Synthesis and characterization of layered and scrolled amine-templated vanadium oxides

In order to fully understand the formation mechanism, structure, and role of structural curvature of vanadium oxide nanotubes (VONTs), two isostructural materials (one planar and the other curved)—ethylenediammonium (enH₂) intercalated V₇O₁₆ and vanadium oxide nanourchins (VONUs)—were synthesized and characterized via X-ray diffraction (XRD), electron microscopy, thermal gravimetric analysis (TGA), Fourier transform infrared spectroscopy, and magnetic measurements. The synthesis route to (enH₂)V₇O₁₆ is developed using vanadium pentoxide as a starting material and employing pH control. VONUs are synthesized using n-dodecylamine as an amine template for the first time. We demonstrate that the structure of the vanadium oxide layer in these compounds is similar to that of VONTs and their magnetic properties all fit to the same model including the temperature-independent, Curie–Weiss, and spin ½ antiferromagnetic dimer contributions. The vanadium oxidation state in tubular structures appears to be higher than in planar compounds such as (eH₂)V₇O₁₆ and BaV₇O₁₆. The role of the template and vanadium reduction in the formation of nanotubes is discussed.