Home About us Contact
|
Home About us Contact | ||
|
|
||
Constant Potential (constant + potential)
Selected AbstractsOn the Initial Stages of Electrooxidation of Aqueous Maleic Acid on Bi-Doped PbO2ELECTROANALYSIS, Issue 15 2007Carlos Borras Abstract Oxidation of maleic acid in aqueous solution on bismuth-doped lead oxide has been studied. The effects of hydrodynamic conditions on the oxidation rate have been identified. The number of electrons transferred during the initial stages of oxidation as well as the apparent heterogeneous rate constant was obtained from the combined analysis of rotating ring-disk currents and the decrease of concentration at constant potential, determined from UV-vis measurements. The number of electrons involved during electrochemical oxidation was found to be 12, indicating full mineralization to CO2, and the heterogeneous rate constant for oxidation at 1.6,V was 9.8×105,cm s,1. [source] Photoelectrocatalytic Oxidation of NADH with Electropolymerized Toluidine Blue OELECTROANALYSIS, Issue 2-3 2007Yusuf Dilgin Abstract A poly(Toluidine Blue O) (poly-TBO) modified electrode was successfully prepared by repeated sweeping the applied potential from ,0.6 to +0.8,V (vs. SCE) on a glassy carbon electrode (GCE) in borate buffer solution at pH,9.1,containing 0.1,M NaNO3 and 0.4,mM Toluidine Blue O (TBO). The poly-TBO modified GCE shows electrocatalytic activity toward NADH oxidation in phosphate buffer solution at pH,7.0, with an overpotential of ca. 350,mV lower than that at the bare electrode. The photoelectrocatalytic oxidation of NADH at this electrode was also successfully investigated by using cyclic voltammetry and amperometry at constant potential. When the modified electrode surface was irradiated with a 250,W halogen lamp, a photoelectrocatalytic effect was observed for NADH oxidation and the current was increased about 2.2 times. The applied potential was selected at +100,mV for amperometric and photoamperometric detection of NADH. A linear calibration graph for NADH was obtained in the range between 1.0×10,5 and 1.0×10,3 M and between 5.0×10,6 and 1.0×10,3 M for amperometric and photoamperometric studies, respectively. The effect of some interfering compounds, such as ascorbic acid and dopamine on the electrocatalytic and photoelectrocatalytic oxidation of NADH was tested. [source] General Steady-State Shape Factor for a Partially Penetrating WellGROUND WATER, Issue 1 2010Vitaly A. Zlotnik We present the closed form of a general steady-state shape factor for a partially penetrating well in a uniform anisotropic aquifer. Our simple analytical expression for the shape factor has a uniform representation for full range of parameters and meets or exceeds the accuracy of previous results obtained through semiempirical methods (e.g., Bouwer and Rice [1976] equations). This general shape factor pertains to the flow of fluids (water or air) in subsurface formations when the upper formation boundary has constant potential and the lower boundary is impermeable. The results of our investigation are directly applicable to analyses of (1) slug tests with falling or rising head and (2) injection/extraction tests with constant head, essential techniques for the characterization of hydraulic conductivity of aquifers, streambeds, or lakebeds as well as the design of aquifer and soil remediation systems. [source] Effects of magnetic field and rare-earth ions on properties of polyaniline nanoparticlesJOURNAL OF APPLIED POLYMER SCIENCE, Issue 4 2007Shuling Zhang Abstract The uniform polyaniline nanoparticles with the size of about 50 nm were electropolymerized using the method of constant potential of 0.8 V. The effects of rare-earth cations and magnetic field on the preparation and properties of polyaniline were investigated. It was found that the addition of rare-earth cations could enhance the effect of magnetic field on the properties of polyaniline. The resulting products were characterized by FTIR spectra, UV,vis spectra and scanning electron microscope (SEM); the conductivity and cyclic voltammetry (CV) were also investigated. The experimental results show that the magnetic field has an orientation effect on polyaniline chain and there exists the interaction between rare-earth cations and polyaniline chain because of the electrostatic interaction. The addition of rare-earth cations can increase electrical conductivity, moreover, the effect of NdCl3 and ErCl3 on properties of polyaniline is more remarkable than LaCl3 and SmCl3. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 2286,2294, 2007 [source] Efficient and reliable method for the simulation of scanning tunneling images and spectra with local basis setsPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 5 2006Óscar Paz Abstract Based on Bardeen's perturbative approach to tunneling, we have found an expression for the current between tip and sample, which can be efficiently coded in order to perform fast ab initio simulations of STM images. Under the observation that the potential between the electrodes should be nearly flat at typical tunnel gaps, we have addressed the difficulty in the computation of the tunneling matrix elements by considering a vacuum region of constant potential delimited by two surfaces (each of them close to tip and sample respectively), then propagating tip and sample wave functions by means of the vacuum Green's function, to finally obtain a closed form in terms of convolutions. The current is then computed for every tip-sample relative position and for every bias voltage in one shot. The electronic structure of tip and sample is calculated at the same footing, within density functional theory, and independently. This allows us to carry out multiple simulations for a given surface with a database of different tips. We have applied this method to the Si(111)-(7 × 7) and Ge(111)- c (2 × 8) surfaces. Topographies and spectroscopic data, showing a very good agreement with experiments, are presented. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Electrosynthesis of Poly(para)phenylene in an Ionic Liquid: Cyclic Voltammetry and in Situ STM/Tunnelling Spectroscopy StudiesCHEMPHYSCHEM, Issue 3 2008T. Carstens Abstract The electropolymerization of benzene in the air and water-stable ionic liquid 1-hexyl-3-methylimidazolium tris(pentafluoroethyl)trifluorophosphate (HMIm)FAP is investigated. The study comprises cyclic voltammetry, IR and in situ STM/tunnelling spectroscopy measurements. The IR results indicate that poly(para)phenylene is the end product of the electropolymerization of benzene in the employed ionic liquid. The resulting conjugation lengths of the product fall between 19 and 21. A polymer reference electrode is used successfully for the electrochemical polymerization of benzene. The first in situ STM results show that the electropolymerization of benzene in the ionic liquid can be probed on the nanoscale and the band gap of the prepared polymer can be determined. The electrodeposited polymer film obtained at a constant potential of 1.0 V vs PPP (polyparaphenylene) exhibits a band gap of 2.9±0.2 eV. [source] | ||||||||||