Polyaniline thin films as a toxic gas sensors in SAW system*

Presented here are the preliminary results concerning an investigations of thin films of polyaniline ($\sim $100 nm) as a toxic gas sensors in a Surface Acoustic Wave system. The investigations were performed with different concentrations of the following toxic gases: NO$_{2}$, SO$_{2}$, CO, H$_{2}$S and hydrogen in synthetic dry air. These thin films were made by vacuum deposition technique and formed in one of the dual delay line systems on a LiNbO$_{3 }$ Y-cut Z-propagation substrate, while the other serves as a reference, permitting an easy detection of the arising differential frequency $\Delta $f. This frequency, depending on the operating frequency modes, is in the range of 50 kHz to 400 kHz, whereas the oscillator frequencies are in the range of 43,6 MHz. The wavelength is 80 $\mu$m