PEDOT-coated counter electrodes for dye-sensitized solar cells

Poly(3,4-ethylenedioxythiophene) (PEDOT)-coated counter electrodes for dye-sensitized solar cells have been prepared at ambient temperature and without the use of iron-based oxidants, using an ionic liquid for the synthesis of the PEDOT. These electrodes show comparable electrocatalytic performance with conventional Pt-coated counter electrodes (solar cell efficiencies >7.5%).

Electrochemical impedance spectroscopy as a tool to measure cathodic disbondment on coated steel surfaces: capabilities and limitations

The disbondment of protective organic coatings under excessive cathodic protection potentials is a widely reported coating failure mechanism. Traditional methods of evaluating cathodic disbondment are based on ex situ visual inspection of coated metal surfaces after being exposed to standard cathodic disbondment testing conditions for a long period of time. Although electrochemical impedance spectroscopy (EIS) has been employed as an effective means of evaluating various anti-corrosion properties of organic coatings; its application for assessing the cathodic disbondment resistance of coatings has not been sufficiently exploited. This paper reports an experimental study aimed at developing EIS into a tool for in situ measurement and monitoring of cathodic disbondment of coatings. A clear correlation between EIS parameters and the disbonded coating areas has been confirmed upon short term exposure of epoxy-coated steel electrodes to cathodic disbondment conditions; however the degree of this correlation was found to decrease with the extension of exposure duration. This observation suggests that EIS loses its sensitivity with the propagation of coating disbondment, and that in order to achieve quantitative determination of the coating cathodic disbondment localized EIS measurements are required to measure the parameters related to local disbonded areas.

Controllable graphene oxide mediated efficient electron transfer pathways across self-assembly monolayers: a new class of graphene based electrodes

In this paper, the influence of chemically reduced graphene oxide sheets (CRGOs) on the electrochemical performance through methyl or carboxylic acid terminated self-assembled monolayers (SAMs) is reported. The gold electrode was initially modified with methyl or carboxylic acid terminated alkanethiols with various carbon chain lengths (n = 4, 6, 8 and 11) and subsequently immobilization of the CRGOs on a SAM surface was achieved via a hydrophobic and electrostatic interaction. By using the potassium ferricyanide as a redox probe, it was observed that CRGOs could effectively enhance the heterogeneous electron transfer (ET) of the SAM due to a tunneling effect. The assemblies based on thiol end groups with methyl head groups were observed to afford more hydrophobic interaction binding with CRGOs with a higher reduction time than the assemblies developed with thiol end groups and a -COOH group which were shown to bind more electrostatically with CRGOs, a lowering reduction time. The Nyquist plots developed show a gradual decrease of the charge transfer resistance (Rct) of [Fe(CN)6]3-/4- redox couple at the CRGOs-SAMs electrode with the controllable adsorption of different CRGO's onto the SAM. Depending on the chain length and terminal functional group the electron transfer rate kinetics were observed to differ considerably.

Characterization of conductive polyprrole coated wool yarns

Wool yarns were coated with conducting polypyrrole by chemical synthesis methods. Polymerization of pyrrole was carried out in the presence of wool yarn at various concentrations of the monomer and dopant anion. The changes in tensile, moisture absorption, and electrical properties of the yarn upon coating with conductive polypyrrole are presented. Coating the wool yarns with conductive polypyrrole resulted in higher tenacity, higher breaking strain, and lower initial modulus. The changes in tensile properties are attributed to the changes in surface morphology due to the coating and reinforcing effect of conductive polypyrrole. The thickness of the coating increased with the concentration of p-toluene sulfonic acid, which in turn caused a reduction in the moisture regain of the wool yarn. Reducing the synthesis temperature and replacing p-toluenesulfonic acid by anthraquinone sulfonic acid resulted in a large reduction in the resistance of the yarn.

