CO₂-sensitive Characteristics of Base-type Polyaniline/Poly(vinyl alcohol) Composites at Room Temperature and Effects of Coexisting Gases

Abstract

The development of a CO₂ sensor capable of operating at room temperature has been desired in order to monitor the concentration of CO₂ in fields such as environment, medical treatment and agriculture. The CO₂-sensitive characteristics of base-type polyaniline (PAn) / poly(vinyl alcohol) (PVA) at room temperature have been presented in which the logarithmic electrical resistance is linearly related with the log of CO₂ concentration in a wide range from 100 ppm to 100%. The response curves of the composite film to CO₂ were measured under the coexistence of various gases. The minimum concentrations of these gases at which the response curves started to be affected were : 3% (methanol, ethanol), 1% (benzene, toluene, xylene), 1000 ppm (NH₃), 100 ppm (NO₂), 50 ppm (HCHO), 10 ppm (HCI). These values were much higher than the maximum permissible limits of these gases, indicating that the composite film is useful as a CO₂ sensor at room temperature in a common living environment.