Vanadium oxide nanotubes (VO_x-NTs) were obtained as the main product in a sol-gel reaction followed by hydrothermal treatment (7d at 180°C) from different vanadium oxide precursors [V₂O₅, VOCl₃, VO(OⁱPr)₃, HVO₃] and primary amines or diamines.

Transmission electron microscopy (TEM) investigations performed along the longitudinal projection direction show that the product consists exclusively of multiwalled nanotubes. The walls comprise between 2 and 30 parallel layers. The outer diameters range from 15 to 100 nm, the inner diameters from 5 to 50 nm. The lengths vary from 0.5 mm to a maximum of 15 mm. Predominantly open tubes are observed.

Cross-sectional TEM images reveal that the majority of the tubes shows a scroll-like morphology instead of concentric circular cylinders.

XRD patterns show the highly intense and sharp 00l reflections that are typical for a well-ordered layered structure at low scattering angles. The inter-layer distances of these reflections range from 1.7 to 3.8 nm and correlate linearly with the template size. This indicates that the template molecules are located in between the vanadium oxide layers. At higher scattering angles, less intense and broad hk0 reflections appear, which can be indexed on the basis of a square lattice with a = 0.61 nm. Their positions are not influenced by the template size.

According to elemental analysis and magnetic measurements, the elemental composition of vanadium oxide nanotubes can be expressed by the general formula [C_nH_2n+1NH₂]_1.9V₇O₁₇ for monoamines with n = 12-18.

F. Krumeich, H.-J. Muhr, M. Niederberger, F. Bieri, B. Schnyder, R. Nesper

J. Am. Chem. Soc. 1999, 121, 8324

Morphology and Topochemical Reactions of Novel Vanadium Oxide Nanotubes

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H.-J. Muhr, F. Krumeich, U. P. Schönholzer, F. Bieri, M. Niederberger, L. J. Gauckler, R. Nesper

Adv. Mater. 2000, 12, 231

Vanadium Oxide Nanotubes - a New Flexible Vanadate Nanophase

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F. Krumeich, H.-J. Muhr, M. Niederberger, F. Bieri, M. Reinoso, R. Nesper

Nanophase and Nanocomposite Materials III, MRS Symp. Proc. 2000, 581, 393

Vanadium Oxide Nanotubes with Diamine Templates

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M. Niederberger, H.-J. Muhr, F. Krumeich, F. Bieri, D. Günther, R. Nesper

Chem. Mater. 2000, 12, 1995

Low-Cost Synthesis of Vanadium Oxide Nanotubes via Two Novel Non-Alkoxide Routes

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F. Krumeich, H.-J. Muhr, M. Niederberger, F. Bieri, R. Nesper

Z. anorg. allg. Chem. 2000, 626, 2208

The Cross-Sectional Structure of Vanadium Oxide Nanotubes Studied by Transmission Electron Microscopy and Electron Spectroscopic Imaging

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Krishnan S. Pillai, F. Krumeich, H.-J. Muhr, M. Niederberger, R. Nesper

Solid State Ionics 2001, 141-142, 185

The First Oxide Nanotubes with Alternating Inter-Layer Distances

In a typical procedure, molybdic acid MoO₃·2H₂O (10 mmol) was mixed with the amine in 5 ml ethanol (molar ratio 2:1). After the addition of 15 ml distilled water, the yellow suspension was stirred at room temperature for 48 hours until a white precipitate was formed. The hydrothermal reaction of this composite was performed in an autoclave at 120°C for 3 to 5 days. After filtering and washing with ethanol and diethyl ether, a white powder resulted. By stirring the molybdenum oxide-amine composite (2.5 g) in 10 ml 33% nitric acid (48 h at RT), the fibrous material was formed. The product was filtered, washed with ethanol and diethyl ether and then dried at 80°C under vacuum (10^-3 mbar).

Electron microscopy investigations have revealed that the molybdenum oxide fibers are up to 15 mm long and their diameters generally range from 50 to 150 nm. According to XRD and chemical analysis, these fibers crystallize in the structure of a-MoO₃.H₂O.

M. Niederberger, F. Krumeich, H.-J. Muhr, M. Müller, R. Nesper

J. Mater. Chem. 2001, 11, 1941-1945

Synthesis and Characterization of Novel Nanoscopic Molybdenum Oxide Fibers

We studied the template-directed synthesis of iron oxides using two different iron oxide precursors, either an iron (III) alkoxide or an air-stable hexanuclear iron alkoxo complex. The hydrolysis in presence of neutral and ionic molecules which act as structure-directing agents followed by hydrothermal treatment yielded micro- and nanostuctured iron oxides with various particle shapes.

M. Niederberger, F. Krumeich, K. Hegetschweiler, R. Nesper

Chem. Mater. 2002, 14, 78-82

An Iron Polyolate Complex as a Precursor for the Controlled Synthesis of Monodispersed Iron Oxide Colloids

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M. Niederberger, F. Krumeich, H.-J. Muhr, M. Müller, R. Nesper

Second International Conference on Inorganic Materials, Santa Barbara, 2000

Template-Directed Synthesis of Structured Iron Oxides

Poster in pdf-format (169 KB)

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M. Niederberger, F. Krumeich, M. Müller, R. Nesper

GDCh-Fachgruppentagung, Münster, 2000

Template-Directed Synthesis of Structured Iron Oxides  

Poster in pdf-format (172 KB)