Novel gas sensor using polymer-film-coated quartz resonator for environmental monitoring

The functional design of the smart electronic nose using polymer-film-coated quartz resonator gas sensors, based on the solubility parameter of sensing membrane and gases, is carried out in order to develop a sensor with excellent selectivity and high sensitivity for harmful gases such as toluene, acetaldehyde and ammonia gases. The polymer films such as propylene-butyl, polycarbonate and acrylic-resin of which the solubility parameter almost coincide with that of toluene, acetaldehyde and ammonia gases, respectively, are chosen as a sensing membrane material coated on the quartz resonator. It is found that propylene-butyl-film-coated quartz resonator gas sensor exhibits a high sensitivity and an excellent selectivity for toluene and p-xylene gas, as expected from a functional design based on solubility parameter. It is also found that polycarbonate-film-coated and acrylic-resin film-coated sensors exhibit high sensitivity and excellent selectivity for acetaldehyde and ammonia, respectively, also as expected. The results strongly suggest that solubility parameter is effective in the functional design of the sensing membrane of quartz resonator gas sensors. The successful identification of a specific gas is possible through the principal component pattern recognition analysis of the transient responses of each sensor for gases.