Polyaniline film

Ideal electrochemical polymerization was considered to give ideal linear and conjugated polymeric chains. The real situation is that films electrogenerated from the basic monomers are insoluble and infusible. Only polyaniline films are partially soluble in some solvents. 

Nucleation models have also been invoked for the oxidation of polyaniline films.209,213 In both cases, the nucleation of electronically conductive zones was assumed, following Aoki s well-documented model. The possibility that the nucleation of ionically conductive regions could be rate limiting does not appear to have been considered. 

Figure 12. Electrocatalytic oxidation of CO (from a CO-saturated 0.1 M HCIO4 solution) on different Pt-based electrodes (sweep rate 5 mV/s, 25 "C) ( ) smooth Pt, (0) 0.1 mg cm Pt dispersed in a polyaniline film,(A) 0.1 mg cm" R-Sn dispersed in a polyaniline film.

The electrochemistry of polyaniline is more complex than that of other conducting polymers and given the large number of possible structures for the material, it is not surprising that many possible reaction schemes have been suggested [181,182, 195-197,205], Many of the properties of the material are pH-dependent [173,174, 206], including the open circuit potential [207] which is most positive at pH 0, and this is further complicated by the fact that not all the polymer chains are necessarily in exactly the same state at any given time [197]. Above pH 3 polyaniline films do not show any electroactivity, but are not electroactive even at low pH with... 

Fig. 12. Absorption spectra of polyaniline film on a semitransparent Pt electrode immersed in 1 M HC1. Spectra (a) to (f) were recorded at potentials of —0.2, +0.6, +0.8, + 1.0, + 1.2 and + 1.4 V relative to a silver reference electrode. Reproduced from [173b],...

Kobayashi T., Yoneyama H., Tamura H. Polyaniline film-coated electrodes as electrochromic display devices J.Electroanal.Chem., 1984 161 429-23... 

Y. Wang, J. Huang, C. Zhang, J. Wei, and X. Zhou, Determination of hydrogen peroxide in rainwater by using a polyaniline film and platinum particles co-modified carbon fiber microelectrode. 

Polyaniline films TiOj Light images were formed in TiOrcontaining polyaniline films 103... 

Fig. 9.9 CV and frequency-potential curves for the oxidation and re-reduction processes of the electropolymerized polyaniline film [26] (a) in 0.5 M LiCICVAN, and (b) in aqueous 0.5 M NaCl04+HCIO4 (pH = 1). Voltage sweep rate 5 mVs-1, quantity of film deposition 0.4Ccm-2, and SSCE = saturated NaCl calomel electrode.

A recent example of the application of in situ FTIR reflectance spectroscopy to modified electrodes can be found in the work of Korzeniewski and her group [54] on Pt electrodes coated with films of the polymer polyaniline. Figure 13.6 shows the reflectance spectrum (in AR/R units) of a polyaniline film-coated electrode as a function of applied potential. As the film becomes more oxidized, the band at 1320 cm-1 is shifted to higher energies, a result consistent with an increasing C-N bond strength upon oxidation [54]. The interac-... 

Eftekhari [30] Glycerol Grape juice Glycerol dehyrogenase (NAD+ dependent)/into polyaniline film Aluminium electrode/ +0.35 V vs. NHE Fe(CN) -... 

Hu et al. [84] Hypoxanthine Fish Xanthine oxidase/within a polyaniline film on the electrode surface by electropolymerisation Sodium montmorillonite-methyl viologen carbon paste modified electrode/-0.72V vs. Ag/ AgCl Methyl viologen... 

On both Pt and polyaniline-coated electrodes, diffusion-limited currents are observed at <250 mV for Fe(CN)500 mV for Fe(CN)g- oxidation. Potentiostatic EHD impedance was measured on both diffusion plateaux (50 mV and 550 mV), using Pt electrodes coated with polyaniline films of various thickness 50 and 130nm. As an example, the results obtained on the cathodic plateau are shown in Fig. 6-13 those observed on the anodic plateau were very similar [93]. 

