Synthesis of V O2(A) nanobelts by the transformation of V O2(B) under the hydrothermal treatment and its optical switching properties

V O2(A) nanobelts had been successfully synthesized by the transformation of V O2(B) using H2O as the solvent under the hydrothermal approach at 280 °C for 48 h. Some parameters, such as the reaction temperature and time, had been briefly discussed to reveal the transition from V O2(B) to V O2(A). It was found that H2O played a crucial role in the transition from V O2(B) to V O2(A). The phase transition of V O2(A) nanobelts was at 162 °C. The optical switching properties of V O2(A) were studied by the variable-temperature infrared spectra for the first time. In addition, V O2(A) nanobelts were calcined at 700 °C for 2 h under a high purity Ar (99.999%) atmosphere to obtain V O2(M) which exhibited a strong crystallographic transition at around 65 °C.