Gas sensor based on montmorillonite/polypyrrole composites prepared by in situ polymerization in aqueous medium

We have synthesized clay/polypyrrole composites via in situ polymerization in aqueous medium, with the anionic surfactant dodecylbenzenesulfonic acid sodium salt (DBSA) playing a dual role as a dopant. We submitted the commercial clay k10 montmorillonite to a previous organophilic treatment with hexadecyltrimethyl ammonium bromide (C19H42NBr). The lattice parameters, as determined by X-ray diffraction, were d = 1.35 nm, 1.9 nm and 4.2 nm, for the pure montmorillonite (MMTK10), organophilic MMT (MMTO), and MMTO/polypyrrole samples, respectively. Infrared absorption spectroscopy analysis confirmed the presence of vibration peaks associated to both C=C and N-H polypyrrole bonds and also to MMT characteristic groups. When tested as active materials in sensors of methanol, ethanol, hexane and benzene vapors, these composites have shown a significant sensitivity to the presence of both polar and nonpolar volatile organic compounds. In special, these hybrid (organophilic clay)/polypyrrole films have shown a better level of recognition towards nonpolar compounds than other doped PPY films previously examined. (c) 2012 Elsevier B.V. All rights reserved.