Poly films cyclic voltammetry

Fig. 4. Voltammograms in 0.1M Eti+NClOi+ZCH CNj rT = 1.2X1 O 8 mol/cm. Curve As Cyclic voltammetry of Pt/poly-Co -NI TPP at 20 mv/s = 200pA/cm. Curve B Four-electrode voltammetry of Pt/poly-Co( -NHi(,)TPP/Au sandwich electrode with E u = 0.0 Vj Ep scanned negatively at 5 mV/s = 400pA/cm. Curve Ci Surface profilometry of a poly-Co(o-NH2)TPP film on Sn02/glassj Tt = 7.6X10 9 mol/cm. (Reproduced from Ref. 6. Copyright 1987 American Chemical Society.)...

The electrochemical behavior of poly(ferrocenylsilanes) has been studied at three levels—in solution by cyclic voltammetry, as films deposited on electrodes, and in the solid state via iodine doping. Solution cyclic voltammetric oxidation and reduction has shown that the polymer, where R/R is Me/Me, reversibly oxidizes in methylene chloride in two stages, apparently with the first oxidation being on alternating iron atoms along the chain.29 Films cast on electrodes behave in a similar way and also show an electrochromic response to oxidation and reduction.30... 

Plasma polymerized N-vinyl-2-pyrrolidone films were deposited onto a poly(etherurethaneurea). Active sites for the immobilization were obtained via reduction with sodium borohydride followed by activation with l-cyano-4-dimethyl-aminopyridinium tetrafluoroborate. A colorometric activity determination indicated that 2.4 cm2 of modified poly(etherurethaneurea) film had an activity approximately equal to that of 13.4 nM glucose oxidase in 50 mM sodium acetate with a specific activity of 32.0 U/mg at pH 5.1 and room temperature. Using cyclic voltammetry of gold in thin-layer electrochemical cells, the specific activity of 13.4 nM glucose oxidase in 0.2 M aqueous sodium phosphate, pH 5.2, was calculated to be 4.34 U/mg at room temperature. Under the same experimental conditions, qualitative detection of the activity of a modified film was demonstrated by placing it inside the thin-layer cell. 

Cyclic voltammetry is also an ideal analytical tool for assessing the electrochemical stability of the polymer films. This is a fundamental requirement for any conducting polymer to be considered for long-term use in electrochemical devices. The use of ionic liquids for the electrochemical cycling of poly(aniline) has been reported to enhance lifetimes to over a million cycles [12], and significant improvements in the cycling stability of poly(pyrrole) have also been reported [32]. 

For poly(9,9-di-n-octylfluorene) (PFO), which is deemed a model polymer in PFs, Janietz and coworkers reported its HOMO (equivalent to ionization potential, Ip) and LUMO (equivalent to electron affinity, Ea) levels as 5.8 and 2.12 eV below the vacuum level, respectively, as determined from cyclic voltammetry (CV) measurements of PFO thin solid film [11] as shown in Fig. la. However, the HOMO and LUMO levels provide a larger band gap of 3.68 eV than the value of 2.95 eV determined from the onset position in the ultraviolet-visible (UV) absorption spectrum of PFO film. If the band gap is taken as 2.95 eV and the HOMO level as 5.8 eV, the LUMO level of PFO... 

The electrochemical behavior of poly(RCOT)s has also been examined [40]. As expected from the electrochemical properties of unsubstituted polyacetylene, films of poly(RCOT)s coated on an electrode and immersed in an acetonitrile electrolyte solution (in which the polymers are not soluble) are found to undergo reversible oxidative and reductive doping. Unlike unsubstituted polyacetylene, these films may be prepared readily by casting from solution, or, in the case of poly(scc-butylCOT), by electrodecomposition from a THF solution. In contrast to the voltammetry of polymer films, cyclic voltammograms of methylene chloride... 

Peerce, P. J., Bard, A. J. (1980). Polymer films on electrodes m. Digital simulation model for cyclic voltammetry of electroactive polymer film and electrochemistry of poly(vinylferrocene) on platinum. J Electroanal Chem 114, 89-115. 

Flavin mononucleotide (FMN) is an anion at pH 7 therefore it can be doped into poly(pyrrole) by growing films in the presence of the ion. Absorption spectra confirm the presence of FMN within films, and cyclic voltammery shows that entrapped flavin can be oxidized and reduced. It appears that entrapped reduced flavin is oxidized before the polymer backbone while the reduction of FMN and the backbone coincide. Electrochemistry of the entrapped material is shifted from that for the solution species, as we expect, due to the difference in the environment. The FMN has also been incorporated into poly(pyrrole-alkylammonium) films by ion exchange of the anion into the polymerized film. Reversible voltammetry for incorporated FMN was observed with a slight shift in potential with respect to the solution species, and it was attributed to microenvironmental effects. These films were shown to catalyze oxygen reduction. 

FIGURE 18.12 Cyclic voltammetry (CV) of a poly(benzimidazobenzophenanthroline) film coated on indium tin oxide (ITO) in acetonitrile. (Reprinted fi-om Quinto, M., S.A. Jenekhe, and A.J. Bard. Chem. Mater., 13, 2824-2832, 2001. With permission.)... 

Hunter et al [102] used both impedance and cyclic voltammetry to measure Cl for poly(vinylferrocene) films. Good agreement was found for Cl determined by the two independent techniques. Ho et al [103] had shown earlier that impedance techniques could be used to study insertion processes for intercalation oxides, but were unable to make observations at low enough frequencies to observe the redox capacity region. Mermillod et al [61] determined Cl with impedance and cyclic voltammetry on electrodes fabricated from poly(pyrrole) powders. 

In further studies, the self-doping mechanism of these polymers was verified by cyclic voltammetry, pH measurements and atomic absorption spectroscopy [17,20]. The cyclic voltammograms of the sodium salt and acid forms of poly(3-thiophene butanesulfonate) cast films are shown in... 

Figure 5.24 Cyclic voltammetry of poly(3-methylpyrrole-4-carboxylic acid) films as a function of pH. (Reprinted from Journal of Electroanalytical Chemistry, 225, P. G. Pickup, 273. Copyright (1987), with permission from Elsevier.)...

Using cyclic voltammetry of Fe(CN)6 at a rotating disk electrode, Schlenoff provided evidence that decreases in Faradaic current due to the presence of P S S/poly(diallydimethylammonium chloride) occur because of slow movement of Fe(CN)6 through the film [37]. Peak currents are independent of potential suggesting that diffusion rather than kinetics is limiting current. This is in agreement... 

Other redox-active polyelectrolyte films were prepared from ferrocene-derivatized polly(allylamine) and poly(vinyl pyridine) as well as an osmium complex of poly(vinyl pyridine) [44-46]. These films were synthesized to mediate electron transfer between the electrode and a charged enzyme that was a constituent of the polyelectrolyte film. In the case of ferrocene-derivatized poly(allylamine) or polyfvinyl pyridine), cyclic voltammetry of the bound ferrocene moiety showed small peak splittings (<50 mV at a scan rate of 50 and 20 mV s respectively) [45, 46). The amount of electroactive material increased with the number of deposited layers, but the first layer contained significantly more electroactive ferrocene than the later layers in the poly(allylamine) system [46]. 

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