Home About us Contact
|
Home About us Contact | ||
|
|
||
Electrochemical Techniques (electrochemical + techniques)
Selected AbstractsElectrochemical detection of neurotransmitters in the gut wallNEUROGASTROENTEROLOGY & MOTILITY, Issue 11 2008P. Vanden Berghe Abstract, Cells interact with each other by releasing signalling molecules, which can activate or inactivate target cells. In order to understand how coordination results from this communication, accurate measurements of these signalling molecules are prerequisite. Several different techniques exist to monitor and quantify these compounds, including enzymatic and histochemical assays, electrophysiological and optical recordings. However, there has been little use of electrochemical recordings in gastroenterological research, although these are very fast and sensitive. Electrochemical techniques rely on the simple fact that electroactive molecules can be oxidized at a given potential. The currents, elicited by the oxidation, are directly proportional to the concentration of the compound. In the current issue of Neurogastroenterology and Motility, electrochemical detection was successfully applied to measure nitric oxide (NO) from intestinal preparations. Although there are some important specificity, timing and spatial aspects to consider, this direct NO-probing technique is definitely a great asset to the field of gastrointestinal research and advances our understanding of NO signalling in the intestinal wall. [source] Green Approaches to Field Nitrate Analysis: An Electroanalytical PerspectiveELECTROANALYSIS, Issue 7 2009Radha Desai Abstract The different approaches that have been taken in the development of analytical methods for the determination of nitrate within the field are reviewed. The emphasis has been placed on providing a critical appraisal of the chemistry that underpins current commercial systems and the need to remove the dependence on heavy metal and concentrated acid components. The search for more environmentally acceptable and user friendly systems has long been pursued and the present communication seeks to explore the recent development in portable testing technologies and how they might evolve in the future. In particular, the role of electrochemical techniques in the latter are investigated and their potential application compared and contrasted with the more traditional wet chemical detection strategies. [source] Preparation of Novel Arrays Silver Nanoparticles Modified Polyrutin Coat-Paraffin-Impregnated Graphite Electrode for Tyrosine and Tryptophan's OxidationELECTROANALYSIS, Issue 8 2008Guan-Ping Jin Abstract A novel array silver nanoparticles and Rutin complex film modified paraffin-impregnated graphite electrode was proposed in this work (denoted as Ag/Rutin/WGE). The characteristics were investigated by the field emission scanning electron microscopy (FE-SEM), infrared spectra (IR), UV-visible (UV), X-ray photoelectron spectroscopy (XPS) and electrochemical techniques. Silver ions were gradually chelated by polyrutin film at 4,-oxo-5,-OH and 5-OH-4-oxo sites accompanying adsorption, then. Silver nanoparticles were highly-dispersed electrodeposited on polyrutin film. The electrochemical behaviors of tyrosine (Tyr) and tryptophan (Trp) were studied by cyclic voltammetry (CV) and differential pulse voltammetry (DPV) techniques. The Ag/Rutin/WGE electrode shows overlapping catalysis for the oxidation of Tyr and Trp. The linear response of Tyr and Trp were 0.3,10.0 and 0.7,70.0,,M with detection limit of 0.07 and 0.1,,M in a signal-to-noise ratio of 3. [source] Recent Advances in Electrochemical Enzyme ImmunoassaysELECTROANALYSIS, Issue 21 2005María Díaz-González Abstract Enzyme immunoassays (EIAs) are currently the predominant analytical technique for the quantitative determination of a broad variety of analytes in clinical, medical, biotechnological, and environmental significance. Although the most common detection methods for EIAs are based on spectroscopic measurements, electrochemical techniques, due to their high sensitivity, selectivity, simplicity and low cost, have emerged as a very attractive alternative to carry out the detection step in this kind of assays. The intention of this review is to cover the progress and development in integrating electrochemical detection methods with EIAs, over the past five years. [source] Amperometric Detection of Catecholamine Neurotransmitters Using Electrocatalytic Substrate Recycling at a Laccase ElectrodeELECTROANALYSIS, Issue 2 2005Yvonne Ferry Abstract An enzyme electrode based on the coimmobilization of an osmium redox polymer and laccase on glassy carbon electrodes has been applied to ultra sensitive amperometric detection of the catecholamine neurotransmitters dopamine, epinephrine and norepinephrine, resulting in nanomolar detection limits, as low as 4,nM for dopamine. The sensitivity of