Authors: A. Teleki, S.E. Pratsinis, K. Kalyanasundaram and P.I. Gouma
Affilation: ETH Zürich, Switzerland
Pages: 423 - 426
Keywords: isoprene, acetone, ethanol, carbon monoxide, titania
Nanostructured anatase TiO2 was produced by flame spray pyrolysis (FSP) and tested for sensing of volatile organic compounds and CO at 500 °C. The as-prepared powders were characterized by transmission/scanning electron microscopy, x-ray diffraction and nitrogen adsorption. Titania films about 30 mm thick on alumina substrates interdigitated with gold electrodes were prepared by drop-coating a heptanol suspension of these powders. The films showed a high n-type sensor signal to isoprene, acetone and ethanol at concentrations ranging from 1 to 75 ppm in dry N2/O2 at 500 °C. The response (within seconds) and recovery (within minutes) times were very fast. Heat-treatment at 900 °C caused a nearly complete anatase to rutile transformation and a transition to p-type sensing behavior. That resulted in a poor sensor signal to all hydrocarbons tested and considerably longer recovery times than that of the anatase sensor. That rutile sensor could detect CO that the original, anatase sensor could not. For ethanol the sensor response changed back to n-type.