electrodes. The battery electrochemistry and catalytic mechanism of oxygen reduction reactions are discussed on the basis of aqueous and organic electrolytes. Four groups of extensively studied catalysts for the cathode oxygen reduction/evolution are selectively surveyed from materials chemistry to electrode properties and battery application: Pt and Pt-based alloys (e.g., PtAu nanoparticles), carbonaceous materials (e.g., graphene nanosheets), transition-metal oxides (e.g., Mn-based spinels and perovskites), and inorganic-organic composites (e.g., metal macrocycle derivatives). The design and optimization of air-electrode structure are also outlined. Furthermore, remarks on the challenges and perspectives of research directions are proposed for further development of metal-air batteries (219 references). PMID:22254234

  7. Numerical Modeling of the Distributed Electrochemistry and Performance of Solid Oxide Fuel Cells

    SciTech Connect

    Recknagle, Kurtis P.; Ryan, Emily M.; Khaleel, Mohammad A.

    2011-12-01

    A cell-level distributed electrochemistry (DEC) modeling tool has been developed to enable prediction of solid oxide fuel cell performance by considering the coupled and spatially varying multi-physics that occur within the tri-layer. The approach calculates the distributed electrochemistry within the electrodes, which includes the charge transfer and electric potential fields, ion transport throughout the tri-layer, and gas distributions within the composite and porous electrodes. The thickness of the electrochemically active regions within the electrodes is calculated along with the distributions of charge transfer. The DEC modeling tool can examine the overall SOFC performance based on electrode microstructural parameters, such as particle size, pore size, porosity factor, electrolyte and electrode phase volume fractions, and triple-phase-boundary length. Recent developments in electrode fabrication methods have lead to increased interest in using graded and nano-structured electrodes to improve the electrochemical performance of SOFCs. This paper demonstrates how the DEC modeling tool can be used to help design novel electrode microstructures by optimizing a graded anode for high electrochemical performance.

  8. Na-Ion Battery Anodes: Materials and Electrochemistry.

    PubMed

    Luo, Wei; Shen, Fei; Bommier, Clement; Zhu, Hongli; Ji, Xiulei; Hu, Liangbing

    2016-02-16

    also outlined, where graphene oxide was employed as dehydration agent and 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) was used to unzip wood fiber. Furthermore, surface modification by atomic layer deposition technology is introduced, where we discover that a thin layer of Al2O3 can function to encapsulate Sn nanoparticles, leading to a much enhanced cycling performance. We also highlight recent work about the phosphorene/graphene anode, which outperformed other anodes in terms of capacity. The aromatic organic anode is also studied as anode with very high initial sodiation capacity. Furthermore, electrochemical intercalation of Na ions into reduced graphene oxide is applied for fabricating transparent conductors, demonstrating the great feasibility of Na ion intercalation for optical applications. PMID:26783764

  9. Effectiveness of Interactive Multimedia Module with Pedagogical Agent (IMMPA) in the Learning of Electrochemistry: A Preliminary Investigation

    ERIC Educational Resources Information Center

    Lee, Tien Tien; Osman, Kamisah

    2011-01-01

    Electrochemistry is found to be a difficult topic to learn due to its abstract concepts that involve the macroscopic, microscopic and symbolic representation levels. Research showed that animation and simulation using Information and Communication Technology (ICT) can help students to visualize and hence enhance students' understanding in learning…

  10. Conceptual Difficulties Experienced by Senior High School Students of Electrochemistry: Electric Circuits and Oxidation-Reduction Equations.

    ERIC Educational Resources Information Center

    Garnett, Pamela J.; Treagust, David F.

    1992-01-01

    Interview data exemplify students' attempts to integrate the concepts of electrochemistry with related knowledge that they had previously constructed or acquired in other classes. The implications for minimizing potential misconceptions center on the difficulties students experience when using more than one model for explaining scientific…

  11. Effects of Lecture Method Supplemented with Music and Computer Animation on Senior Secondary School Students' Academic Achievement in Electrochemistry

    ERIC Educational Resources Information Center

    Akpoghol, T. V.; Ezeudu, F. O.; Adzape, J. N.; Otor, E. E.

    2016-01-01

    The study investigated the effects of Lecture Method Supplemented with Music (LMM) and Computer Animation (LMC) on senior secondary school students' academic achievement in electrochemistry in Makurdi metropolis. Six research questions and six hypotheses guided the study. The design of the study was quasi experimental, specifically the pre-test,…

  12. Relative Effect of Lecture Method Supplemented with Music and Computer Animation on Senior Secondary School Students' Retention in Electrochemistry

    ERIC Educational Resources Information Center

    Akpoghol, T. V.; Ezeudu, F. O.; Adzape, J. N.; Otor, E. E.

    2016-01-01

    The study investigated the effects of Lecture Method Supplemented with Music (LMM) and Computer Animation (LMC) on senior secondary school students' retention in electrochemistry in Makurdi metropolis. Three research questions and three hypotheses guided the study. The design of the study was quasi experimental, specifically the pre-test,…

  13. Impact of Interactive Multimedia Module with Pedagogical Agents on Students' Understanding and Motivation in the Learning of Electrochemistry

    ERIC Educational Resources Information Center

    Osman, Kamisah; Lee, Tien Tien

    2014-01-01

    The Electrochemistry topic is found to be difficult to learn due to its abstract concepts involving macroscopic, microscopic, and symbolic representation levels. Studies have shown that animation and simulation using information and communication technology (ICT) can help students to visualize and hence enhance their understanding in learning…

  14. Serendipity: Genesis of the Electrochemical Instrumentation at Princeton Applied Research Corporation

    NASA Astrophysics Data System (ADS)

    Flato, J. B.

    2007-04-01

    Development of commercial scientific instrumentation is very different from constructing a single device to be used in a researcher's laboratory. The history of the development of Princeton Applied Research Corporation's first electrochemistry instrument is used to illustrate the process and to review, by example, the pitfalls that may arise when scientists with little or no commercial or practical engineering experience undertake the development of a product destined for commercial manufacturing and distribution.

  15. Semiconductor electrochemistry of coal pyrite. Technical progress report, October--December 1993

    SciTech Connect

    Osseo-Asare, K.; Wei, D.

    1994-03-01

    The effects of the semiconductor properties of pyrite on its electrochemical behavior have been explored with the aid of energy level diagram which illustrate the relationship between the energy levels of the solid land the equilibrium potentials of the redox couples in the aqueous solution. A novel approach to the study of pyrite electrochemistry was initiated. This approach is based on pyrite microelectrodes synthesized via aqueous phase precipitation. Preliminary results show that photocurrents can be generated by illumination of the pyrite particles synthesized in our laboratory. Central to this research is the recognition that pyrite is a semiconductor material. (Photo) electrochemical experiments are conducted to unravel the mechanisms of anodic and cathodic processes such as those associated with pyrite decomposition and the reduction of oxidants such as molecular oxygen and the ferric ion.

  16. Applications of the Lithium Focused Ion Beam: Nanoscale Electrochemistry and Microdisk Mode Imaging

    NASA Astrophysics Data System (ADS)

    McGehee, William; Takeuchi, Saya; Michels, Thomas; Oleshko, Vladimir; Aksyuk, Vladimir; Soles, Christopher; McClelland, Jabez; Center for Nanoscale Science; Technology at NIST Collaboration; Materials Measurement Laboratory at NIST Collaboration

    2016-05-01

    The NIST-developed lithium Focused-Ion-Beam (LiFIB) system creates a low-energy, picoampere-scale ion beam from a photoionized gas of laser-cooled atoms. The ion beam can be focused to a <30 nm spot and scanned across a sample. This enables imaging through collection of ion-induced secondary electrons (similar to SEM) as well as the ability to selectively deposit lithium-ions into nanoscale volumes in a material. We exploit this second ability of the LiFIB to selectively ''titrate'' lithium ions as a means of probing the optical modes in microdisk resonators as well as for exploring nanoscale, Li-ion electrochemistry in battery-relevant materials. We present an overview of both measurements, including imaging of the optical mode in a silicon microdisk and a comparison of FIB and electrochemical lithiation of tin.

  17. The edge- and basal-plane-specific electrochemistry of a single-layer graphene sheet

    PubMed Central

    Yuan, Wenjing; Zhou, Yu; Li, Yingru; Li, Chun; Peng, Hailin; Zhang, Jin; Liu, Zhongfan; Dai, Liming; Shi, Gaoquan

    2013-01-01

    Graphene has a unique atom-thick two-dimensional structure and excellent properties, making it attractive for a variety of electrochemical applications, including electrosynthesis, electrochemical sensors or electrocatalysis, and energy conversion and storage. However, the electrochemistry of single-layer graphene has not yet been well understood, possibly due to the technical difficulties in handling individual graphene sheet. Here, we report the electrochemical behavior at single-layer graphene-based electrodes, comparing the basal plane of graphene to its edge. The graphene edge showed 4 orders of magnitude higher specific capacitance, much faster electron transfer rate and stronger electrocatalytic activity than those of graphene basal plane. A convergent diffusion effect was observed at the sub-nanometer thick graphene edge-electrode to accelerate the electrochemical reactions. Coupling with the high conductivity of a high-quality graphene basal plane, graphene edge is an ideal electrode for electrocatalysis and for the storage of capacitive charges. PMID:23896697

  18. Two-Step Bipolar Electrochemistry: Generation of Composition Gradient and Visual Screening of Electrocatalytic Activity.

    PubMed

    Termebaf, Hajar; Shayan, Mohsen; Kiani, Abolfazl

    2015-12-01

    Bipolar electrochemistry (BE) is employed for both creating electrocatalysts composition gradient and visual screening of the prepared composition on a single substrate in just two experiment runs. In a series of proof-of-principle experiments, we demonstrate gradient electrodeposition of Ni-Cu using BE; then the electrocatalytic activity of the prepared composition gradient toward the hydrogen evolution reaction (HER) is visually screened in the BE system using array of BPEs. Moreover, the morphology and the chemical composition of the Ni-Cu gradient are screened along the length of the bipolar electrode (BPE). By measuring the potential gradient over the BPE, it is also demonstrated that by controlling the concentration of the metals precursor and the supporting electrolyte, the length of the bipolar electrodeposited gradient can be controlled. PMID:26595192

  19. In Situ, Real-Time Visualization of Electrochemistry Using Magnetic Resonance Imaging.

    PubMed

    Britton, Melanie M; Bayley, Paul M; Howlett, Patrick C; Davenport, Alison J; Forsyth, Maria

    2013-09-01

    The drive to develop better electrochemical energy storage devices requires the development of not only new materials, but also better understanding of the underpinning chemical and dynamical processes within such devices during operation, for which new analytical techniques are required. Currently, there are few techniques that can probe local composition and transport in the electrolyte during battery operation. In this paper, we report a novel application of magnetic resonance imaging (MRI) for probing electrochemical processes in a model electrochemical cell. Using MRI, the transport and zinc and oxygen electrochemistry in an alkaline electrolyte, typical of that found in zinc-air batteries, are investigated. Magnetic resonance relaxation maps of the electrolyte are used to visualize the chemical composition and electrochemical processes occurring during discharge in this model metal-air battery. Such experiments will be useful in the development of new energy storage/conversion devices, as well as other electrochemical technologies. PMID:24265861

  20. Direct electrochemistry of the hydroxylase of soluble methane monooxygenase from Methylococcus capsulatus (Bath).

    PubMed

    Kazlauskaite, J; Hill, H A; Wilkins, P C; Dalton, H

    1996-10-15

    The redox properties of the hydroxylase component of soluble methane monooxygenase from Methylococcus capsulatus (Bath) have been thoroughly investigated. Previous studies used redox indicator titrations and spectroscopic methods for the determination of the concentrations of reduced species. Herein we report, for the first time, direct electrochemistry (i.e. without the use of mediators) of the diiron centers of the hydroxylase from M. capsulatus (Bath) at a modified gold electrode giving rise to two waves at 4(+/- 10) mV and -386(+/- 14) mV versus saturated calomel electrode (SCE). In addition, the effects of proteins B and B' on the redox reactions were determined. The redox potentials of the complex with protein B are -25(+/- 14) mV and -433(+/- 8) mV versus SCE whereas protein B' had no effect though it did alter the effect of protein B on the redox potentials. PMID:8917455

  1. The electrochemistry in 316SS crevices exposed to PWR-relevant conditions

    NASA Astrophysics Data System (ADS)

    Vankeerberghen, M.; Weyns, G.; Gavrilov, S.; Henshaw, J.; Deconinck, J.

    2009-04-01

    The chemical and electrochemical conditions within a crevice of Type 316 stainless steel in boric acid-lithium hydroxide solutions under PWR-relevant conditions were modelled with a computational electrochemistry code. The influence of various variables: dissolved hydrogen, boric acid, lithium hydroxide concentration, crevice length, and radiation dose rate was studied. It was found with the model that 25 ccH 2/kg (STP) was sufficient to remain below an electrode potential of -230 mV she, commonly accepted sufficient to prevent stress corrosion cracking under BWR conditions. In a PWR plant various operational B-Li cycles are possible but it was found that the choice of the cycle did not significantly influence the model results. It was also found that a hydrogen level of 50 ccH 2/kg (STP) would be needed to avoid substantial lowering of the pH inside a crevice.

  2. Scanning Electrochemical Cell Microscopy: A Versatile Technique for Nanoscale Electrochemistry and Functional Imaging

    NASA Astrophysics Data System (ADS)

    Ebejer, Neil; Güell, Aleix G.; Lai, Stanley C. S.; McKelvey, Kim; Snowden, Michael E.; Unwin, Patrick R.

    2013-06-01

    Scanning electrochemical cell microscopy (SECCM) is a new pipette-based imaging technique purposely designed to allow simultaneous electrochemical, conductance, and topographical visualization of surfaces and interfaces. SECCM uses a tiny meniscus or droplet, at the end of a double-barreled (theta) pipette, for high-resolution functional imaging and nanoscale electrochemical measurements. Here we introduce this technique and provide an overview of its principles, instrumentation, and theory. We discuss the power of SECCM in resolving complex structure-activity problems and provide considerable new information on electrode processes by referring to key example systems, including graphene, graphite, carbon nanotubes, nanoparticles, and conducting diamond. The many longstanding questions that SECCM has been able to answer during its short existence demonstrate its potential to become a major technique in electrochemistry and interfacial science.

  3. Critical transport rates that limit the performance of microbial electrochemistry technologies.

    PubMed

    Popat, Sudeep C; Torres, César I

    2016-09-01

    Microbial electrochemistry technologies (METs) take advantage of the connection of microorganisms with electrodes. In the classic case of a microbial anode, the maximization of current density produced is often the goal. But, current production is dependent on many transport processes occurring, which can be rate-limiting. These include the fluxes of electron donor and acceptor, the ionic flux, the acidity and alkalinity fluxes at anode and cathode respectively, the electron transport flux at the biofilm, and the reactant/product crossover flux. Associated with these fluxes are inherent concentration gradients that can affect performance. This critical review provides an analysis on how these transport processes have hindered the development of METs, and how MET designs have evolved as more knowledge of these transport limitations is gained. Finally, suggestions are provided on how to design MET systems taking into consideration critical transport processes that are intimately linked to the current produced. PMID:27211921

  4. Electrochemistry in Media of Exceptionally Low Polarity: Voltammetry with a Fluorous Solvent.

    PubMed

    Olson, Eric J; Boswell, Paul G; Givot, Bradley L; Yao, Letitia J; Bühlmann, Philippe

    2010-02-15

    This work demonstrates the first cyclic voltammetry in a perfluorocarbon solvent without use of a cosolvent. The novel electrolyte tetrabutylammonium tetrakis[3,5-bis(perfluorohexyl)phenyl]borate (NBu(4)BArF(104); 80 mM) allows for voltammetry of ferrocene in perfluoro(methylcyclohexane) by lowering the specific resistance to Ω268 k cm at 20.8 °C. Despite significant solution resistance, the resulting voltammograms can be fitted quantitatively without difficulty. The thus determined standard electron transfer rate constant, k°, for the oxidation of ferrocene in perfluoro(methylcyclohexane) is somewhat smaller than for many solvents commonly used in electrochemistry, but can be explained readily as the result of the viscosity and size of the solvent using Marcus theory. Dielectric dispersion spectroscopy verifies that addition of NBu(4)BArF(104) does not significantly raise the overall polarity of the solution over that of neat perfluoro(methylcyclohexane). PMID:20212920

  5. Semiconductor electrochemistry of coal pyrite. Technical progress report, January--March 1992

    SciTech Connect

    Osseo-Asare, K.

    1992-05-01

    This project seeks to advance the fundamental understanding of the physicochemical processes occurring at the pyrite/aqueous interface, in the context of coal cleaning, coal desulfurization, and acid mine drainage. A novel approach to the study of pyrite aqueous electrochemistry is proposed, based on the use of both synthetic and natural (i.e. coal-derived) pyrite specimens, the utilization of pyrite both in the form of micro (i.e. colloidal and subcolloidal) and macro (i.e. rotating ring disk)-electrodes, and the application of in-situ direct electroanalytical and spectroelectrochemical characterization techniques. Central to this research is the recognition that pyrite is a semiconductor material. (Photo)electrochemical experiments will be conducted to unravel the mechanisms of anodic and cathodic processes such as those associated with pyrite decomposition and the reduction of oxidants such as molecular oxygen and the ferric ion.

  6. In Situ, Real-Time Visualization of Electrochemistry Using Magnetic Resonance Imaging

    PubMed Central

    2013-01-01

    The drive to develop better electrochemical energy storage devices requires the development of not only new materials, but also better understanding of the underpinning chemical and dynamical processes within such devices during operation, for which new analytical techniques are required. Currently, there are few techniques that can probe local composition and transport in the electrolyte during battery operation. In this paper, we report a novel application of magnetic resonance imaging (MRI) for probing electrochemical processes in a model electrochemical cell. Using MRI, the transport and zinc and oxygen electrochemistry in an alkaline electrolyte, typical of that found in zinc-air batteries, are investigated. Magnetic resonance relaxation maps of the electrolyte are used to visualize the chemical composition and electrochemical processes occurring during discharge in this model metal-air battery. Such experiments will be useful in the development of new energy storage/conversion devices, as well as other electrochemical technologies. PMID:24265861

  7. The Rich Electrochemistry and Redox Reactions of the Copper Sites in the Cellular Prion Protein

    PubMed Central

    Zhou, Feimeng; Millhauser, Glenn L.

    2012-01-01

    This paper reviews recent electrochemical studies of the copper complexes of prion protein (PrP) and its related peptides, and correlates their redox behavior to chemical and biologically relevant reactions. Particular emphasis is placed on the difference in redox properties between copper in the octarepeat (OR) and the non-OR domains of PrP, as well as differences between the high and low copper occupancy states in the OR domain. Several discrepancies in literature concerning these differences are discussed and reconciled. The PrP copper complexes, in comparison to copper complexes of other amyloidogenic proteins/peptides, display a more diverse and richer redox chemistry. The specific protocols and caveats that need to be considered in studying the electrochemistry and redox reactions of copper complexes of PrP, PrP-derived peptides, and other related amyloidogenic proteins are summarized. PMID:23144499

  8. Regal electrochemistry: British 5 pence coins provide useful metallic macroelectrode substrates.

    PubMed

    Tan, Fang; Smith, Jamie P; Kampouris, Dimitrios K; Kamieniak, Joanna; Banks, Craig E

    2015-10-01

    The utilisation of British Currency (GBP) as an electrode substrate is demonstrated for the first time. Termed Regal electrochemistry, a 5 pence (5p) coin (GBP) is electrically wired using a bespoke electrochemical cell and is electrochemically characterised using the outer-sphere redox probe hexaammineruthenium(III) chloride. The electroanalytical utility of the 5p coin electrode is demonstrated towards the novel, proof-of-concept sensing of lead(II) ions using square-wave voltammetry in model buffer solutions over the linear range 5-2000 nM exhibiting a limit of detection (3σ) of 1.97 nM. Interestingly, the actual cost of the electrode is 2.5 pence (GBP) since both sides of the coins can be utilised and provide a cheap yet reproducible and disposable metallic electrode substrate that is electrochemically useful. PMID:26283064

  9. Scanning electrochemical cell microscopy: a versatile technique for nanoscale electrochemistry and functional imaging.

