Branching TiO₂ nanowire arrays for enhanced ethanol sensing

Nanostructure modulation is effective to achieve high performance TiO₂-based gas sensors. We herein report a wet-chemistry route to precipitate directly branched TiO₂ nanowire arrays on alumina tubes for gas sensing applications. The optimized branched TiO₂ nanowire array exhibits a response of 9.2 towards 100 ppm ethanol; whilst those of the pristine TiO₂ nanowire array and the branched TiO₂ nanowire powders randomly distributed are 5.1 and 3.1, respectively. The enhanced response is mainly contributed to the unique porous architecture and quasi-aligned nanostructure, which provide more active sites and also favor gas migration. Phase junctions between the backbone and the branch of the branched TiO₂ nanowire arrays help the resistance modulation as a result of potential barriers. The facile precipitation of quasi-aligned arrays of branched TiO₂ nanowires, which are in situ grown on ceramic tubes, thus provides a new economical synthetic route to TiO₂-based sensors with excellent properties. (paper)