Search results for " electrode"
showing 10 items of 301 documents
Electrochemistry of methylene blue at an alkanethiol modified electrode
2012
International audience; Gold surfaces were derivatized with decanethiol. The electrochemistry of methylene blue at these modified electrodes was investigated in function of the gold cleaning process and compared with the results obtained at a bare gold electrode. Cyclic voltammetry at low methylene blue concentrations (c(MB) <= 16 mu M) yielded surface behavior data. The properties of the film vary with the electrode pretreatment. Without electrochemical cleaning step, the standard potential at a gold electrode modified with 1-decanethiol is nearly the same as on a bare gold electrode. On the other hand, when the electrode is electrochemically cleaned before adsorption of the alkanethiols, …
Ansiedad y respuestas electrofisiológicas a una tarea de estrés mental tras un ejercicio aeróbico máximo
1996
El objetivo del presente trabajo fue analizar las relaciones de la ansiedad con determinadas respuestas fisiológicas a una tarea de estrés mental. Para ello, se tomó una muestra de deportistas de élite varones de la Comunidad Valenciana de diferentes disciplinas deportivas. De acuerdo con las puntuaciones que los sujetos obtuvieron en las escalas STAI-R y STAI-E, completadas antes y después respectivamente, de una ergometría máxima, fueron separados en dos grupos extremos de alta y baja ansiedad. Se registraron de forma computerizada la frecuencia cardíaca y la actividad electrodérmica antes, durante y después de una tarea Stroop en ordenador. Los niveles basales de actividad electrodérmica…
Silver Ion-Selective Electrodes Based on π-Coordinating Ionophores Without Heteroatoms
2002
Ion-selective electrodes (ISEs) were constructed by using spherical hydrocarbons (cyclophanes) as π-coordinating ionophores in solvent polymeric membranes. Four structurally similar cyclophanes, i. e., [2.2.2]p,p,p-cyclophane, [2.2.2]m,p,p-cyclophane, [2.2.1]p,p,p-cyclophane and [2.2.1]m,p,p-cyclophane were studied as ionophores for Ag+. The ion-selective membranes were composed of the corresponding ionophore (1%), potassium tetrakis(4-chlorophenyl)borate (0.5%), 2-nitrophenyl octyl ether (65–66%) and PVC (32–33%). The ion-selective membrane was placed on top of a layer of the conducting polymer, poly(3,4-ethylenedioxythiophene) (PEDOT), working as ion-to-electron transducer. The selectivit…
Nano composite membrane-electrode assembly formation for fuel cell-modeling aspects
2007
Long term stability is an essential requirement for fuel cell applications in automobile and stationary energy systems. In these systems the agglomeration of the catalyst nanoparticles is a well-known phenomenon which cannot be easily overcome or compensated for by re-designing the system. A direct result of this occurrence is the irreversible decrease of the electrochemical performance. Irregularities in electric field distribution are one root cause for migration and subsequent agglomeration of the catalyst nanoparticle. In this work, the impact of the electrode mechanical deformation on electric field distribution was studied using a computer modeling approach. Model of a Proton Exchange…
Measured and Calculated Oxidation Potentials of 1-X-12-Y-CB11Me10– Anions
2012
Cyclic voltammetry of 31 icosahedral carborane anions 1-X-12-Y-CB(11)Me(10)(-) at a Pt electrode in liquid SO(2) revealed a completely reversible one-electron oxidation even at low scan rates, except for the anions with Y = I, which are oxidized irreversibly up to a scan rate of 5.0 V/s, and the anion with X = COOH and Y = H, whose oxidation is irreversible at scan rates below 1.0 V/s. Relative reversible oxidation potentials agree well with RI-B3LYP/TZVPP,COSMO and significantly less well with RI-BP86/TZVPP,COSMO or RI-HF/TZVPP,COSMO calculated adiabatic electron detachment energies. Correlations with HOMO energies of the anions are nearly as good, even though the oxidized forms are subjec…
Synthesis of polymer nanogels by electro-Fenton process: investigation of the effect of main operation parameters
2017
Recently, electro-Fenton (EF) process has been shown as a promising, facile, effective, low cost and environmentally-friendly alternative for synthesizing polymer nanogels suitable as biocompatible nanocarriers for emerging biomedical applications. Here, the electrochemically-assisted modification of poly(vinylpyrrolidone) (PVP) by EF process was studied to assess the role of key operation parameters for a precise modulation of polymer crosslinking and its functionalization with [sbnd]COOH and succinimide groups. The dimensions of the nanogels, in terms of hydrodynamic radius (Rh) and weight-average molecular weight (Mw), can be tuned up by controlling the electrolysis time, current density…
EQCM and EIS studies of Znaq2++2e−⇄Zn0 electrochemical reaction in moderated acid medium
2003
The zinc electrodissolution and electrodeposition have been studied by means of electrochemical quartz crystal microbalance and electrochemical impedance spectroscopy. Relevant information on the mechanism of these electrochemical processes is provided by the analysis of experimental data. The zinc electrodeposition takes place with an important participation of hydrogen ions while the zinc electrodissolution occurs, in these experimental conditions, by a mechanism in two steps. Besides, it is proved that the presence of molecular oxygen in the solution contributes to the formation of a passive layer on the metallic zinc deposit.
Hydrolysis of methyltin(IV) trichloride in aqueous NaCl and NaNO3 solutions at different ionic strengths and temperatures
1999
The hydrolysis of methyltin(IV) trichloride (CH 3 SnCl 3 ) has been studied in aqueous NaCl and NaNO 3 solutions (0 < l/mol dm -3 ≤1), at different temperatures (15 ≤ T/°C ≤ 45) by potentiometric measurements (H + -glass electrode). By considering the generic hydrolytic reaction pCH 3 Sn 3+ + qH 2 O = (CH 3 Sn) p (OH) q 3p-q +qH + (logβ pq ), we have the formation of five species and logβ 12 = -3.36, logβ 13 = -8.99, logβ 14 = -20.27 and logβ 25 = -7.61. The first hydrolysis step is measurable only at very low pH values and was not determined: a rough estimate of the hydrolysis constant is logβ 11 = -1.5 (± 0.5). The dependence on ionic strength of logβ pq is quite different in NaNO 3 and N…
ZnO Nanoestructured Layers Processing with Morphology Control by Pulsed Electrodeposition
2011
The fabrication of nanostructured ZnO thin films is a critic process for a lot of applications of this semiconductor material. The final properties of this film depend fundamentally of the morphology of the sintered layer. In this paper a process is presented for the fabrication of ZnO nanostructured layers with morphology control by pulsed electrodeposition over ITO. Process optimization is achieved by pulsed electrodeposition and results are assessed after a careful characterization of both morphology and electrical properties. SEM is used for nucleation analysis on pulsed deposited samples. Optical properties like transmission spectra and Indirect Optical Band Gap are used to evaluate th…
Electrochemical Deposition Mechanism for ZnO Nanorods: Diffusion Coefficient and Growth Models
2011
Fabrication of nanostructured ZnO thin films is a critical process for many applications based on semiconductor devices. So on understanding of the electrochemical deposition mechanism is also fundamental for knowing the optimal conditions on growth of ZnO nanorods by electrodeposition. In this paper the electrochemical mechanism for ZnO nanorods formation is studied. Results are based on the evolution of the diffusion coefficient using the Cotrell equation, and different growth models proposed by Scharifcker and Hills for nucleation and growth.