2001 Volume 69 Issue 12 Pages 997-1001
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.