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Ultramicroelectrode
An ultramicroelectrode (UME) is a working electrode used in a voltammetry. The small size of UME give them large diffusion layers and small overall currents. These features allow UME to achieve useful steady-state conditions and very high scan rates (V/s) with limited distortion. UME were developed independently by Wightman and Fleischmann around 1980. Small current at UME enables electrochemical measurements in low conductive media (organic solvents), where voltage drop associated with high solution resistance makes these experiments difficult for conventional electrodes. Furthermore, small voltage drop at UME leads to a very small voltage distortion at the electrode-solution interface which allows using two-electrode setup in voltammetric experiment instead of conventional three-electrode setup. Design Ultramicroelectrodes are often defined as electrodes which are smaller than the diffusion layer achieved in a readily accessed experiment. A working definition is an electr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Scanning Electrochemical Microscopy
Scanning electrochemical microscopy (SECM) is a technique within the broader class of scanning probe microscopy (SPM) that is used to measure the local electrochemical behavior of liquid/solid, liquid/gas and liquid/liquid interfaces. Initial characterization of the technique was credited to University of Texas electrochemist, Allen J. Bard, in 1989. Since then, the theoretical underpinnings have matured to allow widespread use of the technique in chemistry, biology and materials science. Spatially resolved electrochemical signals can be acquired by measuring the current at an ultramicroelectrode (UME) tip as a function of precise tip position over a substrate region of interest. Interpretation of the SECM signal is based on the concept of diffusion-limited current. Two-dimensional raster scan information can be compiled to generate images of surface reactivity and chemical kinetics. The technique is complementary to other surface characterization methods such as surface plasmon re ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mark Wightman
Robert Mark Wightman (born July 4, 1947) is an electrochemist and professor of chemistry at the University of North Carolina at Chapel Hill. He is best known for his work in the areas of ultramicroelectrodes, electrochemistry, and neurochemistry. One of Wightman's most notable achievements is the development of the ultramicroelectrode and microelectrode voltammetry. At the same time as Wightman's innovations, the microelectrode was developed independently by Martin Fleischmann at the University of Southampton. In 2011, Wightman had the 192nd highest h-index, 74, of any living chemist. As of 2018, Wightman was an author of over 390 papers and had an h-index of 103. Education and academic career Education Wightman received his B.A. degree with honors from Erskine College in Due West, South Carolina in 1968 and earned a Ph.D. in chemistry from the University of North Carolina at Chapel Hill in 1974, where he worked with Royce Murray. At UNC - Chapel Hill, Wightman began focusing ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Electrochemical Reaction Mechanism
In chemistry, an electrochemical reaction mechanism is the step by step sequence of elementary steps, involving at least one outer sphere electron transfer, by which an overall chemical change occurs. Overview Elementary steps like proton coupled electron transfer and the movement of electrons between an electrode and substrate are special to electrochemical processes. Electrochemical mechanisms are important to all redox chemistry including corrosion, redox active photochemistry including photosynthesis, other biological systems often involving electron transport chains and other forms of homogeneous and heterogeneous electron transfer. Such reactions are most often studied with standard three electrode techniques such as cyclic voltammetry(CV), chronoamperometry, and bulk electrolysis as well as more complex experiments involving rotating disk electrodes and rotating ring-disk electrodes. In the case of photoinduced electron transfer the use of time-resolved spectroscopy ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Martin Fleischmann
Martin Fleischmann FRS (29 March 1927 – 3 August 2012) was a British chemist who worked in electrochemistry. By Associated Press. Premature announcement of his cold fusion research with Stanley Pons, regarding excess heat in heavy water, caused a media sensation and elicited skepticism and criticism from many in the scientific community. Personal life Fleischmann was born in Karlovy Vary, Czechoslovakia, in 1927. His father was a wealthy lawyer and his mother the daughter of a high-ranking Austrian civil officer. Since his father was of Jewish heritage, Fleischmann's family moved to the Netherlands, and then to England in 1938, to avoid Nazi persecution. His father died of the complications of injuries received in a Nazi prison, after which Fleischmann lived for a period with his mother in a leased cottage in Rustington, Sussex. His early education was obtained at Worthing High School for Boys. After serving in the Czech Airforce Training Unit during the war, he moved ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Working Electrode
The working electrode is the electrode in an electrochemical system on which the reaction of interest is occurring. The working electrode is often used in conjunction with an auxiliary electrode, and a reference electrode in a three electrode system. Depending on whether the reaction on the electrode is a reduction or an oxidation, the working electrode is called cathodic or anodic, respectively. Common working electrodes can consist of materials ranging from inert metals such as gold, silver or platinum, to inert carbon such as glassy carbon, boron doped diamond or pyrolytic carbon, and mercury drop and film electrodes. Chemically modified electrodes are employed for the analysis of both organic and inorganic samples. Special types * Ultramicroelectrode (UME) * Rotating disk electrode (RDE) * Rotating ring-disk electrode (RRDE) * Hanging mercury drop electrode (HMDE) * Dropping mercury electrode (DME) See also * Auxiliary electrode * Electrochemical cell * Electrochemistry ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fast-scan Cyclic Voltammetry
