Showing papers on "Voltammetry published in 2007"
TL;DR: It is demonstrated that direct reduction can be almost completely suppressed by using a mercury or amalgamated gold electrode, even at very negative potentials.
Abstract: Voltammetry is widely used for the evaluation of iron-only hydrogenase mimics and other potential catalysts for hydrogen generation using various dipolar aprotic solvents. Effective catalysts show enhanced current in the presence of a proton donor at the potential where the catalyst is reduced. To facilitate the comparison of catalytic efficiencies, this paper provides a simple means of calculating the standard potential for reduction of the acid, HA, according to the half reaction 2HA + 2e- ⇌ H2 + 2A-. This standard potential depends on the pKa of HA in the solvent being used. It is thermodynamically impossible for reduction of HA to occur at less negative potentials than the standard potential, and the most effective catalysts will operate at potentials as close as possible to the standard potential. In addition, direct reduction of HA at the electrode will compete with the catalyzed reduction, thus complicating evaluation of the rate of the catalyzed reaction. Glassy carbon electrodes, commonly used in...
456 citations
TL;DR: The electrocatalytic oxygen reduction reaction on noble metal surfaces is one of the most widely studied reactions in electrochemistry and is based on the fact that the oxygen/water half-cell reaction is a strongly oxidizing and ubiquitous redox couple.
Abstract: The electrocatalytic oxygen reduction reaction (ORR) on noble metal surfaces [Eq. (1), RHE= reversible hydrogen electrode] is one of the most widely studied reactions in electrochemistry. Its fundamental scientific and technological importance is based on the fact that the oxygen/water half-cell reaction is a strongly oxidizing and ubiquitous redox couple. Combined with an electron-supplying redox process, such as shown in Equation (2), a direct electrochemical conversion of
368 citations
TL;DR: The described method was successfully employed for the determination of nandrolone in human serum and urine samples and a cross-validation of observed results by GC-MS indicates that the results are in good agreement with each other.
361 citations
TL;DR: In this article, the surface area of PtRu catalysts in a membrane electrode assembly was determined by applying CO stripping voltammetry and it was shown that the CO charge determined in this way is independent on the sweep rate applied.
250 citations
TL;DR: High-resolution differential surface plasmon resonance (SPR) with anodic stripping voltammetry (ASV) capability with quantitative detection of copper, lead, and mercury ions in water from part-per-million to sub-part- per-billion levels with good linearity.
Abstract: High-resolution differential surface plasmon resonance (SPR) with anodic stripping voltammetry (ASV) capability has been demonstrated for detecting heavy metal ions in water. Metal ions are electroplated onto the gold SPR sensing surface and are quantitatively detected by stripping voltammetry. Both the SPR angular shift and electrochemical current signal are recorded to identify the type and amount of the metal ions in water. The performance of the combined approach is further enhanced by a differential detection approach. The gold sensor surface is divided into a reference and a sensing area, and the difference in the SPR angles from the two areas is detected with a quadrant cell photodetector as a differential signal. Our system demonstrated quantitative detection of copper, lead, and mercury ions in water from part-per-million to sub-part-per-billion levels with good linearity.
231 citations
TL;DR: In this paper, a polyaniline-multi-walled carbon nanotubes (PANI-MWCNTs) composite modified electrode was fabricated and the electrochemical behaviors of acetaminophen on the PANI-MWCNTs composite modified electrodes were investigated by using cyclic voltammetry (CV), single-potential step chronocoulometry and square-wave voltammetric (SWV).
214 citations
TL;DR: The proposed procedure was successfully applied to detect adenosine and guanosine in human blood plasma and urine, without any preliminary pre-treatment, and showed excellent selectivity in the presence of hypoxanthine, xanthines, uric acid and ascorbic acid.
190 citations
TL;DR: In this paper, a poly(3,4-ethylenedioxythiophene)/polypyrrole composite (PEDOT/PPy) was performed on Field Emission Scanning Electron Microscope (SEM).
179 citations
TL;DR: In this paper, the authors used voltammetry based on the single-wall carbon nanotube (SWNT) electrode for simultaneous determination of dihydroxybenzene isomers.
Abstract: Simultaneous determination of o-, m-, and p-dihydroxybenzene isomers were investigated by voltammetry based on the single-wall carbon nanotube (SWNT) electrode. The SWNT electrode exhibited strong and stable recognition ability toward dihydroxybenzene isomers. The oxidation peak potential difference between hydroquinone and catechol was 111 mV, catechol and resorcinol 399 mV, which indicated that the o-, m- and p-dihydroxybenzene could be identify entirely at the SWNT electrode. The peak currents of dihydroxybenzene isomers increased linearly with increasing the dihydroxybenzene isomer contents. The proposed method can be applied to simultaneous determination of dihydroxybenzene isomers.
