Novel synthesis of hexagonal WO3 nanostructures

This paper discusses the synthesis and characterization of a new form of WO3 nanostructures based on the hexagonal WO3 (h-WO3) polymorph. This typically "metastable" phase was synthesized from a substoichiometric metal alkoxide precursor-tungsten (V) isopropoxide, by a novel colloidal synthesis method. Nanowires of h-WO3 were obtained upon heat-treating the sol-gel precursor at 400 A degrees C. Further processing at elevated temperatures (515 A degrees C) resulted in coarsening of the nanowires and the formation of nanowire bundles with polytypic character. Hexagonal WO3 differs from the other tungsten oxide polymorphs in that it possesses unique structural features such as long, hexagonal prism channels parallel to the c-axis and layered oxygen octahedra. This makes it a very attractive host matrix for metal ion intercalation for rechargeable batteries and for the selective gas sensing of amines.