Effect of synthesis parameters on the electrical conductivity of polypyrrole-coated poly(ethylene terephthalate) fabrics

The effects of pyrrole, anthraquinone-2-sulphonic acid (AQSA) and iron(III) chloride (FeCl3) concentrations, reaction time and temperature on the electrical conductivity of polypyrrole (PPy) - coated poly(ethylene terephthalate) (PET) fabrics were investigated. With an increase in both the AQSA and FeCl3 concentrations, resistivity decreased to a point beyond which higher concentrations led to increased surface resistivity. Erosion of the polymer coating, in dynamic synthesis from continual abrasion, manifested as an exponential increase in the resistance of the coated textile substrate. This was not encountered in static synthesis conditions. Temperature affected the degree of surface and bulk polymerisation. The effect of polymerisation temperature on conductivity was negligible. Conductive polymer coating on textiles through chemical polymerisation enabled a smooth coherent film to encase individual fibres, which did not affect the tactile properties of the host substrate. The optimum FeCl3/pyrrole and AQSA FeCl3/pyrrole molar ratios were found to be 2.22 and 0.40 respectively.

Characterization of conducting polymer coated synthetic fabrics for heat generation

Heat generation in fabrics coated with the conductive polymer polypyrrole was investigated. The PET fabrics were coated by chemical synthesis using four different oxidizing agent–dopant combinations. The samples from the four different dopant systems all show an increase in temperature when a fixed voltage is applied to the fabric. The antraquinone-2-sulfonic acid (AQSA) sodium salt doped polypyrrole coating was the most effective in heat generation whereas the sodium perchlorate dopant system was the least effective. The power density per unit area achieved in polypyrrole coated polyester–Lycra® fabric with 0.027 mol/l of AQSA acting as dopant was 430 W/m². The power density per unit area achieved for the sodium perchlorate system, using the same synthesis conditions, was 55 W/m².

Generating heat from conducting polypyrrole-coated PET fabrics

Heating effects in polypyrrole-coated polyethyleneterephthalate (PET)-Lycra® fabrics were studied. Chemical synthesis was employed to coat the PET fabrics by polypyrrole using ferric chloride as oxidant and antraquinone- 2-sulfonic acid (AQSA) and naphthalene sulfonic acid (NSA) as dopants. The coated fabrics exhibited reasonable electrical stability, possessed high electrical conductivity, and were effective in heat generation. Surface resistance of polypyrrole-coated fabrics ranged from approximately 150 to 500 /square. Different connections between conductive fabrics and the power source were examined. When subjected to a constant voltage of 24 V, the current transmitted through the fabric decreased about 10% in 72 h. An increase in resistance of conductive fabrics subjected to constant voltage was observed

Development of a cooling fabric from conducting polymer coated fibres: proof of concept

It is supposed that there should be a thermal electric effect if a dc current is applied across two dissimilar conducting polymers, similar to so called “Peltier effect” in metals or semiconductors. However, this hypothesis has not been tested on conducting polymers and using these materials to make cooling fabrics has never been attempted before. Polypyrrole coated fabrics were used to test the hypothesis in this preliminary study. Seebeck and the Peltier effects were proven to exist. However, thermoelectricity effect between two conducting polymer coated fabric samples was only about 10 μV/°C. Cooling effect by conductive polymer powder was achieved but performance was unsteady due to electrical degradation of the conducting polymer. Nevertheless, the concept was demonstrated and the development of a cooling fabric is possible.

Frictional and tensile properties of conducting polymer coated wool and alpaca fibers

Wool and alpaca fibers were coated with polypyrrole by vapor-phase polymerisation method. The changes in frictional and tensile properties of the single fibers upon coating with the conductive polymer are presented. Coating a thin layer of polypyrrole on the alpaca and wool fibers results in a significant reduction in the fiber coefficient of friction, as the conducting polymer layer smooths the protruding edges of the fiber scales. It also reduces the directional friction effect of the fibers. Depending on the type of fiber, the coating may slightly enhance the tensile properties of the coated fibers.

The relative absorption of fatty acids in brown trout (Salmo trutta) fed a commercial extruded pellet coated with different lipid sources

The objective of the present study was to investigate the fatty acid absorption capabilities of brown trout (Salmo trutta) fed commercial extruded diets. Five commercial extruded pellets, different only in the lipid sources used for fat coating, were tested on juvenile brown trout for 45 days. The trout were reared in fresh water at 14.6 ± 0.4° C and 7.7 ±
0.3 mg/l, temperature and dissolved oxygen, respectively. The tested lipid sources were fish oil, canola oil, oleine oil, swine fat and poultry fat. After the adaptation period faeces were collected by gently stripping from naesthetized fish. Fatty acid analysis was performed on experimental diets and on collected faeces to evaluate the relative absorption capabilities of the trout digestive system with respect to each detected fatty acid. The use of the relative absorption efficiency (rAE) was opted to evaluate the intrinsic capability of each fatty acid to be absorbed. Brown trout showed a
specific preferential order of absorption of the fatty acids, preferring shorter over longer chain fatty acids and preferring the more unsaturated to the more saturated fatty acids. The fatty acid that showed the best relative absorbability was the C18:4n-3 (rAE = 5.14 ± 0.72), which has a fairly short carbon chain, but at the same time a high unsaturation level, followed by the C18:3n-3 (rAE = 3.38 ± 0.30). The fatty acid that showed the worst relative absorbability (rAE = 0.21 ± 0.02) was C24:1n-9.