    PubMed

    Ebejer, Neil; Güell, Aleix G; Lai, Stanley C S; McKelvey, Kim; Snowden, Michael E; Unwin, Patrick R

    2013-01-01

    Scanning electrochemical cell microscopy (SECCM) is a new pipette-based imaging technique purposely designed to allow simultaneous electrochemical, conductance, and topographical visualization of surfaces and interfaces. SECCM uses a tiny meniscus or droplet, at the end of a double-barreled (theta) pipette, for high-resolution functional imaging and nanoscale electrochemical measurements. Here we introduce this technique and provide an overview of its principles, instrumentation, and theory. We discuss the power of SECCM in resolving complex structure-activity problems and provide considerable new information on electrode processes by referring to key example systems, including graphene, graphite, carbon nanotubes, nanoparticles, and conducting diamond. The many longstanding questions that SECCM has been able to answer during its short existence demonstrate its potential to become a major technique in electrochemistry and interfacial science. PMID:23560932

  10. An electrochemistry-based impedance model for lithium-ion batteries

    NASA Astrophysics Data System (ADS)

    Li, Shengbo Eben; Wang, Baojin; Peng, Huei; Hu, Xiaosong

    2014-07-01

    Accurate models of lithium-ion batteries are important for analyzing and predicting battery dynamics and aging. This paper presents an electrochemistry-based impedance model for lithium-ion batteries to better understand the relationship between battery internal dynamics and external measurement. The proposed impedance model is a modified single particle model which balances between simplicity and accuracy. The model includes electrochemical impedance due to charge-transfer reaction, diffusion dynamics in the electrodes, effects of ion concentration, capacitance dispersion in the double layer, and anode insulating film growth, etc. The impedance tests for model validation were performed on two lithium-ion cells at ambient temperature and at different SOC levels. A particle swarm optimization method is employed to identify model parameters. The model accuracy under different conditions is compared with that of conventional Randles model and the parameter variations at different stage of the aging process are studied.

  11. Mechanistic studies of pyridinium electrochemistry: alternative chemical pathways in the presence of CO2.

    PubMed

    Peroff, A G; Weitz, E; Van Duyne, R P

    2016-01-21

    Protonated heterocyclic amines, such as pyridinium, have been utilized as catalysts in the electrocatalytic reduction of carbon dioxide. While these represent a new and exciting class of electrocatalysts, the details of the mechanism and faradaic processes occurring in solution are unclear. We report a series of cyclic voltammetry experiments involving Pt, Ag, Au, and Cu electrodes, under both aqueous and nonaqueous conditions, directed towards gaining an improved mechanistic understanding of pyridinium electrochemistry. Surface-enhanced Raman (SER) spectroelectrochemistry was also performed on Cu film-over-nanosphere electrodes in order to identify adsorbed species. It was found that the reduction potential of pyridinium (-0.58 V vs. SCE) and its electrochemical reversibility are unique features of platinum electrodes. In contrast, the reduction potentials on Ag, Au, and Cu electrodes are ∼400 mV more negative than Pt in both the presence and the absence of CO2. SER spectroelectrochemistry of pyridinium solutions shows no evidence for a pyridinium radical or a pyridinium ion. Increased cathodic current in the presence of CO2 is only detected at scan rates less than 10 mV s(-1) in aqueous solutions. The addition of CO2 resulted in a shift in the potential for the hydrogen evolution reaction. Pyridinium electrochemistry was observed under nonaqueous conditions; however no increase in cathodic current was observed when CO2 was added to the solution. Based on this set of results it is concluded that the reduction potential of pyridinium is surface dependent, CO2 acts as a pseudo-reserve of H(+), and pyridinium and CO2 create an alternative mechanism for hydrogen evolution. PMID:26670579

  12. Interfacial electrochemistry of pyrite oxidation and flotation. 1: Effect of borate on pyrite surface oxidation

    SciTech Connect

    Wang, X.H.

    1996-03-25

    The interfacial chemistry of pyrite is of great industrial importance in complex sulfide ore flotation, coal desulfurization, acid mine drainage mitigation, and conversion of solar energy to electrical or chemical energy. Sodium tetraborate (Na{sub 2}B{sub 4}O{sub 7}) has been widely used as an electrolyte and pH buffer in studying the interfacial electrochemistry of sulfide minerals in relation to sulfide mineral flotation. In all the previous studies published so far, borate was regarded as an inert electrolyte/pH buffer, and its reactions with the sulfide minerals were completely overlooked. In this first part of this series papers, the complicating effects of borate on the interfacial electrochemistry of pyrite have been studied. In the borate solutions, the surface oxidation of pyrite is strongly enhanced. The first and rate-determining step of the reaction between borate and pyrite has been shown to be the following irreversible reaction: FeS{sub 2} + B(OH){sub 4}{sup {minus}} {yields} FeS{sub 2} {hor_ellipsis} [B(OH){sub 4}]{sub ads} + e. This reaction appears in the voltammogram as an anodic oxidation peak at potentials of more than 0.4 V lower than the commencement of pyrite oxidation in sodium perchlorate or nitrate electrolyte solutions. As the borate concentration increases, the peak current increases linearly, while the peak potential shifts positively at 240 mV per decade. On a rotating-disc electrode, the peak becomes a plateau. The limiting current density is a linear function of the square root of the rotation speed at relatively low rotation speeds. The Tafel slope is close to 240 mV per decade and is independent of the rotation speed and borate concentration. The results indicate that charge transfer coefficient is 0.25.

  13. In-Depth Characterization of Protein Disulfide Bonds by Online Liquid Chromatography-Electrochemistry-Mass Spectrometry

    NASA Astrophysics Data System (ADS)

    Switzar, Linda; Nicolardi, Simone; Rutten, Julie W.; Oberstein, Saskia A. J. Lesnik; Aartsma-Rus, Annemieke; van der Burgt, Yuri E. M.

    2016-01-01

    Disulfide bonds are an important class of protein post-translational modifications, yet this structurally crucial modification type is commonly overlooked in mass spectrometry (MS)-based proteomics approaches. Recently, the benefits of online electrochemistry-assisted reduction of protein S-S bonds prior to MS analysis were exemplified by successful characterization of disulfide bonds in peptides and small proteins. In the current study, we have combined liquid chromatography (LC) with electrochemistry (EC) and mass analysis by Fourier transform ion cyclotron resonance (FTICR) MS in an online LC-EC-MS platform to characterize protein disulfide bonds in a bottom-up proteomics workflow. A key advantage of a LC-based strategy is the use of the retention time in identifying both intra- and interpeptide disulfide bonds. This is demonstrated by performing two sequential analyses of a certain protein digest, once without and once with electrochemical reduction. In this way, the "parent" disulfide-linked peptide detected in the first run has a retention time-based correlation with the EC-reduced peptides detected in the second run, thus simplifying disulfide bond mapping. Using this platform, both inter- and intra-disulfide-linked peptides were characterized in two different proteins, ß-lactoglobulin and ribonuclease B. In order to prevent disulfide reshuffling during the digestion process, proteins were digested at a relatively low pH, using (a combination of) the high specificity proteases trypsin and Glu-C. With this approach, disulfide bonds in ß-lactoglobulin and ribonuclease B were comprehensively identified and localized, showing that online LC-EC-MS is a useful tool for the characterization of protein disulfide bonds.

  14. Electrochemistry-mass spectrometry for in-vitro determination of selected chemotherapeutics and their electrochemical products in comparison to in-vivo approach.

    PubMed

    Szultka-Mlynska, Malgorzata; Buszewski, Boguslaw

    2016-11-01

    Chemotherapeutics are among the most frequently prescribed medications in modern medicine. They are widely prescribed; however, problems with organisms developing resistance to these drugs means that their efficacy may be lost, so care should be taken to avoid unnecessary prescription. It is therefore of great interest to study the detailed metabolism of these biologically active compounds. This study aimed at developing an efficient analytical protocol for the determination of in-vitro electrochemical products of selected antibiotic drugs (amoxicillin, cefotaxime, fluconazole, linezolid, metronidazole and moxifloxacin). Combination of electrochemistry (EC) and mass spectrometry (MS) was applied for the in-vitro determination of the studied antibiotics and their electrochemical products. To identify the structure of the detected electrochemical products, MS/MS experiments were performed. This was one of the first applications of the EC system for generation of electrochemical products produced from antibiotic drugs. Adjustment of appropriate conditions and such parameters as the potential value, mobile phase (pH), working electrode and temperature had significant influence on electrochemical simulations and the creation of selected derivatives. Consequently, several working electrodes were evaluated for this purpose. In most of the studied cases, mainly two types of products were observed. One corresponded to an increase in mass by 14Da, which can be explained by a process consisting of oxidation (+16 m/z) and dehydrogenation (-2 m/z); The second in turn showed mass reduction by 14Da, which can be attributed to the loss of -CH2 as a result of N-demethylation. The performed experiments consisted of two stages: electrochemical oxidation of the analyzed samples (phase I of metabolic transformation), and addition of glutathione (GSH) for follow-up reactions (phase II conjunction). The electrochemical results were compared to in-vivo experiments by analyzing urine

  15. Phase I and phase II reductive metabolism simulation of nitro aromatic xenobiotics with electrochemistry coupled with high resolution mass spectrometry.

    PubMed

    Bussy, Ugo; Chung-Davidson, Yu-Wen; Li, Ke; Li, Weiming

    2014-11-01

    Electrochemistry combined with (liquid chromatography) high resolution mass spectrometry was used to simulate the general reductive metabolism of three biologically important nitro aromatic molecules: 3-trifluoromethyl-4-nitrophenol (TFM), niclosamide, and nilutamide. TFM is a pesticide used in the Laurential Great Lakes while niclosamide and nilutamide are used in cancer therapy. At first, a flow-through electrochemical cell was directly connected to a high resolution mass spectrometer to evaluate the ability of electrochemistry to produce the main reduction metabolites of nitro aromatic, nitroso, hydroxylamine, and amine functional groups. Electrochemical experiments were then carried out at a constant potential of -2.5 V before analysis of the reduction products by LC-HRMS, which confirmed the presence of the nitroso, hydroxylamine, and amine species as well as dimers. Dimer identification illustrates the reactivity of the nitroso species with amine and hydroxylamine species. To investigate xenobiotic metabolism, the reactivity of nitroso species to biomolecules was also examined. Binding of the nitroso metabolite to glutathione was demonstrated by the observation of adducts by LC-ESI(+)-HRMS and the characteristics of their MSMS fragmentation. In conclusion, electrochemistry produces the main reductive metabolites of nitro aromatics and supports the observation of nitroso reactivity through dimer or glutathione adduct formation. PMID:25234306

  16. 2D Cross Sectional Analysis and Associated Electrochemistry of Composite Electrodes Containing Dispersed Agglomerates of Nanocrystalline Magnetite, Fe₃O₄.

    PubMed

    Bock, David C; Kirshenbaum, Kevin C; Wang, Jiajun; Zhang, Wei; Wang, Feng; Wang, Jun; Marschilok, Amy C; Takeuchi, Kenneth J; Takeuchi, Esther S

    2015-06-24

    When electroactive nanomaterials are fully incorporated into an electrode structure, characterization of the crystallite sizes, agglomerate sizes, and dispersion of the electroactive materials can lend insight into the complex electrochemistry associated with composite electrodes. In this study, composite magnetite electrodes were sectioned using ultramicrotome techniques, which facilitated the direct observation of crystallites and agglomerates of magnetite (Fe3O4) as well as their dispersal patterns in large representative sections of electrode, via 2D cross sectional analysis by Transmission Electron Microscopy (TEM). Further, the electrochemistry of these electrodes were recorded, and Transmission X-ray Microscopy (TXM) was used to determine the distribution of oxidation states of the reduced magnetite. Unexpectedly, while two crystallite sizes of magnetite were employed in the production of the composite electrodes, the magnetite agglomerate sizes and degrees of dispersion in the two composite electrodes were similar to each other. This observation illustrates the necessity for careful characterization of composite electrodes, in order to understand the effects of crystallite size, agglomerate size, and level of dispersion on electrochemistry. PMID:26024206

  17. Analysis of the electrochemistry of hemes with Ems spanning 800 mV

    PubMed Central

    Zheng, Zhong; Gunner, M. R.

    2009-01-01

    The free energy of heme reduction in different proteins is found to vary over more than 18 kcal/mol. It is a challenge to determine how proteins manage to achieve this enormous range of Ems with a single type of redox cofactor. Proteins containing 141 unique hemes of a-, b-, and c-type, with bis-His, His-Met, and aquo-His ligation were calculated using Multi-Conformation Continuum Electrostatics (MCCE). The experimental Ems range over 800 mV from −350 mV in cytochrome c3 to 450 mV in cytochrome c peroxidase (vs. SHE). The quantitative analysis of the factors that modulate heme electrochemistry includes the interactions of the heme with its ligands, the solvent, the protein backbone, and sidechains. MCCE calculated Ems are in good agreement with measured values. Using no free parameters the slope of the line comparing calculated and experimental Ems is 0.73 (R2 = 0.90), showing the method accounts for 73% of the observed Em range. Adding a +160 mV correction to the His-Met c-type hemes yields a slope of 0.97 (R2 = 0.93). With the correction 65% of the hemes have an absolute error smaller than 60 mV and 92% are within 120 mV. The overview of heme proteins with known structures and Ems shows both the lowest and highest potential hemes are c-type, whereas the b-type hemes are found in the middle Em range. In solution, bis-His ligation lowers the Em by ≈205 mV relative to hemes with His-Met ligands. The bis-His, aquo-His, and His-Met ligated b-type hemes all cluster about Ems which are ≈200 mV more positive in protein than in water. In contrast, the low potential bis-His c-type hemes are shifted little from in solution, whereas the high potential His-Met c-type hemes are raised by ≈300 mV from solution. The analysis shows that no single type of interaction can be identified as the most important in setting heme electrochemistry in proteins. For example, the loss of solvation (reaction field) energy, which raises the Em, has been suggested to be a major factor in

  18. Immobilization and direct electrochemistry of glucose oxidase on a tetragonal pyramid-shaped porous ZnO nanostructure for a glucose biosensor.

    PubMed

    Dai, Zhihui; Shao, Guojian; Hong, Jianmin; Bao, Jianchun; Shen, Jian

    2009-01-01

    A tetragonal pyramid-shaped porous ZnO (TPSP-ZnO) nanostructure is used for the immobilization, direct electrochemistry and biosensing of proteins. The prepared ZnO has a large surface area and good biocompatibility. Using glucose oxidase (GOD) as a model, this shaped ZnO is tested for immobilization of proteins and the construction of electrochemical biosensors with good electrochemical performances. The interaction between GOD and TPSP-ZnO is examined by using AFM, N(2) adsorption isotherms and electrochemical methods. The immobilized GOD at a TPSP-ZnO-modified glassy carbon electrode shows a good direct electrochemical behavior, which depends on the properties of the TPSP-ZnO. Based on a decrease of the electrocatalytic response of the reduced form of GOD to dissolved oxygen, the proposed biosensor exhibits a linear response to glucose concentrations ranging from 0.05 to 8.2mM with a detection limit of 0.01mM at an applied potential of -0.50V which has better biosensing properties than those from other morphological ZnO nanoparticles. The biosensor shows good stability, reproducibility, low interferences and can diagnose diabetes very fast and sensitively. Such the TPSP-ZnO nanostructure provides a good matrix for protein immobilization and biosensor preparation. PMID:18774704

  19. One-step synthesis of large-scale graphene film doped with gold nanoparticles at liquid-air interface for electrochemistry and Raman detection applications.

    PubMed

    Zhang, Panpan; Huang, Ying; Lu, Xin; Zhang, Siyu; Li, Jingfeng; Wei, Gang; Su, Zhiqiang

    2014-07-29

    We demonstrated a facile one-step synthesis strategy for the preparation of a large-scale reduced graphene oxide multilayered film doped with gold nanoparticles (RGO/AuNP film) and applied this film as functional nanomaterials for electrochemistry and Raman detection applications. The related applications of the fabricated RGO/AuNP film in electrochemical nonenzymatic H2O2 biosensor, electrochemical oxygen reduction reaction (ORR), and surface-enhanced Raman scattering (SERS) detection were investigated. Electrochemical data indicate that the H2O2 biosensor fabricated by RGO/AuNP film shows a wide linear range, low limitation of detection, high selectivity, and long-term stability. In addition, it was proved that the created RGO/AuNP film also exhibits excellent ORR electrochemical catalysis performance. The created RGO/AuNP film, when serving as SERS biodetection platform, presents outstanding performances in detecting 4-aminothiophenol with an enhancement factor of approximately 5.6 × 10(5) as well as 2-thiouracil sensing with a low concentration to 1 μM. It is expected that this facile strategy for fabricating large-scale graphene film doped with metallic nanoparticles will spark inspirations in preparing functional nanomaterials and further extend their applications in drug delivery, wastewater purification, and bioenergy. PMID:25015184

  20. Simultaneous determination of atropine, anisodamine, and scopolamine in plant extract by nonaqueous capillary electrophoresis coupled with electrochemiluminescence and electrochemistry dual detection.

    PubMed

    Yuan, Baiqing; Zheng, Chunying; Teng, Hong; You, Tianyan

    2010-01-01

    A rapid and simple method was demonstrated for the analysis of atropine, anisodamine, and scopolamine by nonaqueous capillary electrophoresis (NACE) coupled with electrochemiluminescence (ECL) and electrochemistry (EC) dual detection. The mixture of acetonitrile (ACN) and 2-propanol containing 1M acetic acid (HAc), 20mM sodium acetate (NaAc), and 2.5mM tetrabutylammonium perchlorate (TBAP) was used as the electrophoretic buffer. Although a short capillary of 18cm was used, the decoupler was not needed and the separation efficiency was good. The linear ranges of atropine, anisodamine, and scopolamine were 0.5-50, 5-2000, and 50-2000microM, respectively. For six replicate measurements of 100microM scopolamine, 15microM atropine, and 200microM anisodamine, the RSDs of ECL intensity, EC current, and migration time were less than 3.6%, 4.5%, and 0.3%, respectively. In addition, because the organic buffer was used, the working electrode (Pt) was not easily fouled and did not need reactivation. The method was also applied for the determination of these three alkaloids in Flos daturae extract. PMID:19931863

  1. Electrochemistry and spectroscopy of electrolytes and cathode materials in room-temperature ionic liquids

    NASA Astrophysics Data System (ADS)

    Ryan, David Martin

    The demonstration of a stable, reversible, alkali metal anode is an important step in the development of practical secondary batteries using room temperature chloroaluminate molten salts as electrolytes. Such melts are made by mixing 1-ethyl-3-methylimidazolium chloride (EMIC) with aluminum chloride, and can be Lewis buffered by adding LiCl or NaCl. It has been shown previously that protons added to a sodium chloride buffered melt as 1-ethyl-3-methyfimidazolium hydrogen dichloride (EMIHCl2) provide a more negative voltage window and nearly reversible deposition-stripping behavior for sodium. It is reported here that triethanolamine hydrogen chloride is effective in widening the voltage window, allows the plating and stripping of both lithium and sodium, and is stable in buffered EMIC/AlCl3 melts for months. It is suggested that deprotonation of one ethanolic group of triethanolamine HCl is responsible for the effect. The electrochemistry and UV-visible spectroscopy of several vanadium oxides have been examined in room temperature melts. By varying the mole ratio of the two components, Lewis basic, neutral and acidic melts were made. Most oxides have very low solubility: V2O4 and V2O3 are insoluble and V2O5 has a solubility limit less than 5 mM, but the solubilities of the salts NaVO 3, Na3VO4, and NH4VO3, VOCl 3 and VOF3 are significantly higher. The electrochemistry of V2O5, NaVO3, Na3VO4, NH4VO3, VOCl3 and VOF3 is similar in neutral and acidic melts. In the neutral melt each compound shows an irreversible reduction at about 0.45V vs. an Al wire reference electrode. In an acidic melt (mole fraction AlCl3 = 0.55) each of these compounds exhibit additional reduction peaks at more positive potentials. Coulometric and spectroscopic data for the 0.45V reduction suggest that mixed oxidation state polyvanadates may be formed. Controlled potential coulometry demonstrated that the reduction at 0.45V was the reduction of V(V) to V(IV) and the more positive reduction peaks

  2. Applied Stratigraphy

    NASA Astrophysics Data System (ADS)

    Lucas, Spencer G.

    Stratigraphy is a cornerstone of the Earth sciences. The study of layered rocks, especially their age determination and correlation, which are integral parts of stratigraphy, are key to fields as diverse as geoarchaeology and tectonics. In the Anglophile history of geology, in the early 1800s, the untutored English surveyor William Smith was the first practical stratigrapher, constructing a geological map of England based on his own applied stratigraphy. Smith has, thus, been seen as the first “industrial stratigrapher,” and practical applications of stratigraphy have since been essential to most of the extractive industries from mining to petroleum. Indeed, gasoline is in your automobile because of a tremendous use of applied stratigraphy in oil exploration, especially during the latter half of the twentieth century. Applied stratigraphy, thus, is a subject of broad interest to Earth scientists.

  3. Glucose oxidase-graphene-chitosan modified electrode for direct electrochemistry and glucose sensing

    SciTech Connect

    Kang, Xinhuang; Wang, Jun; Wu, Hong; Aksay, Ilhan A.; Liu, Jun; Lin, Yuehe

    2009-11-01

    Direct electrochemistry of a glucose oxidase (GOD)/graphene/chitosan nanocomposite was studied. The immobilized enzyme retains its bioactivity, exhibits a surface confined, reversible two-proton and two-electron transfer reaction, and has good stability, activity and a fast heterogeneous electron transfer rate with the rate constant (ks) of 2.83 s-1. A much higher enzyme loading (1.12 × 10-9 mol/cm2) is obtained as compared to the bare glass carbon surface. This GOD/graphene/chitosan nanocomposite film can be used for sensitive detection of glucose. The biosensor exhibits a wider linearity range from 0.08 mM to 12 mM glucose with a detection limit of 0.02 mM and much higher sensitivity (37.93 μA mM-1 cm-2) as compared with other nanostructured supports. The excellent performance of the biosensor is attributed to large surface-to-volume ratio and high conductivity of graphene, and good biocompatibility of chitosan, which enhances the enzyme absorption and promotes direct electron transfer between redox enzymes and the surface of electrodes.

