Polypyrrole layer

The polypyrrole molecular interface has been electrochemically synthesized between the self-assembled protein molecules and the electrode surface for facilitating the enzyme with electron transfer to the electrode. Figure 9 illustrates the schematic procedure of the electrochemical preparation of the polypyrrole molecular interface. The electrode-bound protein monolayer is transferred in an electrolyte solution containing pyrrole. The electrode potential is controlled at a potential with a potentiostat to initiate the oxidative polymerization of pyrrole. The electrochemical polymerization should be interrupted before the protein monolayer is fully covered by the polypyrrole layer. A postulated electron transfer through the polypyrrole molecular interface is schematically presented in Fig. 10. 

Photoinduced Changes in Phase Boundary Potentials. The photoinduced membrane potentials were measured by using PVC matrix liquid membranes in contact with a polypyrrole-coated Pt electrode [dibutyl phthalate (DBP) as the membrane solvent]. The polypyrrole layer allows to obtain a stable and sample-in-dependent potential drop between Pt and the PVC membrane. The phase boundary potential at the interface of a membrane containing ionophore and an aqueous RbCl or KCl solution could be reversibly altered by UV and visible light irradiation, as shown for ionophore 89 in Figure 23a,b. The values of the photoinduced potential... 

Fig. 4. Direct light micrograph (side view) of a platinum wire, diameter 1.00 mm, which is coated by a polypyrrole layer (standard conditions, = 65(xm). The layer is in the dry state (cf. [19]).

Fig. 5. A plot of the measured thicknesses d of the polypyrrole layers shown in Fig. 4, but in the wet state, vs. the nominal thickness d , which is calculated by applying Faraday s law. Current densities for electrodeposition o, 0.4 mA/cm , 4 mA/cm. The l.T correlation is drawn as a broken line (cf. [19]).

Recent development in multilayer sensor architecture using sequential electrochemical polymerization of pyrrole and pyrrole derivatives to entrap enzymes was tested on a tyrosinase-based phenol sensor [127]. A phenothia-zine dye, thionine served as redox mediator and was covalently attached to the thin, functionalized first polypyrrole layer on Platinum disk electrodes. Then, a second layer of polypyrrole with entrapped tyrosinase was electrochemically deposited. The phenol sensor constructed in this manner effectively transferred electron from enz3Tne to the electrode surface. As all steps in preparation, including deposition of the enzyme-containing layer are carried out electrochemically, this technique may prove to be applicable for mass production of miniature sensors. 

Thionine-polypyrrole layer topped with enzyme entrapped polypyrrole layer Platinum disk... 

As mentioned previously a hybridization of an insulating PED film and a conductive polymer layer is quite attractive when they are applied to an electric device. In this case a hybridized multi-layered structure is expected to be fabricated, and the throwing power of the PED film can conveniently be utilized for this purpose. Additionally the photoelectrochemical area-selective doping and/or undoping of a polypyrrole film as dascrivec. earlier in this section encourage us to pursue this objective. The key problem in the fabrication of a hybridized multi-layered structure is hov to control the deposition of a PED overcoat onto polypyrrole layer and. vice versa. Figure 5 shows... 

It is apparent from the above results that an asymmetric cation exchange membrane, of which one surface of the membrane has a polypyrrole layer, can be prepared by contacting one surface of the ferric ion form cation exchange membrane with an aqueous pyrrole solution. Figure 5.9 shows a cross-section of a cation exchange membrane having a polypyrrole layer (polymerization period 4 h).57 The dark part of the photograph is where polypyrrole exists. Furthermore, EPMA (electron probe micro analysis) of the cross-section of a similar membrane (polymerization period 1 h) also reveals a thin layer of polypyrrole on the membrane surface.57... 

Figure 5.10 Change in transport number of calcium ions relative to sodium ions of a cation exchange membrane with and without a polypyrrole layer with the concentration of mixed salt solutions in electrodialysis. (A) Cation exchange membrane, NEOSEPTA CM-1 (O) membrane with a polypyrrole layer facing the anode side (X) membrane with polypyrrole layer facing the cathode side. After one surface of the cation exchange membrane (Fe3+ form) had contacted an aqueous pyrrole solution for 4 h, the membrane was immersed in LON hydrochloric acid solution before equilibration with the mixed salt solution used in electrodialysis.