the electrode is due to signal amplification via oxidation of the catecholamine by the immobilized laccase, which is regenerated by concomitant reduction of oxygen to water, coupled to the electrocatalytic re-reduction of the oxidized catecholamine by the osmium redox complex: electrocatalytic substrate recycling. In addition because the sensor can be operated in reductive mode at ,0.2,V (vs. Ag/AgCl), noise and interferences are diminished. Combined with its high sensitivity this enzyme electrode also exhibited excellent selectivity allowing the detection of catecholamines in the presence of ascorbic acid. However, differentiation between the current responses achieved for the three catecholamines is not possible. The effective mode of constant recycling, resulting in amplification of the current response, of the laccase enzyme electrode sensor combined with the inherent advantages of using electrochemical techniques holds great promise for the future of catecholamine detection and monitoring. [source] Study of the Complexation, Adsorption and Electrode Reaction Mechanisms of Chromium(VI) and (III) with DTPA Under Adsorptive Stripping Voltammetric ConditionsELECTROANALYSIS, Issue 19 2003Sylvia Sander Abstract The complexation of Cr(III) and Cr(VI) with diethylenetriaminepentaacetic acid (DTPA), the redox behavior of these complexes and their adsorption on the mercury electrode surface were investigated by a combination of electrochemical techniques and UV/vis spectroscopy. A homogenous two-step reaction was observed when mixing Cr(III), present as hexaquo complex, with DTPA. The first reaction product, the electroactive 1,:,1 complex, turns into an electroinactive form in the second step. The results indicate that the second reaction product is presumably a 1,:,2 Cr(III)/DTPA complex. The electroreduction of the DTPA-Cr(III) complex to Cr(II) was found to be diffusion rather than adsorption controlled. The Cr(III) ion, generated in-situ from Cr(VI) at the mercury electrode at about ,50,mV (vs. Ag|AgCl) (3,mol,L,1 KCl), was found to form instantly an electroactive and adsorbable complex with DTPA. By means of electrocapillary measurements its surface activity was shown to be 30 times higher than that of the complex built by homogenous reaction of DTPA with the hydrated Cr(III). Both components, DTPA and the in-situ built complex Cr(III) ion were found to adsorb on the mercury electrode. The effect of nitrate, used as catalytic oxidant in the voltammetric determination method, on the complexation reaction and on the adsorption processes was found to be negligible. The proposed complex structures and an overall reaction scheme are shown. [source] Sensitive Adsorptive Stripping Voltammetric Methodologies for the Determination of Melatonin in Biological FluidsELECTROANALYSIS, Issue 9 2003L. Corujo-Antuña Abstract The reversible redox process that melatonin presented on carbon paste electrodes was the basis of a sensitive methodology for the determination of this hormone. From all the processes presented by this hormone, this was never used before as the basis of voltammetric measurements for melatonin determination. Therefore, parameters that affected the cyclic voltammetric signal were studied. A limit of detection as low as 9×10,11,M was obtained when optimized alternating current voltammetry was employed. The reproducibility was excellent due to an adequate pretreatment of the solid electrode (RSD=2.7%, n=10). A comparison with methodologies that employ different electrochemical techniques from the point of view of their analytical characteristics was made. This methodology has proved to be suitable for the determination of melatonin in biological fluids. [source] Electrochemical Biosensor for the Detection of Interaction Between Arsenic Trioxide and DNA Based on Guanine SignalELECTROANALYSIS, Issue 7 2003Mehmet Ozsoz Abstract The interaction of arsenic trioxide (As2O3) with calf thymus double-stranded DNA (dsDNA), calf thymus single-stranded DNA (ssDNA) and also 17-mer short oligonucleotide (Probe,A) was studied electrochemically by using differential pulse voltammetry (DPV) with carbon paste electrode (CPE) at the surface and also in solution. Potentiometric stripping analysis (PSA) was employed to monitor the interaction of As2O3 with dsDNA in solution phase by using a renewable pencil graphite electrode (PGE). The changes in the experimental parameters such as the concentration of As2O3, and the accumulation time of As2O3 were studied by using DPV; in addition, the reproducibility data for the interaction between DNA and As2O3 was determined by using both electrochemical techniques. After the interaction of As2O3 with dsDNA, the DPV signal of guanine was found to be decreasing when the accumulation time and the concentration of As2O3 were increased. Similar DPV results were also found with ssDNA and oligonucleotide. PSA