173 citations
TL;DR: A novel composite film modified glassy carbon electrode has been fabricated and characterized by scanning electron microscope (SEM) and voltammetry, and shows good stability, high accumulation efficiency and strong promotion to electron transfer.
TL;DR: The carbon paste electrode modified with SDS (SDS/CPE) exerted discrimination against ascorbic acid in physiological circumstance and can selectively determine dopamine even in the presence of 220-fold AA combined with differential pulse stripping voltammetry.
TL;DR: In this paper, the behavior of folic acid at plain carbon paste electrode and electrode modified with calixarenes has been studied and shown to be rectilinear with concentration by differential pulse voltammetry.
TL;DR: In this paper, a carbon ionic liquid electrode (CILE) was chosen as working electrode to determine hydroquinone by differential pulse voltammetry, which can be used for sensitive, simple and rapid determination of Hydroquinone in medicated skin cosmetic cream.
TL;DR: The accuracy and precision of results were comparable to those obtained by flame atomic absorption spectroscopy (FAAS), when applied for determination of Cu(II) to natural waters and human hairs.
TL;DR: According to the direct electron transfer property and enhanced activity of Hb in cobalt oxide film, a third generation reagentless biosensor without using any electron transfer mediator or specific reagent can be constructed for determination of hydrogen peroxide in anaerobic solutions.
TL;DR: In this paper, the catalytic activity of gold nuclei toward the decomposition of ferricyanide to free ferric ions and controlled generation of gold nanoparticles from HAuCl4 solutions during potential cycling are exploited to form these nanocomposites.
Abstract: In this work, we report for the first time a one-step electrochemical deposition of gold−Prussian blue (PB) nanocomposite films. The catalytic activity of gold nuclei toward the decomposition of ferricyanide to free ferric ions and controlled generation of gold nanoparticles from HAuCl4 solutions during potential cycling are exploited to form these nanocomposites. Concomitant electrochemical formation of both PB and gold phases leads to a “perfect blend”, in which each phase controls the growth of the other. The mechanism of formation and the features that distinguish this approach from others are highlighted. The nanocomposite films were characterized using voltammetry and UV−vis spectroscopy, field emission scanning electron microscopy (FE-SEM), and atomic force microscopy (AFM). Interestingly, reversibility of the redox conversions of PB is enhanced by the presence of Au nanoparticles, as indicated by the reduced ΔEp value in cyclic voltammetry and low charge-transfer resistance in ac impedance spectro...
TL;DR: The results indicated that the electrochemical responses of DIP are apparently improved by CTAB, due to the enhanced accumulation of dipyridamole at the carbon paste electrode surface.
TL;DR: In this paper, a series of Pt-CexZr1−xO2/C catalyst powders with different Ce/Zr ratio were prepared and evaluated in terms of the electrochemical activity for ethanol electro-oxidation using cyclic voltammetry (CV), steady state polarization experiments and CO-stripping technique at room temperature.
Abstract: Pt-CeO2/C and a series of Pt-CexZr1−xO2/C catalyst powders with different Ce/Zr ratio were prepared and evaluated in terms of the electrochemical activity for ethanol electro-oxidation using cyclic voltammetry (CV), steady state polarization experiments and CO-stripping technique at room temperature. XRD results show that CexZr1−xO2 and Pt coexist in the Pt-CexZr1−xO2/C catalyst and CexZr1−xO2 has no effect on the crystalline lattice of Pt. TEM results show that the Pt and CexZr1−xO2 particles dispersed uniformly over the surface of the carbon black. Cyclic voltammetry results show that the mass activity and specific activity of Pt-CeO2/C for ethanol electro-oxidation is higher than that of Pt/C. The structure and Ce/Zr ratio of Pt-CexZr1−xO2/C has effect on the catalytic activity of catalysts. CO-stripping voltammetry showed that the inclusion of CeO2 and CexZr1−xO2 favors the CO oxidation at lower potential.
TL;DR: The effect of adding surface-active agents to electrolytes containing terazosin, an antihypertensive drug, on the voltammetric response of glassy carbon electrode was studied and the validity of using this method in the determination of drug active ingredient in urine samples and tablet formulations was demonstrated.
TL;DR: In this paper, colloidal silver and silver-alloys were evaluated as anode catalysts for sodium borohydride oxidation using cyclic voltammetry (CV), chronoamperometry (CA), chronopotentiometry (CP), and rotating disk electrode (RDE) voltammetrics.
