Fabrication and gas sensing properties of cross-linked TiO2 hollow hemispheres with nanobridges

Fabrication and gas sensing properties of cross-linked TiO2 hollow hemispheres with nanobridges
Issue Date
International Conference on Electronic Materials and Nanotechnology for Green Environment 2010
We report the fabrication of a highly sensitive gas sensor based on a network of nanostructured TiO2 hollow hemispheres (NTHH). O2 plasma etching induces cross-linking of hexagonal-closepacked polystyrene array, which is adopted as a template substrate for room-temperature deposition of TiO2 thin film. High-temperature calcination effectively removes polystyrene template beads and promotes crystallization of TiO2, finally producing cross-linked NTHH via nanobridges. The gassensing capability of a NTHH-based sensor is demonstrated using 1−500 ppm CO. Our sensor exhibits a very high response of 4220% change in resistance when exposed to 500 ppm CO at 250 °C, whereas a gas sensor based on a plain TiO2 film shows a 195% change. The high sensitivity of the NTHHbased sensor is attributed to the enhanced gas sensing performance of the narrow nanobridges between hollow hemispheres. Compared with previously reported gas sensors using nanostructured TiO2 films, the higher sensitivity of our gas sensor reveals the pivotal role of the nanobridges in the conductivity between hollow hemispheres and the resistance modulation with CO gas on and off. The high thermal stability of our sensor clearly suggests that it is a promising candidate for high sensitive CO sensors of air quality monitoring systems of automobiles. The fabrication process and gas sensing properties of NTHH will be presented in detail.
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