bluuebunny/crossref_metadata_2025_split huggingface dataset:
Growth of Copper Films by Metal Organic Vapor Deposition Using (Pyrazolylborate)copper(I) Compounds
Authors: Plappert Elisabeth‐Charlotte , Stumm Thomas , van den Bergh Herbert , Hauert Roland , Dahmen Klaus‐Hermann 
Published: May 2005

AbstractCuCl reacts with Na[HB(R3R5pz)3] and phosphine (PR3) or isonitrile (CNR) to yield volatile (pyrazolylborate)copper(I) complexes. These compounds were evaluated as MOCVD precursors. Using [{HB(pz)3}Cu(PEt3)] and [{HB(pz)3}Cu(PMe3)], thin copper films were grown by thermal metal organic chemical vapor deposition in a low pressure reactor in the temperature range 150–350°C. Polycrystalline Cu‐phases were obtained at temperatures as low as 150°C. The metallic films were characterized by four‐point‐probe resistivity measurements, AES, and XPS, as well as AFM and SEM. Selective deposition on metal‐seeded surface sites was observed on Pt, Au, Al, and W versus SiO2. Anti‐selective deposition was found to occur on Pd‐seeded samples.
The Kinetics of the Catalyzed CVD of Monocrystalline α‐Silicon Nitride Filaments
Authors: Guggenberger Michael A. , Hüttinger Klaus J. 
Published: May 2005

AbstractCatalyzed chemical vapor deposition of α‐silicon nitride filaments from silicon subhydrides and ammonia was studied using calculation of nitrogen solubility in selected catalysts (silicon‐containing iron alloys), both in the solid and liquid‐state, by filament deposition experiments with catalysts of various composition and size, and by variation of the flow rates and partial pressures of precursor gases, the silicon subhydrides and ammonia. The results show that neither nitrogen solubility in, nor nitrogen diffusion through the catalyst plays a determining role in the deposition kinetics, as has been previously suggested. Instead, the deposition rate is determined by the partial dissociation of ammonia, which can be accelerated by adding diluent gases with a sufficiently high collision cross section. The catalyst material has an additional, strongly accelerating effect. The present state of research suggests that nitrogen is the preferred diluent gas and chromium an optimum alloying element.
Structural Properties of Yttria‐Stabilized Zirconia Films Grown on Silicon (001) Using MOCVD
Authors: Garcia Gemma , Casado Juan , Llibre Joan , Cifre Joan , Figueras Albert , Galí Salvador , Bassas Josep 
Published: May 2005

AbstractLayers of yttria‐stabilized zirconia with different yttria content were prepared using MOCVD. The variation of the crystallographic parameters of the cell, as well as the residual stress of the deposits have been studied by XRD as a function of yttria content. The maximum value of the stress has been correlated with a deformation of the cell, in the cubic domain, due to an intrinsic structural modification of the crystals.
Growth of Iron, Nickel, and Permalloy Thin Films by MOCVD for Use in Magnetoresistive Sensors
Authors: Lane Penelope A. , Wright Peter J. , Oliver Peter E. , Reeves Christopher L. , Pitt Anthony D. , Keen John M. , Ward Michael C. L. , Tilsley Matthew E. G. , Smith Nigel A. , Cockayne Brian , Harris I. Rex 
Published: May 2005

AbstractThin films of elemental iron and nickel, plus a wide composition range of iron‐nickel alloys, have been deposited by atmospheric pressure metal organic chemical vapor deposition at a growth temperature of 200°C, using iron pentacarbonyl and nickel tetracarbonyl as the source precursors. Detailed magnetoresistance measurements of the permalloy layers showed that the maximum value of magnetoresistance occurred at a composition of approximately 90 % Ni10 % Fe, and the maximum sensitivity occurred at approximately 80 % Ni20 % Fe, in accordance with literature values. In addition, both the application of an 80 mT magnetic field during deposition and the annealing of samples at temperatures higher than the growth temperature of 200°C improved the magnetic properties.
A new approach to coulometry for flow‐through systems
Authors: Bao L. Y. , Tian Z. W. 
Published: May 2005

AbstractA new method of flow‐through coulometry is presented. The fundamental principle is different from that in the conventional method. Two working electrodes are involved in the coulometric cell. An electrolysis efficiency of only 20 to 30% is required for the measurement. From the response coulombs (Q1 and Q2) of the two working electrodes, the charge (Qc) calculated by using Equation 4 correspond to an electrolysis efficiency of 100% and is independent of the temperature and flow rate.
Characterization of the voltammetric response at intracellular carbon ring electrodes
Authors: Lau Yau Yi , Chien Jennifer B. , Wong Danny K. Y. , Ewing Andrew G. 
Published: May 2005