TL;DR: The inter-electrode spacing, geometry, numbers and dimensions of the electrodes in the arrays were found to influence the voltammetric behaviours obtained, and excellent correlation was found between experimental data and theoretical predictions employing published models of microElectrode behaviour.
TL;DR: In this article, a simple differential pulse voltammetric method based on a Nafion-covered glassy carbon electrode was developed for the quantitative determination of caffeine in cola beverages.
Abstract: A simple differential pulse voltammetric method based on a Nafion-covered glassy carbon electrode was developed for the quantitative determination of caffeine in cola beverages. The modified electrode exhibits a clear improvement of the current response compared to that observed at a bare glassy carbon electrode. The method allows quantifying the analyte in the 9.95×10−7–1.06×10−5 M range, with a detection limit of 7.98×10−7 M in 0.1 M sulfuric acid solutions. The developed procedure was tested by recovery studies. The results are described and discussed in the light of the existing literature.
TL;DR: In this paper, the electrochemical behavior of L-cysteine at the surface of FDCMCPE was studied using cyclic voltammetry, differential pulse voltameters and double potential step chronoamperometry.
Abstract: The electrochemical behavior of L-cysteine studied at the surface of ferrocenedicarboxylic acid modified carbon paste electrode (FDCMCPE) in aqueous media using cyclic voltammetry, differential pulse voltammetry and double potential step chronoamperometry. It has been found that under optimum condition (pH 8.00) in cyclic voltammetry, the oxidation of L-cysteine occurs at a potential about 200 mV less positive than that of an unmodified carbon paste electrode. The kinetic parameters such as electron transfer coefficient, α, and catalytic reaction rate constant, kh were also determined using electrochemical approaches. The electrocatalytic oxidation peak current of L-cysteine showed a linear dependent on the L-cysteine concentration and linear analytical curves were obtained in the ranges of 3.0×10−5 M–2.2×10−3 M and 1.5×10−5 M–3.2×10−3 M of L-cysteine concentration with cyclic voltammetry (CV) and differential pulse voltammetry (DPV) methods respectively. The detection limits (3σ) were determined as 2.6×10−5 M and 1.4×10−6 M by CV and DPV methods.
TL;DR: In this paper, the anodic peak current is linear to quercetin concentration in the ranges of 2.0 -1.928 c (μM, r ǫ = 0.0017−+0.999) and i p (μA) = −0.183−+−0.0731c (μm, rǫ= 0.995), respectively.
TL;DR: It was found that the electrodeposited Au-NP has strong adsorption on Cr( VI) species, which results in an enhanced reduction current of Cr(VI), and this convenient and sensitive technique offers great promise for onsite environmental monitoring and biomonitoring ofCr(VI).
Abstract: Gold nanoparticle (Au-NP) enhanced voltammetric detection of Cr(VI) is developed for determination of trace amounts of Cr(VI) in an acetate buffer media (pH 4.6). The Au-NPs were electrodeposited onto a disposable screen printed electrode (SPE) via an electrodeposition step. It was found that the electrodeposited Au-NP has strong adsorption on Cr(VI) species, which results in an enhanced reduction current of Cr(VI). Compared with the bulk gold electrode, the reduction current of Cr(VI) was enhanced 10 times with the Au-NP-modified SPE electrode. Square wave voltammetric (SWV) measurement with the disposable Au-NP-modified SPE provides a fast, simple and sensitive detection of trace amounts of Cr(VI). The adsorption of Cr(VI) on Au-NP was characterized with voltammetry, X-ray photoelectron spectroscopy and ultraviolet spectra. The different parameters including the electrodepositing time, supporting electrolyte, and pH that govern the analytical performance of the electrode have been studied in detail and ...
TL;DR: In this paper, an overoxidized polypyrrole (OPPy) modified glassy carbon electrode using cyclic voltammetry and chronoamperometry techniques was studied.
TL;DR: In this article, the Eriochrome Blue-Black B (EBB) was used as the counter anion in the EBB/PPy modified electrode for preconcentration and differential pulse anodic stripping voltammetric measurements.
TL;DR: Gold nanorods with suitable aspect ratio were synthesized with a template technique and then dispersed in a saturated sodium citrate solution by ultrasonication to form a GNR suspension as discussed by the authors.
TL;DR: Glassy carbon electrodes modified with CNT-PEI dispersion show an excellent performance as amperometric detector in the electrophoretic separation of phenolic compounds and neurotransmitters making possible highly sensitive and reproducible determinations.