PPy-coated electrodes

For these materials to be utilized in biomedical in vivo and in vitro applications, it is imperative that the material be sterilized before use. Sterilization of these materials can be performed using a variety of methods such as ethylene oxide gas [48-50], ultraviolet light [51,52], ethanol washing [53], and autoclaving [12,54], An alternative approach to sterilization of the formed ICPs is the polymerization of the ICP under sterile conditions. This approach was utilized by Richardson et al. [55] to prepare PPy-coated electrodes for use in auditory nerve studies. 

Other examples have focused on the permselective properties of ECP films rendered nonconjugated and electroinactive after the application of high oxidizing potentials. It has been reported that an overoxidized PPy film acted as a permselective, antifouling membrane capable of rejecting interferents [122-126]. The permselective response of this film arose from the introduction of carbonyl groups onto the polymer backbone during the overoxidation Step. The overoxidized PPy-coated electrode has been successfully used for the detection of neurotransmitters such as dopamine... 

Since the incorporation of a certain anion would take place for the system to reach equilibrium at the polymer coated electrode, the potential at the membrane-electrolyte interface would indicate the amount of anions incorporated. Indeed, a few groups of investigators realized that this was the case [274-276]. The potential at the PPy film coated electrode was shown to vary depending on the concentration of the Fe /Fe + pair [274], hydroxide ion [275], and many other anions and cations [276]. Recently, Hutchins and Bachas have developed a nitrate ion selective sensor using a PPy film coated electrode [277]. The electrode showed a near Nemstial slope of —56 1 mV per decade, good dynamic linearity, and a detection limit of (2 1) X 10 M for nitrate. The selectivity coefficients over CIO4 and 1 were 5.7 x 10 and 5.1 X 10 respectively. 

Figure 16.10 OCP curves of coated PPy zinc electrodes cured In air for 1 h at 180 °C and immersed in 3.5% NaCI solution. PPy films (Ri2iim thick) were synthesized in 2 M NaSac+ 0.5 M Py at pH 5 and 1.9 M NaSac + 0.1 M DISacH + 0.5 M Py at pH 5.4. (Reprinted with permission from Chemistry of Materials, Ultrafast electrosynthesis of high hydrophobic polypyrrole coatings on a Zinc electrode Applications to the protection against Corrosion by E. Hermelin,]. Petitjean, P.C. Lacaze et al., 20, 13, 4447—4456. Copyright (2008) Elsevier Ltd)...

Figure 17.8 Cyclic voltammograms of (a) the TPPS-Co/PPy nanocomposite-coated electrode in the 02-saturated PBS (solid line) (b) the TPPS-Co/PPy nanocomposite-coated electrode in the N2-saturated PBS, and (c) the bare Au electrode in the 02-saturated PBS scan rate is 50 mV s (Reprinted with permission from Journal of Physical Chemistry C., Template-Synthesized Cobalt Porphyrin/Polypyrrole Nanocomposite and Its Electrocatalysis for Oxygen Reduction in Neutral Medium by Qin Zhou, Chang Ming Li, Jun Li et a ., 111, 30, 11216-11222. Copyright (2007) American Chemical Society)...

PPy-coated Si electrodes exhibited much higher discharge capacities than the reported pure Si electrodes in each cycle. However, the capacity fading problem has not been solved. 

Rakhi et al reported the conducting-polymers (polyaniline [PANI] and PPy)-coated carbon nanocoils (CNCs) as efficient binder-free electrode materials for supercapacitors for the first time, in which the CNCs acted as a perfect backbone for the uniform distribution of the conducting polymers in the composites [16]. Ihe SC and maximum storage energy per unit mass of the composites were found to be comparable to one of the best-reported values for polymer-coated MWNTs. Dumanli et al. prepared the chemically bonded carbon nanofibers (CNFs)-PPy composite via electro-polymerization of Py on CNFs [17]. It showed that the final capacitance values were highly dependent on the number of deposition cycles and deposition rates. The best result for the coiled CNF-PPy composite system was found to be 27.6 C/cm at six times cycling using 25 mV/s. 

It is even more difficult to polymerize PPy electrochemically on a zinc electrode than on iron because zinc is more electropositive than iron. It was reported that pretreatment of zinc with Na2S resulted in homogeneous and adherent PPy films by two-step electrochemical polymerization [18]. In step I, very thin and mixed layers of ZnS and ZnO H, were formed by the electrochemical treatment of Zn in 0.3 M Na2S, whereas in step II, strongly adherent PPy films were produced by electrochemical polymerization. It was also reported that adherent PPy coating could be obtained on the zinc electrode by a one-step process when sodium sulfide was added to the electrolyte solution composed of pyrrole and oxalate [19]. 

PPy [129]. Glial cells appeared to attach better to Ppy- and SLPF-coated electrodes than uncoated electrodes, whereas neuroblastoma cells grew preferentially on and around the Ppy- and CDPGYl GSR-coated sites. The PPy-GHsGOO coating on the same probe did not show a preferential attraction to the cells. 

Figure 9.3 Photocurrent-potential curve of ZnTPPS-PPy-coated ITO electrode in Fe(CN)6 " aqueous solution.

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