Polypyrrole film resistance

Figure 16.16. Changes in resistance of polypyrrole films during storage in different atmospheres. The values are normalized to the initial resistance. Adapted from Synih. Met. 10, 303 (1985), with permission of Elsevier Science S.A., Lausanne.

Fig. 8.2. Plots of the drain current, /drain as a function of the drain voltage, / llrain, for a polypyrrole-based micro-eletrochemical transistor operated in MeCN containing 0.1 mol dm 3 B114NCIO4. Each curve corresponds to a different value of the gate voltage, /Jgate. As the gate voltage increases from —0.1 V vs. SCE to 0.6 V the resistance of the polypyrrole film decreases. The inset shows the arrangement used to make the measurement. Reproduced with permission from [1]. Copyright 1984 American Chemical Society...

Figure 12.14 Resistance vs. in-plane magnetic field curves at room temperature for electrodeposited (30 repeats) Co (2 nm)/Cu (3 nm) on conductive polypyrrole film (thickness 5 mm). (Reprinted with permission from Journal of Materials Chemistry, A flexible giant magnetoresistance sensor prepared completely by electrochemical synthesis by F. Van, G. Xue and F. Wan, 12, 2606-2608. Copyright (2002) Royal Society of Chemistry)...

Figure 11.19 High frequency part of capacitance and resistance of a polypyrrole film as function of the potential. The film was prepared by anodic oxidation in a perchlorate electrolyte. Additionally, the cyclic voltammogram is shown. The film has metal-like properties at positive potentials (E> OV) and neutral state properties at negative potentials (E < -0.5 V).

Fig. 7 Correlation of absorbance (at 800 nm) with resonant resistance (left-hand panel) and frequency shift (right-hand panel) during redox cycling of a polypyrrole film on an ITO electrode supported on a 9-MHzTSM resonator. Voltammetric experiment scan rate 50 mV s" Solution aqueous 0.1 mol dm KCIO4. (Reproduced from Ref [55] with permission from The Electrochemical Society.)...

Several recent reports describe using clay or other inorganic fillers to form CP composites. Polyani-line-polypyrrole composite coatings containing clay or yttria stabilized zirconia were electrodeposited onto AA 2024-T3 [158], with improved corrosion resistance of the substrate. Similarly, particulate-filled polyaniline and polypyrrole films on AA 2024-T3 were prepared electrochemically using a variety of fillers, including clay, carbon black, short carbon fiber, zirconia, and silica [159]. Again, enhanced corrosion performance for these composites was observed. 

Kowalski, D Ueda, M and Ohtsuka, T. (2007) The effect of counter anions on corrosion resistance of steel covered by bi-layered polypyrrole film. Corros. Sci.,... 

Fig. 9. Experimental setup for impedance measurements with electrochenucal control of membrane impedance platinized platinum electrodes (a) constant voltage power supply, (b) gold minigrid electrode (c) polypyrrole film, (d) 1 M KCl solution (e) constant current ac circuit, (f). At right is a microscopic view of membrane, illustrating effect of membrane potential on ionic resistance (reprinted with permission ft om Ref.

The conductimetric device based on chemically modulated resistance (chemoresistance) seeks to relate the chemical potential of an analyte to the rate of change (kinetic response) or extent of change (steady-state or equilibrium response) of conductance. For example, the exposure of polypyrrole films to electron-donating gases such as NH3 and H2S compensates free carriers, reduces the carrier density in the polymer, and decreases its conductivity [91]. Conversely, electron-accepting gases... 

When oxalic acid is used to form the polypyrrole coating, the result is a film that is very stable in time without a significant change in the corrosion behaviour properties after 72 h of immersion to sodium chloride solution. The net corrosion current naturally increases after 72 h of immersion and is followed by a decrease in the polarisation resistance, but overall, it is a very stable system, with a safe passivation range (Fig. 15.9a,b. Table 15.5). Over-oxidation of a part of polypyrrole films would have occurred as discussed, but the amount of degraded polypyrrole should be small as the release of doping anions, a property of well formed conducting polymer film, is clearly seen. 

Figure 13. Electroacoustic characterization of the quartz crystal loaded by a polypyrrole film, (a) Butterworth-Van Dyke equivalent circuit, (b) Change of the frequency, fs = l/(2w vTinOn), and motional resistance, Rm, with respect to the polypyrrole film thickness. From AI-Sana et al. ...

It has been shown that the thickness of the polypyrrole (PPy) film has a significant effect on the electrode performance.17 Figure 6 shows the dependence of the response of PPy/PQQ modified electrode to 10 mM DMAET (A) and 10 mM DEAET (B) as a function of PPy film thickness. As film thickness increases the oxidation current increases for both DMAET and DEAET, presumably due to increases in the amount of PQQ loaded in the PPy film. The maximum current for the oxidation of PQQH2 is observed when 200 nm films are used. When the PPy film thickness was larger then 200 nm a decrease in the sensor response was observed, which could be due to increased resistance (R ) of the thicker film. The optimum 200 nm PPy film thickness was used to characterize the performance of the electrode for amperometric detection of thiols. 

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