Search results for "tammet"
showing 10 items of 409 documents
A simulation and experimental study of electrochemical pH control at gold interdigitated electrode arrays
2021
Abstract In electroanalysis, solution pH is a critical parameter that often needs to be tailored and controlled for the detection of particular analytes. This is most commonly performed by the addition of chemicals, such as strong acids or bases. Electrochemical in-situ pH control offers the possibility for the local adjustment of pH at the point of detection, without the need for additional reagents. Finite element analysis (FEA) simulations have been performed on interdigitated electrodes, to guide experimental design in relation to both electroanalysis and in-situ control of solution pH. No previous model exists that describes the generation of protons at an interdigitated electrode arra…
Screening and mapping of pigments in paintings using scanning electrochemical microscopy (SECM)
2015
The use of the scanning electrochemical microscopy (SECM) technique for identifying and mapping of both organic and inorganic pigments in sub-microsamples from pictorial specimens is described. This methodology, inspired by the voltammetry of immobilized particles technique, permits the study of textural properties of paint layers and mapping the distribution of pigment grains upon application of different potentials to the substrate. A combination of the redox competition SECM strategy with voltammetry yields a local identification methodology for different organic and inorganic pigments in paint samples.
Azolylborates for Electrochemical Double Layer Capacitor Electrolytes
2017
Abstract Asymmetric tetraalkylammonium salts of azolylborates were synthesized and studied with respect to their suitability as supporting electrolytes in electrochemical double layer capacitors. In contrast to current conducting salts used in this device, azolylborates exhibit an excellent stability towards thermal load and moisture. In addition to good conductivity and stability towards cathodic reduction we found certain limitations when more positive potentials were applied.
How Electrical Heterogeneity Parameters of Ion-Exchange Membrane Surface Affect the Mass Transfer and Water Splitting Rate in Electrodialysis
2020
Electrodialysis (ED) has been demonstrated as an effective membrane method for desalination, concentration, and separation. Electroconvection (EC) is a phenomenon which can essentially increase the mass transfer rate and reduce the undesirable water splitting effect. Efforts by a number of researchers are ongoing to create conditions for developing EC, in particular, through the formation of electrical heterogeneity on the membrane surface. We attempt, for the first time, to optimize the parameters of surface electrical heterogeneity for ion-exchange membranes used in a laboratory ED cell. Thirteen different patterns on the surface of two Neosepta anion-exchange membranes, AMX and AMX-Sb, w…
"One-touch" voltammetry of microparticles for the identification of corrosion products in archaeological lead
2011
Voltammetry of microparticles is applied to the identification of lead corrosion products by means of an essentially non-invasive 'one-touch' technique based on the use of graphite pencil. This methodology permits the mechanical attachment of few nanograms of sample from the surface of lead archaeological artefacts to a paraffin-impregnated graphite electrode, which, upon immersion in aqueous electrolytes, provides distinctive voltammetric responses for litharge and cotunnite- anglesite-, cerusite-based corrosion products. The reported method is applied to the identification of corrosion products in archaeological lead pieces from different Iberian sites in Valencia (Spain). © 2011 WILEY-VC…
ELECTRODEPOSITION OF NOVEL POLY(NAPHTHALENEDIIMIDE-QUATERTHIOPHENE) THIN FILMS AND APPLICATIONS IN PLASTIC OPTOELECTRONICS DEVICES
2013
A novel symmetric naphthalenediimide-quaterthiophene derivative (NDIT4d) has been polymerized on different substrates including glassy carbon and ITO/PET electrodes by means of electrochemical methods. XPS and UV-VIS spectroscopy as well as cyclic voltammetry have been employed for characterizing the thin film chemical features, the band gap and the HOMO and LUMO levels. DFT computational studies were in close agreement with the experimental observables also showing intriguing geometrical effects on the band gap energy values. The comparison of the energy levels locations of the electrodeposited poly(naphthalenediimide-quaterthiophene) derivative (e-PNDIT4) and P3HT thin films transferred b…
Modeling Corrosion of Archaeological Silver-Copper Coins Using the Voltammetry of Immobilized Particles
2012
Two complementary models to describe the long-term corrosion of silver-copper coins, based on potential rate laws for smooth corrosion and those combined with diffusive law, for gross corrosion, are proposed. Theoretical kinetics can be tested using signatures of copper and silver corrosion products using the voltammetry of immobilized particles technique. The method is applied to silver coins minted during the 13th–14th centuries from the Libertad street hoard in Valencia (Spain) using non-invasive one-touch graphite pencil sampling. Voltammetric features yield functional dependences in agreement with the proposed model potentially useful for distinguishing between different mints.
Characterization of LiFePO4/C Composite Thin Films Using Electrochemical Impedance Spectroscopy
2012
The composite LiFePO4/C thin films were prepared on steel substrate by radio frequency (RF) magnetron sputtering. Electrochemical properties of the obtained thin films were investigated by cyclic voltammetry charge-discharge measurements and electrochemical impedance spectroscopy (EIS). The films annealed at 550 °C exhibited a couple of redox peaks at 3.45 V vs. Li/Li + characteristic for the electrochemical lithium insertion/extraction in LiFePO4. At low current rate such composite thin film showed a discharge capacity of over 110 mAh g -1 . The dependence of charge transfer resistance, double layer capacitance and lithium diffusion coefficients on applied electrode potential were calculat…
Electrochemical Analysis of Catalytic and Oxygen Interfacial Transfer Effects on MnO2 Deposited on Gold Electrodes
2018
[EN] A theoretical model for obtaining thermochemical and kinetic information on oxygen interfacial transfer in metal oxides deposited on gold electrodes, based in the voltammetry of immobilized particle methodology, is presented. It is applied to MnO2 microparticulate deposits on gold in contact with aqueous NaOH solution using the voltammetric signals for the oxidation of gold to gold oxide monolayer and its subsequent desorptive reduction. Assuming reversibility, voltammetric peak potentials permit to estimate a variation of Gibbs free energy of interfacial oxygen transfer of -32 +/- 3 kj mol(-1). Analysis of peak current data based on the Sharp-Hancock formalism of solid-state kinetics …
Electrochemistry of Mesoporous Organosilica of MCM-41 Type Containing 4,4′-Bipyridinium Units: Voltammetric Response and Electrocatalytic Effect on 1…
2003
The electrochemistry of a novel organic−inorganic material in which 4,4‘-bipyridinium units (BP) are covalently attached to the walls of a periodic mesoporous organisilica (PMO) of the MCM-41 type is described. The pristine material (BP@PMO), having its internal space completely filled by the cetyltrimethylammonium structure-directing agent, is almost electrochemically silent. In contrast, the extracted material obtained after removal of the structure-directing agent (BP@PMO-ex) exhibits two reduction peaks at −0.36 and −0.75 V vs AgCl/Ag in contact with aqueous electrolytes. BP@PMO-ex shows a remarkable electrocatalytic effect on the oxidation of 1,4-dihydrobenzoquinone (H2Q) that is studi…