  4. Combinatorial electrochemistry using metal nanoparticles: from proof-of-concept to practical realisation for bromide detection.

    PubMed

    Sljukić, Biljana; Baron, Ronan; Salter, Chris; Crossley, Alison; Compton, Richard G

    2007-05-01

    Principles and practical application of combinatorial electrochemistry in search for new electroactive materials in electroanalysis have been explored. Nanoparticles of three different metals: silver, gold and palladium have been independently synthesized on the glassy carbon spherical powder surface by electroless deposition process and characterized using both spectroscopic and electrochemical techniques. These three materials were then combined together onto basal plane pyrolytic graphite electrode surface and the application of the combinatorial approach to find the electrode material for bromide detection as model target analyte was demonstrated. The component electroactive for bromide detection was next identified and it was found that silver nanoparticles were the active ones. A composite electrode based on silver nanoparticle modified glassy carbon powder and epoxy resin was then fabricated and it was found to allow accurate determination of bromide. The electroactivity for the bromide determination of the composite electrode was compared with that of a bulk silver electrode and it was shown that the composite electrode is very efficient with a comparable electroactivity with only a portion of precious metals being used for its construction. PMID:17416224

  5. Metallic nanoparticles deposited on carbon microspheres: novel materials for combinatorial electrochemistry and electroanalysis.

    PubMed

    Baron, Ronan; Wildgoose, Gregory G; Compton, Richard G

    2009-04-01

    This review deals with the preparation of metallic nanoparticles on glassy carbon microspheres and the use of these new hybrid materials for combinatorial electrochemistry and electroanalysis. First, the preparation of gold, silver and palladium nanoparticles on glassy carbon microspheres by a simple electroless procedure is described. Then, different types of electrodes modified with glassy carbon microspheres are described. These are: (i) glassy carbon electrodes modified by a composite film of glassy carbon microspheres and multi-walled carbon nanotubes, (ii) basal plane pyrolylic graphite electrodes modified by the abrasive attachment of glassy carbon microspheres and (iii) carbon-epoxy composite electrodes loaded with glassy carbon microspheres. The three types of electrode architectures described consist of metallic nanoparticles embedded in a carbon matrix and each of the electrode macrodisc surfaces actually correspond to a random metallic nanoelectrode array. Carbon-epoxy composite electrodes have good characteristics for their use as practical sensors. Furthermore, the use of several kinds of metallic nanoparticles allows the construction of a multi-analyte electrode and the screening of electroactive materials by following a combinatorial approach. PMID:19437964

  6. Electrohydrodynamic jet printing and a preliminary electrochemistry test of graphene micro-scale electrodes

    NASA Astrophysics Data System (ADS)

    Wang, Dazhi; Zha, Wen; Feng, Li; Ma, Qian; Liu, Xianming; Yang, Ning; Xu, Zheng; Zhao, Xiaojun; Liang, Junsheng; Ren, Tongqun; Wang, Xiaodong

    2016-04-01

    This paper reports the use of electrohydrodynamic jet (E-jet) printing technique for producing a wide range of graphene micro-scale structures. Ethyl cellulose-dispersed graphene ink and Nafion-dispersed graphene ink were prepared and used for E-Jet printing. A glass slide and PDMS substrate were used for E-Jet printing of graphene ink. The E-jet printed graphene micro-scale structures using ethyl cellulose-dispersed graphene ink presented a feature of center arrayed graphene surrounded by the track of evaporated solution. However, the E-Jet printed graphene structures using Nafion-dispersed graphene ink exhibited uniform arranged features. It was observed that the resistivity of the graphene structures printed from the ethyl cellulose-dispersed graphene ink was much lower than that from the Nafion-dispersed graphene ink. In addition, the graphene micro-scale electrodes were E-Jet printed for preliminary electrochemical applications. The results showed that the graphene micro-scale electrodes had a distinct response for the lead ion. Furthermore, a Pt/graphene composite electrode was formed and an electrochemistry test was conducted. It was found that the Pt /graphene composite electrode had a more sensitive response compared with the pure Pt electrode for electrochemical sensing.

  7. Water as a promoter and catalyst for dioxygen electrochemistry in aqueous and organic media.

    SciTech Connect

    Staszak-Jirkovsky, Jakub; Subbaraman, Ram; Strmcnik, Dusan; Harrison, Katherine L.; Diesendruck, Charles E.; Assary, Rajeev; Frank, Otakar; Kobr, Lukas; Wiberg, Gustav K.H; Genorio, Bostjan; Connell, Justin G.; Lopes, Pietro P.; Stamenkovic, Vojislav R.; Curtiss, Larry; Moore, Jeffrey S.; Zavadil, Kevin R.; Markovic, Nenad M.

    2015-11-01

    Water and oxygen electrochemistry lies at the heart of interfacial processes controlling energy transformations in fuel cells, electrolyzers, and batteries. Here, by comparing results for the ORR obtained in alkaline aqueous media to those obtained in ultradry organic electrolytes with known amounts of H2O added intentionally, we propose a new rationale in which water itself plays an important role in determining the reaction kinetics. This effect derives from the formation of HOad center dot center dot center dot H2O (aqueous solutions) and LiO2 center dot center dot center dot H2O (organic solvents) complexes that place water in a configurationally favorable position for proton transfer to weakly adsorbed intermediates. We also find that, even at low concentrations (<10 ppm), water acts simultaneously as a promoter and as a catalyst in the production of Li2O2, regenerating itself through a sequence of steps that include the formation and recombination of H+ and OH-. We conclude that, although the binding energy between metal surfaces and oxygen intermediates is an important descriptor in electrocatalysis, understanding the role of water as a proton-donor reactant may explain many anomalous features in electrocatalysis at metal-liquid interfaces.

  8. ZnO/Cu nanocomposite: a platform for direct electrochemistry of enzymes and biosensing applications.

    PubMed

    Yang, Chi; Xu, Chunxiang; Wang, Xuemei

    2012-03-01

    Unique structured nanomaterials can facilitate the direct electron transfer between redox proteins and the electrodes. Here, in situ directed growth on an electrode of a ZnO/Cu nanocomposite was prepared by a simple corrosion approach, which enables robust mechanical adhesion and electrical contact between the nanostructured ZnO and the electrodes. This is great help to realize the direct electron transfer between the electrode surface and the redox protein. SEM images demonstrate that the morphology of the ZnO/Cu nanocomposite has a large specific surface area, which is favorable to immobilize the biomolecules and construct biosensors. Using glucose oxidase (GOx) as a model, this ZnO/Cu nanocomposite is employed for immobilization of GOx and the construction of the glucose biosensor. Direct electron transfer of GOx is achieved at ZnO/Cu nanocomposite with a high heterogeneous electron transfer rate constant of 0.67 ± 0.06 s(-1). Such ZnO/Cu nanocomposite provides a good matrix for direct electrochemistry of enzymes and mediator-free enzymatic biosensors. PMID:22309190

  9. Theoretical evidence for low kinetic overpotentials in Li-O2 electrochemistry

    NASA Astrophysics Data System (ADS)

    Hummelshøj, J. S.; Luntz, A. C.; Nørskov, J. K.

    2013-01-01

    We develop a density functional theory model for the electrochemical growth and dissolution of Li2O2 on various facets, terminations, and sites (terrace, steps, and kinks) of a Li2O2 surface. We argue that this is a reasonable model to describe discharge and charge of Li-O2 batteries over most of the discharge-charge cycle. Because non-stoichiometric surfaces are potential dependent and since the potential varies during discharge and charge, we study the thermodynamic stability of facets, terminations, and steps as a function of potential. This suggests that different facets, terminations, and sites may dominate in charge relative to those for discharge. We find very low thermodynamic overpotentials (<0.2 V) for both discharge and charge at many sites on the facets studied. These low thermodynamic overpotentials for both discharge and charge are in very good agreement with the low kinetic overpotentials observed in recent experiments. However, there are other predicted paths for discharge/charge that have higher overpotentials, so the phase space available for the electrochemistry opens up with overpotential.

  10. Parameter estimation of an electrochemistry-based lithium-ion battery model

    NASA Astrophysics Data System (ADS)

    Masoudi, Ramin; Uchida, Thomas; McPhee, John

    2015-09-01

    Parameters for an electrochemistry-based Lithium-ion battery model are estimated using the homotopy optimization approach. A high-fidelity model of the battery is presented based on chemical and electrical phenomena. Equations expressing the conservation of species and charge for the solid and electrolyte phases are combined with the kinetics of the electrodes to obtain a system of differential-algebraic equations (DAEs) governing the dynamic behavior of the battery. The presence of algebraic constraints in the governing dynamic equations makes the optimization problem challenging: a simulation is performed in each iteration of the optimization procedure to evaluate the objective function, and the initial conditions must be updated to satisfy the constraints as the parameter values change. The ε-embedding method is employed to convert the original DAEs into a singularly perturbed system of ordinary differential equations, which are then used to simulate the system efficiently. The proposed numerical procedure demonstrates excellent performance in the estimation of parameters for the Lithium-ion battery model, compared to direct methods that are either unstable or incapable of converging. The obtained results and estimated parameters demonstrate the efficacy of the proposed simulation approach and homotopy optimization procedure.

  11. Electrochemistry of poly(vinylferrocene) modified electrodes in aqueous acidic media

    NASA Astrophysics Data System (ADS)

    Issa, Touma B.; Singh, Pritam; Baker, Murray V.

    A cyclic voltammetric study of the electrochemistry and chemical stability of the poly(vinylferrocene) (PVFc) redox couple, coated on a gold substrate, in aqueous solutions of H 2SO 4, HClO 4 and HCl was carried out. It was found that the anodic peak potential ( Epa) did not depend on the acid concentration in the range (1.0 × 10 -2 to 1.0 × 10 -7 mol L -1). However, the Epa values shifted linearly to less positive potentials when investigated in more concentrated acid solutions in the range 1-5 mol L -1. The slope of the Epa versus acid concentration graph was found to be in the order H 2SO 4 > HCl > HClO 4. In this regard PVFc behaved very similar to 1,1'-bis(11-mercaptoundecyl)ferrocene (Fc(C 11SH) 2) except for its chemical stability. In H 2SO 4 media the PVFc was found to be much less stable than 1,1'-Fc(C 11SH) 2. The dependence of Epa on acid concentration could be used to monitor state of charge of lead-acid batteries. However, for this application Fc(C 11SH) 2 would be a better choice because of its superior chemical stability.

  12. Reduced Graphene Oxide Thin Film on Conductive Substrates by Bipolar Electrochemistry

    NASA Astrophysics Data System (ADS)

    Anis, Allagui; Mohammad, Ali Abdelkareem; Hussain, Alawadhi; Ahmed, S. Elwakil

    2016-02-01

    Recent years have shown an increased interest in developing manufacturing processes for graphene and its derivatives that consider the environmental impact and large scale cost-effectiveness. However, today’s most commonly used synthesis routes still suffer from their excessive use of harsh chemicals and/or the complexity and financial cost of the process. Furthermore, the subsequent transfer of the material onto a substrate makes the overall process even more intricate and time-consuming. Here we describe a single-step, single-cell preparation procedure of metal-supported reduced graphene oxide (rGO) using the principle of bipolar electrochemistry of graphite in deionized water. Under the effect of an electric field between two stainless steel feeder electrodes, grapheme layers at the anodic pole of the wireless graphite were oxidized into colloidal dispersion of GO, which migrated electrophoretically towards the anodic side of the cell, and deposited in the form of rGO (d(002) = 0.395 nm) by van der Waals forces. For substrates chemically more susceptible to the high anodic voltage, we show that the electrochemical setup can be adapted by placing the latter between the wireless graphite and the stainless steel feeder anode. This method is straightforward, inexpensive, environmentally-friendly, and could be easily scaled up for high yield and large area production of rGO thin films.

  13. Reduced Graphene Oxide Thin Film on Conductive Substrates by Bipolar Electrochemistry.

    PubMed

    Anis, Allagui; Mohammad, Ali Abdelkareem; Hussain, Alawadhi; Ahmed, S Elwakil

    2016-01-01

    Recent years have shown an increased interest in developing manufacturing processes for graphene and its derivatives that consider the environmental impact and large scale cost-effectiveness. However, today's most commonly used synthesis routes still suffer from their excessive use of harsh chemicals and/or the complexity and financial cost of the process. Furthermore, the subsequent transfer of the material onto a substrate makes the overall process even more intricate and time-consuming. Here we describe a single-step, single-cell preparation procedure of metal-supported reduced graphene oxide (rGO) using the principle of bipolar electrochemistry of graphite in deionized water. Under the effect of an electric field between two stainless steel feeder electrodes, grapheme layers at the anodic pole of the wireless graphite were oxidized into colloidal dispersion of GO, which migrated electrophoretically towards the anodic side of the cell, and deposited in the form of rGO (d(002) = 0.395 nm) by van der Waals forces. For substrates chemically more susceptible to the high anodic voltage, we show that the electrochemical setup can be adapted by placing the latter between the wireless graphite and the stainless steel feeder anode. This method is straightforward, inexpensive, environmentally-friendly, and could be easily scaled up for high yield and large area production of rGO thin films. PMID:26883173

  14. Dispersion of Nanocrystalline Fe3O4 within Composite Electrodes: Insights on Battery-Related Electrochemistry.

    PubMed

    Bock, David C; Pelliccione, Christopher J; Zhang, Wei; Wang, Jiajun; Knehr, K W; Wang, Jun; Wang, Feng; West, Alan C; Marschilok, Amy C; Takeuchi, Kenneth J; Takeuchi, Esther S

    2016-05-11

    Aggregation of nanosized materials in composite lithium-ion-battery electrodes can be a significant factor influencing electrochemical behavior. In this study, aggregation was controlled in magnetite, Fe3O4, composite electrodes via oleic acid capping and subsequent dispersion in a carbon black matrix. A heat treatment process was effective in the removal of the oleic acid capping agent while preserving a high degree of Fe3O4 dispersion. Electrochemical testing showed that Fe3O4 dispersion is initially beneficial in delivering a higher functional capacity, in agreement with continuum model simulations. However, increased capacity fade upon extended cycling was observed for the dispersed Fe3O4 composites relative to the aggregated Fe3O4 composites. X-ray absorption spectroscopy measurements of electrodes post cycling indicated that the dispersed Fe3O4 electrodes are more oxidized in the discharged state, consistent with reduced reversibility compared with the aggregated sample. Higher charge-transfer resistance for the dispersed sample after cycling suggests increased surface-film formation on the dispersed, high-surface-area nanocrystalline Fe3O4 compared to the aggregated materials. This study provides insight into the specific effects of aggregation on electrochemistry through a multiscale view of mechanisms for magnetite composite electrodes. PMID:27096464

  15. Carbon nanodots-chitosan composite film: a platform for protein immobilization, direct electrochemistry and bioelectrocatalysis.

    PubMed

    Sheng, Meili; Gao, Yue; Sun, Junyong; Gao, Feng

    2014-08-15

    A novel composite film based on carbon nanodots (CNDs) and chitosan was readily prepared and used as immobilization matrix to entrap a heme protein, hemoglobin (Hb) for direct electrochemistry and bioelectrocatalysis. A modified electrode was obtained by casting Hb-CNDs-chitosan composites on the glassy carbon (GC) electrode surface. Spectroscopic and electrochemical studies showed that Hb entrapped in the composite film remained in its native structures, and CNDs in the film can greatly facilitate DET between the protein and the GC electrode. The electron-transfer kinetics of Hb in composite film was qualitatively evaluated by using the Marcus theory, and the apparent heterogeneous electron-transfer rate constant (ks) was estimated to be 2.39(±0.03)s(-1) with Laviron equations. The modified electrode showed excellent electrocatalytic behavior to the substrate, hydrogen peroxide (H2O2). The linear current response for H2O2 was from 1×10(-6) to 1.18×10(-4)M with a detection limit of 0.27(±0.02)μM at the signal-to-noise ratio of 3, and the apparent Michaelis-Menten constant was 0.067(±0.02)mM. These important features of CNDs-chitosan film have implied to be a promising platform for elaborating bioelectrochemical devices such as biosensors and biofuel cells. PMID:24681154

  16. Three Redox States of Trypanosoma brucei Alternative Oxidase Identified by Infrared Spectroscopy and Electrochemistry

    PubMed Central

    Maréchal, Amandine; Kido, Yasutoshi; Kita, Kiyoshi; Moore, Anthony L.; Rich, Peter R.

    2009-01-01

    Electrochemistry coupled with Fourier transform infrared (IR) spectroscopy was used to investigate the redox properties of recombinant alternative ubiquinol oxidase from Trypanosoma brucei, the organism responsible for African sleeping sickness. Stepwise reduction of the fully oxidized resting state of recombinant alternative ubiquinol oxidase revealed two distinct IR redox difference spectra. The first of these, signal 1, titrates in the reductive direction as an n = 2 Nernstian component with an apparent midpoint potential of 80 mV at pH 7.0. However, reoxidation of signal 1 in the same potential range under anaerobic conditions did not occur and only began with potentials in excess of 500 mV. Reoxidation by introduction of oxygen was also unsuccessful. Signal 1 contained clear features that can be assigned to protonation of at least one carboxylate group, further perturbations of carboxylic and histidine residues, bound ubiquinone, and a negative band at 1554 cm−1 that might arise from a radical in the fully oxidized protein. A second distinct IR redox difference spectrum, signal 2, appeared more slowly once signal 1 had been reduced. This component could be reoxidized with potentials above 100 mV. In addition, when both signals 1 and 2 were reduced, introduction of oxygen caused rapid oxidation of both components. These data are interpreted in terms of the possible active site structure and mechanism of oxygen reduction to water. PMID:19767647

  17. Direct electrochemistry of alcohol oxidase using multiwalled carbon nanotube as electroactive matrix for biosensor application.

    PubMed

    Das, Madhuri; Goswami, Pranab

    2013-02-01

    Rapid detection of alcohol is important in clinical diagnosis and fermentation industry. An octameric alcohol oxidase (AOx) (Mr 675 kDa) from Pichia pastoris, immobilized on multiwalled carbon nanotubes-Nafion® (MWCNT-Nf) matrix and encapsulated with polyethylenimine (PEI) on gold electrode (AuE), showed a redox peak at 0.21V (vs. Ag/AgCl electrode at pH 7.5) for oxidation of alcohol. The electron transfer rate constant and surface coverage of the immobilized AOx were 1.69±0.15 s⁻¹ and 2.43×10⁻¹² mol cm⁻², respectively. Studies on response and kinetics of Au-MWCNT-Nf-AOx-PEI bioelectrodes for alcohol showed a linear response in the range of 8 μM-42 μM, response time of 55 s for steady state current, and detection limit of 5 μM. The bioelectrode retains ~90% of the original response even after four weeks when stored in potassium phosphate buffer pH 7.5 at 4 °C. The fabricated bioelectrode was found to exclude interference caused by the common electroactive species such as ascorbic acid, uric acid, lactic acid, glucose and urea. The bioelectrode also showed reliable response characteristics in blood serum samples. The findings of the investigation have established the direct electrochemistry of the AOx protein and its potential biosensor application for quantitative detection of alcohol in blood serum. PMID:23000393

  18. Dispersion of nanocrystalline Fe3O4 within composite electrodes: Insights on battery-related electrochemistry

    DOE PAGESBeta

    David C. Bock; Takeuchi, Kenneth J.; Pelliccione, Christopher J.; Zhang, Wei; Wang, Jiajun; Knehr, K. W.; Wang, Jun; Wang, Feng; West, Alan C.; Marschilok, Amy C.; et al

    2016-04-20

    Aggregation of nanosized materials in composite lithium-ion-battery electrodes can be a significant factor influencing electrochemical behavior. In this study, aggregation was controlled in magnetite, Fe3O4, composite electrodes via oleic acid capping and subsequent dispersion in a carbon black matrix. A heat treatment process was effective in the removal of the oleic acid capping agent while preserving a high degree of Fe3O4 dispersion. Electrochemical testing showed that Fe3O4 dispersion is initially beneficial in delivering a higher functional capacity, in agreement with continuum model simulations. However, increased capacity fade upon extended cycling was observed for the dispersed Fe3O4 composites relative to themore » aggregated Fe3O4 composites. X-ray absorption spectroscopy measurements of electrodes post cycling indicated that the dispersed Fe3O4 electrodes are more oxidized in the discharged state, consistent with reduced reversibility compared with the aggregated sample. Higher charge-transfer resistance for the dispersed sample after cycling suggests increased surface-film formation on the dispersed, high-surface-area nanocrystalline Fe3O4 compared to the aggregated materials. Furthermore, this study provides insight into the specific effects of aggregation on electrochemistry through a multiscale view of mechanisms for magnetite composite electrodes.« less

  19. Reduced Graphene Oxide Thin Film on Conductive Substrates by Bipolar Electrochemistry

    PubMed Central

    Anis, Allagui; Mohammad, Ali Abdelkareem; Hussain, Alawadhi; Ahmed, S. Elwakil

    2016-01-01

    Recent years have shown an increased interest in developing manufacturing processes for graphene and its derivatives that consider the environmental impact and large scale cost-effectiveness. However, today’s most commonly used synthesis routes still suffer from their excessive use of harsh chemicals and/or the complexity and financial cost of the process. Furthermore, the subsequent transfer of the material onto a substrate makes the overall process even more intricate and time-consuming. Here we describe a single-step, single-cell preparation procedure of metal-supported reduced graphene oxide (rGO) using the principle of bipolar electrochemistry of graphite in deionized water. Under the effect of an electric field between two stainless steel feeder electrodes, grapheme layers at the anodic pole of the wireless graphite were oxidized into colloidal dispersion of GO, which migrated electrophoretically towards the anodic side of the cell, and deposited in the form of rGO (d(002) = 0.395 nm) by van der Waals forces. For substrates chemically more susceptible to the high anodic voltage, we show that the electrochemical setup can be adapted by placing the latter between the wireless graphite and the stainless steel feeder anode. This method is straightforward, inexpensive, environmentally-friendly, and could be easily scaled up for high yield and large area production of rGO thin films. PMID:26883173

  20. Comparison of two different carbon nanotube-based surfaces with respect to potassium ferricyanide electrochemistry

    NASA Astrophysics Data System (ADS)

    Taurino, Irene; Carrara, Sandro; Giorcelli, Mauro; Tagliaferro, Alberto; De Micheli, Giovanni

    2012-02-01

    This paper describes the electrochemical investigation of two multi-walled carbon nanotube-based electrodes using potassium ferricyanide as a benchmark redox system. Carbon nanotubes were fabricated by chemical vapor deposition on silicon wafer with camphor and ferrocene as precursors. Vertically-aligned as well as islands of horizontally-randomly-oriented carbon nanotubes were obtained by varying the growth parameters. Cyclic voltammetry was the employed method for this electrochemical study. Vertical nanotubes showed a slightly higher kinetic. Regarding the sensing parameters we found a sensitivity for vertical nanotubes almost equal to the sensitivity obtained with horizontally/randomly oriented nanotubes (71.5 ± 0.3 μA/(mM cm2) and 62.8 ± 0.3 μA/(mM cm2), respectively). In addition, values of detection limit are of the same order of magnitude. Although tip contribution to electron emission has been shown to be greatly larger than the lateral contribution on single carbon nanotubes per unit area, the new findings reported in this paper demonstrate that the global effects of nanotube surface on potassium ferricyanide electrochemistry are comparable for these two types of nanostructured surfaces.

