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Redox Peaks (redox + peak)
Selected AbstractsInfluence of Metal Nanoparticles on the Electrocatalytic Oxidation of Glucose by Poly(NiIIteta) Modified ElectrodesELECTROANALYSIS, Issue 5 2010Pratap Azad Abstract Conductive polymeric [NiII(teta)]2+ (teta=C-meso-5,5,7,12,12,14-hexamethyl-1,4,8,11-tetra-azacyclotetradecane) films (poly(Ni)) have been deposited on the surface of glassy carbon (GC), Nafion (Nf) modified GC (GC/Nf) and Nf stabilized Ag and Au nanoparticles (NPs) modified GC (GC/Ag-Nf and GC/Au-Nf) electrodes. The cyclic voltammogram of the resulting electrodes, show a well defined redox peak due to oxidation and reduction of poly(Ni) system in 0.1,M NaOH. They show electrocatalytic activity towards the oxidation of glucose. AFM studies reveal the formation of poly(Ni) film on the modified electrodes. Presence of metal NPs increases electron transfer rate and electrocatalytic oxidation current by improving the communication within the Nf and poly(Ni) films. In the presence of metal NPs, 4 fold increase in current for glucose oxidation was observed. [source] Mediated Electron Transfer Across Supported Bilayer Lipid Membrane with TCNQ-Based Organometallic CompoundsELECTROANALYSIS, Issue 4 2010Meili Qu Abstract Supported bilayer lipid membrane (s-BLM) containing one-dimensional compound 1, TCNQ-based (TCNQ=7,7,8,8-tetracyanoquinodimethane) organometallic compound {(Cu2(,-Cl)(,-dppm)2)(,2 -TCNQ)},, was prepared and characterized on the self-assembled monolayer (SAM) of 1-octadecylmercaptan (C18H37SH) deposited onto Au electrode. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) results showed that the compound 1, dotted inside s-BLM, can act as mediator for electron transfer across the membrane. Two redox peaks and the charge-transfer resistance of 400,k, were observed for compound 1 inside s-BLM. The mechanism of the electron transfer across s-BLM by TCNQ is by electron hopping while TCNQ-based organometallic compound is by conducting. Further conclusion drawn from this finding is that the TCNQ-based organometallic compound embedded inside s-BLM exhibits excellent electron transfer ability than that of free TCNQ. This opens a new path for the development of s-BLM sensor and/or biosensor by incorporation with TCNQ-based organometallic compounds. [source] Simultaneous Determination of Dopamine and Ascorbic Acid Using the Nano-Gold Self-Assembled Glassy Carbon ElectrodeELECTROANALYSIS, Issue 10 2009Guangzhi 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] Direct Electrochemistry of Hemoglobin Immobilized on Colloidal Gold-Hydroxyapatite Nanocomposite for Electrocatalytic Detection of Hydrogen PeroxideELECTROANALYSIS, Issue 2 2009Juan You Abstract A novel nanocomposite of colloidal gold (GNPs) and hydroxyapatite nanotubes (Hap) was prepared for immobilization of a redox protein, hemoglobin (Hb), on glassy carbon electrode. The immobilized Hb showed fast direct electron transfer and excellent electrocatalytic behavior toward reduction of hydrogen peroxide. A synergic effect between GNPs and Hap for accelerating the surface electron transfer of Hb was observed, which led to a pair of redox peaks with a formal potential of (,340±2) mV at pH,7.0, and a new biosensor for hydrogen peroxide with a linear range from 0.5 to 25,,M and a limit of detection of 0.2,,M at 3,. Owing to the good biocompatibility of the nanocomposite, the biosensor exhibited good stability and acceptable reproducibility. The as-prepared nanocomposite film provided a good matrix for protein immobilization and biosensor preparation. [source] Direct Electrochemistry and Electrocatalysis of Hemoglobin in Lipid Film Incorporated with Room-Temperature Ionic LiquidELECTROANALYSIS, Issue 20 2008Gaiping Li Abstract A facile phospholipid/room-temperature ionic liquid (RTIL) composite material based on dimyristoylphosphatidylcholine (DMPC) and 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim]PF6) was exploited as a new matrix for immobilizing protein. