Thin films of polypyrrole doped with different counter-ions, prepared by in
situ polymerization on conducting glass electrodes, are used for the devel
opment of gas sensors with fast response time. On exposure to a given vapor
, each individual film exhibits a fast change in the fractional difference
of its electrical resistivity and with the adopted arrays of 7 sensors it w
as possible to detect and identify simple organic solvents. The morphology
and structure of the films, and therefore the level of response to the vola
tile compounds, is determined by the structure of the counter-ion used.