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Electrochemical Behavior (electrochemical + behavior)

Distribution by Scientific Domains

Chemistry	69%
Polymers and Materials Science	23%
3 Other Domains	8%

Selected Abstracts

The Preliminary Studies of Electrochemical Behavior of Paracetamol and Its Metabolites on Glassy Carbon Electrode by Voltammetric Methods

ELECTROANALYSIS, Issue 10 2009
Irena Baranowska
Abstract The new, rapid and sensitive method for the determination of paracetamol (PAR) and its glucuronide (PG) and sulfate (PS) metabolites is proposed. The electrochemical properties of the compounds were examined by cyclic voltammetry (CV) on glassy carbon electrode (GCE). All measurements were carried out in Britton,Robinson buffers (BR) with different pH values over the pH range 1.81,7.24. The preliminary research indicated that PAR could be determined simultaneously with one of its metabolites. The linearity of calibration curves was obtained for concentrations between 1.65×10,5 and 1.65×10,4 M for PAR, 1.53×10,5 and 1.53×10,4 M for PG and 2.17×10,5 and 1.52×10,4 M for PS. [source]

Electrochemical Behavior and Determination of L -Tyrosine at Single-walled Carbon Nanotubes Modified Glassy Carbon Electrode

ELECTROANALYSIS, Issue 11 2008
Xiaozhi Yu
Abstract Based on single-walled carbon nanotubes (SWCNTs) modified glassy carbon electrode (GCE/SWCNTs), a novel method was presented for the determination of L -tyrosine. The GCE/SWCNTs exhibited remarkable catalytic and enhanced effects on the oxidation of L -tyrosine. In 0.10,mol/L citric acid-sodium citrate buffer solution, the oxidation potential of L -tyrosine shifted negatively from +1.23,V at bare GCE to +0.76,V at GCE/SWCNTs. Under the optimized experimental conditions, the linear range of the modified electrode to the concentration of L -tyrosine was 5.0×10,6,2.0×10,5,mol/L (R1=0.9952) and 2.7×10,5,2.6×10,4,mol/L (R2=0.9998) with a detection limit of 9.3×10,8,mol/L. The kinetic parameters such as , (charge transfer coefficient) and D (diffusion coefficient) were evaluated to be 0.66, 9.82×10,5,cm2 s,1, respectively. And the electrochemical mechanism of L -tyrosine was also discussed. [source]

Electrochemical Behavior of Catecholamines and Related Compounds at In Situ Surfactant Modified Carbon Paste Electrodes

ELECTROANALYSIS, Issue 2-3 2007
M.Carmen Blanco-López
Abstract The voltammetric characteristics of catecholamines: epinephrine (E) and norepinephrine (NE) and related compounds: isoproterenol, metanephrine, L -dopa, methyldopa, vanillylmandelic acid (VMA), and homovanillic acid (HVA) at unmodified and in situ surfactant- modified carbon paste electrodes were comparatively evaluated. For the basic and amphoteric compounds the modification of the electrode surface with submicellar concentrations of anionic surfactants (sodium dodecylsulfate, sodium decylsulfate or sodium dodecylsulfonate) produce an important current enhancement in its oxidation and reduction peak current together with the improvement in the reversibility of the processes. These effects were explained in basis on electrostatic and hydrophobic interactions. On the other hand, the oxidation of acidic metabolites, HVA and VMA, was studied at electrodes modified in situ with cationic surfactants. Under certain conditions the surfactant could stabilise some of the electrochemical reaction intermediates, thus explaining the different voltammetric behaviour of HVA and VMA. [source]

Comparison of the Electrochemical Behavior of the High Molecular Mass Cadmium Proteins in Arabidopsis thaliana and in Vegetable Plants on Using Preparative Native Continuous Polyacrylamide Gel Electrophoresis (PNC-PAGE)

ELECTROANALYSIS, Issue 1 2006
Bernd Kastenholz
Abstract In Arabidopsis cytosol (supernatant) and in supernatants of vegetable plants high molecular mass cadmium proteins with molecular mass 200,kDa were isolated by using preparative native continuous polyacrylamide gel electrophoresis (PNC-PAGE). Because of a different electrochemical behavior of the Cd proteins in Arabidopsis and endive supernatants on using the same PAGE method, it is concluded that the high molecular mass cadmium proteins of Arabidopsis and endive possess different isoelectric points. Consequently, different chemical structures of the Cd proteins with molecular mass 200,kDa are present in Arabidopsis thaliana and in endive. During the electrophoretic separation of vegetable metalloproteins by using the Model 491 Prep Cell from BioRad, electroanalytical processes like electrode reactions may play an important role. [source]

