Effect of the wall thickness on the gas-sensing properties of ZnO hollow fibers.

ZnO hollow fibers (HFs) with a range of wall thicknesses were synthesized by electrospinning and atomic layer deposition. The effects of the wall thickness of the HFs on their sensing properties were examined using CO as a representative reducing gas. The thin-walled HFs showed improved sensor responses to CO compared to thick-walled HFs. Most importantly, despite the polycrystalline nature of HFs, their sensing abilities were determined mainly by the wall thickness, not by the size of the nanograins or crystalline quality. In particular, the resistance modulation was attributed mainly to radial suppression/broadening of the underlying conducting channel during adsorption/desorption of gas species on both the inner and outer surface.