A SELECTIVE GAS SENSOR USING A POLYPYRROLE THIN-FILM AS A SENSITIVE MATRIX ON A PIEZOELECTRIC CRYSTAL

A novel gas sensor is fabricated on the basis of simultaneous measurem ents of resistance changes (Delta R) and mass changes (Delta M) of a c onducting polypyrrole (PP) film assembled on a piezoelectric crystal. Molecular species such as acetone, methanol and ethanol can be recogni zed by the (Delta R/R(0))/(Delta M/M(0)) values, where R(0) and M(0) a re the initial resistance and weight of the PP film respectively. In c ontrast, the quantitative analysis of the vapour molecules can be achi eved by measuring the Delta R/R(0) or Delta M/M(0) values. For a serie s of primary alcohols the homologues can also be recognized by the sim ultaneous measurement of Delta R and Delta M. Moreover, it is shown th at this sensor is usable to clarify the interactions between the PP fi lm and the vapour molecules.