Performance of Pt-TiO2 electrocatalyst for CO oxidation in the electrochemical gas sensor

It is reported for the first time that the Pt/TiO2 electrocatalyst was successfully used for the electrocatalytic oxidation of CO in the electrochemical gas sensor with a controlled potential mode. The stability of electrocatalytic activity of the Pt-TiO2 electrocatalyst for the CO oxidation is better than that of Pt.

Synthesis of phenyl/amino-capped tetraaniline by chemical and electrochemical methods

Phenyl/amino-capped tetraaniline was prepared by chemical oxidation coupling and electrochemical cyclic voltammetry methods. The MacDiarmid's method of oxidation coupling was improved. The aqueous HCl was replaced with a mixture solution of HCl and acetone and (NH4)(2)S(2)O(0)8 was used as oxidant instead of FeCl3. The reaction displays a higher yield and the product tetraaniline has a higher purity owing to the improvement. In the mixture solution system, tetraaniline can be synthesized by electrochemical cyclic voltammetry method. The mechanism by which tetraaniline was prepared from p-amino diphenylamine was proposed. The product was characterized by MALDI-TOF MS and FTIR.

Application of modified Nafion membrane to the sulfur dioxide gas electrochemical sensor

The electrochemical SO2 sensor worked at the fixed potential and prepared with Nafion membrane as the solid electrolyte was studied. It v as observed that after Nafion membrane, was treated with H2SO4, the water-preserving ability of the membrane was increased. In turn, the performance of the sensor became stable. After lifetime test for 4 months, the performance of the sensor deceased slightly, Thus this kind of sensor may become a gas sensor for the practical application.

Asymmetric polymerization of menthyl methacrylate by anionic catalysts

In this paper, (-)menthyl methacrylate((-)MnMA) was polymerized at -78degreesC in toluene with three types of anionic catalysts, which were complexes of fluorenyllithium with (-)sparteine -((-)-Sp), (S, S)-(+)-2, 3-dimethoxy-1, 4-bis(dimethylamino)butane((+)DDB) and N,N,N,N'-tetramethylethylenediamine(TMEDA), and the chiral optical property of the obtained polymer was studied. The circular dichroism (CD) spectrum of the polymer showed negative Cotton effect.

Study of electron transfer across the liquid/ice-like matrix interface by scanning electrochemical microscopy

In this work, we report the findings of a study on scanning electrochemical microscopy (SECM) to investigate the interfacial electron-transfer (ET) reaction between the 7,7,8,8-tetracyanoquinodimethane radical anion (TCNQ(.-)) in 1,2-dichloroethane and ferricyanide in an ice-like matrix (a mixture of insulting ice and conductive liquid) under low temperatures. Experimental results indicate that the formed liquid/ice-like matrix interface is superficially similar in electrochemical characteristics to a liquid/liquid interface at temperatures above -20 degreesC. Furthermore, imaging data show that the surface of the ice-like matrix is microscopically flat and physically stable and can be applied as either a conductive or an insulting substrate for SECM studies. Perchlorate ion was selected as the common ion in both phases, the concentrations of which controlled the interfacial potential difference. The effect of perchlorate concentration in the DCE phase on interfacial reactions has been studied in detail. The apparent heterogeneous rate constants for TCNQ(.-) oxidation by Fe(CN)(6)(3-) in another phase under different temperatures have been calculated by a best-fit analysis, where the experimental approach curves are compared with the theoretically derived relationships. Reaction rate data obey Butler-Volmer formulation before and after the freezing point, which is similar to most other known cases of ET reactions at liquid/liquid interfaces. However, there is a sharp change observed for heterogeneous rate constants around the freezing point of the aqueous phase, which reflects the phase transition. At temperatures below -20 degreesC, surface-confined voltammograms for the reduction of ferricyanide were obtained, and the ice-like matrix became an insulating one, which indicates that the aqueous phase is really a frozen phase.

Silane bridged polymerized metallocene catalyst for ethylene polymerization

The polymerized metallocene catalyst 4 was prepared by the co-polymerization of ansa-zirconocene complex [CH3Si(2)]ZrCl2 (3) containing vinyl substituted silane bridge with styrene in the presence of radical initiator. Catalyst 4 was found to display high ethylene polymerization activity of 2.28 x 10(6) g PE/(mol . h) with a viscosity average molecular weight (M-eta) value of 61.6 x 10(3) using methylalumoxane (MAO) as a co-catalyst. The ethylene polymerization has been investigated under different conditions.

Self-immobilized catalysts for ethylene polymerization: neutral, single-component salicylaldiminato phenyl nickel(II) complexes bearing allyl substituents

A new family of self-immobilized ethylene polymerization catalysts, derived from neutral, single-component salicylaldiminato phenyl nickel complexes, is described.

Electrochemical biosensing in extreme environment

This review presents recent developments of electrochemical biosensors in extreme working environments. After a brief introduction to the electrochemical biosensor, the applications of biocatalytic biosensors and bioaffinity biosensors in harsh working conditions, in organic solvent, in gas-phase, in vivo measurement and in toxic environments, are discussed by means of several examples. Methods for improving the stability and extending the biosensor application scope are suggested, and new trends about biosensor development are also discussed.

