Polypyrrole impedance

Figure 15. Complex plane impedance plots for polypyrrole at (A) 0.1, (B) -0.1, (C) -0.2, (D) -0.3, and (E) -0.4 V vs. Ag/AgCl in NaCl04(aq). The circled points are for a bare Pt electrode. Frequencies of selected points are marked in hertz. (Reprinted from X. Ren and P. O. Pickup, Impedance measurements of ionic conductivity as a probe of structure in electrochemi-cally deposited polypyrrole films, / Electmanal Chem. 396, 359-364, 1995, with kind permission from Elsevier Sciences S.A.)...

By comparing impedance results for polypyrrole in electrolyte-polymer-electrolyte and electrode-polymer-electrolyte systems, Des-louis et alm have shown that the charge-transfer resistance in the latter case can contain contributions from both interfaces. Charge-transfer resistances at the polymer/electrode interface were about five times higher than those at the polymer/solution interface. Thus the assignments made by Albery and Mount,203 and by Ren and Pickup145 are supported, with the caveat that only the primary source of the high-frequency semicircle was identified. Contributions from the polymer/solution interface, and possibly from the bulk, are probably responsible for the deviations from the theoretical expressions/45... 

Impedance, for measurement of the potential of zero charge, 35 Impedance blocks, for polypyrrole, 577 Impedance spectroscopy of electronically conducting polymers, 576 Indium... 

Burgmayer and Murray [40] reported electrically controlled resistance to the transport of ions across polypyrrole membrane. The membrane was formed around a folded minigrid sheet by the anodic polymerization of pyrrole. The ionic resistance, measured by impedance, in 1.0 M aqueous KC1 solution was much higher under the neutral (reduced) state of the polymers than under the positively charged (oxidized) state. The redox state of polypyrrole was electrochemically controlled this phenomenon was termed an ion gate, since the resistance was varied from low to high and vice versa by stepwise voltage application. 

C.M. Li, W. Chen, and X. Yang, Impedance labelless detection-based polypyrrole protein biosensor. Front. Biosci. 10, 2518—2526 (2005). 

As expected, the impedance responses obtained in practice do not fully match that of the model of Fig. 9.13. However, as shown by the typical case of Fig. 9.14 which illustrates the response obtained for a 5 mol% ClO -doped polypyrrole electrode in contact with a LiC104-propylene carbonate solution (Panero et al, 1989), the trend is still reasonably close enough to the idealised one to allow (possibly with the help of fitting programmes) the determination of the relevant kinetics parameters, such as the charge transfer resistance, the double-layer capacitance and the diffusion coefficient. 

Fig. 9.14 The ac impedance response of a Q04-doped polypyrrole electrode over a frequency range extending from 0.006 Hz to 6.5 kHz.

Polypyrrole readily forms acceptable films under a wide variety of conditions [86] though there are subtle distinctions in behaviour as a result of exact preparation procedure [87]. Ultrasound at 20 kHz at sufficient intensity impedes polypyrrole formation and removes the polymer coating from the electrode [88]. At higher ultrasonic frequencies (e.g. 800 kHz) a free-standing film is produced which can be peeled from the electrode. This film has the interesting feature that the imprint of the wave-... 

Polypyrrole has the potential to provide an effective method for reagentless transduction by immobilization of the ssDNA probe within the polymer matrix. Significant differences in the impedance profile of ssDNA and dsDNA have been demonstrated [59]. The differences in the impedance profile are purportedly based on intercalation differences of the polymer with ssDNA compared to dsDNA. The exact mechanism for impedimetric change resulting from conducting polymer films has not been identified, although it is likely linked, much like the impedimetric response of pure DNA, to the change in ion density that accompanies the double strand compared to the... 

BSA Selective binding to anti-BSA antibody in electropolymerised polypyrrole film on SPCE surface Impedance... 

Figure 4.38. Equivalent circuits of conducting polymers with a Randles circuit [12]. (Reprinted from Journal of Electroanalytical Chemistry, 420, Ren X, Pickup PG. An impedance study of electron transport and electron transfer in composite polypyrrole plus polystyrenesulphonate films, 251-7, 1997 with permission from Elsevier and from the authors.)...

Ren X, Pickup PG (1997) An impedance study of electron transport and electron transfer in composite polypyrrole plus polystyrenesulphonate films. J Electroanal Chem 420 251-7... 

Ren X, Pickup PG (1993) Impedance of polypyrrole perchlorate/polypyrrole poly(styrenesulfonate) bilayers. J Phys Chem 97 3941-3... 

Pickup PG (1990) Alternating current impedance study of a polypyrrole-based anion-exchange polymer. J Chem Soc Faraday Trans 86 3631-6... 

Burgmayer P and Murray R W 1984 Ion Gate Electrodes. Polypyrrole as a switchable ion conductor membrane J. Phys. Chem. 88 2515-21 Otero T F and de Larreta E 1988 Conductivity and capacity of polythiophene films impedance study J. Electroanal. Chem. 244 311-18 Sunde S, Hagen G and Odegird R 1993 Impedance analysis of the electrochemical doping of poly(3-methyl-thiophene) from aqueous nitrate solutions J. Electroanal. Chem. 345 59-82 Zaborsky O R 1973 Immobilized Enzymes (Cleveland, OH Chemical Rubber Company) (see especially pp 69,87)... 

The variation of transmission, reflection and dielectric properties with doping level and temperature have been investigated in the case of polypyrrole [68,69]. The heterogeneous nature of polyaniline ( metallic islands ) has been used in order to explain experimental results [50] and the tri-dimensional nature of metallic states has been examined [70], Polyaniline has also been characterised in the low-frequency range by impedance measurement [71],... 

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