Molecular recognition using conducting polymers: basis of an electrochemical sensing technology—Plenary lecture

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Abstract
Molecular recognition principles are being increasingly used as the basis for analytical technologies. The combination of a molecular recognition approach with conducting polymer materials has been beneficial, particularly in the field of electrochemical sensing. The electrochemical sensing process usually consists of two steps: analyte recognition and signal generation. Conducting polymers are versatile materials in which molecular/analyte recognition can be achieved in a number of different ways, including the incorporation of counter ions that introduce selective interactions, using the inherent and unusual ion-exchange properties of the conducting polymers; the addition of functional groups to the monomers; and the codeposition of metals within the polymer. Specific examples of these approaches are provided. The molecular recognition properties of conducting polymers can be further refined by the application of appropriate electrochemical potentials, which can induce either large or small changes in the chemical interactions that occur at the polymers. This electroactivity, as well as their conducting properties, also provides the basis for the signal generation steps. A number of electronic signals relating to some chemical or electrochemical change within the polymer can be measured. These include the faradaic electron transfer typically used for electrochemical sensing, the catalysis of the analytically useful electron transfer by the polymer or the analyte, the change in capacitance signals induced by the analyte species and changes in the polymer resistance which can be measured by a recently developed technique. These features, combined with the molecular recognition properties, make conducting polymers a very promising material for electrochemical sensing technology.