Surface-area-controlled synthesis of porous TiO thin films for gas-sensing applications.

Surface-area-controlled porous TiO thin films were prepared via a simple sol-gel chemical route, and their gas-sensing properties were thoroughly investigated in the presence of typical oxidizing NO gas. The surface area of TiO thin films was controlled by developing porous TiO networked by means of controlling the TiO-to-TTIP (titanium isopropoxide, CHOTi) molar ratio, where TiO nanoparticles of size ∼20 nm were used. The sensor's response was found to depend on the surface area of the TiO thin films. The porous TiO thin-film sensor with greater surface area was more sensitive than those of TiO thin films with lesser surface area. The improved sensing ability was ascribed to the porous network formed within the thin films by TiO sol. Our results show that surface area is a key parameter for obtaining superior gas-sensing performance; this provides important guidelines for preparing and using porous thin films for gas-sensing applications.