Quartz crystal microbalance (QCM) sensor for ammonia gas using clay/polyelectrolyte layer-by-layer self-assembly film

An ammonia gas sensor which has a high sensitivity in robust conditions has been investigated. A nanoporous thin film consisting of polyelectrolytes and sheet particulate /spl alpha/-ZrP was assembled by a layer-by-layer self assembly method on the electrode of a quartz crystal microbalance (QCM). This QCM sensor showed an eight times higher sensitivity than that of QCM deposited with /spl alpha/-ZrP by a casting method in low relative humidity. This means that the polyelectrolytes worked not only as a stabilizer to form a porous structure, but also as a material to keep moisture. Consequently, we considered that the gas sensitivity of the thin film is increased for other hydrophilic gases.