A rapidly-responding sensor for benzene, methanol and ethanol vapours based on films of titanium dioxide dispersed in a polymer operating at room temperature

Thin films of titanium dioxide (TiO2) powder, dispersed in poly(vinylidenfluoride) and deposited on glass slides containing gold electrodes, are used as sensors for benzene, ethanol and methanol vapours at room temperature. The resistance of the films at a potential difference of 1.5 V is determined when the films are exposed to atmospheres containing these vapours with concentrations over the range 150-350 ppm. The relative resistance, DeltaR, of the films increases linearly with increasing concentrations of the vapours (regression coefficients, r = 0.90, 0.98 and 0.97 for benzene, methanol and ethanol, respectively). The findings are consistent with the TiO2 films having p-type semiconductor characteristics. The responses of the films are reversible with changes in DeltaR of 0.042, 0.1 and 0.122% ppm(-1) for benzene, ethanol and methanol, respectively. The response times to increasing concentrations of the vapours are about 1, 2 and 2 min for benzene, ethanol and methanol, respectively, and the corresponding values for decreasing concentrations 5, 6 and 6 min, respectively. The limit of detection for the vapours is about 10 ppm. With improvements in the sensitivity, selectivity and stability, the fi:ms could form the basis of a handheld instrument for the atmospheric monitoring of benzene. (C) 2001 Elsevier Science B.V. All rights reserved.