AbstractThe intracellular response of ultrasmall carbon ring electrodes has been investigated. Adsorption of high molecular weight species (e.g., proteins, lipids, sugars) on the electrode surface appears to result in deterioration of the amperometric signal, making in vivo voltammetric measurements difficult. Assuming a linear dependence between the degree of electrode fouling and the number of scans taken in the neuronal microenvironment, an analytical method based on both pre‐ and postcalibration data is presented to evaluate the response obtained at deteriorating ultrasmall carbon ring electrodes during intracellular voltammetry. Additionally, poly(ester sulfonic acid)‐coated carbon ring electrodes have been used in an attempt to increase selectivity in intracellular voltammetry and to reduce the effects of electrode fouling. In vitro results obtained in solutions of dopamine, dihydroxyphenylacetic acid, and ascorbic acid indicate some exclusion of anionic species from the electrode by the negatively charged polymer film. Moreover, use of polymer‐coated electrodes in vivo result in such a decrease in the percentage of electrode fouling that the degradation of the response is only 45%. This leads to a more reproducible response and better detection limits compared to results from naked electrodes.
Use of EXAFS to probe electrode–solution interfaces
Authors: Dewald Howard D. 
Published: May 2005

AbstractA review of the development and application of extended X‐ray absorption fine structure (EXAFS) spectroscopy for in situ structural characterization of chemical processes at he electrode surface is presented. The designs of the in situ electrochemical cells developed to date are shown. Applications are presented from the areas of metal passivation, spectroelectrochemistry, modified electrodes, underpotential deposition, and adsorption.
Highly sensitive and selective voltammetric detection of dopamine with vertically separated interdigitated array electrodes
Authors: Niwa Osamu , Morita Masao , Tabei Hisao 
Published: May 2005

AbstractHighly sensitive (10−8 mol/dm3) and selective voltammetric detection of dopamine can be carried out with a closely spaced planar interdigitated array (IDA) or vertically separated new IDA electrodes. The sensitivity of dopamine was improved up to 10−8 mol/dm3 as a result of high collection efficiency and redox cycling, because twin electrodes with a very small gap make it possible to collect most of the active species oxidized at adjacent electrodes and then to return them to dopamine by reverse reduction before the chemical reaction has terminated. The influence of L‐ascorbic acid, which interferes with the detection of catecholamines, may be removed by oxidizing it at one electrode, because the oxidized acid converts rapidly to an electrochemically inactive species and is not detected at the other electrode. Dopamine was detected quantitatively in the presence of 10‐fold excess of L‐ascorbic acid in the same solution.
An electrochemical immunoassay for Clostridium perfringens phosholipase C
Authors: Cardosi Marco , Birch Stephen , Talbot Jane , Phillips Anthony 
Published: May 2005

AbstractA sensitive two‐site, enzyme‐linked immunoassay utilizing electrochemical detection has been developed for Clostridium perfringens phospholipase C (α toxin). Alkaline phosphatase conjugated to a mouse monoclonal antibody is used as the enzyme label. The enzyme activity is measured using 1‐naphthyl phosphate as the enzyme substrate. The enzyme‐generated naphthol is detected amperometrically in a thin‐layer cell at a glassy carbon electrode after chromatography on a 50 mm C8 reverse phase column. Two assay formats are described, based on either microtiter plates or polydispersed polymeric microbeads. The limits of detection of the two assay formats were 67.1 and 13.0 ng/mL, respectively, with a total assay time of less than one hour. The performance characteristics of three possible substrates for the alkaline phosphatase catalyzed reaction are also described.
Homogeneous light‐induced electron transfer between 9,10‐anthracenedione and sodium tetraphenylborate: A channel electrode study
Authors: Compton Richard G. , Fisher Adrian C. , Wellington R. Geoffrey , Bethell Donald 
Published: May 2005

AbstractThe electron transfer between excited‐state 9,10‐anthracenedione (325 nm) and sodium tetraphenylborate (tetraphenylboron sodium) in acetonitrile solution is shown to form the radical anion of 9,10‐anthracenedione together with the BPh radical. The latter is known to decompose to biphenyl and other Products. A new channel electrode methodology is developed and characterized to deduce the mechanism of the reaction and to quantify its kinetics.
An XPS investigation of the influence of bromide and iodide solutions on the surface of silver chloride coated ion‐selective electrodes
Authors: Strydom C. A. , van Staden J. F. , Strydom H. J. 
Published: May 2005

