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Electrochemical Activity (electrochemical + activity)
Selected AbstractsElectrochemical deposition of Pt nanoparticles on diamond substratesPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 9 2009Jingping Hu Abstract Platinum nanoparticles were deposited on polished smooth, as-grown large grain and small grain diamond substrates by a potentiostatic method. The influence of deposition potential and the morphology of BDD substrates were studied. A progressive nucleation along with spherical clusters was observed on smooth BDD electrode, accompanied with a heterogeneous segregation of platinum on diamond facets of higher electrochemical activities and a weak binding to the substrate. In contrast, an instantaneous nucleation was observed on as-grown small grain and large grain BDD electrodes, with a dendritic microstructure and a much larger specific active area. The platinum decorated as-grown smaller grain BDD electrodes show a much better electrochemical stability than the other electrodes investigated. [source] Electrochemiluminescence Based on Solid State Tri(4,7-diphenyl-1,10-phenanthroline) Ruthenium(II) Ditetrakis(4-chlorophenyl) Borate Immobilized on Carbon FibersELECTROANALYSIS, Issue 12 2010Chunhua Liu Abstract A simple method for immobilization of tri(4,7-diphenyl-1,10-phenanthroline) ruthenium(II) ditetrakis(4-chlorophenyl) borate ([Ru(dpp)3][(4-Clph)4B]2) on carbon fiber electrodes was developed. Excellent electrochemical activity and electrochemiluminescence (ECL) signal of the coated carbon fiber electrodes were observed using oxalate as the co-reactant. In addition, the effects of pH, scan rate, nitrogen and oxygen on ECL intensity were also studied. To demonstrate the reliability, the coated carbon fiber electrodes were used as ECL detectors and very low concentration of phenol was detectable (5.0×10,8,M). [source] Fabrication, Characterization, and Application of ,Sandwich-Type' Electrode Based on Single-Walled Carbon Nanotubes and Room Temperature Ionic LiquidELECTROANALYSIS, Issue 17 2008Xuzhi Zhang Abstract The much-enhanced electrochemical responses of potassium ferricyanide and methylene blue (MB) were firstly explored at the glassy carbon electrode modified with single-walled carbon nanotubes (SWNT/GCE), indicating the distinct electrochemical activity of SWNTs towards electroactive molecules. A hydrophobic room temperature ionic liquid (RTIL), 1-butyl-3-methylimidazolium hexafluorophosphate (BMIMPF6), was used as electrode modification material, which presented wide electrochemical windows, proton permeation and selective extraction ability. In consideration with the advantages of SWNTs and RTIL in detecting target molecules (TMs), a novel strategy of ,sandwich,type' electrode was established with TMs confined by RTIL between the SWNT/GCE and the RTIL membrane. The strategy was used for electrochemical detection of ascorbic acid (AA) and dopamine (DA), and detection limits of 400 and 80 fmol could be obtained, respectively. The selective detection of DA in the presence of high amount of AA could also be realized. This protocol presented many attractive advantages towards voltammetric detection of TMs, such as low sample demand, low cost, high sensitivity, and good stability. [source] Electrochemistry of Cytochrome P450 2B6 on Electrodes Modified with Zirconium Dioxide Nanoparticles and Platin ComponentsELECTROANALYSIS, Issue 7 2008Lei Peng Abstract The direct electrochemical and electrocatalytic behavior of the immobilized cytochrome P450 2B6 (CYP2B6) on zirconium dioxide nanoparticles (ZrO2) was investigated. The film of nano-structured ZrO2 that incorporated cytochrome P450 2B6 (CYP2B6) with colloidal paltin, which was stabilized by poly-lysine (Pt-PLL), was prepared on glassy carbon electrodes. In anaerobic solutions, the immobilized CYP2B6 exhibited a reversible electron transfer between the heme electroactive center of CYP2B6 and electrodes with a formal potential of ,(0.449±0.004) V at pH,7.4. In air-saturated solutions, an increased bioelectrocatalytic reduction current could be obtained with the CYP2B6-modified electrode with the addition of anticancer drugs, such as lidocaine. This leads to the construction of disposable biosensors for drugs by utilizing the electrochemical activity and catalytic reactions of the immobilized CYP2B6. [source] New Methylene Blue (NMB) Encapsulated in Mesoporous AlMCM-41 Material and Its Application for Amperometric Determination of Ascorbic Acid in Real SamplesELECTROANALYSIS, Issue 15 2007Shabnam Sohrabnezhad Abstract New methylene blue (NMB) dye incorporated into AlMCM-41 surfactant-free and hybrid surfactant-AlMCM-41 mesophase. UV-vis evidence shows that new methylene