Electrochemical Behavior and Detection of Dopamine and Ascorbic Acid at an Iron(II)tetrasulfophthalocyanine Modified Carbon Paste Microelectrode

ELECTROANALYSIS, Issue 10 2003
Joshua Oni
Abstract In this article the electrocatalytic behavior of an iron(II)tetrasulfophthalocyanine modified carbon paste microelectrode for the oxidation of dopamine (DA) and ascorbic acid (AA) is described. Although the oxidation potential of ascorbic acid is shifted by over 100,mV to more positive potentials, no peak separation could be obtained. This can be explained by the immediate homogeneous reduction of the oxidation product of dopamine by ascorbic acid in solution. However, this reaction induces a shift of the half-wave potential as a function of ratio of concentration of dopamine to ascorbic acid (cDA/cAA). Therefore it was possible to determine the cAA and cDA from this potential shift and the experimental peak current. Detection limits of 4.5±0.2×10,7 and 7.5±0.5×10,7,mol,L,1 were obtained respectively for dopamine and ascorbic acid for cDA/cAA>0.01. [source]

Structure-Dependent Electrochemical Behavior of Thienylplatinum(II) Complexes of N,N-Heterocycles

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 1 2004
Feng Zhao
Abstract trans -[Pt(MeCN)(PPh3)2(2-thienyl)]BF4 (1) serves as a convenient precursor to bifunctional mononuclear trans -[Pt(PPh3)2(,1 - N - N)(2-thienyl)]BF4 [N - N = pyrazine (2); 2-chloropyrazine, (3)] and dinuclear trans,trans -[Pt2(PPh3)4(,- N - N)(2-thienyl)2](BF4)2 [(N - N = 4,4, -bipyridine (4); 4,4, -vinylenedipyridine (5)] complexes. The nuclear selectivity is conveniently controlled by the choice of the heterocyclic ligands or spacers. Both structural types 3 and 5 were confirmed by single-crystal X-ray crystallographic analyses. Their solution identities were established by positive-ion Electrospray Mass Spectrometry (ESMS). The electroactivities of these complexes were studied by cyclic voltammetry (CV). Continuous CV scans of 4 and 5 revealed variations in the redox waves with the number of scans. While the initial oxidative scan exhibited only a broad, irreversible wave, further cycling showed the growth of two additional redox couples up to about the tenth cycle. The peak currents of these redox couples began to decay with prolonged potential cycling beyond the tenth cycle. These findings are consistent with the formation of electroactive oligomers/polymers, and this conclusion is supported by visible thin film formation on the electrodes. In contrast, the mononuclear complexes (2 and 3) do not show such behavior. The films formed were further studied by repetitive potential cycling and XPS. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source]

Long-Cycle Electrochemical Behavior of Multiwall Carbon Nanotubes Synthesized on Stainless Steel in Li Ion Batteries

ADVANCED FUNCTIONAL MATERIALS, Issue 7 2009
Charan Masarapu
Abstract Carbon nanotubes (CNTs) are considered to be excellent candidates for high performance electrode materials in Li ion batteries. The nanometer-sized pore structures of CNTs can provide the hosting sites for storing large numbers of Li ions. A short diffusion distance for the Li ions may bring about a high discharge rate. The long-cycle performance of aligned multiwalled carbon nanotubes (MWNTs) directly synthesized on stainless-steel foil as an anode material in lithium battery is demonstrated. An increase in the specific capacity with an increase in the cycle number is observed. Starting at a value of 132,mA hg,1 in the first cycle at a current rate of 1,C, the specific capacity increased about 250% to a value of 460,mA hg,1 after 1,200 cycles. This is an unusual but a welcoming behavior for battery applications. It is found that the morphology of the MWNTs with structural and surface defects and the stainless-steel substrate play an important role in enhancing the capacity during the cycling process. [source]

Electrochemical Behavior of Gel-Derived Lanthanum Calcium Cobalt Ferrite Cathode in Contact with LAMOX Electrolyte

JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 7 2008
Tsu-Yung Jin
The electrochemical performance and structural features of (La1,yCay)(CoxFe1,x)O3 cathode prepared via a citrate acid gel route are studied when it is interfaced with the (La1.8Dy0.2)(Mo2,zWz)O9 electrolyte. The resistance and chemical capacitance of a low-frequency arc are extracted from the impedance results to evaluate its catalytic activity in oxygen reduction reaction (ORR). (La0.75Ca0.25)(Co0.8Fe0.2)O3 cathode exhibits the minimum area-specific resistance of 0.9 , cm2 and maximum capacitance of 5.7 mF/cm2 at 800°C among the compositions of x=0.1,0.9 and y=0.25. As the Co content increases, the decrease in resistance outweighs the increase in capacitance so that the product of resistance and capacitance (RC time constant) decreases. In contrast, when varying the Ca content of the A-site, the changes in resistance and the capacitance compensate each other; hence the RC time constant is virtually unchanged with respect to the calcium content. Thus, Co is a more influential element than Ca on the ORR catalytic activity. The pore structure study reveals a small amount of Mo diffuses from the electrolyte into the cathode, and its quantity is reduced when interfaced to an electrolyte of high W content. [source]

ChemInform Abstract: Electrochemical Behavior of Nanoporous/Nanofibrous Si Anode Materials Prepared by Mechanochemical Reduction.

CHEMINFORM, Issue 13 2010
Rongguan Lv
Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source]

ChemInform Abstract: Electrochemical Behavior of Hydrazonates in Protic and Aprotic Medium.

CHEMINFORM, Issue 25 2002
T. Saied
Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source]

Simultaneous Determination of Dopamine and Ascorbic Acid Using the Nano-Gold Self-Assembled Glassy Carbon Electrode

ELECTROANALYSIS, Issue 10 2009
Guangzhi Hu
Abstract Electrochemical behavior of dopamine (DA) was investigated at the gold nanoparticles self-assembled glassy carbon electrode (GNP/LC/GCE), which was fabricated by self-assembling gold nanoparticles on the surface of L -cysteine (LC) modified glassy carbon electrode (GCE) via successive cyclic voltammetry (CV). A pair of well-defined redox peaks of DA on the GNP/LC/GCE was obtained at Epa=0.197,V and Epc=0.146,V, respectively. And the peak separation between DA and AA is about 0.2,V, which is enough for simultaneous determination of DA and AA. The peak currents of DA and AA were proportional with their concentrations in the range of 6.0×10,8,8.5×10,5 mol L,1 and 1.0×10,6,2.5×10,3 mol L,1, with the detection limit of 2.0×10,8 mol L,1 and 3.0×10,7 mol L,1 (S/N=3), respectively. The modified electrode exhibits an excellent reproducibility, sensibility and stability for simultaneous determination of DA and AA in human serum with satisfactory result. [source]

Amperometric Nitrite Sensor Based on PVP-Os Entrapped in Titania Sol-Gel Matrix

ELECTROANALYSIS, Issue 19 2004
Yancai Li
Abstract A novel nitrite sensor was developed based on the immobilization of a partially quaternized poly(4-vinylpyridine) complexed with [Os(bpy)2Cl]+/2+ (PVP-Os) in a porous TiO2 sol-gel matrix by a vapor deposition method. The preparation process simplified the traditional sol-gel process and prevented the cracking of conventional sol-gel derived glasses. Electrochemical behavior of the sensor was characterized by cyclic voltammetry and shows excellent electrocatalytic response for the reduction of nitrite. Effect of operating potential on electrochemical responses of the sensor was explored for optimum analytical performance by using the amperometric method. The stability of the sensor was also evaluated. [source]

Fabrication and Application of a Novel Modified Electrode Based on Multiwalled Nanotubes/Cerium(III) 12-Tungstophosphoric Acid Nanocomposite

ELECTROANALYSIS, Issue 11 2008
Bin Fang
Abstract A novel multiwalled nanotubes (MWNTs)/Cerium(III) 12 - tungstophosphoric acid (CePW) nanocomposite film glassy carbon electrode was prepared in this paper. Electrochemical behaviors of the CePW/MWNTs modified electrode were investigated by electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). This modified electrode brought new capabilities for electrochemical devices by combining the advantages of carbon nanotubes, rare-earth, and heteropoly-acids. The results demonstrated that the CePW/MWNTs modified electrode exhibited enhanced electrocatalytic behavior and good stability for the detection of guanine and adenine in 0.1,M PBS (pH,7.0). The experimental parameters were optimized and a direct electrochemical method for the simultaneous determination of guanine and adenine was proposed. The detection limit (S/N=3) for guanine and adenine was 2.0×10,8,M and 3.0×10,8,M, respectively. Further, the acid-denatured calf thymus DNA was also detected and the result was satisfied. [source]