results observed at a low DNA concentration such as 1,ppm and a different working electrode such as PGE showed that there could be damage to guanine bases. The partition coefficients of As2O3 after interaction with dsDNA and ssDNA in solution by using CPE were calculated. Similarly, the partition coefficients (PC) of As2O3 after interaction with dsDNA in solution was also calculated by PSA at PGE. The features of this proposed method for the detection of DNA damage by As2O3 are discussed and compared with those methods previously reported for the other type of DNA targeted agents in the literature. [source] Ultrasonically Enhanced Voltammetric Analysis and Applications: An OverviewELECTROANALYSIS, Issue 5-6 2003Craig Abstract Ultrasonically enhanced voltammetric measurements have been successfully applied for the detection of a wide range of trace metals. These are reviewed and the beneficial effects of power ultrasound applied to electroanalysis highlighted, most notably the possibility for quantitative analysis in otherwise highly passivating media, where classical electrochemical techniques often fail. [source] Electrochemical Nitric Oxide Sensors for Biological Samples , Principle, Selected Examples and ApplicationsELECTROANALYSIS, Issue 1 2003Fethi Bedioui Abstract The discoveries made in the 1980s that NO could be synthesized by mammalian cells and could act as physiological messenger and cytotoxic agent had elevated the importance of its detection. The numerous properties of NO, that enable it to carry out its diverse functions, also present considerable problems when attempting its detection and quantification in biological systems. Indeed, its total free concentration in physiological conditions has been established to be in nanomolar range. Thus, detection of nitric oxide remains a challenge, pointing out the difficult dual requirements for specificity and sensitivity. Exception made for the electrochemical techniques, most of the approaches (namely UV-visible spectroscopy, fluorescence, electron paramagnetic resonance spectroscopy) use indirect methods for estimating endogenous NO, relying on measurements of secondary species such as nitrite and nitrate or NO-adducts. They also suffer from allowing only ex situ measurements. So, the only strategies that allow a direct and in vivo detection of NO are those based on the use of ultramicroelectrodes. The reality is that surface electrode modification is needed to make the ultramicroelectrode material selective for NO. Therefore, the design of modified electrode surfaces using organized layers is very attractive and provides the ideal strategy. This review addresses a global description of the various approaches that have involved chemically modified microelectrodes specially designed for the electrochemical detection of NO in biological media. Selected significant examples of applications in biological tissues are also reported in order to highlight the importance of this approach in having new insights into the modulatory role of NO in physiology and pathophysiology. [source] Synthesis of Triazole-Bridged Unsymmetrical Porphyrin Dyads and Porphyrin,Ferrocene ConjugatesEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 3 2010Vijayendra S. Shetti Abstract A simple method has been used to synthesize four porphyrin azides with cores such as N4, N3S, N2SO and N2S2 in 60,90,% yields by treating the corresponding aminoporphyrins with tert -butyl nitrite (tBuONO) and azidotrimethylsilane (TMSN3) in THF/CH3CN under mild reaction conditions. The hitherto unknown aminoporphyrins with heteroatom cores were synthesized from their corresponding nitroporphyrins by standard SnCl2/HCl reduction. The azidoporphyrins were used to synthesize six triazole-bridged unsymmetrical porphyrin dyads containing two different types of porphyrin sub-units as well as five triazole-bridged porphyrin,ferrocene conjugates under CuI -catalyzed "click" reaction conditions. Various CuI -catalyzed reaction conditions were studied and the best yields of triazole-bridged dyads and conjugates were obtained with CuI/DIPEA in THF/CH3CN at room temperature for overnight. The unsymmetrical porphyrin dyads and porphyrin,ferrocene conjugates were characterized by various spectroscopic and electrochemical techniques. In unsymmetrical porphyrin dyads, the NMR, absorption and electrochemical studies indicate a weak interaction between the two porphyrin sub-units. However, preliminary photophysical studies support an efficient singlet-singlet energy transfer from one porphyrin unit to another in five unsymmetrical dyads reported here. In porphyrin,ferrocene conjugates, the fluorescence of porphyrin was quenched significantly due to photo-induced electron transfer from ferrocene to porphyrin. [source] Evaluation of corrosion inhibitors for cooling water systems operating at high concentration cyclesMATERIALS