Hydrothermal synthesis and optical properties of ZnO nanostructured films directly grown from/on zinc substrates

Uniform ZnO nanorods arrays are grown directly from and on Zn foils in pure water under hydrothermal conditions at a relatively low temperature. The nanorods are 80-200 nm in diameter and similar to 1 mu m in length, which grow on the Zn foil along the [001] direction. By changing the pure water to a urea solution, a Zn compound [Zn-5(OH)(6)(CO3)(2)], a precursor of ZnO nanoflowers film, is created by self-assembly. The ZnO nanoflowers film can be easily obtained by heating the [Zn-5(OH)(6)(CO3)(2)] compound in N-2 at 350 degrees C for 5-6 hours. Possible growth processes of the ZnO nanorods arrays and the [Zn-5(OH)(6)(CO3)(2)] nanoflowers are discussed. Photoluminescence properties of the as-prepared ZnO nanostructures have been measured. The ZnO nanorods array synthesized using our method has minimal defects so that only band-gap emission is observed. However, the ZnO nanoflowers film, obtained by heating the [Zn-5(OH)(6)(CO3)(2)] nanoflower precursor in N-2, is polycrystalline and displays strong defect-related emission.