Pt doping triggers growth of TiO2 nanorods: nanocomposite synthesis and gas-sensing properties

TiO2 nanocrystals were prepared by solvothermal treatment in oleic acid at 250 degrees C of amorphous TiO2 nanoparticles. The latter were prepared by sol-gel processing in dodecylamine at 100 degrees C of starting solutions synthesized from TiCl4. For preparing Pt/TiO2 nanocomposites, with Pt/Ti nominal atomic ratio of 0.05, the required amount of Pt precursor was added to the amorphous TiO2 nanoparticles before heating at 250 degrees C. Control synthesis experiments, evaluated by X-ray diffraction and X-ray photoelectron spectroscopy showed Pt(acac)(2) as the best Pt precursor, and 250 degrees C as the optimum temperature for simultaneous TiO2 crystallization and efficient Pt nucleation. Transmission electron microscopy observations evidenced Pt nanocrystals dispersed in the surrounding TiO2 host, with a mean size of 4 nm. The TiO2 host was constituted of rod-shaped anatase nanocrystals. Comparison with pure TiO2 showed that the rod shape was favored by the presence of Pt species. As an example of application, the nanocomposites were used for preparing ethanol-sensing devices. The Pt addition remarkably improved the response with respect to pure TiO2 sensors, and electrical characterization of the sensors helped in establishing that the effect of Pt was due to spillover rather than electronic sensitization.