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 CC and NH 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.