Nano-urchin: The formation and structure of high-density spherical clusters of vanadium oxide nanotubes

We report the observation of urchin-like nanostructures consisting of high-density spherical nanotube radial arrays of vanadium oxide nanocomposite, successfully synthesized by a simple chemical route using an ethanolic solution of vanadium tri-isopropoxide and alkylamine hexadecylamine for 7 days at 180 °C. The results show that the growth process of the nano-urchin occurs in stages, starting with a radial self-organized arrangement of lamina followed by the rolling of the lamina into nanotubes. The longest nanotubes are measured to be several micrometers in length with diameters of ∼120 nm and hollow centers typically measured to be ∼75 nm. The nano-urchin have an estimated density of nanotubes of ∼40 sr^-1. The tube walls comprise layers of vanadium oxide with the organic surfactant intercalated between atomic layers. The interlayer distance is measured to be 2.9 ± 0.1 nm, and electron diffraction identified the vanadate phase in the VO_x nanocomposite as orthorhombic V₂O₅. These nanostructures may be used as three-dimensional composite materials and as supports for other materials.