Synthesis, structure, and gas-sensing properties of Pt-functionalized TiO2 nanowire sensors.

TiO2 one-dimensional (1D) nanostrutures were synthesized by using a three-step hydrothermal technique. Subsequently, Pt nanoparticles were coated on the nanowire surface by sputter-deposition of Pt followed by annealing at 800 °C in an Ar atmosphere for 30 min. The morphology, crystal structure, and enhanced sensing characteristics of the TiO2 nanostructures functionalized with Pt to CO and NO2 gases at 300 °C were investigated. The diameter of the 1D nanostructures was in a range from a few tens to a few hundreds of nanometers and the length was up to a few tens of micrometers. The TiO2 nanowires synthesized by the three-step hydrothermal technique comprised two polymorphic (rutile and anatase) TiO2 phases and a Ti2O3 phase. Pt nanoparticle with various sizes ranging from 30 to 200 nm were on the whole uniformly distributed around the surface of each TiO2 nanowire. The sensitivity of the TiO2 nanowires was improved by a factor of 1.55 at a CO concentration of 30 ppm and 1.18 at NO2 concentrations of 50 ppm, respectively, by Pt-functionalization at 300 °C. In addition, the mechanism for the improvement in the gas sensing properties of TiO2 nanowires by Pt functionalization are discussed.