  1. Direct electrochemistry and electrocatalysis of myoglobin immobilized on zirconia/multi-walled carbon nanotube nanocomposite

    SciTech Connect

    Liang, Ruping; Deng, Minqiang; Cui, Sanguan; Chen, Hong; Qiu, Jianding

    2010-12-15

    Zirconia/multi-walled carbon nanotube (ZrO{sub 2}/MWCNT) nanocomposite was prepared by hydrothermal treatment of MWCNTs in ZrOCl{sub 2}.8H{sub 2}O aqueous solution. The morphology and structure of the synthesized ZrO{sub 2}/MWCNT nanocomposite were characterized by transmission electron microscopy and X-ray diffraction analysis. It was found that ZrO{sub 2} nanoparticles homogeneously distributed on the sidewall of MWCNTs. Myoglobin (Mb), as a model protein to investigate the nanocomposite, was immobilized on ZrO{sub 2}/MWCNT nanocomposite. Ultraviolet-visible spectroscopy and electrochemical measurements showed that the nanocomposite could retain the bioactivity of the immobilized Mb to a large extent. The Mb immobilized in the composite showed excellent direct electrochemistry and electrocatalytic activity to the reduction of hydrogen peroxide (H{sub 2}O{sub 2}). The linear response range of the biosensor to H{sub 2}O{sub 2} concentration was from 1.0 to 116.0 {mu}M with the limit of detection of 0.53 {mu}M (S/N = 3). The ZrO{sub 2}/MWCNT nanocomposite provided a good biocompatible matrix for protein immobilization and biosensors preparation.

  2. The electrochemistry of zirconium in aqueous solutions at elevated temperatures and pressures

    NASA Astrophysics Data System (ADS)

    Chen, Yingzi; Urquidi-Macdonald, Mirna; Macdonald, Digby D.

    2006-01-01

    The electrochemistry of zirconium has been explored in borate buffer solution of pH = 6.94 at 250 °C with and without hydrogen by measuring the current, impedance, and capacitance as a function of potential. Data are interpreted in terms of modified point defect models (PDM) that recognize the existence of a thick oxide outer layer over a thin barrier layer. From thermodynamic analysis, it is postulated that a hydride barrier layer forms under PWR coolant conditions whereas an oxide barrier layer forms under BWR primary coolant conditions. Thus, the introduction of hydrogen into the solution lowers the corrosion potential of zirconium to the extent that the formation of ZrH 2 is predicted to be spontaneous rather than the ZrO 2. Mott-Schottky analysis shows that the passive film formed on zirconium is n-type, which is consistent with the PDM, corresponding to a preponderance of oxygen/hydrogen vacancies and/or zirconium interstitials in the barrier layer.

  3. Applied oceanography

    SciTech Connect

    Bishop, J.M.

    1984-01-01

    This book combines oceanography principles and applications such as marine pollution, resources, and transportation. It is divided into two main parts treating the basic principles of physical oceanography, and presenting a unique systems framework showing how physical oceanography, marine ecology, economics, and government policy may be combined to define the newly developing field of applied oceanography.

  4. Applied Nanotoxicology.

    PubMed

    Hobson, David W; Roberts, Stephen M; Shvedova, Anna A; Warheit, David B; Hinkley, Georgia K; Guy, Robin C

    2016-01-01

    Nanomaterials, including nanoparticles and nanoobjects, are being incorporated into everyday products at an increasing rate. These products include consumer products of interest to toxicologists such as pharmaceuticals, cosmetics, food, food packaging, household products, and so on. The manufacturing of products containing or utilizing nanomaterials in their composition may also present potential toxicologic concerns in the workplace. The molecular complexity and composition of these nanomaterials are ever increasing, and the means and methods being applied to characterize and perform useful toxicologic assessments are rapidly advancing. This article includes presentations by experienced toxicologists in the nanotoxicology community who are focused on the applied aspect of the discipline toward supporting state of the art toxicologic assessments for food products and packaging, pharmaceuticals and medical devices, inhaled nanoparticle and gastrointestinal exposures, and addressing occupational safety and health issues and concerns. This symposium overview article summarizes 5 talks that were presented at the 35th Annual meeting of the American College of Toxicology on the subject of "Applied Nanotechnology." PMID:26957538

  5. Applied Koopmanism.

    PubMed

    Budisić, Marko; Mohr, Ryan; Mezić, Igor

    2012-12-01

    A majority of methods from dynamical system analysis, especially those in applied settings, rely on Poincaré's geometric picture that focuses on "dynamics of states." While this picture has fueled our field for a century, it has shown difficulties in handling high-dimensional, ill-described, and uncertain systems, which are more and more common in engineered systems design and analysis of "big data" measurements. This overview article presents an alternative framework for dynamical systems, based on the "dynamics of observables" picture. The central object is the Koopman operator: an infinite-dimensional, linear operator that is nonetheless capable of capturing the full nonlinear dynamics. The first goal of this paper is to make it clear how methods that appeared in different papers and contexts all relate to each other through spectral properties of the Koopman operator. The second goal is to present these methods in a concise manner in an effort to make the framework accessible to researchers who would like to apply them, but also, expand and improve them. Finally, we aim to provide a road map through the literature where each of the topics was described in detail. We describe three main concepts: Koopman mode analysis, Koopman eigenquotients, and continuous indicators of ergodicity. For each concept, we provide a summary of theoretical concepts required to define and study them, numerical methods that have been developed for their analysis, and, when possible, applications that made use of them. The Koopman framework is showing potential for crossing over from academic and theoretical use to industrial practice. Therefore, the paper highlights its strengths in applied and numerical contexts. Additionally, we point out areas where an additional research push is needed before the approach is adopted as an off-the-shelf framework for analysis and design. PMID:23278096

  6. Applied Koopmanisma)

    NASA Astrophysics Data System (ADS)

    Budišić, Marko; Mohr, Ryan; Mezić, Igor

    2012-12-01

    A majority of methods from dynamical system analysis, especially those in applied settings, rely on Poincaré's geometric picture that focuses on "dynamics of states." While this picture has fueled our field for a century, it has shown difficulties in handling high-dimensional, ill-described, and uncertain systems, which are more and more common in engineered systems design and analysis of "big data" measurements. This overview article presents an alternative framework for dynamical systems, based on the "dynamics of observables" picture. The central object is the Koopman operator: an infinite-dimensional, linear operator that is nonetheless capable of capturing the full nonlinear dynamics. The first goal of this paper is to make it clear how methods that appeared in different papers and contexts all relate to each other through spectral properties of the Koopman operator. The second goal is to present these methods in a concise manner in an effort to make the framework accessible to researchers who would like to apply them, but also, expand and improve them. Finally, we aim to provide a road map through the literature where each of the topics was described in detail. We describe three main concepts: Koopman mode analysis, Koopman eigenquotients, and continuous indicators of ergodicity. For each concept, we provide a summary of theoretical concepts required to define and study them, numerical methods that have been developed for their analysis, and, when possible, applications that made use of them. The Koopman framework is showing potential for crossing over from academic and theoretical use to industrial practice. Therefore, the paper highlights its strengths in applied and numerical contexts. Additionally, we point out areas where an additional research push is needed before the approach is adopted as an off-the-shelf framework for analysis and design.

  7. Organometallic electrochemistry based on electrolytes containing weakly-coordinating fluoroarylborate anions.

    PubMed

    Geiger, William E; Barrière, Frédéric

    2010-07-20

    Electrochemistry is a powerful tool for the study of oxidative electron-transfer reactions (anodic processes). Since the 1960s, the electrolytes of choice for nonaqueous electrochemistry were relatively small (heptaatomic or smaller) inorganic anions, such as perchlorate, tetrafluoroborate, or hexafluorophosphate. Owing to the similar size-to-charge ratios of these "traditional" anions, structural alterations of the electrolyte anion are not particularly valuable in effecting changes in the corresponding redox reactions. Systematic variations of supporting electrolytes were largely restricted to cathodic processes, in which interactions of anions produced in the reactions are altered by changes in electrolyte cations. A typical ladder involves going from a weakly ion-pairing tetraalkylammonium cation, [N(C(n)H(2n+1))(4)](+), with n > or = 4, to more strongly ion-pairing counterparts with n < 4, and culminating in very strongly ion-pairing alkali metal ions. A new generation of supporting electrolyte salts that incorporate a weakly coordinating anion (WCA) expands anodic applications by providing a dramatically different medium in which to generate positively charged electrolysis products. A chain of electrolyte anions is now available for the control of anodic reactions, beginning with weakly ion-pairing WCAs, progressing through the traditional anions, and culminating in halide ions. Although the electrochemical properties of a number of different WCAs have been reported, the most systematic work involves fluoro- or trifluoromethyl-substituted tetraphenylborate anions (fluoroarylborate anions). In this Account, we focus on tetrakis(perfluorophenyl)borate, [B(C(6)F(5))(4)](-), which has a significantly more positive anodic window than tetrakis[(3,5-bis(trifluoromethyl)phenyl)]borate, [BArF(24)](-), making it suitable in a larger range of anodic oxidations. These WCAs also have a characteristic of specific importance to organometallic redox processes. Many electron

  8. Synthesis, Electrochemistry and Electrogenerated Chemiluminesce of two BODIPY-Appended Bipyridine Homologues

    PubMed Central

    Qi, Honglan; Teesdale, Justin J.; Pupillo, Rachel C.

    2014-01-01

    Two new 2,2’-bipyridine (bpy) derivatives containing ancillary BODIPY chromophores attached at the 5- and 5’-positions (BB3) or 6- and 6’-positions (BB4) were prepared and characterized. In this work, the basic photophysics, electrochemistry and electrogenerated chemiluminescence (ECL) of BB3 and BB4 are compared with those previously reported for a related bpy-BODIPY derivative (BB2) (J. Phys. Chem. C 2011, 115, 17993–18001). Cyclic voltammetry revealed that BB3 and BB4 display reversible 2e− oxidation and reduction waves, which consist of two closely spaced (50 – 70 mV) 1e− events. This redox behavior is consistent with the frontier molecular orbitals calculated for BB3 and BB4 and indicates that the 2,2’-bipyridine spacer of each bpy- BODIPY homologue does not facilitate efficient electronic communication between the tethered indacene units. In the presence of a coreactant such as tri-n-propylamine (TPA) or benzoyl peroxide (BPO), BB3 and BB4 exhibit strong ECL and produce spectra that are very similar to their corresponding photoluminescence profiles. The ECL signal obtained under annihilation conditions, however, is significantly different and is characterized by two distinct bands. One of these bands is centered at ~570 nm and is attributed to emission via an S- or T-route. The second band, occurs at longer wavelengths and is centered around ~740 nm. The shape and concentration dependence of this long-wavelength ECL signal is not indicative of emission from an excimer or aggregate, but rather is suggests that a new emissive species is formed from the bpy-BODIPY luminophores during the annihilation process. PMID:23980850

  9. Catalytic Protein Film Electrochemistry Provides a Direct Measure of the Tetrathionate/Thiosulfate Reduction Potential.

    PubMed

    Kurth, Julia M; Dahl, Christiane; Butt, Julea N

    2015-10-21

    The tetrathionate/thiosulfate interconversion is a two-electron process: S4O6(2-) + 2 e(-) ↔ 2 S2O3(2-). Both transformations can support bacterial growth since S2O3(2-) provides an energy source, while S4O6(2-) serves as respiratory electron acceptor. Interest in the corresponding S2O3(2-) oxidation also arises from its widespread use in volumetric analysis of oxidizing agents and bleach neutralization during water treatment. Here we report protein film electrochemistry that defines the reduction potential of the S4O6(2-)/S2O3(2-) couple. The relevant interconversion is not reversible at inert electrodes. However, facile reduction of S4O6(2-) to S2O3(2-) and the reverse reaction are catalyzed by enzymes of the thiosulfate dehydrogenase, TsdA, family adsorbed on graphite electrodes. Zero-current potentials measured with different enzymes, at three pH values, and multiple S4O6(2-) and S2O3(2-) concentrations together with the relevant Nernst equation resolved the tetrathionate/thiosulfate reduction potential as +198 ± 4 mV versus SHE. This potential lies in the ∼250 mV window encompassing previously reported values calculated from parameters including the free energy of formation. However, the value is considerably more positive than widely used in discussions of bacterial bioenergetics. As a consequence anaerobic respiration by tetrathionate reduction is likely to be more prevalent than presently thought in tetrathionate-containing environments such as marine sediments and the human gut. PMID:26437022

  10. Endogenous minerals have influences on surface electrochemistry and ion exchange properties of biochar.

    PubMed

    Zhao, Ling; Cao, Xinde; Zheng, Wei; Wang, Qun; Yang, Fan

    2015-10-01

    The feedstocks for biochar production are diverse and many of them contain various minerals in addition to being rich in carbon. Twelve types of biomass classified into 2 categories: plant-based and municipal waste, were employed to produce biochars under 350 °C and 500 °C. Their pH, point of zero net charge (PZNC), zeta potential, cation and anion exchange capacity (CEC and AEC) were analyzed. The municipal waste-based biochars (MW-BC) had higher mineral levels than the plant-based biochars (PB-BC). However, the water soluble mineral levels were lower in the MW-BCs due to the dominant presence of less soluble minerals, such as CaCO3 and (Ca,Mg)3(PO4)2. The higher total minerals in MW-BCs accounted for the higher PZNC (5.47-9.95) than in PB-BCs (1.91-8.18), though the PZNCs of the PB-BCs increased more than that of the MW-BCs as the production temperature rose. The minerals had influence on the zeta potentials via affecting the negative charges of biochars and the ionic strength of solution. The organic functional groups in PB-BCs such as -COOH and -OH had a greater effect on the CEC and AEC, while the minerals had a greater effect on that of MW-BCs. The measured CEC and AEC values had a strong positive correlation with the total amount of soluble cations and anions, respectively. Results indicated that biochar surface charges depend not only on the organic functional groups, but also on the minerals present and to some extent, minerals have more influences on the surface electrochemistry and ion exchange properties of biochar. PMID:25974107

  11. Rapid Nucleation of Iron Oxide Nanoclusters in Aqueous Solution by Plasma Electrochemistry.

    PubMed

    Bouchard, Mathieu; Létourneau, Mathieu; Sarra-Bournet, Christian; Laprise-Pelletier, Myriam; Turgeon, Stéphane; Chevallier, Pascale; Lagueux, Jean; Laroche, Gaétan; Fortin, Marc-A

    2015-07-14

    Progresses in cold atmospheric plasma technologies have made possible the synthesis of nanoparticles in aqueous solutions using plasma electrochemistry principles. In this contribution, a reactor based on microhollow cathodes and operating at atmospheric pressure was developed to synthesize iron-based nanoclusters (nanoparticles). Argon plasma discharges are generated at the tip of the microhollow cathodes, which are placed near the surface of an aqueous solution containing iron salts (FeCl2 and FeCl3) and surfactants (biocompatible dextran). Upon reaction at the plasma-liquid interface, reduction processes occur and lead to the nucleation of ultrasmall iron-based nanoclusters (IONCs). The purified IONCs were investigated by XPS and FTIR, which confirmed that the nucleated clusters contain a highly hydrated form of iron oxide, close to the stoichiometric constituents of α-FeOOH (goethite) or Fe5O3(OH)9 (ferrihydrite). Relaxivity values of r1 = 0.40 mM(-1) s(-1) and r2/r1 = 1.35 were measured (at 1.41 T); these are intermediate values between the relaxometric properties of superparamagnetic iron oxide nanoparticles used in medicine (USPIO) and those of ferritin, an endogenous contrast agent. Plasma-synthesized IONCs were injected into the mouse model and provided positive vascular signal enhancement in T1-w. MRI for a period of 10-20 min. Indications of rapid and strong elimination through the urinary and gastrointestinal tracts were also found. This study is the first to report on the development of a compact reactor suitable for the synthesis of MRI iron-based contrast media solutions, on site and upon demand. PMID:26086241

  12. Semiconductor electrochemistry of coal pyrite. Final technical report, September 1990--September 1995

    SciTech Connect

    Osseo-Asare, K.; Wei, Dawei

    1996-01-01

    This project seeks to advance the fundamental understanding of the physico-chemical processes occurring at the pyrite/aqueous interface, in the context of coal cleaning, coal desulfurization, and acid mine drainage. Central to this research is the use of synthetic microsize particles of pyrite as model microelectrodes to investigate the semiconductor electrochemistry of pyrite. The research focuses on: (a) the synthesis of microsize particles of pyrite in aqueous solution at room temperature, (b) the formation of iron sulfide complex, the precursor of FeS or FeS{sub 2}, and (c) the relationship between the semiconductor properties of pyrite and its interfacial electrochemical behavior in the dissolution process. In Chapter 2, 3 and 4, a suitable protocol for preparing microsize particles of pyrite in aqueous solution is given, and the essential roles of the precursors elemental sulfur and ``FeS`` in pyrite formation are investigated. In Chapter 5, the formation of iron sulfide complex prior to the precipitation of FeS or FeS{sub 2} is investigated using a fast kinetics technique based on a stopped-flow spectrophotometer. The stoichiometry of the iron sulfide complex is determined, and the rate and formation constants are also evaluated. Chapter 6 provides a summary of the semiconductor properties of pyrite relevant to the present study. In Chapters 7 and 8, the effects of the semiconductor properties on pyrite dissolution are investigated experimentally and the mechanism of pyrite dissolution in acidic aqueous solution is examined. Finally, a summary of the conclusions from this study and suggestions for future research are presented in Chapter 9.

  13. Recent Advances in Modeling Transition Metal Oxides for Photo-electrochemistry

    NASA Astrophysics Data System (ADS)

    Caspary Toroker, Maytal

    Computational research offers a wide range of opportunities for materials science and engineering, especially in the energy arena where there is a need for understanding how material composition and structure control energy conversion, and for designing materials that could improve conversion efficiency. Potential inexpensive materials for energy conversion devices are metal oxides. However, their conversion efficiency is limited by at least one of several factors: a too large band gap for efficiently absorbing solar energy, similar conduction and valence band edge characters that may lead to unfavorably high electron-hole recombination rates, a valence band edge that is not positioned well for oxidizing water, low stability, low electronic conductivity, and low surface reactivity. I will show how we model metal oxides with ab-initio methods, primarily DFT +U. Our previous results show that doping with lithium, sodium, or hydrogen could improve iron (II) oxide's electronic properties, and alloying with zinc or nickel could improve iron (II) oxide's optical properties. Furthermore, doping nickel (II) oxide with lithium could improve several key properties including solar energy absorption. In this talk I will highlight new results on our understanding of the mechanism of iron (III) oxide's surface reactivity. Our theoretical insights bring us a step closer towards understanding how to design better materials for photo-electrochemistry. References: 1. O. Neufeld and M. Caspary Toroker, ``Pt-doped Fe2O3 for enhanced water splitting efficiency: a DFT +U study'', J. Phys. Chem. C 119, 5836 (2015). 2. M. Caspary Toroker, ``Theoretical Insights into the Mechanism of Water Oxidation on Non-stoichiometric and Ti - doped Fe2O3 (0001)'', J. Phys. Chem. C, 118, 23162 (2014). This research was supported by the Morantz Energy Research Fund, the Nancy and Stephen Grand Technion Energy Program, the I-CORE Program of the Planning and Budgeting Committee, and The Israel Science

  14. Semiconductor electrochemistry of coal pyrite. Technical progress report, October--December 1992

    SciTech Connect

    Osseo-Asare, K.; Wei, D.

