Polyaniline deposits

However, ultra-thin films of unsubstituted polyaniline deposited on ITO glass electrode produced by dip coating, spin coating and the LB technique showed the most informative voltammetric characteristics. The single-layer LB films of polymer showed much better and reversible electrochromic activity on repeated scanning within up to 0,9 V in 1,0 M HCl solution than in electrochemically prepared materials [287],... 

T.V. Shishkanova, P. Matejka, V. Krai, I. Sedenkova, M. Trchova, and J. Stejskal Optimization of the thickness of a conducting polymer, polyaniline, deposited on the surface of poly(vinyl chloride) membranes A new way to improve their potentiometric response. Anal. Chim. Acta, 624, 238-246 (2008). 

FIGURE 18.10 Cyclic voltammetry (CV) of thin films of highly sulfonated polyaniline deposited from solution (HSPAN) and similar material synthesized by reduction of emeraldine salt by sulphite ion followed by oxidation (ES + HS03 - - O2). (Reprinted from Barbero, C., H.l. Salavagjone, D.E Acevedo, D.E. Grumelli, F. Garay, G.A. Planes, G.M. Morales, and M.C. Miras. Electrochim. Acta., 49, 3671—3686, 2004. With permission.)... 

Xu Z, et al. A study of polyaniline deposited nanocrystalline diamond films for glucose detection. J Nanosci Nanotechnol 2007. 

Elyashevich, G.K., Sidorovich, A.V., Smirnov, M.A., Kuryndin, I.S., Bobrova, N.V., Trchova, M., Stejskal, J. Thermal and stmctural stability of composite systems based on polyaniline deposited on porous polyethylene films. Polym. Degrad. Stab. 91, 2786-2792 (2006)... 

Deposition of condncting polymers can be accomplished by either direct or feedback modes of SECM. In an earlier study, SECM was used to deposit polyaniline on a Pt substrate by scanning a UME tip in thin, ionically conductive Nafion films coated on the Pt surface (127). Anilinium ions were incorporated into Nafion films and the Pt substrate was biased positively, which caused the electropolymerization of aniline. The resolution of the polyaniline deposition is controlled by the tip size, the thickness of Nafion films, and the electric field distribution. 

Scanning electron microscopic investigation indicates the regularity of polyaniline deposit on the substrate which confirm the hypothesis that intermediate cations are adsorbed on the fabric and its further coupling on the fabric surface is responsible for adherent deposits of polyaniline (Figure 12.33a). 

Deng, M., B. Yang, and Y. Hu. 2005. Polyaniline deposition to enhance the specific capacitance of carbon nanotubes for supercapacitors. Journal of Materials Science, 40,5021-5023. 

Figure 9 Evolution of the inverse of surface resistance with thickness of polyaniline deposits.

Fig. 7. Electrical conductivity of a film of polyaniline deposited on a double-band electrode measured as a function of electrode potential in situ in a solution of 1-N H2SO4 with a dc voltage (top) and an ac voltage (bottom) applied. Data for (a) from [72] data for (b) are from [73].

Fig. 35.6 Continuous polyaniline deposition range. (Photo courtesy of Atomic Energy Commission, Monts, France.)...

Ferraris and colleagues studied laminate films of PEDOTT spin coated on electropolymerized N-methylpolypyrrole, polyaniline spin coated on PEDOT PSS, and polyaniline deposited on electropolymerized N-methylpolypyr-role. The films were analyzed using CIE (x, i/)-chromaticity coordinates. The observed colors in their fully doped and reduced states were found to be linearly dependent on the color coordinates of the two individual polymers of the laminate, which allows for adjusting the observed color by variation of layer thickness of an electrochromic device in a viable and predictable way. Inganas ° studied a laminate structure made from polypyrrole electro-chemically deposited on top of a PEDOTPSS layer formed by spin coating. In contrast to Ferraris et al. he found that the spectra of the laminate electrode matches well with spectra of pure polypyrrole. 

Viswanathan S, Radecka H, Radecki J (2009) Electrochemical biosensor for pesticides based on acetylcholinesterase immobilized on polyaniline deposited on vertically assembled carbon nanotubes wrapped with ssDNA. Biosens Bioelectron 24(9) 2772-2777. doi 10.1016/j.bios. 

Functionalized conducting monomers can be deposited on electrode surfaces aiming for covalent attachment or entrapment of sensor components. Electrically conductive polymers (qv), eg, polypyrrole, polyaniline [25233-30-17, and polythiophene/23 2JJ-J4-j5y, can be formed at the anode by electrochemical polymerization. For integration of bioselective compounds or redox polymers into conductive polymers, functionalization of conductive polymer films, whether before or after polymerization, is essential. In Figure 7, a schematic representation of an amperomethc biosensor where the enzyme is covalendy bound to a functionalized conductive polymer, eg, P-amino (polypyrrole) or poly[A/-(4-aminophenyl)-2,2 -dithienyl]pyrrole, is shown. Entrapment of ferrocene-modified GOD within polypyrrole is shown in Figure 7. 

