Preparation of porous chromium oxide nanotubes using carbon nanotubes as templates and their application as an ethanol sensor

Chromium oxide nanotubes were successfully prepared using multi-walled carbon nanotubes (MWCNTs) as a template via a supercritical fluid-mediated route. In this method, with chromium (III) nitrate nonahydrate as precursor, chromium oxide was first deposited on MWCNTs in supercritical ethanol in the presence of NH4HCO3. The as-prepared chromium oxide/MWCNT nanocomposites were characterized by transmission electron microscopy, x-ray diffraction, infrared spectroscopy and thermogravimetric analysis. It was demonstrated that the MWCNTs were coated with a layer of amorphous Cr2O3 center dot xH(2)O. The thickness of the Cr2O3 center dot xH(2)O sheath on MWCNTs could be tuned by manipulating the ratio of precursor to MWCNTs. Calcining the composites at 550 degrees C, the MWCNTs were removed, producing polycrystalline alpha-Cr2O3 nanotubes. The as-prepared alpha-Cr2O3 sample was used as a sensor material to detect ethanol vapor, and it was demonstrated that the alpha-Cr2O3 nanotubes exhibited good performance even at 400 degrees C.