Porous materials with high surface area are available for various applications such as sensor, catalysis, and optoelectronic devices. We applied the porous polyelectrolyte multilayer films with metal ion to Quartz crystal microbalance (QCM) gas sensor. To achieve these films, we developed a novel method; a dense structure transformed into the porous structure by immersing in specific metal ion solution. The sensitivity and selectivity of a sensor were enhanced by a combination of these porous films with metal ion and QCM.<br/>The dense polyelectrolyte multilayer film composed of poly(allylamine hydrochloride) (PAH) / poly(acrylic acid) (PAA) was formed on QCM by layer-by-layer self-assembly technique. The solution pH was adjusted at 11.5 for PAH and 9.0 for PAA. The porous polyelectrolyte multilayer film with metal ion was obtained when the dense PAH/PAA film was immersed in 1mM silver acetate solution (Figure 1). The mass increase due to gas adsorption was estimated from QCM frequency shift. In case the sensor exposed to a very low concentration of methyl mercaptan gas (20ppb), the frequency shift showed regular curve of absorption and desorption (Figure 2), despite it never responded to ammonia gas.<br/>To the best of our knowledge, this was the highest sensitivity among the reports of QCM gas sensors. A high sensitivity gas sensor of volatile sulfur compounds found wide ranging applications such as volcanic eruption prediction, food inspection, environmental analysis and medical diagnostics.

Porous materials consisting of metal ion and polyelectrolyte complex for gas sensor application

251st National Meeting (2016)

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