Differential Pulse Voltammetric Determination of Uric Acid on Carbon-Coated Iron Nanoparticle Modified Glassy Carbon Electrodes

ELECTROANALYSIS, Issue 10 2008
Shengfu Wang
Abstract A carbon-coated iron nanoparticles (CIN, a new style fullerence related nanomaterial) modified glassy carbon electrode (CIN/GCE) has been developed for the determination of uric acid (UA). Electrochemical behaviors of UA on CIN/GCE were explored by cyclic voltammetry (CV) and differential pulse voltammetry (DPV). It was found that the voltammetric response of UA on CIN/GC was enhanced dramatically because of the strong accumulation effect of CIN and the large working area of the CIN/GC electrode. The parameters including the pH of supporting electrolyte, accumulation potential and time, that govern the analytical performance of UA have been studied and optimized. The DPV signal of UA on CIN/GCE increased linearly with its concentration in the range from 5.0×10,7 to 2.0×10,5 M, with a detection limit of 1.5×10,7 M (S/N=3). The CIN/GCE was used for the determination of UA in samples with satisfactory results. The proposed CIN/GCE electrochemical sensing platform holds great promise for simple, rapid, and accurate detection of UA. [source]

Peculiarities of Electrochemical Bismuth Film Formation in the Presence of Bromide and Heavy Metal Ions

ELECTROANALYSIS, Issue 15 2009
Giedr, Grincien
Abstract Bi films were deposited on glassy carbon electrode from solutions with and without KBr. The morphology of both types of the films was characterized by scanning electron microscopy (SEM), and their electrochemical behavior was studied by square wave (SWV) and cyclic voltammetry (CV). Bi films were also co-deposited with common analyte-heavy-metals in the presence of KBr and these films also were characterized by SEM, SWV and CV in order to understand the formation of the mixed metal films. All films studied had a different morphology. Bromide addition made the Bi films more compact and uniform, whereas Pb catalyzed Bi film deposition. [source]

Alkanethiols Modified Gold Electrodes for Selective Detection of Molecules with Different Polarity and Molecular Size.

ELECTROANALYSIS, Issue 3-5 2009
Application to Vitamin B2 Analysis
Abstract The cyclic voltammetry behavior of several molecules with different polarity and molecular size on gold electrodes modified with nonfunctionalized alkanethiols of different chain length, usually employed as chromatographic stationary phases, are studied. The redox systems hexacyanoferrate(II/III), ferrocene/ferrocine and hydroquinone/quinone are chosen as template molecules. As modifiers, ethanethiol, 1-octanethiol and di- n -octadecyldisulfide are selected. We can conclude that polar molecules can reach the electrode surface through channels created by the modifiers. However, when nonpolar compounds are analyzed, the nonpolar interactions between the analyte and the terminal group of the modifier lead to retention of the compound, retarding its arrival to the electrode surface. A molecule with polar and nonpolar part was used for the application of this conclusion. If the gold electrode is modified with di- n -octadecyldisulfide, the electrochemical behavior of vitamin B2 becomes simpler than that observed on a bare one. This result allows a sensitive and selective procedure to be developed for direct determination of vitamin B2 in pharmaceutical formulations. [source]

Amperometric Detection of 4-Chlorophenol on Two Types of Expanded Graphite Based Composite Electrodes

ELECTROANALYSIS, Issue 22 2008
Aniela Pop
Abstract The assessment of an expanded graphite-Ag-zeolite-epoxy composite (EG-Z-Ag-Epoxy) electrode for the determination of 4-chlorophenol (4-CP) is described and compared to the corresponding expanded graphite-epoxy composite (EG-Epoxy) electrode. Cyclic voltammetry was used to characterize the electrochemical behavior and determination of 4-CP at both electrodes in 0.1,M Na2SO4 and 0.1,M NaOH supporting electrolytes. A substantial enhancement of sensitivity for the determination of 4-CP at the EG-Z-Ag-Epoxy electrode was reached by applying a chemical preconcentration step prior to voltammetric quantification. Also, under these last conditions the lowest limit of detection of 1,,M illustrates the analytical versatility of this electrode in a concentration range where aquatic 4-chlorophenol pollution is known to occur. [source]

