Chemical synthesis of zinc oxide nanorods and their transformation intonanotubes

A simple wet chemical method was successfully deployed to synthesize zinc oxide nanorods and nanotubes of hexagonal morphology. Energy dispersive X-ray spectroscopy confirmed the formation of ZnO with almost equal atomic percentages of Zn and O atoms. The FESEM images confirmed the formation of ZnO nanorods and nanotubes of length 1.5 to 2 $\mu $m and diameter 500 nm to 1 $\mu $m. The growth of the nanorods saturated under the combined effect of ionic association of Zn$^{2+}$ and OH$^{-}$ ions, Gibbs' energy of the reaction, reaction temperature, and the enthalpy of the system. Further stirring led to dissolution resulting in coarse edges on the top of the nanorods and finally hollow nanotubes were formed. The synthesized ZnO nanotubes exhibited strong photoluminescence at 649 nm owing to the holes trapped at $\mathrm{V}_{\mathrm{O}}^{\mathrm{++}}$ states and the conduction band edge.