Preparation and band gap energies of ZnO nanotubes, nanorods and spherical nanostructures

Nanostructured zinc oxides were prepared with no catalysts or substrates used. The advantages of this method were a direct and a relatively easy way of getting large amounts of different morphologies of nanostructured ZnO. Another advantage was the formation of the nanotubes at a relatively lower temperature than most other methods. This presented a promising way for commercialization of the ZnO nanomaterials. The materials were characterized using simultaneous thermogravimetric analysis, X-Ray diffraction and transmission electron microscopy. Structures such as nanotubes, nanorods and spherically shaped crystals were formed at certain annealing temperatures. It was found that the ZnO nanotubes grew in the direction of the c-axis. For comparisons of size and morphology, the ZnO precursors were annealed at 300 °C, 400 °C and 700 °C. The lattice parameter of the ZnO nanotube was smaller than conventional micron sized materials. It was also found that the band gap energies of the ZnO nanomaterials were dependent on the morphology of the nanostructures.