Polypyrrole Microwires as Toxic Gas Sensors for Ammonia and Hydrogen Sulphide

Polypyrrole (PPy) microwires synthesized via template assisted chemical polymerization method were investigated as gas sensors for ammonia (NH3) and hydrogen sulphide (H2S) toxic gases. The sensor was fabricated by a facile technique in which polypyrrole microwires were packed between a pair of indium tin oxide (ITO) coated glass slides acting as electrodes. Electrical conductivity of sensor, containing polypyrrole microwires, was examined with the exposure of the toxic gases at room temperature. It was observed that microwires detect the presence of toxic gases in terms of change in electrical conductivity. These microwires can be used as selective toxic gas sensor because conductivity decreases in the presence of NH3 gas and increases in the case of H2S gas. In both the cases, the change in conductivity was found to be reversible and a drift in recovery from the original value of electrical resistance (conductivity) was also observed on the removal of toxic gas environment. This happens as a consequence of the formation of hydronium ion because of the moisture present in the ambient air.