Shinnosuke Miyauchi

Covalent immobilization of glucose oxidase on poly[1-(2-carboxyethyl)pyrrole] film for glucose sensing

Poly[1-(2-carboxyethyl)pyrrole] film (PPy-COOH film) was electrochemically prepared and glucose oxidase (GOD) was covalently immobilized on the PPy-COOH film by the condensation reaction with carboxyl groups of the PPy-COOH. The apparent activity of the GOD immobilized on the PPy-COOH film was 152 mU cm −2 . The GOD-immobilized PPy-COOH film (PPy-GOD film) was applied to amperometric glucose sensing. Plots of response current versus glucose concentration gave a straight line with a slope of 1.7 μ A cm −2 per 1 mM glucose up to 80 mM. The glucose oxidation with the GOD on the PPy-GOD film was considered to proceed through a Michaelis—Menten mechanism.

Covalent Immobilization of Glucose Oxidase on Magnetite Particles via Graft Polymerization of Acrylic Acid

Abstract A new technique for immobilizing enzyme molecules on magnetite particles via the graft polymerization of acrylic acid is presented. The polymerization of acrylic acid was carried out in a redox system consisting of ceric ion and mercapto groups introduced onto magnetite particles. In the course of the polymerization, poly(acrylic acid) was attached to the magnetite particles. Glucose oxidase was covalently immobilized on the magnetite particles by the condensation reaction with the carboxyl groups of the poly(acrylic acid). It was shown that 2.8 mg of glucose oxidase was immobilized on 1 g of the magnetite attached with poly(acrylic acid), and the immobilized glucose oxidase had a specific activity of 81 units/mg, which was 50% of that of the native enzyme. Due to the immobilization, the optimum pH for glucose oxidase was shifted to a higher value and the temperature dependency of activity was diminished. A kinetic study of the glucose oxidation reaction with immobilized enzyme showed that the im...

Schottky barrier formation between polypyrrole and indium

Abstract Junctions between p-type polypyrrole and metals have been studied. Electrical measurements were done with two kinds of geometrically different devices. On a planar type device, where current flows along the polymer film, the junction at In/polypyrrole gave Schottky barrier formation, while the junction at Au/polypyrrole showed ohmic characteristic. But, on a sandwich type device, where current flows transversely toward the film, the junction at In/polypyrrole was ohmic.

Heterojunction devices consisting of conducting polymers

Abstract The oxidation or the reduction behavior of anions and cations in the junctions formed between polypyrrole and polythiophene derivatives were studied. On the basis of the results, the pn-heterojunction type devices were fabricated and then, the rectifying characteristic was found to be stable even after 6 months.

Sugar-binding property of magnetite particles modified with dihydroxyborylphenyl groups via graft polymerization of acrylic acid

Abstract In order to combine sugar-binding property and magnetism, dihydroxyborylphenyl (DHBP) groups were attached to magnetite particles via graft polymerization of acrylic acid. The graft polymerization was carried out in a redox system consisting of mercapto groups introduced onto the surfaces of magnetite particles and ceric ions. DHBP groups were attached through amide linkages by the condensation reaction of 3-aminophenylboronic acid with carboxyl groups of the grafted poly(acrylic acid). Complexation of the attached DHBP groups was examined with various sugars and compared with that of the free phenylboronic acid. The attached DHBP groups gave a large value of binding constant K for the complexation with adenosine having a pair of cis -OH groups, whereas the K values for the DHBP groups with adenosine phosphates were extremely small. With respect to the complexation with 2′-deoxyadenosine, cooperative interaction of neighboring DHBP groups was suggested. Although the value of acidity index p K a of the attached DHBP was larger than that of free phenylboronic acid, the p K a value was decreased by coexistent basic groups.

Temperature-conductivity characteristics of the composites consisting of fractionated poly(3-hexylthiophene) and conducting particles

Poly (3-hexylthiophene) (P3HT) synthesized by oxidative polymerization was fractionated by molecular weight by using organic solvents. The fraction of higher average molecular weight gave higher regioregularity and conductivity. Composites of the P3HT fraction having the highest molecular weight were prepared by use of the following conducting particles as fillers: titanium carbide (TiC), indium tin oxide (ITO), and carbon black (CB). Temperature-conductivity profiles of the composites showed that the resistance change with PTC (positive temperature coefficient) effect was strongly influenced by the content and size of conducting particles and the molecular weight of P3HT. Although no significant PTC effect for P3HT-CB composite and little effect for P3HT-ITO composite system were observed, the P3HT-TiC composite containing TiC of 70-80 wt % showed an obvious PTC effect that brought the conductivity change by about four orders of magnitude near the glass transition temperature of P3HT. However, such a remarkable PTC effect was not observed for the P3HT-TiC composite prepared with the P3HT fraction of low-molecular weight. It was shown that a good PTC effect could be achieved by the composite consisting of the P3HT of high-molecular weight and the conducting particles of relatively large size.

Junction properties between indium and doped polypyrrole

Abstract Junction properties of heavily doped polypyrrole(PPY) with indium were studied in a planer configuration. PPY samples with a different conductivity were prepared by electrochemically polymerizing pyrrole in various reaction conditions. PPY samples with a conductivity in a range of ca.3–70 S/cm were used as a device. As results, PPY with a conductivity below ca.20 S/cm among them showed a rectifying property. From the thermionic theory analysis, the barrier height and the ideality factor were 0.69–0.74 eV and 6.0–8.9, respectively. The capacitance of some devices prepared with the PPY showed a field dependency against the forward bias. It is likely that Schottky barrier is formed in the junction.

Formation of Superconducting Y-Ba-Cu-O Thin Films by the Solid Phase Reaction between BaCo3/Cu/Y2O3 Layers on Single Crystalline SrTiO3 Substrate

Thin films of superconducting Y-Ba-Cu-O were formed on single crystalline SrTiO3 substrate by the solid phase reaction between BaCO3/Cu/Y2O3 layers. The layers were evaporated on the substrate by an electron-beam gun and heated at 900°C in oxygen atmosphere for an hour. Resistivities of the films were measured by the four-probe method and superconduction was observed at Tc=90 K (onset) and 50 K (end).

Chemically oxidative synthesis and hydrolysis of poly[1-(2-cyanoethyl)pyrrole]

Abstract 1-(2-Cyanoethyl)pyrrole was chemically polymerized in acetonitrile by using iron(III) perchlorate as an oxidizing agent. Poly[1-(2-cyanoethyl)pyrrole] obtained as black powder was hydrolysed with potassium hydroxide to convert cyano groups of the polymer to carboxyl groups. The hydrolysis of the cyano groups was confirmed by means of i.r. spectroscopy. The electric conductivities of these polymers were investigated and it was shown that poly[1-(2-cyanoethyl)pyrrole] behaved as a conductive polymer while the hydrolysed polymer behaved as an insulator.

Junction properties between indium and I2 doped polyacetylene

Abstract Junction properties between indium and I 2 -doped polyacetylene with a high conductivity, 0.8–27 S/cm were studied. Devices for measurements were fabricated in a sandwich configuration. Doped polyacetylenes gave a rectifying contact for indium. From the analysis of J-V characteristics, it is estimated that Schottky barriers have been formed between doped polyacetylenes and indium, though the ideality factors of barriers were large. Capacitance-voltage characteristics of Indium/Polyacetylene/ Gold devices at 50 Hz were measured. The plots of 1/C 2 against reverse bias were linear for doped polyacetylenes. The capacitance increased with increasing the dopant concentration. This fact suggests that the depletion layer of the junction decreases with increasing the dopant concentration.