Preparation, Electrochemistry, and Electrocatalytic Activity of Lead Pentacyanonitrosylferrate Film Immobilized on Carbon Ceramic Electrode

ELECTROANALYSIS, Issue 21 2008
H. Razmi
Abstract Lead pentacyanonitrosylferrate (PbPCNF), a new Prussian blue analog, was immobilized on the surface of a carbon ceramic electrode (CCE) prepared by sol-gel method. The immobilization process consists of adding a certain amount of metallic lead to the electrode matrix before gelation, and chemical derivatization of Pb on the electrode surface to a PbPCNF solid film by immersing the electrode in a solution of sodium pentacyanonitrosylferrate (PCNF). The composition of the synthesized PbPCNF was characterized by FTIR, scanning electron microscopy (SEM), and energy-dispersive X-ray (EDX) techniques. The resulting modified electrode showed electroactivity at two redox centers. The electrochemical behavior of the PbPCNF modified carbon ceramic electrode (PbPCNF|CCE) was studied by cyclic voltammetry. Under optimized conditions the peak-to-peak separation is only 39,mV, indicative of a surface reaction. Ion effects of the supporting electrolyte suggest that cations have a considerable effect on the electrochemical behavior of the modified electrode. The transfer coefficient (,) and the charge transfer rate constant at the modifying film|electrode interface (ks) were calculated. The electrocatalytic activity of the modified electrode toward the electro-reduction of peroxodisulfate was studied in details. [source]

Voltammetric Reduction of a 4-Nitroimidazole Derivative on a Multiwalled Carbon Nanotubes Modified Glassy Carbon Electrode

ELECTROANALYSIS, Issue 13 2008
P. Jara-Ulloa
Abstract We report the electrochemical behavior of a 4-nitroimidazole derivative, 1-methyl-4-nitro-2-hydroxymethylimidazole (4-NImMeOH), on glassy carbon electrode (GCE) modified with multiwalled carbon nanotubes (MWCNT). As dispersing agents, dimethylformamide (DMF) and water were used. The electrochemical response of the resulting electrodes was evaluated using linear sweep, cyclic and square-wave voltammetry (LSV, CV and SWV). Several parameters such as medium pH, nature and concentration of the CNTs dispersion and accumulation time were tested. The optimal conditions determined for obtain better response were: pH,2, dispersion concentration=4,mg/mL of CNT in water, accumulation time=7,min. The MWCNT-modified GCE exhibited attractive electrochemical properties producing enhanced currents with a significant reduction in the overpotential and good signal-to-noise characteristics, in comparison with the bare GCE. The modified electrode is highly repeatable for consecutive measurements, reaching a variation coefficient of 2.9% for ten consecutive runs. [source]

Paste Electrode Based on Short Single-Walled Carbon Nanotubes and Room Temperature Ionic Liquid: Preparation, Characterization and Application in DNA Detection

ELECTROANALYSIS, Issue 12 2008
Xuzhi Zhang
Abstract A paste electrode (SWNT&RTIL PE) has been prepared using carboxylic group-functionalized short single-walled carbon nanotubes (SWNTs) mixed with 1-butyl-3-methylimidazolium hexafluorophosphate (BMIMPF6, one kind of room temperature ionic liquid, RTIL). Its electrochemical behavior was investigated by cyclic voltammetry and electrochemical impedance spectroscopy in comparison with the paste electrode using mineral oil as a binder. Results highlighted the advantages of the paste electrode: not only higher conductivity, but also lower potential separation (,Ep), higher peak current (ip) and better reversibility towards dopamine (DA), methylene blue (MB) and K3[Fe(CN)6]. The SWNT&RTIL PE could be used to detect the number of guanine bases and adenine bases contents in per mol oligonucleotides according to the current response in the range of 0.05,2.0,nM. Based on the current response of guanine bases, oligonucleotides could be detected sensitively in the B,R buffer solution with a detection limit of 9.9,pM. The heterogeneous electron transfer rate constant (ks) of guanine bases contents in the oligonucleotides was investigated and its value was 0.90,s,1. In essence the SWNT&RTIL PE showed high sensitivity, reliability, stability and reproducibility for the detection of DNA. [source]

Selective Determination of Dopamine in the Presence of Ascorbic Acid at Porous-Carbon-Modified Glassy Carbon Electrodes