Figure 5.11 Relationship of permeability coefficients of neutral molecules (urea, glucose and saccharose) through the cation exchange membrane NEOSEPTA CM-1 and the same membrane with a polypyrrole layer to the Stokes radius of the solutes. ( ) Cation exchange membrane without the layer (NEOSEPTA CM-1) (O) membrane with a polypyrrole layer facing the dilute side in the measurement (A) membrane with polypyrrole layer facing the concentrated side. One surface of ferric ion form NEOSEPTA CM-1 was in contact with an aqueous pyrrole solution for 10 min to form a polypyrrole layer (polymerization time 10 min.).

For electrodialysis of a cation exchange membrane with a single polyaniline layer facing the cathode side, PNaCa does not decrease, which is in complete contrast to a cation exchange membrane with a polypyrrole layer. The ionic composition in the membrane during electrodialysis, ATNaCa of Eq. (5.5), has been measured (Figure 5.14)60 [the membrane was immediately removed from the cell... 

Figure 5.16 shows the transport numbers of alkaline earth metal cations relative to sodium ions in a cation exchange membrane with and without polyaniline layers.60 The PNaM of the membrane with the polyaniline layers is remarkably low compared with that of the membrane without the layers, and lower than that of the membrane with a polypyrrole layer.57-60 It is interesting that the PNaM values of all alkaline earth metal cations attain almost the same value, independent of ionic species in the cation exchange membrane with the polyaniline layers. 

Conducting polymer films (modified or not) have been also used to perform the oxidation of organic compounds, such as ascorbic acid. For example, the rate of the electro-oxidation of ascorbic acid on glassy carbon is increased when the carbon electrode is previously covered with a polypyrrole layer [164]. In... 

Figure 16.44. Double logarithmic plot of rate constants k versus activity of OH— ions for the corrosion of 10 micron polypyrrole layers in Prideaux-Ward-buffer at pH 1-13. Adapted from Werkstoffe und Korrosion 42, 341 (1991), with permission of VCH, Lizenzen.

P. Hiilser and F. Beck, Electrodeposition of polypyrrole layers on aluminium from aqueous electrolytes, J. Appl. Electrochem. 20, 596-605 (1990). 

K. Naoi, M. Takeda, H. Kanno, M. Sakakura, and A. Shimada, Simultaneous electrochemical formation of A1203 polypyrrole layers (I) effect of electrolyte anion in formation process, Electrochim. Acta, 45, 3413 3421 (2000). 

Kaynak and coworkers [82,128] later reported on the effect of different dopant anions incorporated in the polypyrrole-coated textiles on the heat generation of these materials. The polypyrrole layer was deposited onto a polyester/Lycra fabric using the in situ polymerization approach and was doped with anthraquinone-2-sulfonate, naphthalene-2-sulfonate, p-toluenesulfonate, or perchlorate. At an applied voltage of 24 V, the polypyrrole-coated fabrics, from all the four different dopant systems showed an increase in temperature with the anthraquinone-2-sulfonate-doped polypyrrole coating the most effective heat generator (AT 20°C) whereas the sodium perchlorate dopant system was the least effective (AT 3°C). The power density per unit area achieved in the anthraquinone-2-sulfonate-doped polypyrrole-coated fabric was 430 W/m, 200 W/m for naphthalene-2-sulfonate, 150 W/m for p-toluenesulfonate, and 55 W/m for perchlorate, respectively. 

Huelser, R, and R Beck. 1990. Electrodeposition of polypyrrole layers on aluminum from aqueous... 

Fenelon, A.M., and C.B. Breslin. 2003. Corrosion protection properties afforded by an in situ electropolymerized polypyrrole layer on CuZn. J Electrochem Soc 150 (11) B540. 

Nair et al. reported the high specific capacitance of 1510 F/g synthesized by electrochemical polymerization of polypyrrole-layer on electrophoreti-cally deposited graphene, and demonstrated the improved stability of composite compared to pyrrole [45]. 

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