Hydrothermal Synthesis and Phase Transition Properties of Uniform Free-standing Vanadium Dioxide Nanowires

Vanadium dioxide (VO2) undergoes a Mott metal-insulator transition (MIT) close to room temperature, and has been suggested as a candidate for use in smart window and adaptive infrared camouflage. Here we report the synthesis of uniform free-standing VO2 nanowires using a novel hydrothermal method. The synthetic nanowires have typical diameters of 150±30 nm and lengths of tens of micrometer. These VO2 nanowires exhibit high crystallinity and a pure monoclinic phase, which were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, high resolution transmission electron microscopy and selected area electron diffraction. Moreover, reversible phase transition properties of VO2 nanowires are monitored via differential scanning calorimetry, variable temperature X-ray diffraction and temperature-dependent Raman spectroscopy. The results show VO2 nanowires obtained exhibit a reversible phase transition with an endothermic phase transition at 65.2 °C and a narrow hysteresis width of 6.5 °C. These VO2 nanowires should be promising materials for fundamental investigations of nanoscale metal-insulator transitions.