Facile Route to Polycrystalline Pd/ ${\rm SnO}_{2}$ Nanowires Using ZnO-Nanowire Templates for Gas-Sensing Applications

Polycrystalline Pd/SnO₂ nanowires have been fabricated using ZnO-nanowire templates by the combination of thermal evaporation, pulsed-laser deposition, and dc sputtering. The rutile SnO₂ nanocrystals were grown on the ZnO nanowire with Volmer-Weber mode due to the large lattice mismatch. The discrete Pd nanocrystals were also successfully deposited onto the nanostructures, which were identified by high-angle annual dark field scanning transmission electron microscopy. The 1-D polycrystalline SnO₂ coatings with catalytically active Pd layer can effectively detect air-diluted H₂S. The sensing behaviors can be understood by a Langmuir isotherm absorption model. The fabrication method provides a general strategy to prepare 1-D metal-oxide conductometric gas sensors.