High-frequency measurements of conducting polymers: development of a new technique for sensing volatile chemicals

Electrically conducting polymers have previously been used for the detection of vapours and gases by measuring the reversible change in their DC resistance. The sensors have very broad chemical specificity with higher sensitivity to polar chemicals. The change in the AC impedance characteristics of poly-N-(2-pyridyl)pyrrole in the presence of three different volatile chemicals was investigated, in order to determine whether measurement of multifrequency parameters could be used as the basis of chemical discrimination. The results demonstrate quantification of concentration and discrimination between the chemicals tested on the basis of capacitance, conductance, resistance and dissipation factor as a function of frequency. This technique may be generally applied for discrimination between many chemical species.