The role of electrode-inert metal ions (Zr(IV), Hf(IV), La(III), Mg(II), Ca(II), Sr(II), Ba(II) and Li(I)) in electrochemical reduction of nitrate ion is discussed an the basis of polarographic measurement. No evidence for nitrate-metal ion complexes in the bulk solution was found from UV and Roman spectra under our experimental conditions. No large differential capacity (no double-layer effect) which might be assigned to strong adsorption was observed for all the metal ion solutions. However, our results indicated that the metal ion acted as an intermediary far the charge transfer from the electrode to the nitrate ion and as a proton supplier to the nitrate by the hydrolysis of the metal ion itself in the proximity of the electrode.
n-Alkanethiols (CH3(CH2)nSH, n=3, 5, 11, 13, 15, 17) have been adsorbed at mercury electrodes prom ethanolic solutions. A. c. voltammetry has been carried out of the adsorbed alkanethiol on mercury electrodes in aqueous solutions containing 1M KCl at 25°C. Cyclic d.c. voltammetry of several metal ions also has been performed at these electrodes. The results show that long-chain alka-nethiols n_??_11 can form densely packed monolayers with fully extended alkyl chains in the potential range between 0 and -0.7 volt vs. Ag/AgCl. Metal ions such as Pb2+ are unable to penetrate into the monolayer. In contrast, short-chain alkanethiols with n=3 and 5 form less ordered and loosely packed adsorption layers, which are permeable to the metal ions. A pH dependent a.c. voltammetric peak is observed at a mercury electrode with adsorbed alkanethiol(n=5) in buffer solutions, which is attributable to the redox reaction of the adsorbed thiol: [CH3(CH2)5S]adHg+H++e-_??_[CH3(CH2)SH] adHg.
Diaphorase (DI)-catalyzed electrolytic oxidation of NADH to NAD+ is studied in the presence of flavins and quinones as electron transfer mediators. The behavior of the catalytic current at the mediated DI-electrode is well explained by theoretical equations based on polarographic catalytic current theory using the reaction layer approximation. The bimolecular reaction rate constants between DI and the mediators are determined by the electrochemical method.
Thin films of MgO-doped and CaO-doped iron oxide were prepared by spray pyrolysis. The films were characterized by X-ray diffraction, scanning electron microscopy and voltasmetric techniques. The photo-electrochemical behavior of thin film electrodes depended greatly on the doping level, sintering temperature, substrate temperature and sintering time. Both the MgO and the CaO-doped iron oxide thin films prepared at high temperature showed p-type photoelectrochemical behavior, while the CaO-doped iron oxide thin films prepared at low temperature showed n-type photoelectrochemical behavior. This characteristic change was interpreted in terms of the surface structure change of the thin films and doping effect of metal oxide.
A new alkanethiol derivative containing a 18-crown-6 function (1) was introduced for fabrication of electrode surface. A 1-modified gold electrode was prepared by dipping in the solution of 1. By using a [Fe(CN)6]3-/4- redox couple as an electrochemical probe, a densely packed, electrochemically insulating surface layer formation by 1 was confirmed by cyclic voltammetry. This made the amperometric sensory application of the electrode difficult. On the other hand, this property suggested a possible application to chemical sensors with electrical impedance measurements. The idea was successfully demonstrated by sensing gaseous ammonia. Organic gases such as benzene and chloroform did not give response. The surface-immobilized crown ether played a key function in determining the selectivity.
The specific responsive ISFET were made by a modification on its gate surface with some ion selective materials. In order to make adequate device of an ISFET which indicates an anionic responsive characteristics, the gate surface was coated by an ion-beam (IB) sputtering method using a improved alkali metal-free lead phosphate glass containing silver oxide. When a radio frequency (RF) sputtering method was used, the gate channel would be exposed to bombardment by electron, uv light and soft X-ray, and makes the static characteristics of ISFET worse. On the contrary, when the IB sputtering method was used, the static characteristics did not change and the sputtering damage could be neglected. With this processing technique, damageless anion specific ISFET can be fabricated without annealing. Fabrication conditions of the glass coated ISFET and the anion responsive behavior were discussed.
