Electrochemical growth of gas-sensitive polyaniline thin films across an insulating gap

We have prepared and characterized conductive layers of emeraldine base polyaniline (PANI) and tested them as a transducer for gas/organic vapor sensors. The sensing layers of polyaniline were prepared in situ by electrochemical radical polymerization from a drop of an aqueous aniline solution in sulfuric acid placed in the gap between two gold electrodes separated 7-8 mum from each other. The layers were characterized by optical absorption and temperature-dependent electrical conductance measurements. The change in conductance of the 2-20 mum thin polymer layers was used as a sensor signal. The signal dependencies on both impurity concentration and temperature were investigated. The mechanism of charge carrier transport in the films and the interaction with different gas molecules are discussed. (C) 2004 Elsevier B.V. All rights reserved.