EXAMINATION OF AMMONIA POLY(PYRROLE) INTERACTIONS BY PIEZOELECTRIC AND CONDUCTIVITY MEASUREMENTS

The conducting polymer poly(pyrrole), electrochemically prepared and doped with anions, has been found to be a responsive coating for a piezoelectric gas detection system. Polymers doped with bromide, nitrate and sulphate ions were tested. It was found that samples of ammonia gas cause a measurable frequency decrease, interpreted as adsorption by the polymer coating of the quartz crystal; the linear range was 0.05-1% for mixtures of the gas in nitrogen. These signals were found to correspond to simultaneous conductivity changes of a similarly prepared poly(pyrrole) sample, showing analogies in the two sensing mechanisms. The duality of the poly(pyrrole) response increases the possibilities of using it as a gas sensor.