Search Results - (Author, Cooperation:G. G. Wallace)

2016-03-05

Nature Publishing Group (NPG)

0028-0836

1476-4687

Biology

Chemistry and Pharmacology

Medicine

Natural Sciences in General

Physics

2011-10-15

American Association for the Advancement of Science (AAAS)

0036-8075

1095-9203

Biology

Chemistry and Pharmacology

Computer Science

Medicine

Natural Sciences in General

Physics

*Biomimetic Materials ; Electrodes ; Electrolytes ; *Muscles ; *Nanotubes, Carbon ; Rotation ; Torque ; Torsion, Mechanical

2014-02-22

American Association for the Advancement of Science (AAAS)

0036-8075

1095-9203

Biology

Chemistry and Pharmacology

Computer Science

Medicine

Natural Sciences in General

Physics

*Cotton Fiber ; Humans ; Muscles/chemistry/ultrastructure ; *Nylons ; Polymers ; Porosity ; *Tensile Strength ; *Torsion, Mechanical

1573-4838

Springer Online Journal Archives 1860-2000

Medicine

Technology

Abstract Composite materials comprised of the electrically conducting polymer, polypyrrole, with a variety of biologically active molecules, e.g. proteins or polysaccharides, are emerging as a novel class of “smart” biomaterials. In the present work we have studied the utility of a heparin–polypyrrole composite as a substrate for human umbilical vein endothelial cell (HUVEC) growth. We found that the polymer composites were well suited to support cell attachment and growth; displaying low surface hydrophobicity (water contact angle of approximately 20°) and roughness, Rq of approximately 10–12 nm. Doubling times for HUVEC on heparin–polypyrrole were greater than observed for gelatin-coated tissue culture polystyrene (44 and 36 h, respectively), however, the cells did proliferate to cover the polymer in an even monolayer. The initial mechanism of attachment and subsequent proliferation of HUVEC on heparin–polypyrrole was critically dependent on the presence of the serum adhesion glycoprotein vitronectin. Polymers that were composed of polypyrrole and sodium nitrate were more hydrophobic than heparin–polypyrrole and they did not support HUVEC growth. Given the relative ease with which these polymer composites can be electrochemically synthesized, the diverse range of cellular “signal agents”, e.g. growth factors, that can be incorporated within them, and the high degree of control that can be achieved in the release–surface exposure of these agents, we suggest that polypyrrole composites could serve a useful role as “smart” biomaterials in the near future. © 1999 Kluwer Academic Publishers

Electronic Resource

1612-1112

Column liquid chromatography ; Ion chromatography ; Analysis of metal ions ; Post column derivatisation ; Amperometric detection

Springer Online Journal Archives 1860-2000

Chemistry and Pharmacology

Summary A method for determination of metal ions subsequent to separation by ion chromatography has previously been developed. The method is based on Indirect Amperometric Detection whereby the decrease in the oxidation current, due to a dithiocarbamate ligand added post column, is monitored. Upon elution from the chromatographic column the metal ions are complexed by the ligand. As the complexes formed are electroinactive at the applied potential, the background current decreases according to the metal ion concentration. The method developed in this work involves addition to the reagent of Zn(II) as a auxiliary metal ion to displace the analyte metals from the chromatographic eluent ligand complexes after separation. Sodium bis(2-hydroxy-ethyl) dithiocarbamate was used as the postcolumn derivatising reagent. The addition of Zn(II) to the reagent causes some unforeseen behaviour in the chromatographic system.

Electronic Resource

1612-1112

Column liquid chromatography ; Polymer-modified silica ; Polypyrrole cloride ; Polypyrrole dodecylsulfate ; Small molecules ; Polyaromatic hydrocarbons

Springer Online Journal Archives 1860-2000

Chemistry and Pharmacology

Summary Polypyrrole chloride and polypyrrole dodecylsulfate coated-silica packing materials have been synthesized. Reverse-phase chromtographuy was employed to characterise both packings. A series of test compounds with known properties was used as molecular probes. They included benzene and derivatives, basic drugs, and polyaromatic hydrocarbons. A commericial C18 column was also used for the purpose of comparison in some cases.

Electronic Resource

1612-1112

Column liquid chromatography ; Separation of metal ions ; Formation of complexes ; Ethyl xanthate ; 1,10-Phenanthroline

Springer Online Journal Archives 1860-2000

Chemistry and Pharmacology

Summary On-column adduct formation has been used to enhance the stability of metal xanthate complexes. useful metal xanthate separations have been achieved by including 1,10 phenanthroline in the chromatographic eluent along with the primary complexing agent.

Electronic Resource

1612-1112

Column liquid chromatography ; Polymer-coated silica phase ; Polyaniline ; PAHs

Springer Online Journal Archives 1860-2000

Chemistry and Pharmacology

Summary The use of polyaniline as a chromatographic stationary phase has been examined. In the course of this work the column packing material was prepared by coating silica particles with polyaniline chloride. The aniline monomer was polymerised directly on the surface of the silica particles using a chemical method and was characterised using elemental analysis. A series of standard test compounds were employed for chromatographic characterization. The studies revealed information on the practical utility as well as the molecular interactions that took place on the stationary phase.

