ENHANCED GAS SENSING PROPERTIES OF p-TYPE TeO2 NANORODS FUNCTIONALIZED WITH Pd

TeO2 nanorods functionalized with Pd were prepared by a three-step process comprising thermal evaporation of Te powders, Pd deposition by photo-reduction, and annealing. Sensors were fabricated by using the Pd-functionalized TeO2 nanorods. Scanning electron microscopy images exhibited that the nanorods with diameters in a range of 50-100nm and lengths of a few micrometers were covered with the Pd nanoparticles with an average diameter of similar to 15 nm. Transmission electron microscopy and X-ray diffraction analysis revealed that the nanorods were monocrystalline simple tetragonal TeO2. On the other hand, the nanoparticles on them were confirmed to be nanocrystalline face-centered cubic Pd. The multiple-networked TeO2 nanorod sensors exhibited a sensitivity of 3.13% at 100 ppm NO2 at 300 degrees C, whereas the Pd-functionalized TeO2 nanorod sensors exhibited a sensitivity of 11.97% under the same condition. The recovery time of TeO2 nanorods was decreased considerably at every NO2 concentration by the Pd-functionalization even if the response time decreased or increased slightly depending upon the NO2 concentration. In addition, the origin of the enhancement of the sensing properties of the TeO2 nanorods by functionalization with Pd is discussed.