Electropolymerization membranes

So far, the Zilka group has successfully used this system to study changes in extracellular glutamate associated with several neurological diseases [140-144]. One drawback lies in the rapid deterioration of the electropolymerized membrane, which has to be used within a short time after the preparation to ensure the exclusion of electroactive interferents. 

Diffusion barrier Ion-exchange membranes for immobilization Electropolymerized membranes (various functions) ... 

The enzyme can be immobilized on the electrode by several techniques (53). The simplest method, first used in 1962, is to trap an enzyme solution between the electrode surface and a semipermeable membrane. Another technique is to immobilize the enzyme in a polymer gel such as polyacrylamide which is coated on the electrode surface. Very thin-membrane films can be obtained by electropolymerization techniques (49,54,55) using polypyrrole, polyindole, or polyphenylenediamine films, among others. These thin films (qv) offer the advantage of improved diffusion of substrate and product that... 

An alternate method to produce templated electrodes is the use of chemical reduction of the monomer in the presence of a track-etched or alumina membrane. Parthasarathy et al. [46] have produced enzyme-loaded nanotubules by a combination of both electrochemical and chemical deposition. Initially, the alumina membrane was sealed at one end with a thick Au film (Figure 1.9a), after which the membrane was placed into a mixture of pyrrole and Et4NBF4. The pyrrole was then electropolymerized to form a small plug of polypyrrole at the closed end of the alumina membrane (Figure 1.9b). Subsequently, the membrane was placed into a... 

By electropolymerization of pyrrole in solvents containing polyelectrolytes such as potassium polyvinylsulfate, it is possible to prepare films of polypyrrole with polymeric counterions which have good conductivity (1-10 S cm-1) and strength (49 MPa) 303 304,305). Such a material could be used reversibly to absorb cations in an ion exchange system. Pyrrole has also been electrochemically polymerized in microporous polytetrafluoroethylene membranes (Gore-tex), impregnated with a perfluorosulphonate ionomer 3061. 

Chen X, Hu Y, Wilson GS. Glucose microbiosensor based on alumina sol-gel matrix/ electropolymerized composite membrane. Biosensors Bioelectronics 2002, 17, 1005-1013. 

For microelectronic biosensors a further problem is the immobilization procedure of enzymes. Again different approaches were tried including drop-on techniques [61], ink-jet printing [68], spray techniques [62], electropolymerization [64], lift-off techniques [63,66] and photolithographically patterned enzyme membranes [65]. 

The reported semi-permeable membrane consists of an electropolymerized di-amino-benzene in phosphate buffer (pH 7). Polymerization is achieved by cycling the potential between 200 mV and + 800 mV for a certain period. In principle such an electrode modification hinders fouling in an excellent way [77]. 

The electropolymerization of the semipermeable membrane can be performed on the Pt electrodes on a wafer as well as the photopatterning of the enzyme mem-... 

The incorporation of vitamin B12 derivatives into plasticized poly(vinyl chloride) membranes has resulted in the development of several ion-selective electrodes (ISEs). The response of the electrodes has been related to principles of molecular recognition chemistry. In addition, ISEs have been prepared by electropolymerization of a cobalt porphyrin. These electrodes have selectivity properties that are controlled by both the intrinsic selectivity of the metalloporphyrin and the characteristics of the polymer film (e.g., pore size). 

In summary, it has been demonstrated that ISEs can be designed by employing molecular recognition principles. In particular, the feasibility of using hydrophobic vitamin B12 derivatives and electropolymerized porphyrin films in the development of polymer membrane anion-selective electrodes has been demonstrated. The studies indicated that the changes in the selectivity of these ISEs can be explained by the difference in structure of the ionophores. In addition, it was shown that by electropolymerization of a cobalt porphyrin, anion-selective electrodes can be prepared that have extended lifetimes compared with PVC-based ISEs, which use a similar compound as the ionophore. 

Figure 4. Electropolymerization of conducting polymer in a nanoporous membrane.

Different other attractive way to modify the active electrode of amperometric sensors, besides deposition of polymers or electropolymerization, is formation of self-assembled structures, e.g., self-assembled monolayers (SAM) on solid supports 88 89 or bilayer lipid membranes (BLM) on various types of support.90 Both types of theses structures can either induce selectivity of sensor to particular analytes and... 

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