In an autoclave partly-filled with water wherein a V metal strip is placed 70 degrees to the horizontal we observed that VO2 nanorods and exfoliated microspheres were generally grown on the portion of the strip above the water surface while parallelepiped-like structures were generally grown on the portion below. XRD, HRTEM, showed that VO2 structures produced were monoclinic and base centred in crystal structure. FT-IR, Raman Spectroscopy and XPS suggested that V metal was oxidized by hydrothermal synthesis in water to yield two oxides, V2O3, and VO2, with VO2 forming the bulk of the product. A time-based investigation of the synthesis of VO2 micro-nanostructures on V metal by hydrothermal synthesis suggests that the nucleation and growth of VO2/V2O3 micro-nanostructures is temperature-controlled and not kinetics/diffusion-controlled, with optimal temperatures for the synthesis being in the vicinity of 185-190 degrees C and growth of these oxides taking place in 2 h as opposed to 7 days in previously reported work [L. Jiang et al., VO2 rods with a rectangular cross-section, Journal of Crystal Growth, 310 (2008) 4301-4304]. We propose here a mechanism for the growth of the two types of micro/nanorods above water and the parallelepiped-like structures grown on V metal found below the water level. (c) 2012 Elsevier B.V. All rights reserved.