    1993-02-01

    This project seeks to advance the fundamental understanding of the physics-chemical processes occurring at the pyrite/aqueous interface, in the context of coal cleaning, coal desulfurization, and acid minedrainage. A novel approach to the study of pyrite aqueous electrochemistry is proposed, based on the use of both synthetic and natural ( i.e. coal-derived) pyrite specimens, the utilization of.pyrite both in the form of micro (i.e. colloidal and subcolloidal) and macro (i.e. rotating ring disk) electrodes, and the application of in-situ direct electroanalytical and spectroelectrochemical characterization techniques. The kinetic study of the reaction between sulfide and ferrous ions in solution suggested that the black species formed initially is FeHS{sup +} intermediate. To farther confirm this mechanism, the experiments aimed at establishing the stoichiometry for the intermediate were carried out thermodynamically with a stopped-flow spectrophotometric technique. The results showed that the mole ratio of H{sup {minus}}/Fe{sup 2+} is 1 to 1 for the intermediate product, which is in good agreement with the kinetic results previously obtained. Furthermore, the equilibrium constant for the reaction Fe{sup 2+} + H{sup {minus}} = FeHS{sup +} was determined as K = 10{sup 4.34}. The forward rate constant is 10{sup 3.81}(mol/l){sup {minus}1}sec{sup {minus}1} and the backward rate constant is 10{sup {minus}0.53} (mol/l){sup {minus}1} sec{sup {minus}1}.

  15. Semiconductor electrochemistry of coal pyrite. Technical progress report, January--March 1993

    SciTech Connect

    Osseo-Asare, K.; Wei, D.

    1993-05-01

    This project seeks to advance the fundamental understanding of the physicochemical processes occurring at the pyrite/aqueous interface, in the context of coal cleaning, coal desulfurization, and acid mine drainage. A novel approach to the study of pyrite aqueous electrochemistry is proposed, based on the use of both synthetic and natural ( i.e. coal-derived) pyrite specimens, the utilization of pyrite both in the form of micro (i.e. colloidal and subcolloidal) and macro (i.e. rotating ring disk) electrodes, and the application of in-situ direct electroanalytical and spectroelectrochemical characterization techniques. The work performed during this quarter focuses on the synthesis of pyrite in aqueous solutions at room temperature and atmospheric pressure. The experimental results show that the initial product from the reaction between ferrous ions and sulfide ions is X-ray amorphous iron sulfide, and the final product is mackinawite from this reaction. Both amorphous iron sulfide and mackinawite in wet states are oxidized quickly in air to {gamma}-FeOOH. Pyrite can form in aqueous solution through a simple path from a reaction between ferric ions and sulfide ions at room temperature within 9 days. It is believed that a redox reaction occurs between ferric and sulfide ions to form ferrous ions and elemental sulfur. The Fe{sup 2+}, S{sup 2{minus}} ions and elemental sulfur, S{sup o}, in the system can then react with each other to form pyrite. This pathway of pyrite formation can be used in synthesizing nanoparticles of pyrite in microemulsions.

  16. Semiconductor electrochemistry of coal pyrite. Technical progress report, April--June 1992

    SciTech Connect

    Osseo-Asare, K.; Wei, D.

    1992-12-01

    Pyrite synthesis is of interest in many diverse fields, such as geology, fuel processing technology, chemistry, metallurgy, materials science, and so on. Based on fundamental studies of this process, the formation mechanisms of this important sulfide on the earth can be better understood. The studies can also help us to better understand the surface chemistry and electrochemistry of pyrite, thereby assisting in the development of more efficient processes for removal of the sulfide from coal. The work performed during this quarter focuses on the study of the reaction between aqueous sulfide ions and dissolved Fe(II) salts by using a stopped-flow spectrophotometric technique. At a wavelength of 500 mn, no absorption was observed with either aqueous sulfide or dissolved Fe(II) salt alone. However, when the two solutions were mixed, a strong absorbance appeared at the same wavelength. The absorbance-time curve showed that a black material formed at the first few seconds of the reaction, then this material decayed and changed gradually to a lighter dark material within the following several minutes. These processes were pH-dependent. It was more likely to form the black intermediate at the pH range from 7 to 8. This indicates that the reaction between Fe{sup 2+} and HS{sup {minus}} results in the formation of the black intermediate because in this pH range, both Fe{sup 2+} and HS{sup {minus}} are the predominant species. The absorbance varied linearly with the concentration of the reactant for the first step of the reaction. The absorptivity of the black intermediate was determined as 4800 l/mol/cm. By means of this spectrophotometric technique, the stoichiometry, the equilibrium constant and the rate constant of the reaction will be determined.

  17. Direct electrochemistry of cytochrome c entrapped in agarose hydrogel in room temperature ionic liquids.

    PubMed

    Wang, Sui; Guo, Zhiyong; Zhang, Huina

    2011-08-01

    Direct electrochemistry of cytochrome c (cyt-c) entrapped in agarose hydrogel on gold electrode (Au), edge plane pyrolytic graphite electrode (EPPGE) and glassy carbon electrode (GC) in two room temperature ionic liquids was investigated. The effects of the addition of N,N-dimethylformamide (DMF) in the agarose-cyt-c film, water concentration in ionic liquids and exterior metal ions on the electrochemical behavior of cyt-c were monitored, and electrocatalytic properties of cyt-c were also done. Results showed that a good quasi-reversible redox behavior of cyt-c could be found after adding DMF in agarose-cyt-c film, and peak shape would not change after continuously scanning for 50 cycles. In addition, a certain amount of water in hydrophilic ionic liquids is necessary to maintain electrochemical activities of cyt-c, electrochemical performance of cyt-c is the best when the water content is 5.2% and 5.8% for 1-butyl-3-methylimidazolium bromide ([Bmim][Br]) and 1-butyl-3-methylimidazolium tetrafluoroborate([Bmim][BF(4)]) respectively. However, electrochemical activities of cyt-c are inhibited by exterior metal ions. Interestingly, cyt-c entrapped in agarose hydrogel on EPPGE and GC could catalyze the electroreduction of trichloroacetic acid (TCA) and tert-butyl hydroperoxide (t-BuOOH) in [Bmim][BF(4)], but could not in [Bmim][Br]. Reasons for above-mentioned differences of electrochemical properties of cyt-c in different ionic liquids were preliminarily discussed. PMID:21659008

  18. Integrating bipolar electrochemistry and electrochemiluminescence imaging with microdroplets for chemical analysis.

    PubMed

    Wu, Suozhu; Zhou, Zhenyu; Xu, Linru; Su, Bin; Fang, Qun

    2014-03-15

    Here we develop a microdroplet sensor based on bipolar electrochemistry and electrochemiluminescence (ECL) imaging. The sensor was constructed with a closed bipolar cell on a hybrid poly(dimethylsioxane) (PDMS)-indium tin oxide (ITO) glass microchip. The ITO microband functions as the bipolar electrode and its two poles are placed in two spatially separate micro-reservoirs predrilled on the PDMS cover. After loading microliter-sized liquid droplets of tris(2,2'-bipyridyl) ruthenium (II)/2-(dibutylamino) ethanol (Ru(bpy)3(2+)/DBAE) and the analyte to the micro-reservoirs, an appropriate external voltage imposed on the driving electrodes could induce the oxidation of Ru(bpy)3(2+)/DBAE and simultaneous reduction of the analyte at the anodic and cathodic poles, respectively. ECL images generated by Ru(bpy)3(2+)/DBAE oxidation at the anodic pole and the electrical current flowing through the bipolar electrode can be recorded for quantitative analyte detection. Several types of quinones were selected as model analytes to demonstrate the sensor performance. Furthermore, the cathodic pole of bipolar electrode can be modified with (3-aminopropyl)triethoxysilane-gold nanoparticles-horseradish peroxidase composites for hydrogen peroxide detection. This microdroplet sensor with a closed bipolar cell can avoid the interference and cross-contamination between analyte solutions and ECL reporting reagents. It is also well adapted for chemical analysis in the incompatible system, e.g., detection of organic compounds insoluble in water by aqueous ECL generation. Moreover, this microdroplet sensor has advantages of simple structure, high sensitivity, fast response and wide dynamic response, providing great promise for chemical and biological analysis. PMID:24140829

  19. The preparation of a novel polymer film based on salicylaldoxime and its influence on aqueous copper electrochemistry

    SciTech Connect

    Davis, J.; Vaughan, D.H.; Cardosi, M.F.

    1994-07-01

    The metal complexing ligand salicylaldoxime was electropolymerized onto platinum electrodes and the resulting film characterized by reflectance FT-IR spectroscopy. The modified electrode response to aqueous iron, copper, cobalt and lead ions was investigated with the iron(III) and copper (II) ions showing significantly altered electrochemistry. The response of the modified electrode towards aqueous copper ion was found to be directly proportional to copper concentration with little interference from lead ions. The retention of copper ions, film stability and the nature of the film action are discussed along with its potential use in sensor construction.

  20. Applied geodesy

    SciTech Connect

    Turner, S.

    1987-01-01

    This volume is based on the proceedings of the CERN Accelerator School's course on Applied Geodesy for Particle Accelerators held in April 1986. The purpose was to record and disseminate the knowledge gained in recent years on the geodesy of accelerators and other large systems. The latest methods for positioning equipment to sub-millimetric accuracy in deep underground tunnels several tens of kilometers long are described, as well as such sophisticated techniques as the Navstar Global Positioning System and the Terrameter. Automation of better known instruments such as the gyroscope and Distinvar is also treated along with the highly evolved treatment of components in a modern accelerator. Use of the methods described can be of great benefit in many areas of research and industrial geodesy such as surveying, nautical and aeronautical engineering, astronomical radio-interferometry, metrology of large components, deformation studies, etc.

  1. Conceptual difficulties experienced by senior high school students of electrochemistry: Electric circuits and oxidation-reduction equations

    NASA Astrophysics Data System (ADS)

    Garnett, Pamela J.; Treagust, David F.

    The purpose of this research was to investigate students' understanding of electrochemistry following a course of instruction. A list of conceptual and propositional knowledge statements was formulated to identify the knowledge base necessary for students to understand electric circuits and oxidation-reduction equations. The conceptual and propositional knowledge statements provided the framework for the development of a semistructured interview protocol which was administered to 32 students in their final year of high school chemistry. The interview questions about electric circuits revealed that several students in the sample were confused about the nature of electric current both in metallic conductors and in electrolytes. Students studying both physics and chemistry were more confused about current flow in metallic conductors than students who were only studying chemistry. In the section of the interview which focused on oxidation and reduction, many students experienced problems in identifying oxidation-reduction equations. Several misconceptions relating to the inappropriate use of definitions of oxidation and reduction were identified. The data illustrate how students attempted to make sense of the concepts of electrochemistry with the knowledge they had already developed or constructed. The implications of the research are that teachers, curriculum developers, and textbook writers, if they are to minimize potential misconceptions, need to be cognizant of the relationship between physics and chemistry teaching, of the need to test for erroneous preconceptions about current before teaching about electrochemical (galvanic) and electrolytic cells, and of the difficulties experienced by students when using more than one model to explain scientific phenomena.

  2. Synthesis, Assembly, and Characterization of Monolayer Protected Gold Nanoparticle Films for Protein Monolayer Electrochemistry

    PubMed Central

    Doan, Tran T.; Freeman, Michael H.; Schmidt, Adrienne R.; Nguyen, Natalie D. T.; Leopold, Michael C.

    2011-01-01

    Colloidal gold nanoparticles protected with alkanethiolate ligands called monolayer protected gold clusters (MPCs) are synthesized and subsequently incorporated into film assemblies that serve as adsorption platforms for protein monolayer electrochemistry (PME). PME is utilized as the model system for studying electrochemical properties of redox proteins by confining them to an adsorption platform at a modified electrode, which also serves as a redox partner for electron transfer (ET) reactions. Studies have shown that gold nanoparticle film assemblies of this nature provide for a more homogeneous protein adsorption environment and promote ET without distance dependence compared to the more traditional systems modified with alkanethiol self-assembled monolayers (SAM).1-3 In this paper, MPCs functionalized with hexanethiolate ligands are synthesized using a modified Brust reaction4 and characterized with ultraviolet visible (UV-Vis) spectroscopy, transmission electron microscopy (TEM), and proton (1H) nuclear magnetic resonance (NMR). MPC films are assembled on SAM modified gold electrode interfaces by using a "dip cycle" method of alternating MPC layers and dithiol linking molecules. Film growth at gold electrode is tracked electrochemically by measuring changes to the double layer charging current of the system. Analogous films assembled on silane modified glass slides allow for optical monitoring of film growth and cross-sectional TEM analysis provides an estimated film thickness. During film assembly, manipulation of the MPC ligand protection as well as the interparticle linkage mechanism allow for networked films, that are readily adaptable, to interface with redox protein having different adsorption mechanism. For example, Pseudomonas aeruginosa azurin (AZ) can be adsorbed hydrophobically to dithiol-linked films of hexanethiolate MPCs and cytochrome c (cyt c) can be immobilized electrostatically at a carboxylic acid modified MPC interfacial layer. In this

  3. Electrochemistry of Iodide, Iodine, and Iodine Monochloride in Chloride Containing Nonhaloaluminate Ionic Liquids.

    PubMed

    Bentley, Cameron L; Bond, Alan M; Hollenkamp, Anthony F; Mahon, Peter J; Zhang, Jie

    2016-02-01

    The electrochemical behavior of iodine remains a contemporary research interest due to the integral role of the I(-)/I3(-) couple in dye-sensitized solar cell technology. The neutral (I2) and positive (I(+)) oxidation states of iodine are known to be strongly electrophilic, and thus the I(-)/I2/I(+) redox processes are sensitive to the presence of nucleophilic chloride or bromide, which are both commonly present as impurities in nonhaloaluminate room temperature ionic liquids (ILs). In this study, the electrochemistry of I(-), I2, and ICl has been investigated by cyclic voltammetry at a platinum macrodisk electrode in a binary IL mixture composed of 1-butyl-3-methylimidazolium chloride ([C4mim]Cl) and 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide ([C2mim][NTf2]). In the absence of chloride (e.g., in neat [C2mim][NTf2]), I(-) is oxidized in an overall one electron per iodide ion process to I2 via an I3(-) intermediate, giving rise to two resolved I(-)/I3(-) and I3(-)/I2 processes, as per previous reports. In the presence of low concentrations of chloride ([Cl(-)] and [I(-)] are both <30 mM), an additional oxidation process appears at potentials less positive than the I3(-)/I2 process, which corresponds to the oxidation of I3(-) to the interhalide complex anion [ICl2](-), in an overall two electron per iodide ion process. In the presence of a large excess of Cl(-) ([I(-)] ≈ 10 mM and [Cl(-)] ≈ 3.7 M), I(-) is oxidized in an overall two electron per iodide ion process to [ICl2](-) via an [I2Cl](-) intermediate (confirmed by investigating the voltammetric response of ICl and I2 under these conditions). In summary, the I(-)/I2/I(+) processes in nonhaloaluminate ILs involve a complicated interplay between multiple electron transfer pathways and homogeneous chemical reactions which may not be at equilibrium on the voltammetric time scale. PMID:26708364

  4. Roles of surface chemistry on safety and electrochemistry in lithium ion batteries.

    PubMed

    Lee, Kyu Tae; Jeong, Sookyung; Cho, Jaephil

    2013-05-21

    Motivated by new applications including electric vehicles and the smart grid, interest in advanced lithium ion batteries has increased significantly over the past decade. Therefore, research in this field has intensified to produce safer devices with better electrochemical performance. Most research has focused on the development of new electrode materials through the optimization of bulk properties such as crystal structure, ionic diffusivity, and electric conductivity. More recently, researchers have also considered the surface properties of electrodes as critical factors for optimizing performance. In particular, the electrolyte decomposition at the electrode surface relates to both a lithium ion battery's electrochemical performance and safety. In this Account, we give an overview of the major developments in the area of surface chemistry for lithium ion batteries. These ideas will provide the basis for the design of advanced electrode materials. Initially, we present a brief background to lithium ion batteries such as major chemical components and reactions that occur in lithium ion batteries. Then, we highlight the role of surface chemistry in the safety of lithium ion batteries. We examine the thermal stability of cathode materials: For example, we discuss the oxygen generation from cathode materials and describe how cells can swell and heat up in response to specific conditions. We also demonstrate how coating the surfaces of electrodes can improve safety. The surface chemistry can also affect the electrochemistry of lithium ion batteries. The surface coating strategy improved the energy density and cycle performance for layered LiCoO2, xLi2MnO3·(1 - x)LiMO2 (M = Mn, Ni, Co, and their combinations), and LiMn2O4 spinel materials, and we describe a working mechanism for these enhancements. Although coating the surfaces of cathodes with inorganic materials such as metal oxides and phosphates improves the electrochemical performance and safety properties of

  5. Chemistry and electrochemistry of environment-assisted cracking of an aluminum-zinc-magnesium-copper alloy

    NASA Astrophysics Data System (ADS)

    Cooper, Kevin Richard

    2001-11-01

    The mechanism of environment-assisted cracking (EAC) of 7xxx-series alloys is unclear, involving uncertain contributions of hydrogen embrittlement (HE) and anodic dissolution (AD). Fundamental understanding of the EAC mechanism is lacking in part because the role of the crack environment is not well understood. The objective of this research was to characterize and understand the role of the crack chemistry and electrochemistry during aqueous EAC of AA 7050. The crack environment can differ significantly from bulk conditions. Cations, produced by AD, hydrolyze causing local acidification; anions from the bulk electrolyte concentrate within the crack to maintain charge neutrality; ohmic potential drop results from ion migration and diffusion. A positive correlation exists between da/dt and [Al3+]Tip in chromate-chloride electrolyte wherein tip dissolution dominates flank corrosion in establishing the crack chemistry. Tip pH was 2 to 4 and determined by the reaction Al3+ + H 2O = AlOH2+ + H+. The tip potential (ETip) was approximately -0.90 VSCE and independent of EApp . The low ETip and pH promote H+ reduction, generating atomic and molecular H. Hydrogen bubbles restrict ion movement, substantially increasing the effective crack resistance over bulk conditions. Absorbed atomic hydrogen facilitates HE. The spontaneous transition from slow, incubation to high-rate da/dt coincides with the establishment of a critical aggressive tip chemistry and tip depolarization. Development of the critical occluded chemistry necessary for accelerated da/dt is a competitive process between opposing forces: AD, hydrolysis and migration promote an aggressive environment whereas diffusion reduces concentration gradients, thereby retarding the formation of an aggressive chemistry. Quantitative assessment of the contribution of tip dissolution to crack advance is hindered by a lack of knowledge of two key parameters: the tip corrosion front height and the effective crack conductivity

  6. Core-perfluoroalkylated perylene diimides and naphthalene diimides: versatile synthesis, solubility, electrochemistry, and optical properties.

    PubMed

    Yuan, Zhongyi; Li, Jing; Xiao, Yi; Li, Zheng; Qian, Xuhong

    2010-05-01

    By a strategy featuring perfluoroalkylation of the highly soluble intermediates and their further efficient transformations to target compounds, a versatile synthesis of core-perfluoroalkylated perylene diimides (PDIs) and naphthalene diimides (NDIs) was developed, and PDIs perfluoroalkylated at 1-position or 1,6-positions and core-perfluoroalkylated NDIs were first obtained. By esterification, perfluoroalkylation, hydrolysis, and condensation with amine, 1-perfluorooctyl-PDIs (7b, 7c, and 7e), 1,7-bis(perfluorooctyl)-PDIs (8a-c and 8e-g), 1,6-bis(perfluorooctyl)-PDIs (8'e), a mixture of 1,7-bis(trifluoromethyl)-PDIs and 1,6-bis(trifluoromethyl)-PDIs (11b and 11'b, 11d and 11'd, in a ratio of 19:1), 2-perfluorooctyl-NDIs (20a-d), and 2,6-bis(perfluorooctyl)-NDIs (21a-21d) were efficiently synthesized. Five valuable intermediates--1-perfluorooctylperylene dianhydride (5), 1,7-bis(perfluorooctyl)perylene dianhydride (6) 1,6-bis(perfluorooctyl)perylene dianhydride (6'), 2-perfluorooctylnaphthalene dianhydride (18), and 2,6-bis(perfluorooctyl) naphthalene dianhydride (19)--were also obtained, and they can condense with many amines to produce PDIs containing different functional side chains on the imide nitrogen atoms. Solubility, electrochemistry, and optical properties of the above core-perfluoroalkylated PDIs and NDIs were investigated. Core-perfluoroalkylated 8e, 8f, 8'e, mixture of 11d and 11'd, 20b, and 20d with excellent solubility in common organic solvents are competitive as candidates as solution processable semiconductors. Core-perfluoroalkylated PDIs and NDIs with experimental LUMO energy of 4.04-4.34 eV demonstrate strong electron accepting ability. For core-perfluoroalkylated PDIs, the maximum absorptions display blue shifts of 6-18 nm and the maximum molar extinction coefficients decrease obviously relative to those of unsubstituted PDIs, and they inherit the strong fluorescence from the PDIs family, which makes them promising fluorescent dyes. PMID

  7. Conceptual Difficulties Experienced by Prospective Teachers in Electrochemistry: Half-Cell Potential, Cell Potential, and Chemical and Electrochemical Equilibrium in Galvanic Cells.

