Thin polyaniline and polyaniline/carbon nanocomposite films for gas sensing

We have studied the gas sensing properties of five polyaniline-based materials—thick and thin PANI films, nanocomposite PANI/MWNT and PANI/SWNT films, and PANI nanogranules embedded in a polyvinylpyrrolidone matrix. The films (except for the latter) were deposited within the induction period of the polymerization process on gold interdigitated micro electrodes. Their sensitivity to NH₃, H₂, ethanol, methanol, and acetone was measured. The thin PANI film (~ 100 nm thick) prepared by a lift-off process had the sensitivity to ammonia below 0.5 ppm, which was higher than that of nanocomposite films. Two materials—thick PANI film and nanocomposite PANI/MWNT film—exhibited a shallow minimum in the temperature dependence of resistance (at 313 K and 319 K), which is a feature exploitable in practical applications, since the gas sensors should be insensitive to small temperature fluctuations at these temperatures.