blue dye protonated in both cases of zeolites. New methylene blue is electroactive in zeolites and their electrochemical activity has been studied by cyclic voltammetry and compared to that of NMB in aqueous solutions. New methylene blue molecules are not released to the solution during CV measurements and are accessible to H3O+ ions. The presence of surfactant affects the kinetics of the redox process through proton ions diffusion. The midpoint potentials (Em) values show that new methylene blue dye incorporated into AlMCM-41 can be reduced easily with respect to solution new methylene blue. New methylene blue interacting with surfactant polar heads and residual Br, ions as a results, it shows a couple of peaks in high potential with respect to new methylene blue solution. The electrode made with methylene blue-AlMCM-41 without surfactant was used for the mediated oxidation of ascorbic acid. The anodic peak current observed in cyclic voltammetry was linearly dependent on the ascorbic acid concentration. The calibration plot was linear over the ascorbic acid concentration range 1.0×10,5 to 5.0×10,4 M. The detection limit of the method is 1.0×10,5 M, low enough for trace ascorbic acid determination in various real samples. [source] Characterization of Nanopore Electrode Structures as Basis for Amplified Electrochemical AssaysELECTROANALYSIS, Issue 19-20 2006Sebastian Neugebauer Abstract A nanopore electrode structure was fabricated consisting of ensembles of nanopores with separately addressable electrodes at the pore bottoms and the rims. A metal/insulator/metal layer structure allowed for adjusting the spacing between the bottom and rim electrodes to be in the range of about 200,nm. Pore diameters varied between 200 and 800,nm. The electrochemical properties of this electrode structure and its perspectives for applications in bioelectronics were studied using cyclic voltammetry and chronoamperometry along with high-resolution scanning electrochemical microscopy (SECM) in constant-distance mode. It was possible to visualize the electrochemical activity of a single nanometric electrode using high-resolution SECM in a combination of sample-generation-tip-collection mode and positive feedback mode. The SECM images suggested an influence of the unbiased rim electrode on redox amplification which was used as a basis for evaluating the feasibility of current amplification by means of redox cycling between the bottom and rim electrodes. Amplification factors superior to those obtained with interdigitated array electrodes could be demonstrated. [source] The Large Electrochemical Capacitance of Microporous Doped Carbon Obtained by Using a Zeolite Template,ADVANCED FUNCTIONAL MATERIALS, Issue 11 2007O. Ania Abstract A novel microporous templated carbon material doped with nitrogen is synthesized by using a two-step nanocasting process using acrylonitrile (AN) and propylene as precursors, and Na,Y zeolite as a scaffold. Liquid-phase impregnation and in,situ polymerization of the nitrogenated precursor inside the nanochannels of the inorganic scaffold, followed by gas-phase impregnation with propylene, enables pore-size control and functionality tuning of the resulting carbon material. The material thereby obtained has a narrow pore-size distribution (PSD), within the micropore range, and a large amount of heteroatoms (i.e., oxygen and nitrogen). In addition, the carbon material inherits the ordered structure of the inorganic host. Such features simultaneously present in the carbon result in it being ideal for use as an electrode in a supercapacitor. Although presenting a moderately developed specific surface area (SBET,=,1680,m2,g,1), the templated carbon material displays a large gravimetric capacitance (340,F,g,1) in aqueous media because of the combined electrochemical activity of the heteroatoms and the accessible porosity. This material can operate at 1.2,V in an aqueous medium with good cycleability,-beyond 10,000,cycles,and is extremely promising for use in the development of high-energy-density supercapacitors. [source] Bacterial community structure, compartmentalization and activity in a microbial fuel cellJOURNAL OF APPLIED MICROBIOLOGY, Issue 3 2006G.T. Kim Abstract Aims:, To characterize bacterial populations and their activities within a microbial fuel cell (MFC), using cultivation-independent and cultivation approaches. Methods and Results:, Electron microscopic observations showed that the fuel cell electrode had a microbial biofilm attached to its surface with loosely associated microbial clumps. Bacterial 16S rRNA gene libraries were constructed and analysed from each of four compartments within the fuel cell: the planktonic community; the membrane biofilm; bacterial clumps (BC) and