    ERIC Educational Resources Information Center

    Ozkaya, Ali Riza

    2002-01-01

    A previous study of prospective teachers found that students from different countries and different levels of electrochemistry hold common misconceptions, indicating that concepts were presented to them poorly. Reports on how prospective teachers' scientifically incorrect ideas were used to form assertion-reason-type questions and how these…

  8. Guiding Principles of Hydrogenase Catalysis Instigated and Clarified by Protein Film Electrochemistry.

    PubMed

    Armstrong, Fraser A; Evans, Rhiannon M; Hexter, Suzannah V; Murphy, Bonnie J; Roessler, Maxie M; Wulff, Philip

    2016-05-17

    Protein film electrochemistry (PFE) is providing cutting-edge insight into the chemical principles underpinning biological hydrogen. Attached to an electrode, many enzymes exhibit "reversible" electrocatalytic behavior, meaning that a catalyzed redox reaction appears reversible or quasi-reversible when viewed by cyclic voltammetry. This efficiency is most relevant for enzymes that are inspiring advances in renewable energy, such as hydrogen-activating and CO2-reducing enzymes. Exploiting the rich repertoire of available instrumental methods, PFE experiments yield both a general snapshot and fine detail, all from tiny samples of enzyme. The dynamic electrochemical investigations blaze new trails and add exquisite detail to the information gained from structural and spectroscopic studies. This Account describes recent investigations of hydrogenases carried out in Oxford, including ideas initiated with PFE and followed through with complementary techniques, all contributing to an eventual complete picture of fast and efficient H2 activation without Pt. By immobilization of an enzyme on an electrode, catalytic electron flow and the chemistry controlling it can be addressed at the touch of a button. The buried nature of the active site means that structures that have been determined by crystallography or spectroscopy are likely to be protected, retained, and fully relevant in a PFE experiment. An electrocatalysis model formulated for the PFE of immobilized enzymes predicts interesting behavior and gives insight into why some hydrogenases are H2 producers and others are H2 oxidizers. Immobilization also allows for easy addition and removal of inhibitors along with precise potential control, one interesting outcome being that formaldehyde forms a reversible complex with reduced [FeFe]-hydrogenases, thereby providing insight into the order of electron and proton transfers. Experiments on O2-tolerant [NiFe]-hydrogenases show that O2 behaves like a reversible inhibitor: it

  9. Field Effect Modulation of Outer-Sphere Electrochemistry at Back-Gated, Ultrathin ZnO Electrodes.

    PubMed

    Kim, Chang-Hyun; Frisbie, C Daniel

    2016-06-15

    Here we report field-effect modulation of solution electrochemistry at 5 nm thick ZnO working electrodes prepared on SiO2/degenerately doped Si gates. We find that ultrathin ZnO behaves like a 2D semiconductor, in which charge carriers electrostatically induced by the back gate lead to band edge shift at the front electrode/electrolyte interface. This, in turn, manipulates the charge transfer kinetics on the electrode at a given electrode potential. Experimental results and the proposed model indicate that band edge alignment can be effectively modulated by 0.1-0.4 eV depending on the density of states in the semiconductor and the capacitance of the gate/dielectric stack. PMID:27249050

  10. Direct electrochemistry and electrocatalysis of glucose oxidase immobilized on reduced graphene oxide and silver nanoparticles nanocomposite modified electrode.

    PubMed

    Palanisamy, Selvakumar; Karuppiah, Chelladurai; Chen, Shen-Ming

    2014-02-01

    The direct electrochemistry of glucose oxidase (GOx) was successfully realized on electrochemically reduced graphene oxide and silver nanoparticles (RGO/Ag) nanocomposite modified electrode. The fabricated nanocomposite was characterized by field emission scanning electron microscope and energy dispersive spectroscopy. The GOx immobilized nanocomposite modified electrode showed a pair of well-defined redox peaks with a formal potential (E°) of -0.422 V, indicating that the bioactivity of GOx was retained. The heterogeneous electron transfer rate constant (Ks) of GOx at the nanocomposite was calculated to be 5.27 s(-1), revealing a fast direct electron transfer of GOx. The GOx immobilized RGO/Ag nanocomposite electrode exhibited a good electrocatalytic activity toward glucose over a linear concentration range from 0.5 to 12.5 mM with a detection limit of 0.16 mM. Besides, the fabricated biosensor showed an acceptable sensitivity and selectivity for glucose. PMID:24184536

  11. Achieving direct electrochemistry of glucose oxidase by one step electrochemical reduction of graphene oxide and its use in glucose sensing.

    PubMed

    Shamsipur, Mojtaba; Tabrizi, Mahmoud Amouzadeh

    2014-12-01

    In this paper, the direct electrochemistry of glucose oxidase (GOD) was accomplished at a glassy carbon electrode modified with electrochemically reduced graphene oxide/sodium dodecyl sulfate (GCE/ERGO/SDS). A pair of reversible peaks is exhibited on GCE/ERGO/SDS/GOD by cyclic voltammetry. The peak-to-peak potential separation of immobilized GOD is 28 mV in 0.1 M phosphate buffer solution (pH7.0) with a scan rate of 50 mV/s. The average surface coverage is 2.62×10(-10) mol cm(-2). The resulting biosensor exhibited a good response to glucose with linear range from 1 to 8 mM (R(2)=0.9878), good reproducibility and detection limit of 40.8 μM. The results from the biosensor were similar (±5%) to those obtained from the clinical analyzer. PMID:25491807

  12. Application of Carbon-Microsphere-Modified Electrodes for Electrochemistry of Hemoglobin and Electrocatalytic Sensing of Trichloroacetic Acid

    PubMed Central

    Wang, Wen-Cheng; Yan, Li-Jun; Shi, Fan; Niu, Xue-Liang; Huang, Guo-Lei; Zheng, Cai-Juan; Sun, Wei

    2015-01-01

    By using the hydrothermal method, carbon microspheres (CMS) were fabricated and used for electrode modification. The characteristics of CMS were investigated using various techniques. The biocompatible sensing platform was built by immobilizing hemoglobin (Hb) on the micrometer-sized CMS-modified electrode with a layer of chitosan membrane. On the cyclic voltammogram, a couple of quasi-reversible cathodic and anodic peaks appeared, showing that direct electrochemistry of Hb with the working electrode was achieved. The catalytic reduction peak currents of the bioelectrode to trichloroacetic acid was established in the linear range of 2.0~70.0 mmol·L−1 accompanied by a detection limit of 0.30 mmol·L−1 (3σ). The modified electrode displayed favorable sensitivity, good reproducibility and stability, which suggests that CMS is promising for fabricating third-generation bioelectrochemical sensors. PMID:26703621

  13. Combined optical and electrochemical methods for studying electrochemistry at the single molecule and single particle level: recent progress and perspectives.

    PubMed

    Hill, Caleb M; Clayton, Daniel A; Pan, Shanlin

    2013-12-28

    We present a review of recent efforts aimed at understanding interfacial charge transfer at the single molecule and single nanoparticle level using the combined methods of traditional electrochemistry and optical spectroscopy with high spatial, spectral, and temporal resolution. Elastic light scattering, surface enhanced Raman scattering (SERS), fluorescence, and electrogenerated chemiluminescence (ECL) techniques have been demonstrated to be powerful tools for the study of interfacial charge transfer events involving a single molecule or nanoparticle and for the characterization of nanostructured electrodes. It is shown that these optical methods enable the exploration of electrochemical events with improved temporal and spatial resolution which are usually obstructed by the ensemble averaging inherent in conventional electrochemical methods. In this report, the current status of the field is reviewed and challenges for future work are discussed. PMID:24196825

  14. The relationship between redox enzyme activity and electrochemical potential-cellular and mechanistic implications from protein film electrochemistry.

    PubMed

    Gates, Andrew J; Kemp, Gemma L; To, Chun Yip; Mann, James; Marritt, Sophie J; Mayes, Andrew G; Richardson, David J; Butt, Julea N

    2011-05-01

    In protein film electrochemistry a redox protein of interest is studied as an electroactive film adsorbed on an electrode surface. For redox enzymes this configuration allows quantification of the relationship between catalytic activity and electrochemical potential. Considered as a function of enzyme environment, i.e., pH, substrate concentration etc., the activity-potential relationship provides a fingerprint of activity unique to a given enzyme. Here we consider the nature of the activity-potential relationship in terms of both its cellular impact and its origin in the structure and catalytic mechanism of the enzyme. We propose that the activity-potential relationship of a redox enzyme is tuned to facilitate cellular function and highlight opportunities to test this hypothesis through computational, structural, biochemical and cellular studies. PMID:21423952

  15. Experimental and theoretical study of possible correlation between the electrochemistry of canthin-6-one and the anti-proliferative activity against human cancer stem cells

    NASA Astrophysics Data System (ADS)

    Cebrián-Torrejón, G.; Doménech-Carbó, A.; Scotti, M. T.; Fournet, A.; Figadère, B.; Poupon, E.

    2015-12-01

    This work presents an approach to study the performance of novel targets able to overcome cancer stem cell chemoresistance, based on the voltammetric data for microparticulate films of natural or synthetic alkaloids from the canthin-6-one series. A comparison of this voltammetric technique with conventional solution phase electrochemistry suggests the differences in the anti-proliferative activity of canthin-6-ones could be tentatively correlated to their different capacity to generate semiquinone radical anions. These data also match theoretical calculations.

  16. 99Tc and Re incorporated into metal oxide polyoxometalates: oxidation state stability elucidated by electrochemistry and theory.

    PubMed

    McGregor, Donna; Burton-Pye, Benjamin P; Mbomekalle, Israel M; Aparicio, Pablo A; Romo, Susanna; López, Xavier; Poblet, Josep M; Francesconi, Lynn C

    2012-08-20

    The radioactive element technetium-99 ((99)Tc, half-life = 2.1 × 10(5) years, β(-) of 253 keV), is a major byproduct of (235)U fission in the nuclear fuel cycle. (99)Tc is also found in radioactive waste tanks and in the environment at National Lab sites and fuel reprocessing centers. Separation and storage of the long-lived (99)Tc in an appropriate and stable waste-form is an important issue that needs to be addressed. Considering metal oxide solid-state materials as potential storage matrixes for Tc, we are examining the redox speciation of Tc on the molecular level using polyoxometalates (POMs) as models. In this study we investigate the electrochemistry of Tc complexes of the monovacant Wells-Dawson isomers, α(1)-P(2)W(17)O(61)(10-) (α1) and α(2)-P(2)W(17)O(61)(10-) (α2) to identify features of metal oxide materials that can stabilize the immobile Tc(IV) oxidation state accessed from the synthesized Tc(V)O species and to interrogate other possible oxidation states available to Tc within these materials. The experimental results are consistent with density functional theory (DFT) calculations. Electrochemistry of K(7-n)H(n)[Tc(V)O(α(1)-P(2)W(17)O(61))] (Tc(V)O-α1), K(7-n)H(n)[Tc(V)O(α(2)-P(2)W(17)O(61))] (Tc(V)O-α2) and their rhenium analogues as a function of pH show that the Tc-containing derivatives are always more readily reduced than their Re analogues. Both Tc and Re are reduced more readily in the lacunary α1 site as compared to the α2 site. The DFT calculations elucidate that the highest oxidation state attainable for Re is VII while, under the same electrochemistry conditions, the highest oxidation state for Tc is VI. The M(V)→ M(IV) reduction processes for Tc(V)O-α1 are not pH dependent or only slightly pH dependent suggesting that protonation does not accompany reduction of this species unlike the M(V)O-α2 (M = (99)Tc, Re) and Re(V)O-α1 where M(V/IV) reduction process must occur hand in hand with protonation of the terminal M═O to

  17. Teaching Physiology and the World Wide Web: Electrochemistry and Electrophysiology on the Internet.

    ERIC Educational Resources Information Center

    Dwyer, Terry M.; Fleming, John; Randall, James E.; Coleman, Thomas G.

    1997-01-01

    Presents two examples of laboratory exercises using the World Wide Web for first-year medical students. The first example introduces the physical laws that apply to osmotic, chemical, and electrical gradients and a simulation of the ability of the sodium-potassium pump to establish chemical gradients and maintain cell volume. The second module…

  18. Direct electrochemistry of cytochrome c immobilized on titanium nitride/multi-walled carbon nanotube composite for amperometric nitrite biosensor.

    PubMed

    Haldorai, Yuvaraj; Hwang, Seung-Kyu; Gopalan, Anantha-Iyengar; Huh, Yun Suk; Han, Young-Kyu; Voit, Walter; Sai-Anand, Gopalan; Lee, Kwang-Pill

    2016-05-15

    In this report, titanium nitride (TiN) nanoparticles decorated multi-walled carbon nanotube (MWCNTs) nanocomposite is fabricated via a two-step process. These two steps involve the decoration of titanium dioxide nanoparticles onto the MWCNTs surface and a subsequent thermal nitridation. Transmission electron microscopy shows that TiN nanoparticles with a mean diameter of ≤ 20 nm are homogeneously dispersed onto the MWCNTs surface. Direct electrochemistry and electrocatalysis of cytochrome c immobilized on the MWCNTs-TiN composite modified on a glassy carbon electrode for nitrite sensing are investigated. Under optimum conditions, the current response is linear to its concentration from 1 µM to 2000 µM with a sensitivity of 121.5 µA µM(-1)cm(-2) and a low detection limit of 0.0014 µM. The proposed electrode shows good reproducibility and long-term stability. The applicability of the as-prepared biosensor is validated by the successful detection of nitrite in tap and sea water samples. PMID:26748372

  19. Impact of Soil Composition and Electrochemistry on Corrosion of Rock-cut Slope Nets along Railway Lines in China.

    PubMed

    Chen, Jiao; Chen, Zhaoqiong; Ai, Yingwei; Xiao, Jingyao; Pan, Dandan; Li, Wei; Huang, Zhiyu; Wang, Yumei

    2015-01-01

    Taking the slope of Suiyu Railway to study, the research separately studied soil resistivity, soil electrochemistry (corrosion potential, oxidization reduction potential, electric potential gradient and pH), soil anions (total soluble salt, Cl(-), SO4(2-) and ), and soil nutrition (moisture content, organic matter, total nitrogen, alkali-hydrolysable nitrogen, available phosphorus, and available potassium) at different slope levels, and conducted corrosion grade evaluation on artificial soil according to its single index and comprehensive indexes. Compared with other factors, water has the biggest impact on the corrosion of slope protection net, followed by anion content. Total soluble salt has the moderate impact on the corrosion of slope protection net, and stray current has the moderate impact on the corrosion of mid-slope protection net. Comprehensive evaluation on the corrosive degree of soil samples indicates that the corrosion of upper slope is moderate, and the corrosion of mid-slope and lower slope is strong. Organic matter in soil is remarkably relevant to electric potential gradient. Available nitrogen, available potassium and available phosphorus are remarkably relevant to anions. The distribution of soil nutrient is indirectly relevant to slope type. PMID:26450811

  20. Coupling Electrochemistry with Fluorescence Confocal Microscopy To Investigate Electrochemical Reactivity: A Case Study with the Resazurin-Resorufin Fluorogenic Couple.

    PubMed

    Doneux, Thomas; Bouffier, Laurent; Goudeau, Bertrand; Arbault, Stéphane

    2016-06-21

    The redox couple resazurin-resorufin exhibits electrofluorochromic properties which are investigated herein by absorption and fluorescence spectroelectrochemistry and by electrochemically coupled-fluorescence confocal laser scanning microscopy (EC-CLSM). At pH 10, the highly fluorescent resorufin dye is generated at the electrode surface by the electrochemical reduction of the poorly fluorescent resazurin. Performing EC-CLSM at electrode surfaces allows to monitor spatially resolved electrochemical processes in situ and in real time. Using a small (315 μm diameter) cylindrical electrode, a steady-state diffusion layer builds up under potentiostatic conditions at -0.45 V vs Ag|AgCl. Mapping the fluorescence intensity in 3D by CLSM enables us to reconstruct the relative concentration profile of resorufin around the electrode. The comparison of the experimental diffusion-profile with theoretical predictions demonstrates that spontaneous convection has a direct influence on the actual thickness of the diffusion layer, which is smaller than the value predicted for a purely diffusional transport. This study shows that combining fluorescence CLSM with electrochemistry is a powerful tool to study electrochemical reactivity at a spatially resolved level. PMID:27247989

  1. Conducting Polymer Nanostructures and Nanocomposites with Carbon Nanotubes: Hierarchical Assembly by Molecular Electrochemistry, Growth Aspects and Property Characterization.

    PubMed

    Gupta, Sanju; Price, Carson; Heintzman, Eli

    2016-01-01

    Conducting (or π-conjugated) polymers are promising materials for preparing supramolecular nano-structures and nanocomposites. We report controlled nanostructure syntheses of polypyrrole (PPy) and poylaniline (PANi) via electropolymerization (i.e., in-situ electrochemical anodic oxidation). The density, shape, caliber and thickness of self-assembled PPy micro-containers are regulated by electrochemical potential window for H2 bubbles and number of cyclic voltammetric (potentiodynamic) scans. Likewise, we employed amperometry, chronopotentiometry and potentiodynamic modes using hydrochloric acid as oxidizing agent to prepare PANi nanoparticles and nanotubules. We present our findings from the viewpoint of molecular electrochemistry with growth kinetic aspects yielding mechanistic details (initially forming dimers and oligomers as nucleating agents followed by polymer growth). Also targeted is forming nanocomposites with functionalized single- and multi-walled carbon nanotubes (FSWCNTs and FMWCNTs) as reinforced agent to optimize structural and functional properties. All of these novel nanomaterials are characterized using a range of complementary techniques to establish microscopic structure-property-function relationship. PMID:27398466

  2. Impact of Soil Composition and Electrochemistry on Corrosion of Rock-cut Slope Nets along Railway Lines in China

    NASA Astrophysics Data System (ADS)

    Chen, Jiao; Chen, Zhaoqiong; Ai, Yingwei; Xiao, Jingyao; Pan, Dandan; Li, Wei; Huang, Zhiyu; Wang, Yumei

    2015-10-01

    Taking the slope of Suiyu Railway to study, the research separately studied soil resistivity, soil electrochemistry (corrosion potential, oxidization reduction potential, electric potential gradient and pH), soil anions (total soluble salt, Cl-, SO42- and ), and soil nutrition (moisture content, organic matter, total nitrogen, alkali-hydrolysable nitrogen, available phosphorus, and available potassium) at different slope levels, and conducted corrosion grade evaluation on artificial soil according to its single index and comprehensive indexes. Compared with other factors, water has the biggest impact on the corrosion of slope protection net, followed by anion content. Total soluble salt has the moderate impact on the corrosion of slope protection net, and stray current has the moderate impact on the corrosion of mid-slope protection net. Comprehensive evaluation on the corrosive degree of soil samples indicates that the corrosion of upper slope is moderate, and the corrosion of mid-slope and lower slope is strong. Organic matter in soil is remarkably relevant to electric potential gradient. Available nitrogen, available potassium and available phosphorus are remarkably relevant to anions. The distribution of soil nutrient is indirectly relevant to slope type.

  3. Impact of Soil Composition and Electrochemistry on Corrosion of Rock-cut Slope Nets along Railway Lines in China

    PubMed Central

    Chen, Jiao; Chen, Zhaoqiong; Ai, Yingwei; Xiao, Jingyao; Pan, Dandan; Li, Wei; Huang, Zhiyu; Wang, Yumei

    2015-01-01

    Taking the slope of Suiyu Railway to study, the research separately studied soil resistivity, soil electrochemistry (corrosion potential, oxidization reduction potential, electric potential gradient and pH), soil anions (total soluble salt, Cl−, SO42− and ), and soil nutrition (moisture content, organic matter, total nitrogen, alkali-hydrolysable nitrogen, available phosphorus, and available potassium) at different slope levels, and conducted corrosion grade evaluation on artificial soil according to its single index and comprehensive indexes. Compared with other factors, water has the biggest impact on the corrosion of slope protection net, followed by anion content. Total soluble salt has the moderate impact on the corrosion of slope protection net, and stray current has the moderate impact on the corrosion of mid-slope protection net. Comprehensive evaluation on the corrosive degree of soil samples indicates that the corrosion of upper slope is moderate, and the corrosion of mid-slope and lower slope is strong. Organic matter in soil is remarkably relevant to electric potential gradient. Available nitrogen, available potassium and available phosphorus are remarkably relevant to anions. The distribution of soil nutrient is indirectly relevant to slope type. PMID:26450811

  4. Electrochemistry and analytical determination of lysergic acid diethylamide (LSD) via adsorptive stripping voltammetry.