AND CORROSION/WERKSTOFFE UND KORROSION, Issue 5 2009E. A. de Souza Abstract The present work aimed at evaluating AISI 1020 carbon steel corrosion resistance of a 6:4:1:1 (MoO/HEDP/PO/Zn2+) inhibitor mixture present in a solution which simulates an industrial cooling water system operating at high concentration cycles (1050 ppm Cl, and 450 ppm Ca2+). High concentration cycles are desirable, because system purge and treated water consumption are decreased. On the other hand, a high number of concentration cycles can increase the concentration of salts and dissolved impurities, causing corrosion, incrustations, and deposits inside the pipes, heat exchangers, and cooling towers. Thus, the chloride (Cl,) and calcium (Ca2+) ions aggressiveness was studied on the proposed inhibiting mixture, at the temperatures of 40 and 60,°C, through electrochemical techniques like open circuit potential measurements, anodic and cathodic polarization, and weight loss. The results showed that the inhibitor mixture conferred adequate protection to carbon steel in low concentrations, even in high aggressive media. [source] Comparison of electrochemical techniques during the corrosion of X52 pipeline steel in the presence of sulfate reducing bacteria (SRB)MATERIALS AND CORROSION/WERKSTOFFE UND KORROSION, Issue 10 2005R. Galvan-Martinez Abstract This work compares three electrochemical techniques, linear polarization resistance (LPR), electrochemical impedance spectroscopy (EIS) and electrochemical noise (EN), used in the study of corrosion of X52 steel samples in an environment containing a culture of sulfate reducing bacteria (SRB). The study emphasizes the different electrochemical information obtained when using these techniques in microbiologically influenced corrosion (MIC) studies. [source] Vertically aligned diamond nanowires: Fabrication, characterization, and application for DNA sensingPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 9 2009Nianjun Yang Abstract In this review, we introduce a novel procedure to fabricate vertically aligned diamond nanowires with controlled geometrical properties like length and distance between wires by use of nanodiamond particles as a hard mask and by use of reactive ion etching. We summarize the characterizations of nanowires by atomic force microscopy and scanning tunneling microscopy as well as electrochemical techniques. In the last section, we show biofunctionalization of nucleic acid molecules on diamond nanowires using electrochemically bond nitrophenyl molecules as linker for deoxyribonucleic acid (DNA) sensing. The tip biofunctionalization and performance of as-prepared DNA sensors are discussed in detail. [source] Gold-coated fused-silica sheathless electrospray emitters based on vapor-deposited titanium adhesion layersRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 14 2003Stefan Nilsson Gold-coated fused-silica electrospray (ES) emitters based on vapor-deposited adhesion layers of titanium have been manufactured to investigate the possibilities of producing durable ES emitters applicable in chip-based analytical devices. The stabilities of the emitters were studied by both electrospray and electrochemical experiments and a marked increase in the emitter lifetime, compared to that for Cr/Au coated emitters, was found for the Ti/Au emitters in the ES durability tests. This indicates that Ti (rather than Cr) adhesion layers should be used in association with large-scale fabrication of ES emitters by vapor-deposition techniques. The lifetime of about 500,700 hours also allowed the Ti/Au-coated emitter to be used as an integrated part of a capillary liquid chromatography column coupled to a mass spectrometer in a series of LC/MS experiments. The Ti/Au coating was further studied by electrochemical techniques and scanning electron microscopy in conjunction with X-ray spectroscopy. It is shown that the eventual failure of the Ti/Au emitters in ES experiments was due to an almost complete detachment of the gold layer. Experimental evidence suggests that the detachment of the gold coating was due to a reduced adhesion to the titanium layer during oxidation in positive electrospray. Most likely, this was caused by the formation of an oxide layer on the titanium film. It is thus shown that unlimited emitter stabilities are not automatically obtained even if the metallic adhesion layer is stabilized by an oxide formation under positive electrospray conditions. Copyright © 2003 John Wiley & Sons, Ltd. [source] Real-time measurement of serotonin release and motility in guinea pig ileumTHE JOURNAL OF PHYSIOLOGY, Issue 2 2006Paul P. Bertrand Enterochromaffin (EC) cells are sensors that detect chemical or mechanical stimuli and respond with release of serotonin (5-HT). 