Surface-area-controlled synthesis of porous TiO ₂ thin films for gas-sensing applications

Surface-area-controlled porous TiO 2 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 2 gas. The surface area of TiO 2 thin films was controlled by developing porous TiO 2 networked by means of controlling the TiO 2 -to-TTIP (titanium isopropoxide, C 12 H 28 O 4 Ti) molar ratio, where TiO 2 nanoparticles of size ∼20 nm were used. The sensor’s response was found to depend on the surface area of the TiO 2 thin films. The porous TiO 2 thin-film sensor with greater surface area was more sensitive than those of TiO 2 thin films with lesser surface area. The improved sensing ability was ascribed to the porous network formed within the thin films by TiO 2 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.