Home About us Contact
|
Home About us Contact | ||
|
|
||
Electrochemical Study (electrochemical + study)
Selected AbstractsElectrochemical Study of Anionic Ferrocene Derivatives Intercalated in Layered Double Hydroxides: Application to Glucose Amperometric BiosensorsELECTROANALYSIS, Issue 3-5 2009Christine Mousty Abstract Layered double hydroxides (Zn2Cr(OH)6X,nH2O LDH) containing (3-sulfopropyl)ferrocene-carboxylate (FcPSO3) and 1,1,-bis(3-sulfopropyl)ferrocene-carboxylate (Fc(PSO3)2) as interlayer anions (X) have been prepared by the co-precipitation method and characterized by PXRD, FTIR, SEM and XPS. The electrochemical behavior of these hybrid materials has been evaluated by cyclic voltammetry. A new amperometric biosensor based on the immobilization of glucose oxidase in ZnCr-FcPSO3 hybrid material was presented, the intercalated anions playing the role of mediators that shuttle electrons between the FAD centers in the enzyme and the electrode surface. The performance of the resulting biosensor for glucose determination under anaerobic conditions was evaluated by chronoamperometry at 0.5,V. The sensitivity (65,mA M,1 cm,2) determined in the concentration range 10,25,,M is higher than sensitivities reported for other glucose biosensors based on LDH host matrices. [source] Biosensor for Hepatitis B Virus DNA PCR Product and Electrochemical Study of the Interaction of Di(2,2,-bipyridine)osmium(III) with DNAELECTROANALYSIS, Issue 19 2004Hongtao Zhao Abstract The strategy for electrochemical detection of HBV DNA PCR product (181,bps) was designed by covalently immobilizing single-stranded HBV DNA on preoxidized glassy carbon electrode surface. The immobilization of single stranded DNA was verified by AC impedance spectra. The following hybridization reaction on surface was evidenced by electrochemical methods using [Os(bpy)2Cl2]+ as an electroactive indicator. The interactions of [Os(bpy)2Cl2]+ with calf thymus single and double stranded DNA immobilized on preoxidized glassy carbon electrodes were studied. [Os(bpy)2Cl2]+ could bind preferentially to the duplex DNA by intercalating to base pairs. The intrinsic binding constant of [Os(bpy)2Cl2]+ with calf thymus DNA was calculated to be 1.21×104,M,1. Using [Os(bpy)2Cl2]+ as an electrochemical hybridization indicator, the HBV DNA sensor has been used to detect qualitatively target HBV DNA in solution with high sensitivity and selectivity. [source] Synthesis and Electrochemical Study of an Original Copper(II)-Capped Salen,Cyclodextrin ComplexEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 29 2010Elise Deunf Abstract A new metallocapped cyclodextrin (CD) was synthesized by the regioselective debenzylation, induced by diisobutylaluminium hydride (DIBAL-H), of perbenzylated cyclodextrins. This reaction allowed for the efficient preparation of an unprecedented CD,salen type copper(II) complex. The electrochemical behavior of both the bound and unbound CD,salen compounds was investigated by cyclic voltammetry. Notably, it was shown that the presence of tert -butyl groups at the ortho - and para -positions of the salen aromatic rings stabilized the copper(II) phenoxyl radical species that was generated upon the one-electron oxidation of the starting compound. Importantly, this stabilization remained effective when the salen-type ligand was covalently attached to the CD. This allowed for investigations of the reactivity of the copper(II) phenoxyl radical complex towards a primary alcohol to be performed by cyclic voltammetry. This reaction can be considered as mimicking the behavior of galactose oxidase. However, under these conditions, no reactivity was observed in the presence of benzyl alcohol. This may be due to distortion, either of the initially square planar salen ligand after its grafting to the CD primary face, and/or of the CD itself. On the other hand, the electrochemical reduction of the un-grafted copper(II) salen-type ligand led to a transient anionic species that exhibited significant stability on the time-scale of the slow cyclic voltammetry measurement in the absence of the CD, but was unstable