Preparation of layered organic–inorganic nanohybrid thin films of molybdenum trioxide with polyaniline derivatives for aldehyde gases sensors of several tens ppb level

The present study is an investigation of the aldehyde gas sensing property of MoO3 with polyaniline (PANI) or poly(o-anisidine) (PoANIS) thin films, which are one of the layered organic–inorganic hybrids. The (PANI)xMoO3 and (PoANIS)xMoO3 hybrid thin films are formed by a modified intercalation process. A sodium molybdenum oxide ([Na(H2O)2]xMoO3) thin film is soaked in an intercalation solution, i.e. PANI or PoANIS solution, which is synthesized by polymerization of aniline or o-anisidine hydrochloride in a water solution. In this modified process, the intercalation solutions are filtrated in order to remove insoluble polymers possessing a high-polymerization degree. The (PANI)xMoO3 and (PoANIS)xMoO3 hybrid thin films prepared by the modified process can exhibit excellent response of a resistance increase when exposed to formaldehyde and acetaldehyde of several tens ppb because insoluble PANI or PoANIS impurities possessing opposite response of resistance decreases against the hybrids are prevented adsorbing onto the surfaces of the hybrid thin films.