Vanadium dioxide with metal insulator transition property at about 68 ℃ [1,2] has attracted wide attention over the past decades. During the phase transition, VO 2 undergoes a sudden change of resistivity, accompanied by a sharp change of optical transmittance, especially in NIR and IR wave band. Because of these unique behaviors, VO 2 can be used in a wide variety of potential applications, such as optical data storage, protective films for laser irradiation, and smart window material for solar energy utilization. Researches in the past about VO 2 mainly focuses on the materials with amorphous or crystalline structure. To our best knowledge, there are few reports on nanostructured VO 2 in the open literatures. Recently, we developed a technique for preparing nanostructured VO 2 based on Tsang′s work [3] . This technique includes a chemical reaction procedure and a vacuum heat treatment process. First, we let K 3VO 4 solution react with KBH 4 solution, then wash and dry the resulting sediments at room temperature, thus we obtain amorphous structured vanadium oxide. Finally, we change it into nanostructured VO 2 by heating it at about 180～350 ℃ in a vacuum chamber under a pressure of 0.5～5 Pa. Fig. 1 gives the XRD spectra of four samples prepared at different temperatures (room temperature, 180 ℃, 220 ℃ and 300 ℃). It shows that when the processing temperature increases from room temperature to 300 ℃, the amorphous structure is changed into nanostructure. We can also see from Fig.1 that the sample thus prepared is not pure VO 2. It contains a small amount of other oxides such as V 6O 13 and VO 2·xH 2O. It is well known that properties of nanostructured materials differs widely from those of ordinary structured materials. Ordinary VO 2 exhibits metal insulator phase transition, but we still do not know if nanostructured VO 2 has the same property. Further investigation is needed to explore the properties of nanostructured VO 2.