in the presence of the CD. In the latter case, it was demonstrated that the anionic species was protonated by the CD. Importantly, this protonation was not fast enough to prevent catalytic activation of iodomethane by the electro-generated copper(I)-capped salen CD complex. [source] A Magnetostructural and Electrochemical Study of CuII and FeIII Complexes Containing a Tetradentate Aminebis(phenolate) Ligand with a Pendent Tetrahydrofuran GroupEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 16 2007Elham Safaei Abstract Ligating properties of a tetradentate ligand 2-{bis[(3,5-di- tert -butyl-2-hydroxybenzyl)amino]methyl}tetrahydrofuran,H2L, with [O,O,N,O]-donor atoms towards CuII and FeIII are described. The ligand H2L yields both mononuclear LFeIII(acac) (1) and dinuclear [L2FeIII2(,-OCH3)-(,-OH)] (2), [L2FeIII2(,-C2O4)] (3) and [L2CuII2] (4) complexes, which were characterized by various physical techniques, including X-ray diffraction, Mössbauer, electrochemical and magnetic susceptibility (2,290 K) measurements. That the electrochemical oxidations are ligand-centered, i.e. formation of phenoxyl radicals from the coordinated phenolates, have been shown by voltammetric methods. Complexes 2,4 display antiferromagnetic exchange coupling of the neighbouring metal centers. Comparison of the evaluated weak exchange coupling constants (J) with the literature values leads to the conclusion that the angle Cu,O,Cu, is not the only determinant for the nature of the exchange coupling and the capability of the bridging ligands as mediators for spin coupling in case of FeIII follows the order phenoxide , methoxide > hydroxide. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source] Comparative Electrochemical Study of Unsubstituted and Substituted Bis(phthalocyaninato) Rare Earth(III) ComplexesEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 3 2004Peihua Zhu Abstract The electrochemistry of homoleptic substituted phthalocyaninato rare earth double-decker complexes M(TBPc)2 and M(OOPc)2 [M = Y, La...Lu except Pm; H2TBPc = 3(4),12(13),21(22),30(31)-tetra- tert -butylphthalocyanine, H2OOPc = 3,4,12,13,21,22,30,31-octakis(octyloxy)phthalocyanine] has been comparatively studied by cyclic voltammetry (CV) and differential pulse voltammetry (DPV) in CH2Cl2 containing 0.1 M tetra- n -butylammonium perchlorate (TBAP). Two quasi-reversible one-electron oxidations and three or four quasi-reversible one-electron reductions have been revealed for these neutral double-deckers of two series of substituted complexes, respectively. For comparison, unsubstituted bis(phthalocyaninato) rare earth analogues M(Pc)2 (M = Y, La...Lu except Pm; H2Pc = phthalocyanine) have also been electrochemically investigated. Two quasi-reversible one-electron oxidations and up to five quasi-reversible one-electron reductions have been revealed for these neutral double-decker compounds. The three bis(phthalocyaninato)cerium compounds display one cerium-centered redox wave between the first ligand-based oxidation and reduction. The half-wave potentials of the first and second oxidations and first reduction for double-deckers of the tervalent rare earths depend on the size of the metal center. The difference between the redox potentials of the second and third reductions for MIII(Pc)2, which represents the potential difference between the first oxidation and first reduction of [MIII(Pc)2],, lies in the range 1.08,1.37 V and also gradually diminishes along with the lanthanide contraction, indicating enhanced ,,, interactions in the double-deckers connected by the smaller, lanthanides. This corresponds well with the red-shift of the lowest energy band observed in the electronic absorption spectra of reduced double-decker [MIII(Pc,)2], (Pc, = Pc, TBPc, OOPc). (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source] Synthesis and Electrochemical Study of Novel Thiadiazolo-Ferrocene DerivativesCHINESE JOURNAL OF CHEMISTRY, Issue 1 2005Yong-Jia Shang Abstract Three novel thiadiazolo-ferrocence derivatives containing long chain alkyl group were synthesized and characterized. The voltammetric