Vanadium oxides and compounds derived from them have attracted interest because of their potential use as cathode materials for rechargeable lithium batteries [1–3] and their important role in catalysis [4, 5]. Depending on the nature of the species present in the reaction medium, vanadium oxides may exhibit a wide range of morphologies (lamellar structures, molecular clusters, etc.) [6, 7]. Among them, the vanadium oxide nanotubes are unique because of their strongly anisotropic geometry, which is associated with interesting chemical and physical properties. Recently, Nesper and co-workers synthesized novel vanadium oxide nanotubes using vanadium alkoxides as starting materials in a Chimia Douce route [7, 8]. However, vanadium alkoxides are very expensive. Therefore, in the present work, vanadium oxide nanotubes have been prepared by reacting vanadium oxide, instead of vanadium alkoxides, with a structure-directing agent followed by hydrothermal treatment. FTIR investigation was performed to study the structural changes of vanadium oxide before and after hydrothermal treatment to get a better understanding of nanotube formation. 10 mmol V2O5 (99.5%) and 10 mmol 1-hexadecylamine (ACROS CRGANICS Company) were mixed with 5 ml distilled water. After stirring for 1 h, to give an orange solution, 15 ml distilled water was added. The mixture was allowed to hydrolyze under vigorous stirring for 48 h, then a yellow composite of the organic template and the vanadium oxide component was obtained. The composite was then treated hydrothermally in a Teflon-lined autoclave with a stainless steel shell at 140 ◦C for 24 h and then 180 ◦C for 3 days. The obtained black product was washed with distilled water to remove the unreacted amine and decomposition product and finally dried at 70 ◦C in air atmosphere for 6 h. X-ray power diffraction (XRD) experiments were done on a D/MAX-III powder diffractometer with Cu Kα radiation (λ = 1.5406 A) and graphite monochrometer, with a scanning rate of 0.1 ◦/s. Scanning electron microscopy (SEM) images were collected on a JSM5610LV microscope operated at 20 kV. The transmission electron microscopy (TEM) images were obtained on a Jeol JEM-2010F microscope operated at 200 kV. The sample was deposited onto a perforated carbon foil supported on a copper grid. The Fourier transform infrared (FTIR) instrument used was a Nicolet 60-SXB spectrometer with a resolution of 4 cm−1. The XRD pattern of vanadium oxide nanotubes (Fig. 1) shows the low-angle reflection peaks, which are characteristic of the layered structure [7]. The peak with the highest intensity is located at d = 3.53 nm, and this corresponds to the distance between the VOx layers. The SEM images of the vanadium oxidehexadecylamine composite after aging for 48 h and the final products after hydrothermal treatment indicate that the vanadium oxide-hexadecylamine composite exhibits a well-ordered lamellar structure, but this is transformed into nanotubes after autoclave reaction, as shown in Fig. 2. The final products consist almost exclusively of vanadium oxide nanotubes. Vanadium oxide nanotubes are frequently grown together in the form of bundles, but individual nanotubes with open ends can also be observed, which can be confirmed by the TEM investigations (see Fig. 3). The nanotube lengths range from 1 to 8 μm. Lengths and diameters of the nanotubes depend on the conditions of the preparation, such as different template molecules, concentration and reaction time [8]. The FTIR spectra for the vanadium oxidehexadecylamine composites and vanadium oxide nanotubes are represented in Fig. 4a and b, respectively. For comparison, FTIR measurement of pure hexadecylamine was made, as shown in Fig. 4c. This spectrum shows two sharp peaks between 3300 and 3500 cm−1, which can be associated with the NH2 vibration [9]. In the FTIR spectrum for the vanadium oxidehexadecylamine composites, the sharp peaks between 3300 and 3500 cm−1 disappear while the peaks at 2956 and 1589 cm−1 are observed. These are assigned to the stretching vibration and asymmetric bending vibration of the N H bonds in the NH3 group [9]. Therefore,
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