Pt doping triggers growth of TiO2nanorods: nanocomposite synthesis and gas-sensing properties

Abstract

TiO₂ nanocrystals were prepared by solvothermal treatment in oleic acid at 250 °C of amorphous TiO₂ nanoparticles. The latter were prepared by sol–gel processing in dodecylamine at 100 °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 °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 °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.