AbstractX‐Ray photoelectron spectroscopic (XPS) data of AgCl‐coated, ion‐selective electrodes exposed to solutions containing high concentrations of bromide and iodide ions revealed that the surface properties of the original electrode changed. The mixed phases, AgBrsCl1–s and AgIsCl1–s, seem to form initially on the electrode surface, with the existence of the AgICl phase much shorter than that of the AgBrCl phase. This indicates that the formation of the Agl surface layer is kinetically faster than the formation of the AgBr layer. In both cases XPS data showed the ultimate formation of AgBr and AgI layers on top of the original AgCl‐coated, ion‐selective electrode surface after being subjected to solutions containing either bromide or iodide ions. The conversion of the crystalline‐coated, chloride‐selective electrode surfaces to AgBr and AgI layers, however, transformed the chloride‐selective electrodes into bromide‐ or iodide‐selective electrodes with electrode properties different from those of the original electrode.
Flow injection analysis of myoglobin and hemoglobin at toluidine blue chemically modified electrode
Authors: Zhou Jianxun , Wang Erkang 
Published: May 2005

AbstractElectrodeposition of the phenothiazine mediator titrant toluidine blue onto a glassy carbon substrate at an appropriate potential was used to construct a toluidine blue chemically modified electrode (CME) exhibiting electrocatalytic reduction for myoglobin and hemoglobin. The CME catalyzed the hemoprotein electroreduction at the reduction potential of the mediator molecule. When the CME as used as a detector for flow injection analysis at a constant applied potential of −0.30 V vs. a saturated calomel electrode, it gave detection limits of 20 and 50 ng (1.2 and 0.78 pmol) injected myoglobin and hemoglobin, respectively, with a dynamic linear concentration range over 2 orders of magnitude. After a brief equilibration period, the CME retained nearly 90% of its initial myoglobin response over 8 hours of continuous exposure to the flow‐through system.
Peroxidase–ferrocene modified carbon paste electrode as an amperometric sensor for the hydrogen peroxide assay
Authors: Sánchez Pilar Domínguez , Ordieres Arturo José Miranda , García Agustín Costa , Blanco Paulino Tuñón 
Published: May 2005

AbstractA new enzymatic amperometric sensor for hydrogen peroxide based on a modified carbon paste electrode is described. Horseradish peroxidase and ferrocene mediator were immobilized by dissolution or dispersion in a graphite–paraffin oil paste. To prevent losses of immobilized chemicals under operational conditions, the electrode surface was coated with a Nafion membrane. The device exhibits a relatively fast response time (42 s for 95% of the steady‐state response) and yields currents linearly related to the hydrogen peroxide concentration over the 10−7 to 10−5 mol/L range in both static and flow injection operations. The slope of the calibration plot remained constant for more than 20 days. Flow injection assays of hydrogen peroxide at a sampling rate of about 70 injections per hour, with a relative standard deviation of 1.4%, are possible. An easy and low cost preparation procedure is described.
Voltammetric study of cadmium(II) ion in the presence of polysaccharides
Authors: Nadaly Anna M. , Ariño Cristina , Esteban Miquel , Casassas Enric 
Published: May 2005

AbstractComplex formation of Cd(II) with alginic and polygalacturonic acids is studied by normal pulse (NPP), reverse pulse (RPP), and differential pulse polarography (DPP), as well as by cyclic voltammetry (CV) and differential pulse anodic stripping voltammetry (DPASV). Titrations of Cd(II) with partially neutralized alginic or polygalacturonic acids, at different ionic strengths, by DPP and DPASV allow the precise determination of the apparent formation constant K of both systems. The systems appear to be labile on the different time scales of the various techniques. Adsorption of both polysaccharides, and the further induced adsorption of Cd(II), is evidenced clearly by NPP. On the other hand, the induced adsorption of Cd(II) is minimized under the conditions of RPP. The reversibility of the redox couple Cd2+/Cd(Hg) is not strongly affected by the presence of polysaccharides. Dependence of the apparent formation constants on the total ionic strength is reported.
Study of the radial and axial distribution of heavy metals in oak growth rings by stripping voltammetry
Authors: Queirolo F. , Valenta P. , Stegen S. , Sanchez A. M. 
Published: May 2005

