Study of ferric oxide nanoparticles-tris-(2,4-di-t-amylphenoxy)-(8-quinolinolyl) copper phthalocyanine composite LB film

The ferric oxide nanoparticles-tris-(2,4-di-t-amylphenoxy)-(8-quinolinolyl) copper phthalocyanine (CuPcA(2)) composite ultrathin film was obtained by LB (Langmuir-Blodgett) technique. Structure of the composite LB film was characterized by X-ray photoelectron spectra, transmission electron microscopy, infrared spectra and visible spectra. Gas sensitivity measurements indicate that the composite LB film is sensitive to 100-200 ppm C2H5OH at room temperature. (C) 2000 Elsevier Science S.A. All rights reserved.

Electrochemical behavior and electrocatalytic properties of ultrathin films containing silicotungstic heteropolyanion SiW12O404-

We describe here a controlled fabrication of ultrathin monolayer and multilayer films consisting of silicotungstic heteropolyanion SiW12O404- and a cationic polymer of quaternized poly(4-vinylpyridine) partially complexed with osmium bis(2,2'-bipyridine) on Au electrodes previously self-assembled with cysteamine monolayers based on layer-by-layer electrostatic interaction. The thus-forming monolayer and multilayer chemically modified electrodes are investigated by cyclic voltammetry on their electrochemical behavior and electrocatalytic properties. The composite ultrathin films exhibit remarkable electrocatalytic effects on the reduction of BrO3-, H2O2, and HNO2. The electrocatalytic effects on HNO2 reduction are enhanced with increasing layer number from 1 to 3 but level off with much thicker multilayers. The stability of the monolayer and multilayer films is also examined. (C) 2000 The Electrochemical Society. S0013-4651(99)04-057-4. All rights reserved.

Amperometric tyrosinase biosensor based on a sol-gel-derived titanium oxide-copolymer composite matrix for detection of phenolic compounds

A new type of tyrosinase biosensor was developed for the detection of phenolic compounds, based on the immobilization of tyrosinase in a sol-gel-derived composite matrix that is composed of titanium oxide sol and a grafting copolymer of poly(vinyl alcohol) with 4-vinylpyridine. Tyrosinase entrapped in the composite matrix can retain its activity to a large extent owing to the good biocompatibility of the matrix. The parameters of the fabrication process and the variables of the experimental conditions for the enzyme electrode were optimized. The resulting sensor exhibited a fast response (20 s), high sensitivity (145.5 muA mmol(-1) 1) and good storage stability. A detection limit of 0.5 muM catechol was obtained at a signal-to-noise ratio of 3.

Renewable manganous hexacyanoferrate-modified graphite organosilicate composite electrode and its electrocatalytic oxidation of L-cysteine

Manganous hexacyanoferrate (MnHCF) supported on graphite powder was dispersed into methyltrimethoxysilane-derived gels to yield a conductive composite, which was used as electrode material to construct a renewable three-dimensional MnHCF-modifed electrode. MnHCF acts as a catalyst, graphite powder ensures conductivity by percolation, the silicate provides a rigid porous backbone, and the methyl groups endow hydrophobicity and thus limit the wetting section of the modified electrode. Cyclic voltammetry was exploited to investigate the dependence of electrochemical behavior on supporting electrolytes containing various cations. The chemically modified electrode can electrocatalytically oxidize L-cysteine, and exhibits a distinct advantage of polishing in the event of surface fouling, as well as simple preparation, good chemical and mechanical stability, and good repeatability of surface renewal.

Water soluble polyaniline and its blend films prepared by aqueous solution casting

Polyaniline (PAn) was doped with phosphonic acid containing hydrophilic tails. The solubility of the doped PAn in water was controlled by changing the length of hydrophilic chain in the dopant. When poly(ethylene glycol) monomethyl ether (PEGME) with molecular weight M-w = 550 was used as the hydrophilic chain of the dopant, the doped PAn was entirely soluble in water. The film cast from aqueous solution showed good electrochemical redox reversibility, Aqueous solution blending of PAn with poly(ethylene glycol) (PEG, M-w = 20 000) and poly(N-vinyl pyrrolidone) (PVP, M-w = 360 000) was achieved. Percolation threshold of the composite film was lower than 3 wt.%. Electrical conductivity of the composite film was in the range of 10(-1)-10(-5) S cm(-1), depending on molecular weight of the acid and the content of PAn in the composite. (C) 1999 Elsevier Science Ltd. All rights reserved.

Preparation of a composite film electrode containing 12-tungstosilicic acid and its electrocatalytic reduction for nitrite

A novel organic-inorganic composite film was formed by attaching Keegin-type heteropolyanion, SiW12O404- (devoted briefly as SiW12), on a glassy carbon electrode derivatized by 4-aminophenyl group. The composite film has an ionic bonding character between SiW12 and the surface amino group, which greatly improves the Blm stability and exhibits a more reversible electrochemical behavior. The modified electrode offers an excellent and stable electrocatalytic response for the reduction of nitrite. Possible mechanism was provided for the reaction of nitrite with SiW12O404-/aminophenyl composite film.

Microstructure and wear properties of laser clad Fe based amorphous composite coatings

A FeNiSiBV amorphous composite coating was developed by laser cladding of metallic powders on AISI 1020 low carbon steel substrate. The coatings were studied using X-ray diffraction, transmission electron microscopy and scanning electron microscopy. The coating reveals different microstructures along the depth of the coating. The transition zone exhibits good metallurgical bonding between the substrate and the coating. The layer consists of amorphous phase in majority and nanocrystalline phase/crystalline phase in minority. Accompanied with the nanocrystalline phase, the amorphous phase is concentrated in the middle of the coating. The crystalline phase in the coating is identified as Fe2B. A gradient distribution of the microhardness ranges from 1208 HV0.2 to 891 HV0.2 in the coating along the depth. The coating shows higher microhardness and better wear property than the substrate.