Formation of self-aligned ZnO nanorods in aqueous solution

Abstract

In this work, controllable growth of ZnO nanorods by hydrothermal process was achieved on a seeded substrate prepared by thermal oxidation of Zn foil. The Zn foil was oxidised so that the surface grain would consists of only uniform circular nanosized grains and hence, suitable as a template for the formation of ZnO nanorods. The formation of ZnO nanorods occurred via the reaction of hydroxyl ions released during the thermal degradation of hexamethylamine (HMT) with Zn ions in the precursor solution. By keeping the ratio of Zn ions to HMT constant at 1:1, the dimensions of the nanorods are found to be a function on the properties of HMT which are time and temperature dependent. The optimum hydrothermal reaction parameters of 4–6 h at 80 °C are found suitable to grow needle-like nanorods with length of ∼700 nm and base diameter of ∼200 nm and top diameter of less than 30 nm. The results prove that ZnO nanorods formation via hydrothermal process is highly dependent on the rate of HMT decomposition. Suitable temperature and hydrothermal reaction time are essential to allow decomposition of HMT to produce the hydroxyl ions as oxygen source for ZnO formation. The success in the formation of ZnO nanorods of controllable dimensions on seeded substrate formed by the oxidized Zn foil is noteworthy as an alternative approach in the formation of self-aligned ZnO nanostructures.