AbstractThe concentrations of the heavy metals (Cd, Pb, Cu, and Zn) have been determined in oak growth rings from the polluted region of Königstein, Germany, by differential pulse anodic stripping voltammetry and compared to those in soil. The radial distribution was found to be the same for all four metals studied and features a distinct increase in the recent growth rings and a marginal increase in the transition zone between sapwood and heartwood. The toxic metals cadmium and lead are preferentially bound to lower parts of the tree, whereas for essential metals copper and zinc, monotonous axial distribution has been found in the range 0–5 m. This points to different degrees of mobility of heavy metal complexes in wood material.
Theoretical model of the response of pH‐based enzyme sensors
Authors: Głab Stanisław , Koncki Robert , Hulanicki Adam 
Published: May 2005

AbstractA theoretical kinetic model of a pH‐based enzymatic sensor has been developed. The transport phenomena of substrates and products of enzymatic reactions as well as of buffer components were taken into account. Protolytic equilibria were described by dissociation constants. It was also assumed that the kinetics of the enzymatic reaction is described by the Michaelis–Menten equation. The final equation for the steady‐state response of an enzyme‐based pH sensor describes the form of the calibration curve for this type of biosensor. This equation takes into account sample pH and buffer concentration, as well as kinetic parameters (Vmax, KM) of the enzymatic reaction. The proposed model is particularly useful for describing pH‐based enzyme sensors with thin enzymatic membranes.
Dissociation constants of sore anti‐inflammatory agents (α‐phenylpropionic acids) in lsopropyl and tert‐butyl alcohol media
Authors: Bosch Elisabeth , Rodés Carles , Rosés Martí 
Published: May 2005

AbstractThe pKa of several α‐phenylcarboxilic anti‐inflammatory drugs in both isopropyl and tert‐butyl alcohols have been determined by means of potentiometry. The dissociation constant values of their tetrabutylammonium salts, which are necessary for computation of the acidity constants, have been determined conductometrically. The results show that both the drug acid strength resolution and the pH break in titration curves are greater in tert‐butyl than in isopropyl alcohol, but both alcohols can be used in everyday titrations. Titrations in one commercial pharmaceutical preparation have been carried out successfully.
Assessment of sodium‐selective ion‐selective electrodes based on methyl ketone derivative of p‐tert‐butylcalix[4]arene
Authors: Telting‐Diaz Martin , Diamond Dermot , Smyth Malcolm R. , Seward Eileen M. , McKervey Anthony M. 
Published: May 2005

AbstractThe performance of a newly synthesized tetramethyl ketone calyx [4]arene ionophore in ion‐selective electrodes has been investigated. Optimization of the plasticized polyvinyl chloride membrane composition has produced electrodes that exhibit a Nernstian response for sodium ions. The best general characteristics exhibited by the electrodes were found when the ionophore mixed with 2‐nitrophenyl octyl ether as plasticizing agent, and potassium tetrakis (p‐chlorophenyl) rate as ion exchanger. Selectivity studies carried out with the electrode have shown excellent discrimination for sodium against potassium and lithium ions. In addition, the electrode displays a rapid response time, a detection limit be low 10−6 M for sodium, and a working life of at least 4 months. Determinations of sodium in plasma patient samples have been performed and the results obtained compared to those from flame photometry and two commercial clinical analyzers.
Amperometric glucose sensor using silicon oxide deposited gold electrodes
Authors: Yokoyama Kenji , Tamiya Eiichi , Karube Isao 
Published: May 2005

AbstractGlucose oxidase (GOD) immobilized electrodes using silicon oxide, were fabricated and their characteristics were evaluated. Silicon oxide deposited gold band (200 μm wide) and disk (1 mm diameter) electrodes were fabricated by vapor deposition of silicon monoxide. Alkylaminosilan and glutaraldehyde treatments were performed on the silicon oxide surface, followed by GOD immobilization. The GOD‐immobilized band electrode treated with 3‐aminopropyltriethoxysilane was characterized in a flow injection system. Hydrogen peroxide produced by the enzyme reaction was measured, resulting in a good response capable of high glucose concentration determination. The calibration curve was linear in the range between 1 to 200 mM. The GOD‐immobilized disk electrode treated with 3‐aminopropyldimethylethoxysilane was examined using electron transfer mediators. The effect of the thickness of silicon oxide on the response to glucose was investigated, leading to the highest, response at the electrode with the silicon oxide film that was 400 nm thick. In addition, a numerical analysis was performed, suggesting that immobilized GOD was located mainly in the vicinity of the silicon oxide surface.
Highly sensitive determination of L‐lactate and pyruvate by liquid chromatography and amperometric detection with lactate oxidase‐lactate dehydrogenase coimmobilized reactor involving amplification by substrate recycling
Authors: Yao Toshio , Kobayashi Naokazu , Wasa Tamotsu 
Published: May 2005