Electronic Resource

0959-8103

polyaniline ; inverse chromatography ; thin layer chromatography ; amino acids ; characterisation of chemical interactions ; Chemistry ; Polymer and Materials Science

Wiley InterScience Backfile Collection 1832-2000

Chemistry and Pharmacology

Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics

Physics

Inverse thin layer chromatography is used to characterise the chemical interactions that occur on polyaniline that has been electrochemically deposited on to a support. Amino acids are used as the molecular probe species by which the retention behaviour can be related to particular chemical interactions. The mobile phase is also varied, with respect to its polarity and pH, in order to add a further dimension to the qualitative information that is obtained. Anion exchange interactions are found to be the dominant interaction type. However, the behaviour seems to be different to that which occurs on conventional anion exchange materials. The behaviour was dependent upon the number of negative sites and also their spatial arrangement. A configurational-selective ionic interaction with the polaron lattice of the polyaniline is proposed. The response of the anion exchange behaviour to a change of pH suggested that protonated sites remained within the polymer, even at high pH values (c 9).

4 Ill.

Electronic Resource

0959-8103

polyaniline ; colloids ; electrodeposition ; electroactivity ; Chemistry ; Polymer and Materials Science

Wiley InterScience Backfile Collection 1832-2000

Chemistry and Pharmacology

Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics

Physics

The voltammetric properties of colloid dispersions of polyaniline have been studied. It has been found that with the use of appropriate oxidants, spherical polyaniline colloids with well defined voltammetric characteristics can be obtained.It has also been found that these colloids can be electrocoagulated to form coatings by imposition of a negative potential. Novel ‘Composite films’ can also be deposited from mixtures of colloids and show unique properties.

5 Ill.

Electronic Resource

1040-0397

Sulfite ; Biosensor ; Polypyrrole ; Chemistry ; Polymer and Materials Science

Wiley InterScience Backfile Collection 1832-2000

Chemistry and Pharmacology

An amperometric biosensor for sulfite determination, based on the incorporation of sulfite oxidasen (SOD) into a polypyrrole film by galvanostatic formation, has been successfully developed. The use of the biosensor involves the application of a constant potential of -700 mV, which promotes oxgen reduction as the predominant reaction. The optimum analytical conditions for the biosensor were 0.1 M phosphate buffer with 0.5 M KC1. pH 7.0, and a platinum disk electrode. The response of the biosensor to sulfite was linear from 0 to 80 mg/L, and the minimum detectable amount was found to be 5 mg/L. Usual interferants in sulfite determination such as ascorbic acid, sodium nitrite, and sodium sulfate did not interfere with the biosensor. The excellent resproducibility of the sulfite response with 4 hours of repeated use provides the basis for the construction of a disposable or renewable biosensor for sulfite determination.

7 Ill.

Electronic Resource

1040-0397

Photoelectrochemistry ; Flow cells ; Irradiation ; Chemistry ; Polymer and Materials Science

Wiley InterScience Backfile Collection 1832-2000

Chemistry and Pharmacology

Several photoelectrochemical flow cells have been designed and their analytical performances evaluated and compared. Two cell geometries, thin-layer and wall-jet, and three irradiation configurations differing in the relative position of the irradiation and detection points have been considered. In the first configuration (“adjacent”), the irradiation point is located upstream of the working electrode. In the second arrangement (“above”), the light irradiates the solution above the working electrode as well as the electrode surface. The third configuration (“on”) involves the use of an optically transparent electrode through which the light passes before irradiating the solution present on the electrode surface. The “adjacent” thin-layer cell was found to be the most practical and useful design. The photoelectrochemical efficiency of this cell was optimized and evaluated in terms of window and channel size.

5 Ill.

Electronic Resource

1040-0397

Amperometric detection of electroinactive anions ; Chloride-containing polypyrrole electrode ; Ion chromatography ; Chemistry ; Polymer and Materials Science

Wiley InterScience Backfile Collection 1832-2000

Chemistry and Pharmacology

The use of a chloride-containing polypyrrole electrode for the amperometric detection of electroinactive anions subsequent to separation by ion chromatography in suppressed, low conductivity eluent is described. It is demonstrated that changes in selectivity can be obtained by the application of different potential waveforms and current sampling protocols. The approach described is based on the anion dependence of the oxidation/reduction kinetics of the conducting polymer film induced by the applied potential.

9 Ill.

Electronic Resource

1040-0397

Chemistry ; Polymer and Materials Science

Wiley InterScience Backfile Collection 1832-2000

Chemistry and Pharmacology

Various methods have been investigated to stabilize a ruthenium polymer-modified electrode for use in flow-injection analysis. These include treatment with ultraviolet irradiation as well as coating the modified electrode with electrochemically generated conductive and nonconductive polymer layers. The stabilization procedures tested proved effective in improving the operational half-life of a nonstabilized electrode from 8 hours to more than 48 hours for the determination of test analyte species such as nitrite and nickel bis-2-hydroxyethyl dithiocarbamate.

1 Ill.

Electronic Resource

1040-0397

Stripping voltammetry ; mercury film electrode ; polymer coating ; Chemistry ; Polymer and Materials Science

Wiley InterScience Backfile Collection 1832-2000

Chemistry and Pharmacology

A chemically modified mercury thin-film electrode (MTFE) is presented that employs an electrochemically generated nonconducting polymer (poly-N-ethyltyramine), which has been derivatized with surface dithiocarbamate groups. Mercury is deposited chemically onto the electrode by complexation and, following electrochemical reduction of the mercury, is used as a substrate for anodic stripping voltammetry (ASV) of cadmium, lead, and copper. The properties of a conventional MTFE are compared with the modified electrode.

11 Ill.

Electronic Resource