Abstract
The formation mechanism of highly pure H <sub>2</sub> V <sub>3</sub> O <sub>8</sub> single-crystal nanobelts is clarified in a hydrothermal synthesis process with a specially designed precursor solution containing V <sup>5+</sup> and V <sup>4+</sup> in a fixed ratio of 2/1. This specially designed precursor solution provides an additional merit for the rapid fabrication of highly pure H <sub>2</sub> V <sub>3</sub> O <sub>8</sub> nanobelts through a simple hydrothermal route. During the hydrothermal synthesis process, V <sup>5+</sup> species initially reacts with some V <sup>4+</sup> to form a metastable, whisker-like V <sub>10</sub> O <sub>24</sub> · nH <sub>2</sub> O (n < 12). The V <sup>5+</sup> species dissolved from the whisker-like V <sub>10</sub> O <sub>24</sub> · nH <sub>2</sub> O reacts continuously with residual V <sup>4+</sup> ions in the precursor solution to form seeds of H <sub>2</sub> V <sub>3</sub> O <sub>8</sub> single-crystals. The anisotropic growth of H <sub>2</sub> V <sub>3</sub> O <sub>8</sub> single-crystal nanobelts with length > 10 μm and width between 50 and 150 nm occurs with prolonging the hydrothermal time. Finally, highly pure H <sub>2</sub> V <sub>3</sub> O <sub>8</sub> single-crystal nanobelts are obtained when the hydrothermal time reaches 4 h. The textures of vanadium oxides prepared at different hydrothermal times are systematically compared through X-ray diffraction, transmission electron microscopic and X-ray photoelectron spectroscopic analyses to clarify the synthesis mechanism of H <sub>2</sub> V <sub>3</sub> O <sub>8</sub> single-crystal nanobelts. © 2007 Acta Materialia Inc.