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were adopted to characterize this composite film. Hemoglobin (Hb) was chosen as a model protein to investigate the composite system. UV-vis absorbance spectra showed that Hb still maintained its heme crevice integrity in this composite film. By virtue of the Hb/DMPC/[bmim]PF6 composite film-modified glassy carbon electrode (GCE), a pair of well-defined redox peaks of Hb was obtained through the direct electron transfer between protein and underlying GCE. Moreover, the reduction of O2 and H2O2 at the Hb/DMPC/[bmim]PF6 composite film-modified GCE was dramatically enhanced. [source] Direct Electron Transfer and Electrocatalysis of Hemoglobin on Chitosan-TiO2 Nanorods-Glass Carbon ElectrodeELECTROANALYSIS, Issue 20 2008Xiaoling Xiao Abstract The direct electron transfer between hemoglobin (Hb) and the glassy carbon electrode (GC) can be readily achieved via a high biocompatible composite system based on biopolymer chitosan (CHT) and TiO2 nanorods (TiO2 -NRs). TiO2 -NRs greatly promote the electron transfer between Hb and GC, which contribute to the higher redox peaks. UV-vis spectra result indicated the Hb entrapped in the composite film well keep its native structure. The immobilized Hb remains its bioelectrocatalytical activity to the reduction of H2O2 with a lower detection limit. A novel, sensitive, reproducible and stable electrochemical biosensing platform of H2O2 based on Hb-TiO2 -CHT electrode is explored. [source] Electrochemistry of Mitochondria: A New Way to Understand Their Structure and FunctionELECTROANALYSIS, Issue 14 2008Jing Zhao Abstract In this article, electrochemistry of mitochondria is achieved. Cyclic voltammograms of freshly prepared mitochondria were obtained by immobilizing mitochondria together with glutaraldehyde and bovine serum albumin on the surface of a pyrolytic graphite electrode. Two pairs of redox peaks could be observed which were ascribed to the electron transfer reactions of cytochrome c and FAD/FADH2. Study of submitochondrial particles was also conducted, which could confirm the results of the study of the entire mitochondria. The redox wave of NADH could be obtained due to the destruction of the membrane of mitochondria. We have also checked the function of succinate in mitochondria by employing the electrochemical method. This work is not only the first to be able to obtain the direct electrochemistry of mitochondria, but is also beneficial to the further understanding of the structure and function of mitochondria in vitro. [source] Reagentless Glucose Biosensor Based on the Direct Electrochemistry of Glucose Oxidase on Carbon Nanotube-Modified ElectrodesELECTROANALYSIS, Issue 11 2006Xiliang Luo Abstract The direct electrochemistry of glucose oxidase (GOD) was revealed at a carbon nanotube (CNT)-modified glassy carbon electrode, where the enzyme was immobilized with a chitosan film containing gold nanoparticles. The immobilized GOD displays a pair of redox peaks in pH,7.4 phosphate buffer solutions (PBS) with the formal potential of about ,455,mV (vs. Ag/AgCl) and shows a surface-controlled electrode process. Bioactivity remains good, along with effective catalysis of the reduction of oxygen. In the presence of dissolved oxygen, the reduction peak current decreased gradually with the addition of glucose, which could be used for reagentless detection of glucose with a linear range from 0.04 to 1.0,mM. The proposed glucose biosensor exhibited high sensitivity, good stability and reproducibility, and was also insensitive to common interferences such as ascorbic and uric acid. The excellent performance of the reagentless biosensor is attributed to the effective enhancement of electron transfer between enzyme and electrode surface by CNTs, and the biocompatible environment that the chitosan film containing gold nanoparticles provides for immobilized GOD. [source] Direct Electrochemistry of Cytochrome c at Gold Electrode Modified with Fumed SilicaELECTROANALYSIS, Issue 20 2005Hongjun Chen Abstract Direct electrochemistry of horse heart cytochrome c (cytc) has been obtained at a gold electrode constructed by self-assembling fumed silica particles (FSPs) onto a silane monolayer. A pair of well-defined and nearly symmetrical redox peaks of cytc is obtained at the FSPs film modified gold electrode. Cyclic voltammetry (CV) and tapping-mode atomic force microscopy (AFM) are used to characterize the FSPs film modified electrode, showing that the FSPs can provide a favorable microenvironment for cytc and facilitate the direct electron transfer between the cytc and the gold electrode, which may propose an approach to realize the direct electrochemistry of other proteins. [source] The Solid State Electrochemistry of Dysprosium(III) Hexacyanoferrate(II)ELECTROANALYSIS, Issue 17 2005Ping Wu Abstract A new electroactive polynuclear inorganic compound of rare earth metal hexacyanoferrate, dysprosium hexacyanoferrate (DyHCF), was prepared chemically and characterized using techniques of FTIR spectroscopy, thermogravimetric analysis (TGA), UV-vis spectrometry and X-ray photoelectron spectroscopy (XPS) etc. The cyclic voltammetric behavior of DyHCF mechanically