Fast-scan cyclic voltammetry (FSCV) is cyclic voltammetry with a very high scan rate (up to ). Application of high scan rate allows rapid acquisition of a voltammogram within several milliseconds and ensures high temporal resolution of this electroanalytical technique. An acquisition rate of 10 Hz is routinely employed. FSCV in combination with carbon-fiber microelectrodes became a very popular method for detection of neurotransmitters, hormones and metabolites in biological systems. Initially, FSCV was successfully used for detection of electrochemically active biogenic amines release in chromaffin cells (adrenaline and noradrenaline), brain slices (5-HT, dopamine, norepinephrine) and in vivo in anesthetized or awake and behaving animals (dopamine). Further refinements of the method have enabled detection of 5-HT, HA, norepinephrine, adenosine, oxygen, pH changes in vivo in rats and mice as well as measurement of dopamine and serotonin concentration in fruit flies. Prin ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Multielectrode Array
Microelectrode arrays (MEAs) (also referred to as multielectrode arrays) are devices that contain multiple (tens to thousands) microelectrodes through which neural signals are obtained or delivered, essentially serving as neural interfaces that connect neurons to electronic circuitry. There are two general classes of MEAs: implantable MEAs, used ''in vivo'', and non-implantable MEAs, used ''in vitro''. Theory Neurons and muscle cells create ion currents through their membranes when excited, causing a change in voltage between the inside and the outside of the cell. When recording, the electrodes on an MEA transduce the change in voltage from the environment carried by ions into currents carried by electrons (electronic currents). When stimulating, electrodes transduce electronic currents into ionic currents through the media. This triggers the voltage-gated ion channels on the membranes of the excitable cells, causing the cell to depolarize and trigger an action potential if ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bioelectronics
Bioelectronics is a field of research in the convergence of biology and electronics. Definitions At the first C.E.C. Workshop, in Brussels in November 1991, bioelectronics was defined as 'the use of biological materials and biological architectures for information processing systems and new devices'. Bioelectronics, specifically bio-molecular electronics, were described as 'the research and development of bio-inspired (i.e. self-assembly) inorganic and organic materials and of bio-inspired (i.e. massive parallelism) hardware architectures for the implementation of new information processing systems, sensors and actuators, and for molecular manufacturing down to the atomic scale'. The National Institute of Standards and Technology (NIST), an agency of the United States Department of Commerce, defined bioelectronics in a 2009 report as "the discipline resulting from the convergence of biology and electronics". Sources for information about the field include the Institute of Electr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Kinetic Energy
In physics, the kinetic energy of an object is the energy that it possesses due to its motion. It is defined as the work needed to accelerate a body of a given mass from rest to its stated velocity. Having gained this energy during its acceleration, the body maintains this kinetic energy unless its speed changes. The same amount of work is done by the body when decelerating from its current speed to a state of rest. Formally, a kinetic energy is any term in a system's Lagrangian which includes a derivative with respect to time. In classical mechanics, the kinetic energy of a non-rotating object of mass ''m'' traveling at a speed ''v'' is \fracmv^2. In relativistic mechanics, this is a good approximation only when ''v'' is much less than the speed of light. The standard unit of kinetic energy is the joule, while the English unit of kinetic energy is the foot-pound. History and etymology The adjective ''kinetic'' has its roots in the Greek word κίνησις ''kinesis'', m ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fast-scan Cyclic Voltammetry
Fast-scan cyclic voltammetry (FSCV) is cyclic voltammetry with a very high scan rate (up to ). Application of high scan rate allows rapid acquisition of a voltammogram within several milliseconds and ensures high temporal resolution of this electroanalytical technique. An acquisition rate of 10 Hz is routinely employed. FSCV in combination with carbon-fiber microelectrodes became a very popular method for detection of neurotransmitters, hormones and metabolites in biological systems. Initially, FSCV was successfully used for detection of electrochemically active biogenic amines release in chromaffin cells (adrenaline and noradrenaline), brain slices (5-HT, dopamine, norepinephrine) and in vivo in anesthetized or awake and behaving animals (dopamine). Further refinements of the method have enabled detection of 5-HT, HA, norepinephrine, adenosine, oxygen, pH changes in vivo in rats and mice as well as measurement of dopamine and serotonin concentration in fruit flies. Prin ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cottrell Equation
In electrochemistry, the Cottrell equation describes the change in electric current with respect to time in a controlled potential experiment, such as chronoamperometry. Specifically it describes the current response when the potential is a step function in time. It was derived by Frederick Gardner Cottrell in 1903. For a simple redox event, such as the ferrocene/ferrocenium couple, the current measured depends on the rate at which the analyte diffuses to the electrode. That is, the current is said to be "diffusion controlled." The Cottrell equation describes the case for an electrode that is planar but can also be derived for spherical, cylindrical, and rectangular geometries by using the corresponding Laplace operator and boundary conditions in conjunction with Fick's second law of diffusion.Bard, A. J.; Faulkner, L. R. “Electrochemical Methods. Fundamentals and Applications” 2nd Ed. Wiley, New York. 2001. : i = \frac where, : i = current, in units of A : n = numbe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Voltammetry
Voltammetry is a category of electroanalytical methods used in analytical chemistry and various industrial processes. In voltammetry, information about an analyte is obtained by measuring the current as the potential is varied. The analytical data for a voltammetric experiment comes in the form of a voltammogram which plots the current produced by the analyte versus the potential of the working electrode. Theory Voltammetry is the study of current as a function of applied potential. Voltammetric methods involve electrochemical cells, and investigate the reactions occurring at electrode/electrolyte interfaces. The reactivity of analytes in these half-cells is used to determine their concentration. It is considered a dynamic electrochemical method as the applied potential is varied over time and the corresponding changes in current are measured. Most experiments control the potential(volts) of an electrode in contact with the analyte while measuring the resulting current (amperes). ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