5-HT activates local motor reflexes, but whether local motor reflexes also evoke 5-HT release is unknown. The aim of the present study was to establish the relationship between the release of 5-HT and the enteric neural circuits controlling the movements of the intestine. Recordings were made from full-thickness preparations of guinea pig ileum using electrochemical techniques with carbon fibre electrodes to measure local concentrations of 5-HT. The tension in the circular muscle (CM) and longitudinal muscle (LM) was recorded with force transducers. The release of 5-HT from the EC cells was detected selectively and the timing of the events quantified. Pressure-evoked peristalsis caused detectable 5-HT release only when the recording site was invaded by a ring of CM contraction. Spontaneous and stretch-evoked reflex contraction of the CM and LM occurred simultaneously with 5-HT release. Paralysis of the smooth muscle significantly reduced the stretch-evoked release. Muscarinic agonists evoked reflexes that were associated with increases in tension in CM and LM simultaneous with 5-HT release. Tetrodotoxin abolished the coordination between the CM contraction and 5-HT release but not the direct activation of the CM and EC cells by the agonists. In conclusion, the correlation between local motor reflexes and 5-HT release observed in the present study is caused primarily by the contraction of the smooth muscle and subsequent deformation of the mucosa. The EC cell is, thus, a site of convergence for mechanical forces that contribute to the release of 5-HT during motor reflexes. [source] Fluorescent and Electrochemical Sensing of Polyphosphate Nucleotides by Ferrocene Functionalised with Two ZnII(TACN)(pyrene) ComplexesCHEMISTRY - A EUROPEAN JOURNAL, Issue 30 2010Zhanghua Zeng Dr. Abstract The [Fcbis{ZnII(TACN)(Py)}] complex, comprising two ZnII(TACN) ligands (Fc=ferrocene; Py=pyrene; TACN=1,4,7-triazacyclononane) bearing fluorescent pyrene chromophores linked by an electrochemically active ferrocene molecule has been synthesised in high yield through a multistep procedure. In the absence of the polyphosphate guest molecules, very weak excimer emission was observed, indicating that the two pyrene-bearing ZnII(TACN) units are arranged in a trans -like configuration with respect to the ferrocene bridging unit. Binding of a variety of polyphosphate anionic guests (PPi and nucleotides di- and triphosphate) promotes the interaction between pyrene units and results in an enhancement in excimer emission. Investigations of phosphate binding by 31P,NMR spectroscopy, fluorescence and electrochemical techniques confirmed a 1:1 stoichiometry for the binding of PPi and nucleotide polyphosphate anions to the bis(ZnII(TACN)) moiety of [Fcbis{ZnII(TACN)(Py)}] and indicated that binding induces a trans to cis configuration rearrangement of the bis(ZnII(TACN)) complexes that is responsible for the enhancement of the pyrene excimer emission. Pyrophosphate was concluded to have the strongest affinity to [Fcbis{ZnII(TACN)(Py)}] among the anions tested based on a six-fold fluorescence enhancement and 0.1,V negative shift in the potential of the ferrocene/ferrocenium couple. The binding constant for a variety of polyphosphate anions was determined from the change in the intensity of pyrene excimer emission with polyphosphate concentration, measured at 475,nm in CH3CN/Tris-HCl (1:9) buffer solution (10.0,mM, pH,7.4). These measurements confirmed that pyrophosphate binds more strongly (Kb=(4.45±0.41)×106,M,1) than the other nucleotide di- and triphosphates (Kb=1,50×105,M,1) tested. [source] A Radical-Anion Chain Mechanism Initiated by Dissociative Electron Transfer to a Bicyclic Endoperoxide: Insight into the Fragmentation Chemistry of Neutral Biradicals and Distonic Radical AnionsCHEMISTRY - A EUROPEAN JOURNAL, Issue 6 2008David Abstract The electron-transfer (ET) reduction of two diphenyl-substituted bicyclic endoperoxides was studied in N,N -dimethylformamide by heterogeneous electrochemical techniques. The study provides insight into the structural parameters that affect the reduction mechanism of the OO bond and dictate the reactivity of distonic radical anions, in addition to evaluating previously unknown thermochemical parameters. Notably, the standard reduction potentials and the bond dissociation energies (BDEs) were evaluated to be ,0.55±0.15,V and 20±3,kcal,mol,1, respectively, the last representing some of the lowest BDEs ever reported. The endoperoxides react by concerted dissociative electron transfer (DET) reduction of the OO bond yielding a distonic radical-anion intermediate. The reduction of 1,4-diphenyl-2,3-dioxabicyclo[2.2.2]oct-5-ene (1) results in the quantitative formation of 1,4-diphenylcyclohex-2-ene- cis -1,4-diol by an overall two-electron mechanism. In contrast, ET to 1,4-diphenyl-2,3-dioxabicyclo[2.2.2]octane (2) yields 1,4-diphenylcyclohexane- cis -1,4-diol as the major product; however, in competition with the second ET from the electrode, the