Development and characterization of gas sensors using thin films of polyaniline as active layer

This work aimed at the development and characterization of gas sensing devices using thin films of polyaniline (PAni) as active layer, deposited by in situ polymerization. The polyaniline, an intrinsically conductive polymer, was used due to its high sensitivity to gases, low response time and stability, ease of synthesis and low cost. The sensor was built on a glass fiber reinforced substrate with interdigitated gold electrodes coated with a PAni film layer whose thickness variation was fixed as a function of deposition time. The PAni characterization by Infrared Spectroscopy (FTIR) showed that the exposure to ethanol does not change the chemical structure of PAni. The thickness (3.5 mu m) and morphology of PAni films through Scanning Electron Microscopy (SEM) were compatible to those found in the literature. The electrical resistance of the sensors was evaluated as function of ethanol concentration and varied between 60 kohms for lower ethanol concentrations and 140 kohms for higher concentrations. Nevertheless, a statistical analysis of the measurements in five sensors with different ethanol concentrations demonstrated that the sensors have not been able to differentiate ethanol concentrations to the level of significance of 5%.