A thin layer deposited between the electrode and the charge transport material can be used to modify the injection process. Some of these arc (relatively poor) conductors and should be viewed as electrode materials in their own right, for example the polymers polyaniline (PAni) [81-83] and polyethylenedioxythiophene (PEDT or PEDOT) [83, 841 heavily doped with anions to be intrinsically conducting. They have work functions of approximately 5.0 cV [75] and therefore are used as anode materials, typically on top of 1TO, which is present to provide lateral conductivity. Thin layers of transition metal oxide on ITO have also been shown [74J to have better injection properties than ITO itself. Again these materials (oxides of ruthenium, molybdenum or vanadium) have high work functions, but because of their low conductivity cannot be used alone as the electrode. 

Polymerization at constant current is most convenient for controlling the thickness of the deposited film. Charges of ca. 0.3, 0.2, and 0.08 C cm-2 are required to produce 1 fim of polypyrrole,59 poly(3-methylthio-phene)60 (no data are available for polythiophene), and polyaniline 43 respectively. Although these values can reasonably be used to estimate the thicknesses of most electrochemically formed conducting polymer films, it should be noted that they have considerable (ca. 30%) uncertainties. For each polymer, the relationship between charge and film thickness can... 

A number of approaches are available to improve the morphology and homogeneity of electrochemically deposited conducting polymer films. Priming of the electrode surface with a monolayer of adsorbed or covalently bonded monomer leads to more compact deposits of polyaniline,87,88 poly thiophene,80 and polypyrrole.89,90 Electrode rotation has been shown to inhibit the deposition of powdery overlayers during poly(3-methylthiophene) deposition.81... 

Incorporation into a Polymer Layer In recent years a new electrode type is investigated which represents a layer of conducting polymer (such as polyaniline) into which a metal catalyst is incorporated by chemical or electrochemical deposition. In some cases the specific catalytic activity of the platinum crystallites incorporated into the polymer layer was found to be higher than that of ordinary dispersed platinum, probably because of special structural features of the platinum crystallites produced within the polymer matrix. A variant of this approach is that of incorporating the disperse catalyst directly into the surface layer of a solid polymer electrolyte. 

The polymerisation appears to involve a nucleation process similar to that of the deposition of metals [182], and electrochemically-prepared polyaniline will form dense, non-fibrillar thin films [165, 173], but thicker films ( > 150nm) become less densely packed and more fibrous [176, 182]. This may be due a change in the deposition mechanism when the film becomes sufficiently thick to inhibit direct access to the platinum by unreacted monomer [176],... 

Qiu, J.-D., et al., Controllable deposition of a platinum nanoparticle ensemble on a polyaniline/graphene hybrid as a novel electrode material for electrochemical sensing. Chemistry - A European Journal, 2012.18(25) p. 7950-7959. 

Similar approach has also been taken by Ferain and Legras [133,137,138] and De Pra et al. [139] to produce nanostructured materials based on the template of the membrane with etched pores. Polycarbonate film was also of use as the base membrane of the template, and micro- and nanopores were formed by precise control of the etching procedure. Their most resent report showed the successful formation of ultrasmall pores and electrodeposited materials of which sizes were as much as 20 nm [139]. Another attractive point of these studies is the deposited materials in the etched pores. Electrochemical polymerization of conjugated polymer materials was demonstrated in these studies, and the nanowires based on polypyrrole or polyaniline were formed with a fairly cylindrical shape reflecting the side wall structure of the etched pores. Figure 10 indicates the shape of the polypyrrole microwires with their dimension changes by the limitation of the thickness of the template. 

ZnO displays similar redox and alloying chemistry to the tin oxides on Li insertion [353]. Therefore, it may be an interesting network modifier for tin oxides. Also, ZnSnOs was proposed as a new anode material for lithium-ion batteries [354]. It was prepared as the amorphous product by pyrolysis of ZnSn(OH)6. The reversible capacity of the ZnSn03 electrode was found to be more than 0.8 Ah/g. Zhao and Cao [356] studied antimony-zinc alloy as a potential material for such batteries. Also, zinc-graphite composite was investigated [357] as a candidate for an electrode in lithium-ion batteries. Zinc parhcles were deposited mainly onto graphite surfaces. Also, zinc-polyaniline batteries were developed [358]. The authors examined the parameters that affect the life cycle of such batteries. They found that Zn passivahon is the main factor of the life cycle of zinc-polyaniline batteries. In recent times [359], zinc-poly(anihne-co-o-aminophenol) rechargeable battery was also studied. Other types of batteries based on zinc were of some interest [360]. 

Other Substrates Deposition of cadmium was also studied on Bi, Sn and Pb [303], Ni [304], reticulated vitreous carbon [305], Ti [306], and indium tin oxide [307]. UPD of Cd on tellurium results in CdTe formation [270, 308]. Electrodes coated with conducting polymers were also used to deposit cadmium electrochemi-cally. In the case of polyaniline, the metal reduction potential corresponds to the neutral (nonconducting) state of the polymer, therefore cadmium was found to deposit on the substrate-glassy carbon electrode surface, in the open pores of the polymer film [309, 310]. 

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