    PubMed

    Merli, Daniele; Zamboni, Daniele; Protti, Stefano; Pesavento, Maria; Profumo, Antonella

    2014-12-01

    Lysergic acid diethylamide (LSD) is hardly detectable and quantifiable in biological samples because of its low active dose. Although several analytical tests are available, routine analysis of this drug is rarely performed. In this article, we report a simple and accurate method for the determination of LSD, based on adsorptive stripping voltammetry in DMF/tetrabutylammonium perchlorate, with a linear range of 1-90 ng L(-1) for deposition times of 50s. LOD of 1.4 ng L(-1) and LOQ of 4.3 ng L(-1) were found. The method can be also applied to biological samples after a simple extraction with 1-chlorobutane. PMID:25159435

  5. Oxygen-participated electrochemistry of new lithium-rich layered oxides Li3MRuO5 (M = Mn, Fe).

    PubMed

    Laha, S; Natarajan, S; Gopalakrishnan, J; Morán, E; Sáez-Puche, R; Alario-Franco, M Á; Dos Santos-Garcia, A J; Pérez-Flores, J C; Kuhn, A; García-Alvarado, F

    2015-02-01

    We describe the synthesis, crystal structure and lithium deinsertion-insertion electrochemistry of two new lithium-rich layered oxides, Li3MRuO5 (M = Mn, Fe), related to rock salt based Li2MnO3 and LiCoO2. The Li3MnRuO5 oxide adopts a structure related to Li2MnO3 (C2/m) where Li and (Li0.2Mn0.4Ru0.4) layers alternate along the c-axis, while the Li3FeRuO5 oxide adopts a near-perfect LiCoO2 (R3[combining macron]m) structure where Li and (Li0.2Fe0.4Ru0.4) layers are stacked alternately. Magnetic measurements indicate for Li3MnRuO5 the presence of Mn(3+) and low spin configuration for Ru(4+) where the itinerant electrons occupy a π*-band. The onset of a net maximum in the χ vs. T plot at 9.5 K and the negative value of the Weiss constant (θ) of -31.4 K indicate the presence of antiferromagnetic superexchange interactions according to different pathways. Lithium electrochemistry shows a similar behaviour for both oxides and related to the typical behaviour of Li-rich layered oxides where participation of oxide ions in the electrochemical processes is usually found. A long first charge process with capacities of 240 mA h g(-1) (2.3 Li per f.u.) and 144 mA h g(-1) (1.38 Li per f.u.) is observed for Li3MnRuO5 and Li3FeRuO5, respectively. An initial sloping region (OCV to ca. 4.1 V) is followed by a long plateau (ca. 4.3 V). Further discharge-charge cycling points to partial reversibility (ca. 160 mA h g(-1) and 45 mA h g(-1) for Mn and Fe, respectively). Nevertheless, just after a few cycles, cell failure is observed. X-ray photoelectron spectroscopy (XPS) characterisation of both pristine and electrochemically oxidized Li3MRuO5 reveals that in the Li3MnRuO5 oxide, Mn(3+) and Ru(4+) are partially oxidized to Mn(4+) and Ru(5+) in the sloping region at low voltage, while in the long plateau, O(2-) is also oxidized. Oxygen release likely occurs which may be the cause for failure of cells upon cycling. Interestingly, some other Li-rich layered oxides have been reported to

  6. Probing Protein 3D Structures and Conformational Changes Using Electrochemistry-Assisted Isotope Labeling Cross-Linking Mass Spectrometry.

    PubMed

    Zheng, Qiuling; Zhang, Hao; Wu, Shiyong; Chen, Hao

    2016-05-01

    This study presents a new chemical cross-linking mass spectrometry (MS) method in combination with electrochemistry and isotope labeling strategy for probing both protein three-dimensional (3D) structures and conformational changes. For the former purpose, the target protein/protein complex is cross-linked with equal mole of premixed light and heavy isotope labeled cross-linkers carrying electrochemically reducible disulfide bonds (i.e., DSP-d0 and DSP-d8 in this study, DSP = dithiobis[succinimidyl propionate]), digested and then electrochemically reduced followed with online MS analysis. Cross-links can be quickly identified because of their reduced intensities upon electrolysis and the presence of doublet isotopic peak characteristics. In addition, electroreduction converts cross-links into linear peptides, facilitating MS/MS analysis to gain increased information about their sequences and modification sites. For the latter purpose of probing protein conformational changes, an altered procedure is adopted, in which the protein in two different conformations is cross-linked using DSP-d0 and DSP-d8 separately, and then the two protein samples are mixed in 1:1 molar ratio. The merged sample is subjected to digestion and electrochemical mass spectrometric analysis. In such a comparative cross-linking experiment, cross-links could still be rapidly recognized based on their responses to electrolysis. More importantly, the ion intensity ratios of light and heavy isotope labeled cross-links reveal the conformational changes of the protein, as exemplified by examining the effect of Ca(2+) on calmodulin conformation alternation. This new cross-linking MS method is fast and would have high value in structural biology. Graphical Abstract ᅟ. PMID:26902947

  7. Fullerene-nitrogen doped carbon nanotubes for the direct electrochemistry of hemoglobin and its application in biosensing.

    PubMed

    Sheng, Qinglin; Liu, Ruixiao; Zheng, Jianbin

    2013-12-01

    The direct electrochemistry of hemoglobin (Hb) immobilized by a fullerene-nitrogen doped carbon nanotubes and chitosan (C60-NCNTs/CHIT) composite matrix is demonstrated. The cyclic voltammetry and electrochemical impedance spectroscopy were used to characterize the modified electrode. In the deaerated buffer solution, the cyclic voltammogram of the Hb/C60-NCNTs/CHIT composite film modified electrode showed a pair of well-behaved redox peaks with the E°'=-0.335 (± 0.3) V (vs. SCE). The redox peaks are assigned to the redox reaction of Hb(Fe(III)/Fe(II)) and confirm the effective immobilization of Hb on the composite film. The large value of ks = 1.8 (± 0.2)s(-1) suggests that the immobilized Hb achieved a relative fast electron transfer process. The fast electron transfer interaction between protein and electrode surface suggested that the C60-NCNTs/CHIT composite film may mimic some physiological process and further elucidate the relationship between protein structures and biological functions. Moreover, the resulting electrode exhibited excellent electrocatalytic ability towards the reduction of hydrogen peroxide (H2O2) with the linear dynamic range of 2.0-225.0 μM. The linear regression equation was Ip/μA=7.35 (± 0.08)+0.438 (± 0.007)C/μM with the correlation coefficient of 0.9993. The detection limit was estimated at about 1 μM (S/N=3). The sensitivity was 438.0 (± 2.5) μA mM(-1). It is expected that the method presented here can not only be easily extended to other redox enzymes or proteins, but also be used as an electrochemical sensing devices for the determination of H2O2 in cell extracts or urine. PMID:23787095

  8. Sol-gel derived silica/chitosan/Fe3O4 nanocomposite for direct electrochemistry and hydrogen peroxide biosensing

    NASA Astrophysics Data System (ADS)

    Satvekar, R. K.; Rohiwal, S. S.; Tiwari, A. P.; Raut, A. V.; Tiwale, B. M.; Pawar, S. H.

    2015-01-01

    A novel strategy to fabricate hydrogen peroxide third generation biosensor has been developed from sol-gel of silica/chitosan (SC) organic-inorganic hybrid material assimilated with iron oxide magnetic nanoparticles (Fe3O4). The large surface area of Fe3O4 and porous morphology of the SC composite facilitates a high loading of horseradish peroxidase (HRP). Moreover, the entrapped enzyme preserves its conformation and biofunctionality. The fabrication of hydrogen peroxide biosensor has been carried out by drop casting of the SC/F/HRP nanocomposite on glassy carbon electrode (GCE) for study of direct electrochemistry. The x-ray diffraction (XRD) pattern and transmission electron microscopy (TEM) confirms the phase purity and particle size of as-synthesized Fe3O4 nanoparticles, respectively. The nanocomposite was characterized by UV-vis spectroscopy, fluorescence spectroscopy and Fourier transform infrared (FTIR) for the characteristic structure and conformation of enzyme. The surface topographies of the nanocomposite thin films were investigated by scanning electron microscopy (SEM). Dynamic light scattering (DLS) was used to determine the particle size distribution. The electrostatic interactions of the SC composite with Fe3O4 nanoparticles were studied by the zeta potential measurement. Electrochemical impedance spectroscopy (EIS) of the SC/F/HRP/GCE electrode displays Fe3O4 nanoparticles as an excellent candidate for electron transfer. The SC/F/HRP/GCE exhibited a pair of well-defined quasi reversible cyclic voltammetry peaks due to the redox couple of HRP-heme Fe (III)/Fe (II) in pH 7.0 potassium phosphate buffer. The biosensor was employed to detect H2O2 with linear range of 5 μM to 40 μM and detection limit of 5 μM. The sensor displays excellent selectivity, sensitivity, good reproducibility and long term stability.

  9. A quantitative assay for reductive metabolism of a pesticide in fish using electrochemistry coupled with liquid chromatography tandem mass spectrometry.

    PubMed

    Bussy, Ugo; Chung-Davidson, Yu-Wen; Li, Ke; Li, Weiming

    2015-04-01

    This is the first study to use electrochemistry to generate a nitro reduction metabolite as a standard for a liquid chromatography-mass spectrometry-based quantitative assay. This approach is further used to quantify 3-trifluoromethyl-4-nitrophenol (TFM) reductive metabolism. TFM is a widely used pesticide for the population control of sea lamprey (Petromyzon marinus), an invasive species of the Laurentian Great Lakes. Three animal models, sea lamprey, lake sturgeon (Acipenser fulvescens), and rainbow trout (Oncorhynchus mykiss), were selected to evaluate TFM reductive metabolism because they have been known to show differential susceptibilities to TFM toxicity. Amino-TFM (aTFM; 3-trifluoromethyl-4-aminophenol) was the only reductive metabolite identified through liquid chromatography-high-resolution mass spectrometry screening of liver extracts incubated with TFM and was targeted for electrochemical synthesis. After synthesis and purification, aTFM was used to develop a quantitative assay of the reductive metabolism of TFM through liquid chromatography and tandem mass spectrometry. The concentrations of aTFM were measured from TFM-treated cellular fractions, including cytosolic, nuclear, membrane, and mitochondrial protein extracts. Sea lamprey extracts produced the highest concentrations (500 ng/mL) of aTFM. In addition, sea lamprey and sturgeon cytosolic extracts showed concentrations of aTFM substantially higher than those of rainbow trout. However, other fractions of lake sturgeon extracts tend to show aTFM concentrations similar to those of rainbow trout but not with sea lamprey. These data suggest that the level of reductive metabolism of TFM may be associated with the sensitivities of the animals to this particular pesticide. PMID:25730707

  10. Probing the nature of electron transfer in metalloproteins on graphene-family materials as nanobiocatalytic scaffold using electrochemistry

    NASA Astrophysics Data System (ADS)

    Gupta, Sanju; Irihamye, Aline

    2015-03-01

    Graphene-based nanomaterials have shown great promise not only in nanoelectronics due to ultrahigh electron mobility but also as biocatalytic scaffolds owing to irreversible protein surface adsorption and facilitating direct electron transfer. In this work, we synthesized stable dispersions of graphene using liquid-phase exfoliation approach based on non-covalent interactions between graphene and 1-pyrenesulfonic acid sodium salt (Py-1SO3), 1-pyrenemethylamine salt (Py - Me-NH2) and Pluronic® P-123 surfactant using only water as solvent compatible with biomolecules. The resulting graphene nanoplatelets (Gr_LPE) are characterized by a combination of analytical (microscopy and spectroscopy) techniques revealing mono- to few-layer graphene displaying that the exfoliation efficiency strongly depends upon the type of pyrene-based salts and organic surfactants. Moreover being completely water-based approach, we build robust nanoscaffolds of graphene-family nanomaterials (GFNs) namely, monolayer graphene, Gr_LPE (the one prepared with Pluronic® P-123), graphene oxide (GO) and its reduced form (rGO) on glassy carbon electrode surface with three important metalloproteins include cytochrome c (Cyt c) [for electron transfer], myoglobin (Mb) [for oxygen storage] and horseradish peroxidase (HRP) [for catalyzing the biochemical reaction]. In order to demonstrate the nanobiocatalytical activity of these proteins, we used electrochemical interfacial direct electron transfer (DET) kinetics and attempt to determine the rate constant (kET) using two different analytical approaches namely, linear sweep voltammetry and Laviron's theory. We elucidated that all of the metalloproteins retain their structural integrity (secondary structure) upon forming mixtures with GFNs confirmed through optical and vibrational spectroscopy and biological activity using electrochemistry. Among the GFNs studied, Gr-LPE, GO and rGO support the efficient electrical wiring of the redox centers (with an

  11. Probing Protein 3D Structures and Conformational Changes Using Electrochemistry-Assisted Isotope Labeling Cross-Linking Mass Spectrometry

    NASA Astrophysics Data System (ADS)

    Zheng, Qiuling; Zhang, Hao; Wu, Shiyong; Chen, Hao

    2016-02-01

    This study presents a new chemical cross-linking mass spectrometry (MS) method in combination with electrochemistry and isotope labeling strategy for probing both protein three-dimensional (3D) structures and conformational changes. For the former purpose, the target protein/protein complex is cross-linked with equal mole of premixed light and heavy isotope labeled cross-linkers carrying electrochemically reducible disulfide bonds (i.e., DSP-d0 and DSP-d8 in this study, DSP = dithiobis[succinimidyl propionate]), digested and then electrochemically reduced followed with online MS analysis. Cross-links can be quickly identified because of their reduced intensities upon electrolysis and the presence of doublet isotopic peak characteristics. In addition, electroreduction converts cross-links into linear peptides, facilitating MS/MS analysis to gain increased information about their sequences and modification sites. For the latter purpose of probing protein conformational changes, an altered procedure is adopted, in which the protein in two different conformations is cross-linked using DSP-d0 and DSP-d8 separately, and then the two protein samples are mixed in 1:1 molar ratio. The merged sample is subjected to digestion and electrochemical mass spectrometric analysis. In such a comparative cross-linking experiment, cross-links could still be rapidly recognized based on their responses to electrolysis. More importantly, the ion intensity ratios of light and heavy isotope labeled cross-links reveal the conformational changes of the protein, as exemplified by examining the effect of Ca2+ on calmodulin conformation alternation. This new cross-linking MS method is fast and would have high value in structural biology.

  12. Fully solar-driven thermo- and electrochemistry for advanced oxidation processes (STEP-AOPs) of 2-nitrophenol wastewater.

    PubMed

    Nie, Chunhong; Shao, Nan; Wang, Baohui; Yuan, Dandan; Sui, Xin; Wu, Hongjun

    2016-07-01

    The STEP (Solar Thermal Electrochemical Process) for Advanced Oxidation Processes (AOPs, combined to STEP-AOPs), fully driven by solar energy without the input of any other forms of energy and chemicals, is introduced and demonstrated from the theory to experiments. Exemplified by the persistent organic pollutant 2-nitrophenol in water, the fundamental model and practical system are exhibited for the STEP-AOPs to efficiently transform 2-nitrophenol into carbon dioxide, water, and the other substances. The results show that the STEP-AOPs system performs more effectively than classical AOPs in terms of the thermodynamics and kinetics of pollutant oxidation. Due to the combination of solar thermochemical reactions with electrochemistry, the STEP-AOPs system allows the requisite electrolysis voltage of 2-nitrophenol to be experimentally decreased from 1.00 V to 0.84 V, and the response current increases from 18 mA to 40 mA. STEP-AOPs also greatly improve the kinetics of the oxidation at 30 °C and 80 °C. As a result, the removal rate of 2-nitrophenol after 1 h increased from 19.50% at 30 °C to 32.70% at 80 °C at constant 1.90 V. Mechanistic analysis reveals that the oxidation pathway is favorably changed because of thermal effects. The tracking of the reaction displayed that benzenediol and hydroquinone are initial products, with maleic acid and formic acid as sequential carboxylic acid products, and carbon dioxide as the final product. The theory and experiments on STEP-AOPs system exemplified by the oxidation of 2-nitrophenol provide a broad basis for extension of the STEP and AOPs for rapid and efficient treatment of organic wastewater. PMID:27093694

  13. Probing Protein 3D Structures and Conformational Changes Using Electrochemistry-Assisted Isotope Labeling Cross-Linking Mass Spectrometry

    NASA Astrophysics Data System (ADS)

    Zheng, Qiuling; Zhang, Hao; Wu, Shiyong; Chen, Hao

    2016-05-01

    This study presents a new chemical cross-linking mass spectrometry (MS) method in combination with electrochemistry and isotope labeling strategy for probing both protein three-dimensional (3D) structures and conformational changes. For the former purpose, the target protein/protein complex is cross-linked with equal mole of premixed light and heavy isotope labeled cross-linkers carrying electrochemically reducible disulfide bonds (i.e., DSP-d0 and DSP-d8 in this study, DSP = dithiobis[succinimidyl propionate]), digested and then electrochemically reduced followed with online MS analysis. Cross-links can be quickly identified because of their reduced intensities upon electrolysis and the presence of doublet isotopic peak characteristics. In addition, electroreduction converts cross-links into linear peptides, facilitating MS/MS analysis to gain increased information about their sequences and modification sites. For the latter purpose of probing protein conformational changes, an altered procedure is adopted, in which the protein in two different conformations is cross-linked using DSP-d0 and DSP-d8 separately, and then the two protein samples are mixed in 1:1 molar ratio. The merged sample is subjected to digestion and electrochemical mass spectrometric analysis. In such a comparative cross-linking experiment, cross-links could still be rapidly recognized based on their responses to electrolysis. More importantly, the ion intensity ratios of light and heavy isotope labeled cross-links reveal the conformational changes of the protein, as exemplified by examining the effect of Ca2+ on calmodulin conformation alternation. This new cross-linking MS method is fast and would have high value in structural biology.

  14. Modeling the electrochemistry of the primary circuits of light water reactors

    SciTech Connect

    Bertuch, A.; Macdonald, D.D.; Pang, J.; Kriksunov, L.; Arioka, K.

    1994-12-31

    To model the corrosion behaviors of the heat transport circuits of light water reactors, a mixed potential model (NTM) has been developed and applied to both boiling water reactors (BWRs) and pressurized water reactors (PWRs). Using the data generated by the GE/UKEA-Harwell radiolysis model, electrochemical potentials (ECPs) have been calculated for the heat transport circuits of eight BWRs operating under hydrogen water chemistry (HWC). By modeling the corrosion behaviors of these reactors, the effectiveness of HWC at limiting IGSCC and IASCC can be determined. For simulating PWR primary circuits, a chemical-radiolysis model (developed by the authors) was used to generate input parameters for the MPM. Corrosion potentials of Type 304 and 316 SSs in PWR primary environments were calculated using the NTM and were found to be in good agreement with the corrosion potentials measured in the laboratory for simulated PWR primary environments.

  15. Lithiated cobaltates for lithium-ion batteries. Structure, morphology and electrochemistry of oxides grown by solid-state reaction, wet chemistry and film deposition

    NASA Astrophysics Data System (ADS)

    Julien, C.; Gastro-Garcia, S.

    We present the structural (XRD and Raman) and electrochemical properties of various oxides of the cobaltate family (with the α-NaFeO 2-type structure) grown by solid-state reaction, wet chemistry and film deposition techniques. It is shown that synthesis greatly affects the electrochemistry and cycle life characteristics of these layer structured cathode materials. HT-LiCoO 2, LT-LiCoO 2, doped LiCo 1- yAl yO 2 and LiCoO 2 films are investigated.

  16. Insight in layer-by-layer assembly of cysteamine and L-cysteine on the copper surface by electrochemistry and Raman spectroscopy

    NASA Astrophysics Data System (ADS)

    Song, Ping; Shen, Shu; Li, Chuan-Chuan; Guo, Xiao-Yu; Wen, Ying; Yang, Hai-Feng

    2015-02-01

    In this work, we examined the relationship between the anticorrosion behavior and the structure of the cysteamine/L-cysteine layer-by-layer coating on the copper surface via the self-assembled monolayers (SAMs) technique with electrochemistry and surface-enhanced Raman scattering (SERS) spectroscopy. SERS results elucidated the layer-by-layer adsorption mechanism of cysteamine/L-cysteine at the copper surface. Electrochemical investigations explored the inhibition behavior of cysteamine/L-cysteine for copper from corrosion with a high protection efficiency of 91.4%.

