Ammonia gas sensors based on polypyrrole films: Influence of electrodeposition parameters

A gas sensor consisting in polypyrrole films electrochemically deposited on microelectrodes arrays was fabricated using silicon microtechnologies. Polypyrrole was electrodeposited on platinum microelectrodes using four different electrodeposition potentials, five counter-ions and three salt concentrations to assess the effects of these parameters on the sensing properties of polypyrrole films. The change in conductance of thin polymer layers, due to adsorption of ammonia gas, was used as a sensor signal. The behaviors of the polymer-based gas sensors, including response time, response amplitude, reproducibility and reversibility, to various ammonia gas concentrations ranging from 1 to 100 ppm were investigated. The experimental results showed that these ammonia gas sensors were efficient since they were sensitive to ammonia, and since their response was fast and reproducible at room temperature. The most efficient ammonia gas sensor was obtained with a 248 nm-thick polypyrrole film electrosynthesized from 0.1 M pyrrole and 0.1 M LiClO4 under an electrodeposition potential of +2.0 V/SCE.