distonic radical anion undergoes a ,-scission fragmentation yielding 1,4-diphenyl-1,4-butanedione radical anion and ethylene in a mechanism involving less than one electron. These observations are rationalized by an unprecedented catalytic radical-anion chain mechanism, the first ever reported for a bicyclic endoperoxide. The product ratios and the efficiency of the catalytic mechanism are dependent on the electrode potential and the concentration of weak non-nucleophilic acid. A thermochemical cycle for calculating the driving force for ,-scission fragmentation is presented, and provides insight into why the fragmentation chemistry of distonic radical anions is different from analogous neutral biradicals. [source] Electron Transfer to Sulfides and Disulfides: Intrinsic Barriers and Relationship between Heterogeneous and Homogeneous Electron-Transfer KineticsCHEMISTRY - A EUROPEAN JOURNAL, Issue 28 2007Belèn Meneses Abstract The electron-acceptor properties of series of related sulfides and disulfides were investigated in N,N -dimethylformamide with homogeneous (redox catalysis) and/or heterogeneous (cyclic voltammetry and convolution analysis) electrochemical techniques. The electron-transfer rate constants were determined as a function of the reaction free energy and the corresponding intrinsic barriers were determined. The dependence of relevant thermodynamic and kinetic parameters on substituents was assessed. The kinetic data were also analyzed in relation to corresponding data pertaining to reduction of diaryl disulfides. All investigated reductions take place by stepwise dissociative electron transfer (DET) which causes cleavage of the CalkylS or SS bond. A generalized picture of how the intrinsic electron-transfer barrier depends on molecular features, ring substituents, and the presence of spacers between the frangible bond and aromatic groups was established. The reduction mechanism was found to undergo a progressive (and now predictable) transition between common stepwise DET and DET proceeding through formation of loose radical anions. The intrinsic barriers were compared with available results for ET to several classes of dissociative- and nondissociative-type acceptors, and this led to verification that the heterogeneous and the homogeneous data correlate as predicted by the Hush theory. [source] A Ru-Hbpp-Based Water-Oxidation Catalyst Anchored on Rutile TiO2,CHEMSUSCHEM CHEMISTRY AND SUSTAINABILITY, ENERGY & MATERIALS, Issue 4 2009Laia Francàs Abstract In support of a split: A water oxidation catalyst based on ruthenium bis-(2-pyridyl)pyrazole anchored on rutile TiO2 was prepared. The performance of this new material with regard to its capacity to catalytically oxidize water to molecular oxygen in a heterogeneous phase was evaluated. Two organic ligands based on bis-(2-pyridyl)pyrazole (Hbpp) functionalized with a para -methylenebenzoic acid (Hbpp-Ra) or its ester derivative (Hbpp-Re) were prepared and characterized. The ester-functionalized ligand was then used to prepare a series of related dinuclear ruthenium complexes of general formula [RuII2(L- L)(bpp-Rn)(trpy)2]m+ (L-L=,-Cl, ,-acetato, or (H2O)2; n=e or a; trpy=2,2,:6,,2,,-terpyridine; m=2 or 3). The complexes were characterized in solution by 1D and 2D,NMR spectroscopy, UV/Vis spectroscopy, and electrochemical techniques. The [RuII2(,-Cl)(bpp-Re)(trpy)2](PF6)2 complex was further characterized in the solid state by X-ray diffraction. The complexes containing the free carboxylic acid ligand were anchored onto rutile TiO2 and treated with 0.1,M triflic acid solution to generate the homologous water-oxidation catalysts TiO2 -[RuII2(H2O)2(bpp-Ra)(trpy)2]2+. This new hybrid material catalytically oxidizes water to molecular oxygen in a heterogeneous manner using CeIV as chemical oxidant. The generation of molecular oxygen is accompanied by the formation of carbon dioxide as well as some leaching of the Ru catalyst. [source] Electrodeposition, Structure and Corrosion Resistance of Nanocrystalline Ni-W AlloyCHINESE JOURNAL OF CHEMISTRY, Issue 3 2004Fang-Zu Yang Abstract Ni,W alloy was electrodeposited from the electrolyte solution containing sodium tungstate, nickel sulfate and ammonium citrate. The electrodeposition, heat treatment, structure, surface morphology and corrosion resistance in w=0.03 NaCl solution, of Ni,W alloys were studied by means of DSC, XRD, SEM and electrochemical techniques. The results showed that the obtained Ni,W alloy electrodeposit with W weight content (ww=0.471) was presented in more typical nanocrystalline. After heat treatment at 400 C for 1 h, the phase structure of the deposits was not obviously changed whereas the agglomerate for the reunion of tiny grains on deposit surface caused the granule in a more smooth morphology, the microhardness was slightly increased and the corrosion resistance was enhanced. [source] | ||||||||||