Morphology and Topochemical Reactions of Novel Vanadium Oxide Nanotubes

Abstract

Vanadium oxide nanotubes were obtained as the main product in a sol−gel reaction followed by hydrothermal treatment from vanadium(V) alkoxide precursors and primary amines (C n H 2 n +1 NH 2 with 4 ≤ n ≤ 22) or α,ω-diamines (H 2 N[CH 2 ] n NH 2 with 14 ≤ n ≤ 20). The structure of the nanotubes has been characterized by transmission electron microscopy, X-ray powder diffraction, X-ray photoelectron spectroscopy, and magnetic measurements. The tubes are up to 15 μm long and have outer diameters ranging from 15 to 150 nm and inner diameters from 5 to 50 nm. The tube walls consist of 2−30 crystalline vanadium oxide layers with amine or diamine molecules intercalated in between. The distance between the layers (1.7−3.8 nm) is proportional to the length of the alkylamine, which acts as a structure-directing template. The structure within the layers has a square metric with a ≈ 0.61 nm. Cross-sectional TEM images demonstrate the predominance of serpentine-like scrolls rather than of concentric tubes. The intercalated templates can be easily substituted, e.g. by diamines, while the tubular morphology is preserved. This points to a highly flexible structure.