attached to the surface of graphite electrode was well defined and exhibited a pair of redox peaks with the formal potential of 217,mV (vs. SCE) at a scan rate of 100,mV/s in 0.2,M NaCl solution and the redox peak currents increased linearly with the square root of the scan rates. [source] Electroconductive Hydrogels: Electrical and Electrochemical Properties of Polypyrrole-Poly(HEMA) CompositesELECTROANALYSIS, Issue 7 2005Sean Brahim Abstract Composites of inherently conductive polypyrrole (PPy) within highly hydrophilic poly(2-hydroxyethyl methacrylate)-based hydrogels (p(HEMA)) have been fabricated and their electrochemical properties investigated. The electrochemical characteristics observed by cyclic voltammetry suggest less facile reduction of PPy within the composite hydrogel compared to electropolymerized PPy, as shown by the shift in the reduction peak potential from ,472,mV for electropolymerized polypyrrole to ,636,mV for the electroconductive composite gel. The network impedance magnitude for the electroconductive hydrogel remains quite low, ca. 100,,, even upon approach to DC, over all frequencies and at all offset potentials suggesting retained electronic (bipolaronic) conductivity within the composite. In contrast, sustained application of +0.7 V (vs. Ag/AgCl, 3,M Cl,) for typically 100,min. (conditioning) to reduce the background amperometric current to <1.0,,A, resulted in complete loss of electroactivity. Nyquist plots suggest that sustained application of such a modest potential to the composite hydrogel results in impedance characteristics that resembles p(HEMA) without evidence of the conducting polymer component. PPy composite gels supported a larger ferrocene monocarboxylate diffusivity (Dappt=7.97×10,5,cm2,s,1) compared to electropolymerized PPy (Dappt=5.56×10,5,cm2,s,1), however a marked reduction in diffusivity (Dappt=1.01×10,5,cm2,s,1) was observed with the conditioned hydrogel composite. Cyclic voltammograms in buffer containing H2O2 showed an absence of redox peaks for electrodes coated with PPy-containing membranes, suggesting possible chemical oxidation of polypyrrole by the oxidant [source] Construction of a novel sensor based on electropolymerization of carmine for voltammetric determination of 4-nitrophenolJOURNAL OF APPLIED POLYMER SCIENCE, Issue 5 2007Chunya Li Abstract 4-Nitrophenol (4-NP) has been determined with voltammetric technique based on a novel sensor fabricated by electropolymerization of carmine on a glassy carbon electrode (GCE). An obvious reduction peak located at about ,0.700 V and a couple of redox peaks that were not well-defined were observed in the potential range of ,1.00 to 0.600 V. Compared with its voltammetric behavior on a bare GCE, the reduction peak potential shifted positively and the peak current increased significantly. All experimental parameters were optimized and linear sweep voltammetry was proposed for its determination. In the optimal conditions, the reduction peak current was proportional to the 4-NP concentration over the concentration range from 5.00 × 10,8 to 1.00 × 10,5 mol L,1, and the detection limit was 1.00 × 10,8 mol L,1 after 200 s of accumulation. The high sensitivity and selectivity of the sensor was demonstrated by its practical application for the determination of trace amounts of 4-NP in lake water. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3271,3277, 2007 [source] Electroactive Copolymers with Oligoanilines in the Main Chain via Oxidative Coupling PolymerizationMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 18 2006Danming Chao Abstract Summary: By oxidative coupling polymerization of the macromonomer of oligoaniline and p -phenylenediamine, we have prepared an electroactive copolymer, exhibiting an exciting molecular structure, and interesting spectroscopic and electrochemical properties. The polymerization characteristics and structure of the copolymer were systematically studied by gel permeation chromatography (GPC), Fourier-transform infrared (FTIR) spectroscopy, 1H NMR spectroscopy and X-ray powder diffraction (XRD). UV-vis spectra were used to monitor the chemical oxidation process of the reduced copolymer. The electrochemical activity of the copolymer was tested in 1.0 M H2SO4 aqueous solution. Three redox peaks were shown, which is different to that for polyaniline. The thermal properties of the copolymer were also evaluated, by thermogravimetric analysis (TGA); the electrical conductivity is about 5.53,×,10,5 Scm,1 at room temperature, upon a preliminarily, proton-doped experiment. Synthesis of the copolymer. [source] Electricity