ELECTROANALYSIS, Issue 11 2008
Shuqing Song
Abstract Selective dopamine (DA) determinations using porous-carbon-modified glassy carbon electrodes (GCE) in the presence of ascorbic acid (AA) were studied. The effects of structure textures and surface functional groups of the porous carbons on the electrochemical behavior of DA was analyzed based on both cyclic voltammetry (CV) and differential pulse voltammetry (DPV) measurements. The differential pulse voltammetry of DA on the modified GCE was determined in the presence of 400-fold excess of AA, and the linear determination ranges of 0.05,0.99, 0.20,1.96, and 0.6,12.60,,M with the lowest detected concentrations of 4.5×10,3, 4.4×10,2, and 0.33,,M were obtained on the mesoporous carbon, mesoporous carbon with carboxylic and amino groups modified electrodes, respectively. [source]

Disposable Gold Electrode Array for Simultaneous Electrochemical Studies

ELECTROANALYSIS, Issue 1 2008
Graciela Priano
Abstract An efficient and inexpensive eight gold electrode array has been manufactured by a combination of screen printing and gold electrodeposition techniques. Gold electrodeposition was performed in potentiostatic and galvanostatic conditions. Different treatments, involving temperature and polishing control, led to electrodes with different roughness. The electrochemical behavior of the generated gold surface was studied by cyclic voltammetry showing the characteristic response of polycrystalline gold, in contrast with disposable gold electrodes fabricated by screen printing from gold inks. The electrodes were chemically modified through the adsorption of alkanethiols self-assembled monolayers and the coupling of a model protein. Both reactions were followed by cyclic voltammetry and Electrochemical Impedance Spectroscopy (EIS). The electrodes have shown high reproducibility in their electrochemical behavior as well as in their modifications. [source]

Carbon Ceramic Electrodes Modified with Laccase from Trametes hirsuta: Fabrication, Characterization and Their Use for Phenolic Compounds Detection

ELECTROANALYSIS, Issue 9 2007
Behzad Haghighi
Abstract Fungal laccase (Lc) from the basidiomycete Trametes hirsuta was immobilized on top of a carbon ceramic electrode using physical absorption. Direct, unmediated heterogeneous electron transfer between Lc and the carbon ceramic electrode (CCE) under aerobic conditions was shown. The bioelectrocatalytic reduction of oxygen on Lc-CCE started at about 430,mV vs. Ag|AgCl|KClsat at pH,3.5 and moved with about 57,mV in the cathodic region per pH unit. The Lc-modified CCE was then used as a biosensing detection element in a single line flow injection system for the amperometric determination of a variety of phenolic substrates of the enzyme. The experimental conditions were studied and optimized for catechol serving as a model compound. Statistical aspects were applied and the sensor characteristics and Michaelis-Menten constants of the investigated phenolic compounds were calculated and compared with those obtained for solid graphite electrodes modified with Trametes hirsuta laccase. The results showed that the CCE based biosensor in comparison with the solid graphite based biosensor offers a lower detection limit, a wider linear dynamic range, and excellent operational stability with no sensor passivation, indicating that the sol,gel lattice improves the electrochemical behavior of the biosensor. [source]

Dramatic Effects of Ionic Liquid on Platinum Electrode Surface and Electron-Transfer Rates of meso -Tetraphenylporphyrins

ELECTROANALYSIS, Issue 12 2006
Afsaneh Safavi
Abstract The effect of addition of a room temperature ionic liquid, 1-butyl-3-methyl imidazolium hexafluorophosphate [bmim][PF6], on the electrochemical behavior of different free-base para-substituted meso -tetraphenylporphyrins in dichloromethane solution has been studied using cyclic voltammetric technique. It has been found that the ionic liquid has the ability to regenerate platinum electrode surface and improves the reversibility of electrode processes. This has been true for the case of all the porphyrins studied. [source]

Determination of Rutin in Green Tea Infusions Using Square-Wave Voltammetry with a Rigid Carbon-Polyurethane Composite Electrode

ELECTROANALYSIS, Issue 10 2006
Andréa
Abstract This paper presents a comparative study on the electrochemical behavior of the flavonoid rutin on a rigid carbon-polyurethane composite electrode and on a glassy carbon electrode. The electrochemical oxidation reaction of rutin was found to be quasireversible and affected by adsorption on the electrode surface. A square-wave voltammetric method was developed for determination of rutin in green tea infusion samples using the RCPE electrode and data treatment by a deconvolution procedure. The detection limit achieved in buffered solutions was 7.1×10,9,mol L,1 using the RCPE and 1.7×10,8,mol L,1 using the GC electrode the average reproducibility for five determinations being 3.5%. [source]