the anode biofilm. Results showed that the bacterial community structure varied significantly between these compartments. It was observed that Gammaproteobacteria phylotypes were present at higher numbers within libraries from the BC and electrode biofilm compared with other parts of the fuel cell. Community structure of the MFC determined by analyses of bacterial 16S rRNA gene libraries and anaerobic cultivation showed excellent agreement with community profiles from denaturing gradient gel electrophoresis (DGGE) analysis. Conclusions:, Members of the family Enterobacteriaceae, such as Klebsiella sp. and Enterobacter sp. and other Gammaproteobacteria with Fe(III)-reducing and electrochemical activity had a significant potential for energy generation in this system. Significance and Impact of the Study:, This study has shown that electrochemically active bacteria can be enriched using an electrochemical fuel cell. [source] Chemical synthesis and electric properties of the conducting copolymer of aniline and o -aminophenolJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 23 2007Jing Zhang Abstract A copolymer, poly(aniline- co-o -aminophenol), was prepared chemically by using ammonium peroxydisulfate as an oxidant. The monomer concentration ratio of o -aminophenol to aniline strongly influences the copolymerization rate and properties of the copolymer. The optimum composition of a mixture for the chemical copolymerization consisted of 0.3 M aniline, 0.021 M o -aminophenol, 0.42 M ammonium peroxydisulfate, and 2 M H2SO4. The result of cyclic voltammograms in a potential region of ,0.20 to 0.80 V (vs.SCE) indicates that the electrochemical activity of the copolymer prepared under the optimum condition is similar to that of polyaniline in more acid solutions. However, the copolymer still holds the good electrochemical activity until pH 11.0. Therefore, the pH dependence of the electrochemical property of the copolymer is improved, compared with poly(aniline- co-o -aminophenol) prepared electrochemically, and is much better than that of polyaniline. The spectra of IR and 1H NMR confirm that o -aminophenol units are included in the copolymer chain, which play a key role in extending the usable pH region of the copolymer. The visible spectra of the copolymers show that a high concentration ratio of o -aminophenol to aniline in a mixture inhibits the chain growth. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5573,5582, 2007 [source] Comparative studies of solid-state synthesized poly(o -methoxyaniline) and poly (o -toluidine)POLYMERS FOR ADVANCED TECHNOLOGIES, Issue 11 2008Ruxangul Jamal Abstract Poly(o -methoxyaniline) (POMA) and poly(o -toluidine) (POT) salts doped with different acids (methanesulphonic acid (MeSA), trifluoroacetic acid (TFA), and hydrochloric acid (HCl)) were synthesized by using solid-state polymerization method. The polymers were characterized by Fourier transform infrared (FTIR) spectra, ultraviolet,visible (UV,Vis) spectrometry, X-ray diffraction (XRD), cyclic voltammetry (CV), and conductivity measurements. Transmission electron microscopy (TEM) was done to study the morphologies of POMA and POT salts. The FTIR and UV-Vis absorption spectra revealed that the reduced phase was predominant in POMA salts, and the pernigraniline phase was predominant in POT salts. It was found that POMA salts displayed higher doping level and conductivity. In contrast, POT salts were lower at doping levels and conductivity. In accordance with these results, the electrochemical activity was also found to be lower in POT salts. The XRD patterns showed that the POMA salts displayed higher crystallinity than POT salts. The results from TEM revealed that the morphologies of POMA salts were different from those of POT salts. Copyright © 2008 John Wiley & Sons, Ltd. [source] Characterization of electrochemical activity of a strain ISO2-3 phylogenetically related to Aeromonas sp. isolated from a glucose-fed microbial fuel cellBIOTECHNOLOGY & BIOENGINEERING, Issue 5 2009Kyungmi Chung Abstract The microbial communities associated with electrodes in closed and open circuit microbial fuel cells (MFCs) fed with glucose were analyzed by 16S rRNA approach and compared. The comparison revealed that bacteria affiliated with the Aeromonas sp. within the Gammaproteobacteria constituted the major population in the closed circuit MFC (harvesting electricity) and considered to play important roles in current generation. We, therefore, attempted to isolate the dominant bacteria from the anode biofilm, successfully isolated a Fe (III)-reducing bacterium phylogenetically related to Aeromonas sp. and designated as strain ISO2-3. The isolated strain ISO2-3 could grow and concomitantly produce current (max. 0.24,A/m2) via oxidation of glucose or hydrogen with an electrode serving as the sole electron acceptor. The strain could ferment glucose, but generate less electrical current. Cyclic voltammetry supported the strain ISO2-3 was electrically active and likely to transfer electrons to the electrode though membrane-associated compounds (most likely c-type cytochrome). This mechanism requires intimate contact with the anode surface. Scanning electron microscopy revealed that the strain ISO2-3 developed multiplayer biofilms on the anode surface and also produced anchor-like filamentous appendages (most likely pili) that may promote long-range electron transport across the thick biofilm. Biotechnol. Bioeng. 