generation from the treatment of wastewater with a hybrid up-flow microbial fuel cellBIOTECHNOLOGY & BIOENGINEERING, Issue 1 2010Krishna P. Katuri Abstract The performance of a prototype up-flow single-chambered microbial fuel cell (MFC) for electrical power generation using brewery wastewater as fuel is reported. The designed reactor consisted of three zones, namely a lower anaerobic digestion zone, a central MFC zone, and an upper effluent clarifier zone. Tests were conducted in batch mode using a beer wastewater as the fuel/electron donor (COD concentration: 430,mg/L) and mixed consortia (both sewage microflora and anaerobic sludge) as a source of electrogenic bacteria. A stable current density of ,2,270,mA/m2 was generated under continuous polarization with a constant external resistance (0.01,k,) and cell polarization gave a peak power density of 330,mW/m2 at a current density of 1,680,mA/m2. Electrochemical impedance analysis showed that the overall internal resistance of the reactor was quite low, that is, 8.0,,. Cyclic voltammetric analysis of the anodic biofilm at low scan rate revealed quite complex processes at the anode, with three redox peaks, at potentials of 116, 214, and 319,mV (vs. NHE). Biotechnol. Bioeng. 2010;107: 52,58. © 2010 Wiley Periodicals, Inc. [source] Chemical Bonding of Fullerene and Fluorinated Fullerene on Bare and Hydrogenated DiamondCHEMPHYSCHEM, Issue 9 2008Ti Ouyang Abstract We investigate the interface between a C60 fullerite film, C60F36, and diamond (100) by using core-level photoemission spectroscopy, cyclic voltammetry (CV), and high-resolution electron energy loss spectroscopy (HREELS). We show that C60 can be covalently bonded to reconstructed C(100)-2×1 and that the bonded interface is sufficiently robust to exhibit characteristic C60 redox peaks in solution. The bare diamond surface can be passivated against oxidation and hydrogenation by covalently bound C60. However, C60F36 is not as stable as C60 and desorbs below 300,°C (the latter species being stable up to 500,°C on the diamond surface). Neither C60 fullerite nor C60F36 form reactive interfaces on the hydrogenated surface,they both desorb below 300,°C. The surface transfer doping process of hydrogenated diamond by C60F36 is the most evident one among all the adsorbate systems studied (with a coverage-dependent band bending induced by C60F36). [source] Nucleic Acid Biosensor for Detection of Human Immunodeficiency Virus Using Aquabis(1,10-phenanthroline)copper(II) Perchlorate as Electrochemical IndicatorCHINESE JOURNAL OF CHEMISTRY, Issue 1 2008Shu-Yan NIU Abstract The electrochemical behavior of aquabis(1,10-phenanthroline)copper(II) perchlorate [Cu(H2O)(phen)2]·2ClO4, where phen=1,10-phenanthroline, on binding to DNA at a glassy carbon electrode (GCE) and in solution, was described. Cyclic voltammetry (CV) and differential pulse voltammetry (DPV) results showed that [Cu(H2O)(phen)2]2+ had excellent electrochemical activity on the GCE with a couple of quasi-reversible redox peaks. The interaction mode between [Cu(H2O)(phen)2]2+ and double-strand DNA (dsDNA) was identified to be intercalative binding. An electrochemical DNA biosensor was developed with covalent immobilization of human immunodeficiency virus (HIV) probe for single-strand DNA (ssDNA) on the modified GCE. Numerous factors affecting the probe immobilization, target hybridization, and indicator binding reactions were optimized to maximize the sensitivity and speed of the assay. With this approach, a sequence of the HIV could be quantified over the range from 7.8×10,9 to 3.1×10,7 mol·L,1 with a linear correlation of ,=0.9987 and a detection limit of 1.3×10,9 mol·L,1. [source] Electrochemical Preparation and Characterization of Lanthanum Hexacyanoferrate Modified ElectrodeCHINESE JOURNAL OF CHEMISTRY, Issue 2 2005Wu Ping Abstract An electroactive polynuclear inorganic compound of rare earth metal hexacyanoferrate, lanthanum hexacyanoferrate (LaHCF), was prepared by electrochemical deposition on the surface of a glassy carbon electrode with a potential cycling procedure. The cyclic voltammogram of LaHCF exhibits a pair of well-defined redox peaks with the formal potential of 208 mV (vs. SCE) at a scan rate of 100 mV/s in 0.2 mol/L NaCl solution and the redox peak currents increase linearly with the square root of the scan rate up to 1000 mV/s. The effects of the concentration of supporting electrolyte on the electrochemical characteristics of LaHCF were studied by voltammetry. LaHCF was also characterizated by scanning electron microscope (SEM), FTIR and XPS techniques. [source] | |||||||||||||