Polypyrrole-coated electrospun nanofibre membranes for recovery of Au(III) from aqueous solution

In this paper, for the first time, polypyrrole-coated electrospun nanofibre mats have been used as separation membranes to electrolessly recover Au from aqueous [Au(III)Cl₄]− solutions, based on a continuous-flow membrane separation process. With a [Au(III)Cl₄]− solution passing through the nanofibre membrane, the Au(III) ions were converted into elemental Au. The gold recovered was deposited on the nanofibre membranes in the form of Au particles, as confirmed by EDX and XPS measurements. It has been found that the polypyrrole-coated electrospun nanofibres are good candidate membrane material for the recovery of Au, and the recovery efficiency is affected by the membrane thickness, the permeate flux rate and the initial [Au(III)Cl₄]− concentration.

Conductive poly(α,ω-bis(3-pyrrolyl)alkanes)-coated wool fabrics

Cross-linked poly(α,ω-bis(3-pyrrolyl)alkanes) were directly applied to woven wool substrates by either chemical, vapour or mist polymerization methods. Choice of dopant could greatly improve the surface resistance. The optimum coating on textiles with the lowest surface resistance, highest colour-fastness and stability was achieved using a mist polymerization method with 1,8-bis(pyrrolyl)octane, iron(III) chloride (FeCl₃) as the oxidant and p-toluene sulfonic acid sodium salt (pTSA) as the dopant.

Effect of weight reduction pre-treatment on the electrical and thermal properties of polypyrrole coated woven polyester fabrics

Weight reduction increased the amount of deposited polypyrrole (PPy) on the polyester (PET) fiber surface, leading to a considerable decrease in electrical resistance and improved heat generation capacity for the PPy coated PET fabrics. Application of dc voltages to an insulated roll of PPy-coated fabric increased the temperature to about 90 °C. This showed the suitability of these fabrics for heating applications. The optimum PPy deposition of about 2.8% was obtained in samples weight reduced by aqueous sodium hydroxide treatment. AFM images revealed a smooth surface morphology of the untreated fiber whereas the treated fiber had a high surface roughness.

Conducting polymer coated fabrics for potential applications in microwave frequencies : a study of electromagnetic properties

The microwave reflection, transmission and complex permittivity of paratoluene-2-sulfonic acid doped conducting polypyrrole (PPy/pTSA) coated Nylon-Lycra textiles in the 1-18 GHz frequency were investigated. The real part of permittivity increased with polymerization time and dopant concentration, reaching a plateau at certain dopant concentration and polymerization time. The imaginary part of permittivity showed a frequency dependent change throughout the tested range. All the samples had higher values of absorption than reflection. The total electromagnetic shielding effectiveness exceeded 80% for the highly pTSA doped samples coated for 3 hours.

Effects of laundering on conductivity of polypyrrole-coated textiles

This study examines the resistance change in conductive polypyrrole-coated PET fabrics under the AS 2001.4.15 – 1994 laundering test conditions. The effects of individual detergent components of a standard detergent, including auxiliary chemicals, at four different temperatures were studied. When the coated fabric was washed under the AS 2001.4.15-1994 conditions, the ECE reference detergent and pure soap flakes (sodium sterate) both decreased the conductivity of the coating at a rate exponentially proportional to the laundering temperature. Detergent types had an influence over the rate of degradation; pH conditions had a large influence on the rate of polymer deterioration with the acidic nonionic detergent giving rise to significantly improved laundering conditions. The auxiliary chemicals, sodium carbonate and sodium perborate were seen to cause large degradation of polymers during laundering. Ethylene diamine tetra acetic acid was seen to have only a slight influence on the reduction of conductivity of polymers.