Ion-sensitive oxide films were deposited on a Si wafer to make a MOS-diode structure in a biased RF (radio frequency) sputtering system using Ar+O2 as reactant gas. Various kinds of oxide films such as SiO2, Ta2O5, Mg-Al-Ag-P-O, Pb-Al-Ag-P-O and Si-N-O of about 1, 000Å in thickness, were formed. The adsorption of ion on the MOS-diode surface in an electrolytic solution was induced the change of the surface capacitance. The capacitance change of the MOS-diode in the standard pH buffer solutions and some anion solutions were closely related to the adsorption properties of those ions on the oxide film surface. In the standard pH solutions, the adsorption-layer capacitance of SiO2 and Ta2O5 film increases with increasing the values of pH. The capacitance of the alkali metal-free phosphate glass films, however, was independent of the pH in the electrolyte. On the other hand, the capacitance of these glass films increases with increasing anion concentration. In relation to the variation of nitrogen and oxygen in the Si-N-O film, the slope of the capacitance-pH relationship decreses with decresing oxygen content in the film.
A flow injection voltammetric method has been developed for the determination of surfactants and ethanol. The effect of the volume of the injected solution, the effect of adsorption potential and the effect of flow rate of the carrier solution on differential capacity - time curves were investigated. After above fundamental studies surfactants in waters and ethanol in an alcoholic drink were determined.
A new solvent-independent reference potential has been proposed on the basis of the Born-Haber cycle as the average of the formal redox potentials for the two redox couples which are [Fe(cp)2]+/0 (cp=cyclopentadienyl) and [Fe(cp)(cb)]0/- (cb (3)-1, 2-dicarbollyl). The voltammetric and conductometric results shows the proposed reference potential is valid for ten aprotic and six protic solvents examined.
Nafion films were coated on glassy carbon electrode surfaces and these chemically modified electrodes were used to characterize the incorporation of Cu(II) complexes with imidazole and its derivatives. These Cu(II) complexes could be concentrated inside Nafion films without the interference of another metal ions at pH 6.0. The calibration curve was linear in the range 10-7-10-6M of Cu2+ containing 10-2M imidazole.
A very sensitive adsorptive stripping voltammetric method is studied on the In-morin complex at a HMDE in 0.1M acetate buffer (pH=3.20) solution. The effects of various analytical conditions are discussed on the reduction peak current of the adsorbed complex on the surface of HMDE. Interferences by other trace metals and surfactant are also discussed. Detection limit is 2.6nM of indium with 90 seconds deposition time, and the RSD (n=7) at 4μg/l indium is 2.0%.
Comparative study on electrochemistry and NMR has been carried out on a series of Ru(bpy)2Ln+ and Ru(phen)2Ln+. Linear relations were found between the 13C chemical shifts and Eox for these mixed ligand ruthenium(II) complexes.
A kinetic model is proposed to characterize the hydrolysis of phosphatidylcholine monolayers by phospholipase D (E.C. 18.104.22.168, PLD). The model consists of diffusion-controlled adsorption of PLD and catalysis at the monolayer. Theoretical curves obtained numerically from the method well reproduced the experimental sigmoid reaction-progress curves.
CAPDAS, a polymer information-base system contains data, knowledge, and other types of information which are necessary for advanced research and development of polymer science. It was designed to provide comprehensive information as well as the domain specialists oriented functions to manage and to use the available information to the maximal extent. The contents are scientific and technical articles, C-13 NMR spectra, some of which were measured originally for numerical standardization of data, catalogs of commercial polymers including data of fundamental and practical properties, a thesaurus, a taxonomy and so on. These data were collected according to the request of wide range of potential users such as chemists, physicists, engineers, users in the polymer and related fields. The system was developed on a basis of a new information model called PIBS-SORITES(Polymer Information Base Systems with Self Organizing Receptor Interconnections), which can handle semantics through dynamic structures of composite information for materials research and development.
The paper introduce the concept of reliability in analytical chemistry for all the steps of the analytical process. The analytical information is a complex function of the reliabilities corresponding to the sampling, method, instrument and data-processing.