Mixed SnO 2/TiO 2 included with carbon nanotubes for gas-sensing application

Abstract

TiO 2 and SnO 2 are the well-known sensing materials with a good thermal stability of the former and a high sensitivity of the latter. Carbon nanotubes (CNTs) have also gas sensing ability at room temperature. CNTs-included SnO 2/TiO 2 material was a new exploration to combine the advantages of three kinds of materials for gas-sensing property. In this work, a uniform SnO 2/TiO 2 solution was prepared by the sol–gel process with the ratio 3:7 in mole. The CNTs with contents in the range of 0.001–0.5 wt% were dispersed in a mixed SnO 2/TiO 2 matrix by using an immersion-probe ultrasonic. The SnO 2–TiO 2 and the CNTs-included SnO 2–TiO 2 thin films were fabricated by the sol–gel spin-coating method over Pt-interdigitated electrode for gas-sensor device fabrication and they were heat treated at 500 °C for 30 min. FE-SEM and XRD characterizations indicated that the inclusion of CNTs did not affect the particle size as well as the morphology of the thin film. The sensing properties of all as-fabricated sensors were investigated with different ethanol concentrations and operating temperatures. An interesting sensing characteristic of mixed SnO 2/TiO 2 sensors was that there was a two-peak shape in the sensitivity versus operating temperature curve. At the region of low operating temperature (below 280 °C), the hybrid sensors show improvement of sensing property. This result gives a prospect of the stable gas sensors with working temperatures below 250 °C.