AbstractAn amperometric flow injection system with a lactate oxidase–lactate dehydrogenase coimmobilized reactor involving amplification by substrate recycling is used as a specific postcolumn detector system in liquid chromatography, to detect L‐lactate and pyruvate with high sensitivity. Both components are separated at a reversed phase column and are recycled enzymatically during the passage through the enzyme reactor in the presence of reduced nicotinamide adenine dinucleotide (NADH) and oxygen in the carrier stream. As a result of this recycling reaction, a large amount of hydrogen peroxidase is generated in the enzyme reactor which is detected amperometrically at a flow‐through peroxidase electrode in the presence of hexacyanoferrate(II) as a mediator. Linear determination range is 0.2–200 pmol for both L lactate and pyruvate. The detection limit is 0.02 pmol. The relative standard deviation obtained for this system at 2 pmol L‐lactate and pyruvate (n=5)is about 3.8%.
Synthesis and potentiometric selectivity study of acyclic formazanes
Authors: Attiyat A. S. , Badawy M. A. , Barsoum B. N. , Hanna H. R. , Ibrahim Y. A. , Christian G. D. 
Published: May 2005

AbstractSeven compounds of a new class of ionophores, acyclic formazanes, were synthesized and tested for the potentiometric selectivity for lithium ion, in polyvinyl chloride (PVC) membrane electrodes. Four different plasticizers were studied: o‐nitrophenyloctyl ether (NPOE), o nitrophenylphenyl ether (NPPE), o‐nitrophenylbutyl ether (NPBE), and o‐nitrophenylbenzyl ether (NPBnE), as was the addition of trioctylphosphine oxide (TOPO). The ionophore, 1, 5‐bis‐(o‐butoxyphenyl)−3‐cyanoformazane (IIB) exhibited sodium–lithium selectivity, KpotLi, Na, of 6.2 × 10−3 by the matched potential method in the presence of 1% TOPO using NPPE plasticizer. The presence of TOPO generally causes a substantial increase in the lithium selectivity. Selectivities with respect to the lithium ion are reported for sodium, potassium, ammonium, barium, and calcium ions.
Electrochemical and spectroscopic monitoring of the interaction between hydrogen peroxide and tungstophosphate heteropolyanion in homogeneous phase and in a polymer matrix
Authors: Keita Bineta , Bouaziz Djemai , Nadjo Louis 
Published: May 2005

AbstractCyclic voltammetry and UV‐visible spectroscopy have‐been used to monitor the reaction of tungstophosphate anion (PW12O3−40, abbreviated PW12 with hydrogen peroxide. The structures of some of the resulting peroxy complexes were also studied by IR spectroscopy. Depending on the experimental conditions, two different series of peroxy compounds are obtained as major products. It is also Shown that these species are easily extracted into a poly(4‐vinylpyridinium) film (PVP). Alternatively, the synthesis of, the peroxy, compounds has been performed directly by contacting a PVP film containing PW12 with an H2O2 solution. The facile entrapping of this series of peroxides in an appropriate polymer matrix creates new assemblies, stable and useful in the detection and study of the true catalytic species in oxygen transfer processes based on heteropolyanion/H2O2 systems.
Computerized potentiometric determination of stability constants of metal ion‐crown complexes by the method of corresponding solutions
Authors: Grabarić B. S. , Tkalčec M. , Merzel V. , Filipović I. 
Published: May 2005

AbstractTwo computerized potentiometric methods have been used to determine the stability constants of Na+, K+, and NH+4 complexes with 18‐crown‐6 in methanol‐water solutions (70% volume fraction of methanol) at 25.0 ± 01°C, and at constant ionic strength I = 0.1 M, adjusted with tetrabutylammonium iodide (TBAI). One method assumes a single complex equilibrium, while the method of corresponding solutions assumes the presence of simultaneous multiequilibria. It has been shown using the second method that K+ ion, even with 18‐crown‐6 ligand, can form both ML and sandwich‐type ML2 complexes, found so far only with smaller crown rings. The other two cations investigated form only ML complexes, as was confirmed by both methods.
Tomato seed‐based amperometric sensor for the determination of alcohols
Authors: Ozsoz Mehmet , Wang Joseph 
Published: May 2005

AbstractThe use of tomato seeds as a source for alcohol dehydrogenase (ADH) for the determination of alcohols is described. The unique reactivity pattern of the tomato ADH is coupled with the speed and sensitivity of the mixed tissue/carbon paste configuration. The effect of experimental variables, such as pH, cofactor concentration, applied potential, or paste composition, is explored. In accordance to the substrate specificity, the lowest detection limits (in the micromolar level) are obtained for allyl alcohol and ethanol.