Electro-conductive nanotubular sheet of indium tin oxide as fabricated from the cellulose template

Abstract

Free-standing, nanotubular ITO sheet with different In/Sn ratios was fabricated by the surface sol–gel process using cellulose filter paper as template. The resulting materials have a hierarchical structure originating from the morphology of cellulosic paper, and the ITO nanotubes are composed of interconnected layers of ITO nanocrystals of a few nanometres. Semiconducting behavior was observed at temperatures above room temperature, probably because electronic migration is strongly affected by the scattering at the boundary between nanocrystals. The ITO sheet with In/Sn ratio of 93.5/6.5 showed an intrinsic electronic conductivity (0.53 S cm⁻¹) that is higher than those of other nanostructured ITO, and a very low apparent density (3.3% of neat ITO). These features indicate that the nanotubular ITO sheet has a potential use for chemical sensors and other devices.