Sensitivity of Polyaniline-Zinc Oxide Composite to Humidity

The paper presents synthesis, characterization and humidity sensing properties of polyaniline-zinc oxide composites. Polyaniline is prepared by oxidative polymerization of aniline under acidic condition and is mixed with different proportions of ZnO. These mixtures were pressed into pellets of organic-inorganic composite and then subjected to varying humidity. The pellets show change in their electrical resistance with change in relative humidity of the ambience. Critical dopant concentration leads to higher sensitivity to humidity and lower response and recovery times as compared to that for polyaniline reported earlier by the authors. The resistance falls from MW to kW as relative humidity increases from 20 to 90 RH %. The structural, morphological, FTIR and transmission studies of the composites have also been done. The XRD pattern of the composites at low metal composition is similar to polyaniline. Peaks corresponding to ZnO appear as the percentage doping increases. The FTIR spectra recorded in the range 4000-400 cm-1 show characteristic polyaniline bands between 750 –1800 cm-1. SEM shows rods and pebble-like aggregates which are evenly distributed on the surface of the samples. The increased surface area is useful for adsorption of gases and vapours for their detection