behaviour of these thiadaizolo-ferrocene derivatives was studied on gold electrode (diameter 1 mm) in CH2Cl2/0.2 mol/L tetra- n -butylammonium hexafluorophosphate. The influence of , -cyclodextrin on the voltammetric behaviour of the compounds was also studied. [source] Synthesis and Crystal Structure of the Copper Complex of 7,16-Bis(2-hydroxy-5-methylbenzyl)-1,4,10,13-tetraoxa-7,16-diazacyclooctadecaneCHINESE JOURNAL OF CHEMISTRY, Issue 1 2004Shu-Lan Ma Abstract A lariat crown ether ligand 7.16-bis (2-hydroxy-5-methylbenzyl)-1,4,10,13-tetraoxa-7,16-diazacyclooctadecane (Ll) has been prepared via one-pot Mannich reaction. Its copper(II) complex Cu-Ll was synthesized and characterized by elemental analysis, IR and UV-visible spectroscopy. The crystal structure of the complex has been determined by X-ray diffraction analysis. The result shows that the copper(II) ion is six-coordinated by two nitrogen and four oxygen atoms, two from the crown ether and the other two from the deprotonated phenolate anions, forming an elongated octahedral complex. Electrochemical study indicates that the complex undergoes reversible reduction in DMF solution. [source] Electrochemical study on interaction of vincristine with tubulinCHINESE JOURNAL OF CHEMISTRY, Issue 11 2001Yong Yu Abstract In Tris (0.005 mol/L)-NaCl (0.05 mol/L) buffer solution (pH = 7.10), keeping temperature at 37°C, a highly sensitive reduction peak of the antitumor agent was obtained by linear sweep voltammetry. The peak potential is-1.56 V (vs. SCE). The peak current is proportional to the concentration of vincristine over the range of 2.1 ± 10,7 -4.2 ± 10,6 mol/L with the detection limit of 1.0 ± 10,7 mol/L. The behavior of the binding of vincristine to tubulin was studied. The results showed that the reaction of tubulin dimer with vincristine formed an electrochemically active complex to be 1:2. Its stability constant is 2.5 ± 1014. The reduction process of the complex is irreversible with adsorptive characteristics. [source] Comparison of the Electrochemical Reactivity of Carbon Nanotubes Paste Electrodes with Different Types of Multiwalled Carbon NanotubesELECTROANALYSIS, Issue 17 2008Xueling Li Abstract Carbon nanotubes (CNTs) are widely used in electrochemical studies. It is reported that CNTs with different source and dispersed in different agents [1] yield significant difference of electrochemical reactivity. Here we report on the electrochemical performance of CNTs paste electrodes (CNTPEs) prepared by multiwalled carbon nanotubes (MWNTs) with different diameters, lengths and functional groups. The resulting electrodes exhibit remarkable different electrochemical reactivity towards redox molecules such as NADH and K3[Fe(CN)6]. It is found that CNTPEs prepared by MWNTs with 20,30,nm diameter show highest catalysis to NADH oxidation, while CNTPEs prepared by MWNTs with carboxylate groups have best electron-transfer rate (The peak-peak separation (,Ep) is +0.108,V for MWNTs with carboxylate groups, +0.155,V for normal MWNTs, and +0.174,V for short MWNTs) but weak catalysis towards oxidation of NADH owing to the hydrophilicity of carboxylate groups. The electrochemical reactivity depends on the lengths of CNTs to some extent. The ,long' CNTs perform better in our study (The oxidation signals of NADH appear below +0.39,V for ,long' CNTs and above +0.46,V for the ,short' one totally). Readers may get some directions from this article while choose CNTs for electrochemical study. [source] Synthesis and Characterization of MWNTs/Au NPs/HS(CH2)6Fc Nanocomposite: Application to Electrochemical Determination of Ascorbic AcidELECTROANALYSIS, Issue 16 2008Jian-Ding Qiu Abstract In this article, a detailed electrochemical study of a novel 6-ferrocenylhexanethiol (HS(CH2)6Fc) self-assembled multiwalled carbon nanotubes-Au nanoparticles (MWNTs/Au NPs) composite film was demonstrated. MWNTs/Au NPs were prepared by one-step in situ synthesis using linear polyethyleneimine (PEI) as bifunctionalizing agent. HS(CH2)6Fc, which acted as the redox mediator, was self-assembled to MWNTs/Au NPs via Au-S bond. Transmission