Polypyrrole matrix, electrochemical

A similar catalytic activity with a monomeric porphyrin of iridium has been observed when adsorbed on a graphite electrode.381-383 It is believed that the active catalyst on the surface is a dimeric species formed by electrochemical oxidation at the beginning of the cathodic scan, since cofacial bisporphyrins of iridium are known to be efficient electrocatalysts for the tetraelectronic reduction of 02. In addition, some polymeric porphyrin coatings on electrode surfaces have been also reported to be active electroactive catalysts for H20 production, especially with adequately thick films or with a polypyrrole matrix.384-387... 

Some applications of polypyrrole, such as drug delivery devices, require specific ion transport. Control of the ion transport process requires determination of the identity of the mobile ion, which is complicate by the fact that there are several ions present in the system. Moreover, Shimidzu and co-woiicers [138,139] demonstrated that ion transport in polypyrrole can be modified by the use of polymeric anions as dopants. Miller and Zhou [140] proved that the electrochemical switching of polypyrrole could achieve controlled release of small anions (such as CIO4), while the incorporation of an immobile polyanion (such as polystyrene sulfonate) resulted in cation transport. The polyanions become trapped within the polypyrrole matrix due to their large size and, perhaps more important, their entanglement with the polypyrrole chains. This increases the stability and mechanical strength of polypyrrole and improves electrical conductivity and electroactivity [141,142]. Therefore it has been of significant interest in the polymerization of pyrrole in polyanion electrolyte solutions [143,144]. 

Madasamy, T., Pandiar, M., Balamurugan, M., Santosh, K., Benjamin, A.R., Arunvenkatesh, K., Vairamani, K., Kotamraju, S., Karunakaran, C., 2012. Virtual electrochemical nitric oxide analyzer using copper, zinc superoxide dismutase immobilized on carbon nanotubes in polypyrrole matrix. Talanta... 

Rajesh, S., Kanugula, A.K., Bhargava, K., Ilavazhagan, G., Kotamr u, S., Karunakaran, C., 2010. Simultaneous electrochemical determination of superoxide anion radical and nitrite using Cu,ZnSOD immo-bihzed on carbon nanotube in polypyrrole matrix. Biosens. Bioelectron. 26, 689—695. 

An electron transfer type of enzyme sensor was thus fabricated by a electrochemical process. Although no appreciable leakage of ADH and MB from the membrane matrix was detected, NAD leaked slightly. To prevent this leakage, the ADH-MB-NAD/polypyrrole electrode was coated with Nation. A calibration curve is presented in Fig.25 for ethanol determination in an aquous solution with the enzyme sensor. Ethanol is selectively and sensitively determined in the concentration range from 0.1 nM to 10 mM. 

Perhaps the original hope for these polymers was that they would act simultaneously as immobilisation matrix and mediator, facilitating electron transfer between the enzyme and electrode and eliminating the need for either O2 or an additional redox mediator. This did not appear to be the case for polypyrrole, and in fact while a copolymer of pyrrole and a ferrocene modified pyrrole did achieve the mediation (43), the response suggested that far from enhancing the charge transport, the polypyrrole acted as an inert diffusion barrier. Since these early reports, other mediator doped polypyrroles have been reported (44t45) and curiosity about the actual role of polypyrrole or any other electrochemically deposited polymer, has lead to many studies more concerned with the kinetics of the enzyme linked reactions and the film transport properties, than with the achievement of a real biosensor. 

Polypyrrole electrochemically polymerized within a matrix resin electrically conducting material with improved mechanical properties over those of PPy Lindsey Street, 1985... 

Novel conductive composite films have been developed by Kaplin and Qutubuddin [101] using a two-step process microemulsion polymerization to form a porous conductive coating on an electrode followed by electropolymerization of an electroactive monomer such as pyrrole. The porous matrix was prepared by polymerizing an SDS microemulsion containing two monomers, acrylamide and styrene [102], The electropolymerization of pyrrole was performed in an aqueous perchlorate or toluenesulfonate solution. The effects of polymerization potential on the electropolymerization, morphology, and electrochemical properties were reported [101]. The copolymer matrix improves the mechanical behavior of the polypyrrole composite film. 

An approach which is now becoming of more importance in the development of enzyme-based biosensors is that of immobilisation of the active protein in a polymer matrix. We have now carried out a preliminary investigation into the incorporation of anti-HSA into an electrochemically-generated conducting polypyrrole film. Conducting polymers such as polypyrrole (I)... 

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