Comparison of the Electrochemical Behavior of the High Molecular Mass Cadmium Proteins in Arabidopsis thaliana and in Vegetable Plants on Using Preparative Native Continuous Polyacrylamide Gel Electrophoresis (PNC-PAGE)

The Influence of Doping Levels and Surface Termination on the Electrochemistry of Polycrystalline Diamond

ELECTROANALYSIS, Issue 6 2004
Matthew
Abstract The influence of surface chemistry and boron doping density on the redox chemistry of Fe(CN) at CVD polycrystalline diamond electrodes is considered. It is demonstrated that for this couple both the doping density and the surface chemistry are important in determining the rate of charge transfer at the electrode/electrolyte interface. For hydrogen terminated CVD diamond metallic electrochemical behavior is always observed, even at boron doping densities as low as 7×1018,cm,3. In contrast, the electrochemical behavior of oxygen terminated CVD diamond varies with doping density, a metallic response being observed at high doping density and semiconductor behavior at low doping density. It is shown that the results attained may be explained by a surface state mediated charge transfer mechanism, thus demonstrating the importance of controlling surface chemistry in electroanalytical applications of diamond. [source]

Carbon nanotube disposable detectors in microchip capillary electrophoresis for water-soluble vitamin determination: Analytical possibilities in pharmaceutical quality control

ELECTROPHORESIS, Issue 14 2008
Agustín G. Crevillén
Abstract In this work, the synergy of one mature example from "lab-on-chip" domain, such as CE microchips with emerging miniaturized carbon nanotube detectors in analytical science, is presented. Two different carbon electrodes (glassy carbon electrode (GCE) 3,mm diameter, and screen-printed electrode (SPE) 0.3,mm×2.5,mm) were modified with multiwalled carbon nanotubes (MWCNTs) and their electrochemical behavior was evaluated as detectors in CE microchip using water-soluble vitamins (pyridoxine, ascorbic acid, and folic acid) in pharmaceutical preparations as representative examples. The SPE modified with MWCNT was the best electrode for the vitamin analysis in terms of analytical performance. In addition, accurate determination of the three vitamins in four different pharmaceuticals was obtained (systematic error less than 9%) in only 400,s using a protocol that combined the sample analysis and the methodological calibration. [source]

Characterization of Ti-Ta Alloys Synthesized by Cold Crucible Levitation Melting,

ADVANCED ENGINEERING MATERIALS, Issue 8 2008
D.-M. Gordin
Ti-Ta alloys are potentially interesting for many applications including chemistry industries, marine environment and biomedical devices. In this study, the Ti-Ta alloys were synthesized by cold crucible levitation melting (CCLM) in the whole range of composition. The different microstructures were characterized by X-ray diffraction and optical microscopy, the ,-transus was detected by electrical resistivity, the mechanical properties were evaluated by compression tests and microhardness measurements and the electrochemical behavior was carried out in Ringer's solution. [source]

Preparation, Structure, and Electrochemical Properties of Reduced Graphene Sheet Films

ADVANCED FUNCTIONAL MATERIALS, Issue 17 2009
Longhua Tang
Abstract This paper describes the preparation, characterization, and electrochemical properties of reduced graphene sheet films (rGSFs), investigating especially their electrochemical behavior for several redox systems and electrocatalytic properties towards oxygen and some small molecules. The reduced graphene sheets (rGSs) are produced in high yield by a soft chemistry route involving graphite oxidation, ultrasonic exfoliation, and chemical reduction. Transmission electron microscopy (TEM), X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy clearly demonstrate that graphene was successfully synthesized and modified at the surface of a glassy carbon electrode. Several redox species, such as Ru(NH3)63+/2+, Fe(CN)63,/4,, Fe3+/2+ and dopamine, are used to probe the electrochemical properties of these graphene films by using the cyclic voltammetry method. The rGSFs demonstrate fast electron-transfer (ET) kinetics and possess excellent electrocatalytic activity toward oxygen reduction and certain biomolecules. In our opinion, this microstructural and electrochemical information can serve as an important benchmark for graphene-based electrode performances. [source]