electron microscopy (TEM), energy-dispersive X-ray analysis (EDX), Fourier transformed infrared absorption spectroscopy (FT-IR), UV-visible absorption spectroscopy, and cyclic voltammetry were used to characterize the properties of the MWNTs/Au NPs/HS(CH2)6Fc nanocomposite. The preparation of the nanocomposite was very simple and effectively prevented the leakage of the HS(CH2)6Fc mediator during measurements. The electrooxidation of AA could be catalyzed by Fc/Fc+ couple as a mediator and had a higher electrochemical response due to the unique performance of MWNTs/Au NPs. The nanocomposite modified electrode exhibited excellent catalytic efficiency, high sensitivity, good stability, fast response (within 3,s) and low detection limit toward the oxidation of AA at a lower potential. [source] Electrochemical performance and microstructure characterization of nickel yttrium-stabilized zirconia anodeAICHE JOURNAL, Issue 6 2010Jingbo Liu Abstract A nickel and yttrium-stabilized zirconia (Ni-YSZ) composite is one of the most commonly used anode materials in solid oxide fuel cells (SOFCs). One of the drawbacks of the Ni-YSZ anode is its susceptibility to deactivation due to the formation of carbonaceous species when hydrocarbons are used as fuel supplies. We therefore initiated an electrochemical study of the influence of methane (CH4) on the performance of Ni-YSZ anodes by examining the kinetics of the oxidation of CH4 and H2 over operating temperatures of 600,800°C. Anode performance deterioration was then correlated with the degree of carbonization observed on the anode using ex-situ X-ray powder diffraction and scanning electron microscopy techniques. Results showed that carbonaceous species led to a significant deactivation of Ni-YSZ anode toward methane oxidation. © 2009 American Institute of Chemical Engineers AIChE J, 2010 [source] Synthesis and optical and electrochemical properties of novel copolymers containing alternating 2,3-divinylquinoxaline and hole-transporting unitsJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 24 2002Tzi-Yi Wu Abstract For the enhancement of charge affinity, electron-affinitive 2,3-divinylquinoxaline and a series of hole-transporting chromophores (iminodibenzyl, phenothiazine, dihexyloxybenzene, and didodecyloxydistyrylbenzene) were incorporated alternately into the polymeric main chain. The resulting copolymers (P1,P4) were basically amorphous materials and were thermally stable below 300 °C. The electronic structures, photoluminescence, and electrochemical properties of these copolymers were mainly determined by the electron-donating chromophores in the backbone. They showed significant positive solvatochromism in formic acid. An electrochemical study revealed that they exhibited lower band gaps (<2.3 eV) due to alternating donor and acceptor conjugated units (push,pull structure). Single-layer light-emitting diodes of aluminum, P1,P4, and indium tin oxide glass were fabricated, and preliminary electroluminescence spectra showed that P1, P3, and P4 were orange-emitting materials. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 4570,4580, 2002 [source] A comparative electrochemical study of commercial and model aluminium alloy (AA5050)MATERIALS AND CORROSION/WERKSTOFFE UND KORROSION, Issue 6 2009P. Premendra Abstract A comparative electrochemical study of commercially recycled AA5050 and model AA5050, in their as-cast state, is carried out to investigate the effect of recycling and furthermore the effect of trace elements like Pb, Cu, etc on electrochemical activation and filiform corrosion (FFC) susceptibility. A systematic combination of surface analytical techniques like scanning Kelvin probe force microscopy (SKPFM), scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) is used to study the composition and electrochemical behaviour of second phase particles. These results, together with localized breakdown measurements using the electrochemical micro-cell, elucidate the effect of recycling and the role played by trace elements in influencing the electrochemical behaviour of the alloy. [source] | |||||||||||||