ELECTROCONDUCTING CONJUGATED POLYMERS - NEW SENSITIVE MATRICES TO BUILD UP CHEMICAL OR ELECTROCHEMICAL SENSORS - A REVIEW

Electroconducting conjugated polymers, ECPs, appear very attractive for use in sensors either as sensitive components or as a matrix for easy immobilization of specific substrates. This is due to their intrinsic properties: a one-step electrosynthesis in the form of an adherent film deposited at the surface of the electrode with anionic species being included by doping. This doping reaction makes it possible to modulate the conductivity reversibly over several orders of magnitude via redox interactions. ECP-based gas sensors are sensitive to gases (NO2, NH3, etc.) affecting the doping level, which results in a straightforward conductance monitoring. ECP-based ionic sensors amperometrically detect electroinactive ions, since the doping of the ECP results in a current flow. The ion-sieving effect allows some selectivity by cut-off size. SGFET microelectrochemical 'transistor' devices are sensitive to pH. Immobilization with a good 'electrical wiring' of enzymes in ECP films explains the increasing interest in research on ECP-based biosensors. An interesting approach is the simultaneous inclusion of the enzyme (glucose oxidase) with an anionic electron relay. A lifetime of 60 days has been reported. The versatile properties of ECP promise improvements in specificity, enzyme wiring and lifetime.