a) XRD patterns of monoclinic VO2 (B) nanostructuctures. (b) SEM, (c) TEM, and (d) high-resolution TEM images of VO2 (B) nanorods synthesized with 0.06 mol/L oxalic acid at 180 °C for 48 h. Inset in (b), the high-magnification SEM image of nanorods. Inset in (d), the corresponding fast Fourier transform (FFT) pattern.