  17. A study of the electrochemistry of nickel hydroxide electrodes with various additives

    NASA Astrophysics Data System (ADS)

    Zhu, Wen-Hua; Ke, Jia-Jun; Yu, Hong-Mei; Zhang, Deng-Jun

    Nickel composite electrodes (NCE) with various additives are prepared by a chemical impregnation method from nitrate solutions on sintered porous plaques. The electrochemical properties, such as utilization of active material, swelling and the discharge potential of the nickel oxide electrode (NOE) are determined mainly through the composition of the active material and the characteristics of nickel plaques. Most additives (Mg, Ca, Sr, Ba, Zn, Cd, Co, Li and Al hydroxide) exert effects on the discharge potential and swelling of the NOE. Chemical co-precipitation with the addition of calcium, zinc, magnesium and barium hydroxide increases the discharge potential by more than 20 mV, but that with zinc hydroxide results in an obvious decrease of active-material utilization and that with calcium and magnesium hydroxide produces a larger increase of electrode thickness. The effects of anion additives are also examined. Less than 1% mol of NiS in the active material increases the discharge potential. Cadmium, cobalt and zinc hydroxide are excellent additives for preventing swelling of the NCE. Slow voltammetry (0.2 mV s -1) in 6 M KOH is applied to characterize the oxygen-evolving potential of the NCE. The difference between the oxygen-evolution potential and the potential of the oxidation peak for the NCE with additives of calcium, lithium, barium and aluminium hydroxide is at least + 60 mV.

  18. Atomic-scale electrochemistry on the surface of a manganite by scanning tunneling microscopy

    SciTech Connect

    Vasudevan, Rama K. Tselev, Alexander; Baddorf, Arthur P.; Gianfrancesco, Anthony G.

    2015-04-06

    The doped manganese oxides (manganites) have been widely studied for their colossal magnetoresistive effects, for potential applications in oxide spintronics, electroforming in resistive switching devices, and are materials of choice as cathodes in modern solid oxide fuel cells. However, little experimental knowledge of the dynamics of the surfaces of perovskite manganites at the atomic scale exists. Here, through in-situ scanning tunneling microscopy (STM), we demonstrate atomic resolution on samples of La{sub 0.625}Ca{sub 0.375}MnO{sub 3} grown on (001) SrTiO{sub 3} by pulsed laser deposition. Furthermore, by applying triangular DC waveforms of increasing amplitude to the STM tip, and measuring the tunneling current, we demonstrate the ability to both perform and monitor surface electrochemical processes at the atomic level, including formation of oxygen vacancies and removal and deposition of individual atomic units or clusters. Our work paves the way for better understanding of surface oxygen reactions in these systems.

  19. Transport and electrochemistry based characterization of porous electrodes for CDI applications and comparison with desalination performance

    NASA Astrophysics Data System (ADS)

    Rios Perez, Carlos; Wilkes, Ellen; Guitierrez, Luis; Hidrovo, Carlos

    2014-11-01

    Development of carbon-based materials with high specific surface area at the end of last century has made researchers to look back at capacitive deionization as a potential desalination technique for brackish water. Several publications evaluate the adsorption capacity of electrode materials under different conditions. Many others present the development/characterization of new electrode materials using electrochemical analysis and other techniques. Although some work has been done to model the electro-adsorption process at the macro and micro-scale, there is still a gap to tie the characterization of the electrodes to their performance. Here a simplified one-dimensional model is used to estimate the characteristic net electro-adsorption velocities for fully-developed or developing regimes in a flow-by capacitive deionization system. This methodology is applied to three commercially available materials with very distinct structure topology to estimate electromigration velocities at a specific solution flow rate. The calculated electro-adsorption rates and other characterization parameters obtained using traditional electrochemical techniques were compared against important desalination performance parameters such as amount of salt adsorbed and desalination proficiency (amount of salt adsorbed per unit of energy). The results obtained show interesting correlations and sometimes-unexpected behavior under constant current and constant voltage operation.

  20. Electrochemistry of cholesterol biosensor based on a novel Pt-Pd bimetallic nanoparticle decorated graphene catalyst.

    PubMed

    Cao, Shurui; Zhang, Lei; Chai, Yaqin; Yuan, Ruo

    2013-05-15

    A new electrochemical biosensor with enhanced sensitivity was developed for detection of cholesterol by using platinum-palladium-chitosan-graphene hybrid nanocomposites (PtPd-CS-GS) functionalized glassy carbon electrode (GCE). An electrodeposition method was applied to form PtPd nanoparticles-doped chitosan-graphene hybrid nanocomposites (PtPd-CS-GS), which were characterized by scanning electron microscopy (SEM) and electrochemical methods. The presence of the PtPd-CS-GS nanocomposites not only accelerated direct electron transfer from the redox enzyme to the electrode surface, but also enhanced the immobilized amount of cholesterol oxidase (ChOx). Under optimal conditions, the fabricated biosensor exhibited wide linear ranges of responses to cholesterol in the concentration ranges of 2.2×10(-6) to 5.2×10(-4)M, the limit of detection was 0.75 μM (S/N=3). The response time was less than 7s and the Michaelis-Menten constant (Km(app)) was found as 0.11 mM. In addition, the biosensor also exhibited excellent reproducibility and stability. Along with these attractive features, the biosensor also displayed very high specificity to cholesterol with complete elimination of interference from UA, AA, and glucose. PMID:23618155

  1. Detection of DNA Hybridization by Methylene Blue Electrochemistry at Activated Nanoelectrode Ensembles.

    PubMed

    Silvestrini, Morena; Fruk, Ljiljana; Moretto, Ligia Maria; Ugo, Paolo

    2015-05-01

    Nanoelectrode ensembles (NEEs) obtained by electroless gold deposition in track-etched poly-carbonate (PC) membranes are functionalized and applied for DNA hybridization detection, using methylene blue (MB) as electroactive probe. To this aim, an amine terminated (ss)DNA probe is immobilized on the PC surface of the NEE by reaction via carbodiimide and N-hydroxysulfosuccinimide. In order to increase the number of carboxylic groups present on PC and suitable for the functionalization, the surface of NEEs is oxidized with potassium permanganate. The presence of carboxylic functionalities is verified by spectrochemical titration with thionin acetate (THA) and the effect of the activation treatment on the electrode performances is evaluated by cyclic voltammetry (CV). After activation and functionalization with the probes, the NEE-based sensor is hybridized with complementary target sequences. The effect of the functionalization of the NEEs both with the (ss)DNA probe alone and after hybridization with the target, is studied by measuring the changes in the MB reduction signal by square wave voltammetry (SWV), after incubation in a suitable MB solution, rinsing and transfer to the measurement cell. It was observed that this peak signal decreases significantly after hybridization of the probe with the complementary target. Experimental evidences suggest that the interaction between MB and the guanines of (ss)DNA and (ds)DNA is at the basis of the development of the here observed analytical signal. The proposed approach allows the easy preparation and testing of NEE-based sensors for the electrochemical DNA hybridization detection. PMID:26504963

  2. Electrochemistry of surfactant-doped polypyrrole film(I): Formation of columnar structure by electropolymerization

    SciTech Connect

    Naoi, Katsuhiko; Oura, Yasushi; Maeda, Michiko; Nakamura, Sadako

    1995-02-01

    Electroactive polypyrrole (PPy) films have been studied widely in the field of applied material science for high energy/power storage applications. Perpendicularly oriented columnar structure was obtained for electropolymerized polypyrrole films formed from micellar solution of anionic surfactants. The surfactants used as dopants were a class of anionic surfactant, namely, Na salts of dodecyl sulfate (SDS) and dodecylbenzene sulfonate (SDBS). The formation process of polypyrrole films on electrode surfaces was studied with in situ atomic force microscopy (AFM) and electrochemical quartz crystal microbalance (EQCM) methods to monitor the structure of the grown polymers. In EQCM measurement, the frequency shift ({Delta}f) and the resonance resistance ({Delta}R) of the quartz crystal electrode were obtained simultaneously. An abrupt increase in {Delta}R was observed for both PPy/DS and PPy/DBS films at about 60--100mC/cm{sup 2}. Such a drastic change in {Delta}R, which may be associated with the emergence of the viscoelastic properties of the films, could be explained by the formation of columnar structure. In situ AFM observation clearly indicated that such a structure started to form around these critical charges. The cyclic voltammograms for the PPy/DS and PPy/DBS{sup {minus}} films showed sharp redox couples observed around {minus}0.5 to 0.6 V. The diffusion rate of cations for the resulting films was studied with ac impedance measurement as a function of the concentration of surfactant dopants. As the PPy film was prepared in higher concentration of the surfactant dopant, where the micelles are formed in solution, the resulting film showed a considerably higher (ca. 3 orders of magnitude) diffusion coefficient compared to ordinary PPy films so far reported. Such an enhanced diffusivity of ions could be attributed to a special formation process of polypyrrole in micelle solution: the mechanism is discussed here.

  3. Whole cell electrochemistry of electricity-producing microorganisms evidence an adaptation for optimal exocellular electron transport.

    PubMed

    Busalmen, Juan Pablo; Esteve-Nuñez, Abraham; Feliu, Juan Miguel

    2008-04-01

    The mechanism(s) by which electricity-producing microorganisms interact with an electrode is poorly understood. Outer membrane cytochromes and conductive pili are being considered as possible players, but the available information does not concur to a consensus mechanism yet. In this work we demonstrate that Geobacter sulfurreducens cells are able to change the way in which they exchange electrons with an electrode as a response to changes in the applied electrode potential. After several hours of polarization at 0.1 V Ag/AgCl-KCl (saturated), the voltammetric signature of the attached cells showed a single redox pair with a formal redox potential of about -0.08 V as calculated from chronopotentiometric analysis. A similar signal was obtained from cells adapted to 0.4 V. However, new redox couples were detected after conditioning at 0.6 V. A large oxidation process beyond 0.5 V transferring a higher current than that obtained at 0.1 V was found to be associated with two reduction waves at 0.23 and 0.50 V. The apparent equilibrium potential of these new processes was estimated to be at about 0.48 V from programmed current potentiometric results. Importantly, when polarization was lowered again to 0.1 V for 18 additional hours, the signals obtained at 0.6 V were found to greatly diminish in amplitude, whereas those previously found at the lower conditioning potential were recovered. Results clearly show the reversibility of cell adaptation to the electrode potential and pointto the polarization potential as a key variable to optimize energy production from an electricity producing population. PMID:18504979

  4. Direct electrochemistry of Shewanella oneidensis cytochrome c nitrite reductase: evidence for interactions across the dimeric interface

    PubMed Central

    Judd, Evan T.; Youngblut, Matthew; Pacheco, A. Andrew; Elliott, Sean J.

    2013-01-01

    Shewanella oneidensis cytochrome c nitrite reductase (soNrfA), a dimeric enzyme that houses five c-type hemes per protomer, carries out the six-electron reduction of nitrite and the two-electron reduction of hydroxylamine. Protein film voltammetry (PFV) has been used to study the cytochrome c nitrite reductase from Escherichia coli (ecNrfA) previously, revealing catalytic reduction of both nitrite and hydroxylamine substrates by ecNrfA adsorbed to a graphite electrode that is characterized by ‘boosts’ and attenuations in activity depending on the applied potential. Here, we use PFV to investigate the catalytic properties of soNrfA during both nitrite and hydroxylamine turnover and compare those properties to ecNrfA. Distinct differences in both the electrochemical and kinetic characteristics of soNrfA are observed, e.g., all detected electron transfer steps are one-electron in nature, contrary to what has been observed in ecNrfA (Angove, H. C., Cole, J. A., Richardson, D. J., and Butt, J. N. (2002) Protein film voltammetry reveals distinctive fingerprints of nitrite and hydroxylamine reduction by a cytochrome C nitrite reductase, J Biol Chem 277, 23374-23381). Additionally, we find evidence of substrate inhibition during nitrite turnover and negative cooperativity during hydroxylamine turnover, neither of which have previously been observed in any cytochrome c nitrite reductase. Collectively these data provide evidence that during catalysis, potential pathways of communication exist between the individual soNrfA monomers comprising the native homodimer. PMID:23210513

  5. Direct electrochemistry of glucose oxidase at electrochemically reduced graphene oxide-multiwalled carbon nanotubes hybrid material modified electrode for glucose biosensor.

    PubMed

    Mani, Veerappan; Devadas, Balamurugan; Chen, Shen-Ming

    2013-03-15

    Direct electrochemistry of glucose oxidase (GOx) at an electrochemically reduced graphene oxide-multiwalled carbon nanotubes hybrid (ERGO-MWCNT) modified glassy carbon electrode (GCE) has been reported. The π-π stacking interaction operating between the MWCNT and graphene oxide (GO) has been revealed by UV-Vis absorption spectroscopy. GOx was well immobilized onto the ERGO-MWCNT hybrid film, as a result direct electrochemistry of GOx has been achieved. Compared with pristine MWCNT, 2.1 fold higher peak current and very low peak to peak separation (ΔE(p)) of 26 mV were observed at the hybrid film, demonstrating faster electron transfer between GOx and the modified electrode surface. Moreover, the modified film exhibited high electrocatalytic activity towards glucose via reductive detection of oxygen consumption and in the presence of mediator. The proposed biosensor exhibits low detection limit of 4.7 μM with wide linear range of 0.01-6.5mM and acquires excellent storage and operational stabilities. The accurate glucose determination in human blood serum and good recoveries achieved in spiked urine samples revealed their great potential in the practical applications. PMID:22964382

  6. Electrocatalytic O2 reduction reaction by synthetic analogues of cytochrome P450 and myoglobin: in-situ resonance Raman and dynamic electrochemistry investigations.

    PubMed

    Chatterjee, Sudipta; Sengupta, Kushal; Samanta, Subhra; Das, Pradip Kumar; Dey, Abhishek

    2013-09-01

    Bioinspired electrodes have been constructed by physiabsorption of two air stable iron porphyrin complexes, one bearing an imidazole coordination and the other bearing a thiolate coordination. To control the electron transfer (ET) rate to these O2 reducing electrocatalysts, the complexes were immobilized on edge plane graphite electrode and alkyl thiol self-assembled monolayer (SAM) modified Au electrodes with varying chain lengths of the thiols. Catalyst immobilized SAM modified surfaces were characterized using surface enhanced resonance Raman spectroscopy (SERRS), and their electrocatalytic O2 reduction properties were investigated using rotating ring disc electrochemistry (RRDE). While the imidazole bound complex showed increase in partially reduced oxygen species (PROS) on decreasing ET rate, the thiolate bound complex showed the opposite trend, that is, the value of PROS reduced on decreasing the ET rate. SERRS coupled to rotating disc electrochemistry (SERRS-RDE) technique helps gain insight into the O2 reduction mechanism. The results obtained indicate that while the imidazole bound iron porphyrin complex reduces O2 through an inner sphere mechanism using a high-spin (HS) Fe(II) species, the thiolate ligated complex shows an inner sphere as well as outer sphere mechanism using a HS Fe(II) and low-spin (LS) Fe(II) species, respectively. The PROS formation by a HS Fe(II) species of this thiolate bound complex increases with decreasing ET rates while that of a LS Fe(II) species decreases with decreasing ET rates. PMID:23961832

  7. Mathematical modeling of synthesis gas fueled electrochemistry and transport including H2/CO co-oxidation and surface diffusion in solid oxide fuel cell

    NASA Astrophysics Data System (ADS)

    Bao, Cheng; Jiang, Zeyi; Zhang, Xinxin

    2015-10-01

    Fuel flexibility is a significant advantage of solid oxide fuel cell (SOFC). A comprehensive macroscopic framework is proposed for synthesis gas (syngas) fueled electrochemistry and transport in SOFC anode with two main novelties, i.e. analytical H2/CO electrochemical co-oxidation, and correction of gas species concentration at triple phase boundary considering competitive absorption and surface diffusion. Staring from analytical approximation of the decoupled charge and mass transfer, we present analytical solutions of two defined variables, i.e. hydrogen current fraction and enhancement factor. Giving explicit answer (rather than case-by-case numerical calculation) on how many percent of the current output contributed by H2 or CO and on how great the water gas shift reaction plays role on, this approach establishes at the first time an adaptive superposition mechanism of H2-fuel and CO-fuel electrochemistry for syngas fuel. Based on the diffusion equivalent circuit model, assuming series-connected resistances of surface diffusion and bulk diffusion, the model predicts well at high fuel utilization by keeping fixed porosity/tortuosity ratio. The model has been validated by experimental polarization behaviors in a wide range of operation on a button cell for H2-H2O-CO-CO2-N2 fuel systems. The framework could be helpful to narrow the gap between macro-scale and meso-scale SOFC modeling.

  8. Probing the nature of electron transfer in metalloproteins on graphene-family materials as nanobiocatalytic scaffold using electrochemistry

    SciTech Connect

    Gupta, Sanju; Irihamye, Aline

    2015-03-15

    Graphene-based nanomaterials have shown great promise not only in nanoelectronics due to ultrahigh electron mobility but also as biocatalytic scaffolds owing to irreversible protein surface adsorption and facilitating direct electron transfer. In this work, we synthesized stable dispersions of graphene using liquid-phase exfoliation approach based on non-covalent interactions between graphene and 1-pyrenesulfonic acid sodium salt (Py–1SO{sub 3}), 1-pyrenemethylamine salt (Py − Me-NH{sub 2}) and Pluronic{sup ®} P-123 surfactant using only water as solvent compatible with biomolecules. The resulting graphene nanoplatelets (Gr-LPE) are characterized by a combination of analytical (microscopy and spectroscopy) techniques revealing mono- to few-layer graphene displaying that the exfoliation efficiency strongly depends upon the type of pyrene-based salts and organic surfactants. Moreover being completely water-based approach, we build robust nanoscaffolds of graphene-family nanomaterials (GFNs) namely, monolayer graphene, Gr-LPE (the one prepared with Pluronic{sup ®} P-123), graphene oxide (GO) and its reduced form (rGO) on glassy carbon electrode surface with three important metalloproteins include cytochrome c (Cyt c) [for electron transfer], myoglobin (Mb) [for oxygen storage] and horseradish peroxidase (HRP) [for catalyzing the biochemical reaction]. In order to demonstrate the nanobiocatalytical activity of these proteins, we used electrochemical interfacial direct electron transfer (DET) kinetics and attempt to determine the rate constant (k{sub ET}) using two different analytical approaches namely, linear sweep voltammetry and Laviron’s theory. We elucidated that all of the metalloproteins retain their structural integrity (secondary structure) upon forming mixtures with GFNs confirmed through optical and vibrational spectroscopy and biological activity using electrochemistry. Among the GFNs studied, Gr-LPE, GO and rGO support the efficient electrical

  9. Electrochemistry for Energy Conversion

    NASA Astrophysics Data System (ADS)

    O'Hayre, Ryan

    2010-10-01

    Imagine a laptop computer that runs for 30 hours on a single charge. Imagine a world where you plug your house into your car and power lines are a distant memory. These dreams motivate today's fuel cell research. While some dreams (like powering your home with your fuel cell car) may be distant, others (like a 30-hour fuel cell laptop) may be closer than you think. If you are curious about fuel cells---how they work, when you might start seeing them in your daily life--- this talk is for you. Learn about the state-of-the art in fuel cells, and where the technology is likely to be headed in the next 20 years. You'll also be treated to several ``behind-the scenes'' glimpses of cutting-edge research projects under development in the Renewable Energy Materials Center at the Colorado School of Mines--- projects like an ``ionic transistor'' that works with protons instead of electrons, and a special ceramic membrane material that enables the ``uphill'' diffusion of steam. Associate Professor Ryan O'Hayre's laboratory at the Colorado School of Mines develops new materials and devices to enable alternative energy technologies including fuel cells and solar cells. Prof. O'Hayre and his students collaborate with the Colorado Fuel Cell Center, the Colorado Center for Advanced Ceramics, the Renewable Energy Materials Science and Engineering Center, and the National Renewable Energy Laboratory.[4pt] In collaboration with Ann Deml, Jianhua Tong, Svitlana Pylypenko, Archana Subramaniyan, Micahael Sanders, Jason Fish, Annette Bunge, Colorado School of Mines.

  10. Electrostatic electrochemistry at insulators.

    PubMed

    Liu, Chongyang; Bard, Allen J

    2008-06-01

    The identity of charges generated by contact electrification on dielectrics has remained unknown for centuries and the precise determination of the charge density is also a long-standing challenge. Here, electrostatic charges on Teflon (polytetrafluoroethylene) produced by rubbing with Lucite (polymethylmethacrylate) were directly identified as electrons rather than ions by electrochemical (redox) experiments with charged Teflon used as a single electrode in solution causing various chemical reactions: pH increases; hydrogen formation; metal deposition; Fe(CN)(6)(3-) reduction; and chemiluminescence in the system of Teflon(-)/Ru(bpy)(3)(2+)/S(2)O(8)(2-) (analogous to electrogenerated chemiluminescence). Moreover, copper deposition could be amplified by depositing Pd first in a predetermined pattern, followed by electroless deposition to produce Cu lines. This process could be potentially important for microelectronic and other applications because Teflon has desirable properties including a low dielectric constant and good thermal stability. Charge density was determined using Faraday's law and the significance of electron transfer processes on charged polymers and potentially other insulators have been demonstrated. PMID:18362908