2009; 104: 901,910. © 2009 Wiley Periodicals, Inc. [source] Electrochemical Quartz Crystal Microbalance Studies on Enzymatic Specific Activity and Direct Electrochemistry of Immobilized Glucose Oxidase in the Presence of Sodium Dodecyl Benzene Sulfonate and Multiwalled Carbon NanotubesBIOTECHNOLOGY PROGRESS, Issue 1 2008Yuhua Su The electrochemical quartz crystal microbalance (EQCM) technique was utilized to monitor in situ the adsorption of glucose oxidase (GOD) and the mixture of GOD and sodium dodecyl benzene sulfonate (SDBS) onto Au electrodes with and without modification of multiwalled carbon nanotubes (MWCNTs) or SDBS/MWCNTs composite, and the relationship between enzymatic specific activity (ESA) and direct electrochemistry of the immobilized GOD was quantitatively evaluated for the first time. Compared with the bare gold electrode at which a little GOD was adsorbed and the direct electrochemistry of the adsorbed GOD was negligible, the amount and electroactivity of adsorbed GOD were greatly enhanced when the GOD was mixed with SDBS and then adsorbed onto the SDBS/MWCNTs modified Au electrode. However, the ESA of the adsorbed GOD was fiercely decreased to only 16.1% of the value obtained on the bare gold electrode, and the portion of adsorbed GOD showing electrochemical activity exhibited very low enzymatic activity, demonstrating that the electroactivity and ESA of immobilized GOD responded oppositely to the presence of MWCNTs and SDBS. The ESA results obtained from the EQCM method were well supported by conventional UV-vis spectrophotometry. The direct electrochemistry of redox proteins including enzymes as a function of their biological activities is an important concern in biotechnology, and this work may have presented a new and useful protocol to quantitatively evaluate both the electroactivity and ESA of trace immobilized enzymes, which is expected to find wider applications in biocatalysis and biosensing fields. [source] A General Method for the Rapid Synthesis of Hollow Metallic or Bimetallic Nanoelectrocatalysts with Urchinlike MorphologyCHEMISTRY - A EUROPEAN JOURNAL, Issue 15 2008Shaojun Guo Abstract We have reported a facile and general method for the rapid synthesis of hollow nanostructures with urchinlike morphology. In-situ produced Ag nanoparticles can be used as sacrificial templates to rapidly synthesize diverse hollow urchinlike metallic or bimetallic (such as Au/Pt) nanostructures. It has been found that heating the solution at 100,°C during the galvanic replacement is very necessary for obtaining urchinlike nanostructures. Through changing the molar ratios of Ag to Pt, the wall thickness of hollow nanospheres can be easily controlled; through changing the diameter of Ag nanoparticles, the size of cavity of hollow nanospheres can be facilely controlled; through changing the morphologies of Ag nanostructures from nanoparticle to nanowire, hollow Pt nanotubes can be easily designed. This one-pot approach can be extended to synthesize other hollow nanospheres such as Pd, Pd/Pt, Au/Pd, and Au/Pt. The features of this technique are that it is facile, quick, economical, and versatile. Most importantly, the hollow bimetallic nanospheres (Au/Pt and Pd/Pt) obtained here exhibit an area of greater electrochemical activity than other Pt hollow or solid nanospheres. In addition, the ,6,nm hollow urchinlike Pt nanospheres can achieve a potential of up to 0.57,V for oxygen reduction, which is about 200,mV more positive than that obtained by using a ,6,nm Pt nanoparticle modified glassy carbon (GC) electrode. Rotating ring-disk electrode (RRDE) voltammetry demonstrates that ,6,nm hollow Pt nanospheres can catalyze an almost four-electron reduction of O2 to H2O in air-saturated H2SO4 (0.5,M). Finally, compared to the ,6,nm Pt nanoparticle catalyst, the ,6,nm hollow urchinlike Pt nanosphere catalyst exhibits a superior electrocatalytic activity toward the methanol oxidation reaction at the same Pt loadings. [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] | ||||||||||||||||