Thermally crosslinkable poly(phenylene sulfide)/poly (ether sulfone)/polymerization of monomer reactant-polyimide blends

The effects of thermally crosslinkable polymerization of monomer reactant-polyimide (POI) on the miscibility, morphology, and crystallization of partially miscible poly(ether sulfone) (PES)/poly(phenylene sulfide) (PPS) blends were investigated with differential scanning calorimetry and scanning electron microscopy. The addition of POI led to a significant reduction in the size of PPS particles, and the interfacial tension between PPS and crosslinked POI was smaller than that between PES and crosslinked POI. During melt blending, crosslinking and grafting reactions of POI with PES and PPS homopolymers were detected; however, the reaction activity of POI with PPS was much higher than that with PES. The crosslinking and grafting reactions were developed further when blends were annealed at higher temperatures. Moreover, POI was an effective nucleation agent of the crystallization of PPS, but crosslinking and grafting hindered the crystallization of PPS. The final effect of POI on the crystallinity of the PPS phase was determined by competition between the two contradictory factors. The crosslinking and grafting reactions between the two components was controlled by the dosage of POI in the blends, the premixing sequence of POI with the two components, the annealing time, and the temperature.

Polymerized unsymmetrical iron post-metallocene catalyst for ethylene polymerization

The unsymmetrical allyl containing post-metallocene complex [ArN = C( Me)] [(ArN)-N-' = C(Me)]C5H3NFeCl2 [Ar = 2,6(i- Pr)(2)C6H3, Ar' = 4-allyl-2,6-(i-Pr)(2)C6H3] (3) has been prepared and characterized. Complex (3) can be co-polymerized with styrene in the presence of radical initiator to produce polymerized post-metallocene catalyst which exhibits high activity for ethylene polymerization (2.5 x 10(6) g PE/mol Fe.h).

Electrochemical characteristic of LaNi-based hydrogen storage alloys

Effect of purity of alloy components on the electrode performance of LaNi2 alloys was investigated. The results showed the purity of components had less effect on discharge capacity and self-discharge of LaNi2 alloys. Partial substitution of Al or Mn for Ni greatly improved discharge properties of LaNi2-xAlx, or LaNi2-yMny alloys as negative electrodes in MFl-Ni battery, 0.15less than or equal toxless than or equal to0.25; 0.15less than or equal toyless than or equal to0.25. In addition, surface treatment of LaNi1.8Al0.2 alloy electrode was performed by polymerizing cis-butenedioate with Co-60- gamma -ray radiation, which. had better affect on self-discharge and cycle life of the alloy electrodes at low temperature(-28 C-degrees).

Electrochemical properties of rare earth AB(3)-type alloy as negative electrode material in MH-Ni battery

Electrochemical properties of rare earth AB(3)-type hydrogen storage alloys as negative electrode material and a polymer instead of 6 M KOH aqueous solution as solid state electrolyte in MH-Ni battery have been investigated at room temperature and 28degreesC first time. The partial replacement of Ni by Al and Mn elements increases the specific capacity and cycle stability of the alloy.

Synthesis and electrochemical characteristics of lanthanide complexes with 2-nitro-5,10,15,20-tetraphenylporphyrin and acetylacetonate

Four lanthanide complexes with 2-nitro-5,10,15,20-tetraphenylporphyrin and acetylacetonate were prepared and characterized by elemental analyses, LR, UV-Visible,H-1 NMR, XPS and molar conductance. The redox properties of the lutetium complex with 2-nitro-5,10,15,20-tetraphenylporphyrin and acetylacetonate in dichloromethane were studied by cyclic voltammetry.

Synthesis, structure and ring-opening polymerization of phenolphthalein macrocyclic polyarylates

Phenolphthalein based polyarylate macrocyclic oligomers were selectively synthesized by an interfacial polycondensation reaction of o-phthaloyl dichloride with phenolphthalein. The high selectivity benefits from the role of phenolphthalein as a color indicator, an efficient phase transfer catalyst, acid a preferred conformation of the starting materials as indicated by analyzing a single-crystal X-ray structure of an analogous macrocycle. The melt ROP of phenolphthalein polyarylate cyclic dimer was studied using nucleophilic initiators, The molecular weight of the resulting polymers builds up very rapidly at the very early stage of polymerization but decreases with time. During the ROP of cyclic dimer, analogous macrocycles with higher degree of polymerization (n greater than or equal to 3) and linear oligomers were produced by backbiting reaction especially at later stage of polymerization. Conversion of cyclic dimer is very fast at the earlier stage of polymerization and then increases slowly with time as analyzed by gel permeation chromatography. However, the total amount of cyclic oligomers in the ROP system increases with time at the later stage of polymerization because of the formation of larger macrocycles. The resulting polymers are amorphous. Glass transition temperatures (T(g)s) of these polymers are influenced by the polymerization time, type of initiator, and initiator concentration.

Study on surface acid-base property of carboxylic acid-terminated self-assembled monolayers by cyclic voltammetry and electrochemical impedance spectroscopy

Cyclic voltammetry and electrochemical impedance spectroscopy were used to study the surface acid-base property of carboxylic acid-terminated self-assembled monolayers (SAMs). A carboxylic acid-terminated thiol, such as thioctic acid (1,2-dithiolane-3-pentanoic add), was self-assembled on gold electrodes. Electron transfer between the bulk solution and the SAM modified electrode was studied at different pH using Fe(CN)(6)(3-) as a probe. The surface pK(a) of thioctic acid was determined by cyclic voltammetry and electrochemical impedance spectroscopy to be 5.6 +/- 0.1 and 5.8 +/- 0.1, respectively. The method is compared with other methods of monolayer pK(a) measurement.