Consider the polymer-on-metal interface, which might be prepared by coating a thin metal film with polymer in a polymer-based LED. The case of the counter electrode, formed by vapor-deposition, is discussed subsequently. First, assume that the substrates have clean surfaces hydrocarbon and oxide free, or naturally oxidized but still hydrocarbon free (pointed out as necessary). Typically, in connection with polymer-based LEDs, the metallic substrate could be gold, ITO (indium tin oxide) coated glass, the clean natural oxide of aluminum ( 20 A in thickness), the natural oxide which forms upon freshly etched Si( 110) wafers ( 10 A), or possibly even a polyaniline film. Dirt , which may be either a problem or an advantage, will not be taken up here. Discussions will alternate between coated polymer films and condensed model molecular solid films, as necessary to illustrate points. 

Aizawa presented an overview on the principles and applications of the electrochemical and optical biosensors [61]. The current development in the biocatalytic and bioaffinity bensensor and the applications of these sensors were given. The optical enzyme sensor for acetylcholine was based on use of an optical pH fiber with thin polyaniline film. 

Andreev, V.N., Effect of solution acidity on the electrochemical behavior of Nafion-polyaniline films, Russ. J. Electrochem., 41, 200, 2005. 

Figure 1 Cyclic voltammograms recorded at 50mV/s during the electropolymerization on a gold surface of 0.1 M aniline in 0.5 M sulphuric acid (a), and of the polyaniline film in the supporting electrolyte (0.5 M sulphuric acid) alone after polymerization (b).

In a recent paper, Coutanceau et al. made a detailed kinetic study of the ORR on Pt particles dispersed in a polyaniline film with several Pt loadings ranging from a fewpgcm to a few hundred pgcm [20]. The PAni film (0.5-pm thickness) was... 

This section discusses the reactivities and biosensor applications of functionalized electrosynthetic polyanilines prepared by (i) electropolymerization and (ii) chemical polymerization of aniline on the surfaces of Au, glassy carbon or Pt disk electrodes. Four such polyaniline or substituted composite polyaniline films developed by our research group are (a) nanofibrillar polyaniline-polyvinyl sulfonate (PANI-PVS), (b) poly(2,5-... 

Kobayashi T., Yoneyama H., Tamura H. Polyaniline film-coated electrodes as electrochromic display devices J.Electroanal.Chem., 1984 161 429-23 Kobayashi T., Yoneyama H., Tamura H. Electrochemical reactions concerned with electrochromism of polyaniline film-coated electrodes. J.Electroanal.Chem 1984 177 ... 

A polyaniline film prepared by doping an emeral-dine base with optically active CSA showed a CD spectrum. Even after dedoping, the film exhibited CD bands which were different in pattern from those of the original dedoped film, suggesting that a chiral conformation such as a helix remains in the polymer chain. The dedoped film exhibited chiral recognition ability toward phenylalanine.235... 

Svetiidc, V. Schmidt, A. J. Miller, L. L., Conductometric sensors based on the hypersensitive response of plasticized polyaniline films to organic vapors, Chem. Mater. 1998,10,3305-3307... 

Chaubey, A., Pande, K.K., Singh, V.S., and Malhotra, B.D. (2000) Coimmobilization of lactate oxidase and lactate dehydrogenase on conducting polyaniline films. Analytica Chimica Acta, 407 (1-2), 97-103. 

Li ZF, Kang ET, Neoh KG, Tan KL (1998) Covalent immobilization of glucose oxidase on the surface of polyaniline films graft copolymerized with acrylic acid. Biomat 19 45-53... 

Salgaonkar, L.P. and Jayaram, R.V., Polyaniline film formation in hexadecyl trimethyl ammonium bromide admicelles on hydrous zirconia surface, J. Colloid Interf. Sci., 291. 92, 2005. 

Recent applications of SPM techniques have revealed new details of the electrical properties of conducting polymers. In one example, STM images were taken of the granular structure of electrochemically prepared polyaniline films. Simultane-... 

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