Electrochemical impedance characterisation of tungsten trioxide–polyaniline nanocomposites for room temperature acetone sensing

Composites of WO3 nanoparticles and water-soluble polyaniline (PANI) particles doped with dodecyl benzenesulphonic acid at different mass ratios were deposited onto interdigitated electrodes and characterised using electrochemical impedance spectroscopy in air and in acetone vapour. The nanocomposites displayed an approximate equivalent circuit model of a parallel resistance and small inductance due to the PANI and a constant phase element (CPE) due to the WO3. The contribution of the CPE increased with increased WO3 loading. The nanocomposites mostly displayed increases in their real impedance on exposure to acetone at frequencies below 1 kHz, as well as a small increase in imaginary impedance. However, low WO3 loadings and low acetone concentrations resulted in decreases in film resistance. This effect is due to the balance of charge carriers in the film. The resulting sensors were able to detect 10 ppmv acetone at room temperature.