Preparation and characterization of ZnO nanorods from NaOH solutions with assisted electrical field

ZnO naorods on ZnO-coated seed substrates were fabricated by solution chemical method from Zn(NO₃)₂/NaOH under assisted electrical field. The working mechanism of electrical field was analyzed and the factors affecting the rod growth such as potential, precursor concentration and growth temperature were elucidated. The structural and optical properties are characterized by SEM, TEM, XRD, HRTEM and UV-vis. The results indicated that the nanorods have wurtzite structure without electrical field and are primarily of zincite structure under electrical field; when the electrical field is 1.1-1.3 V, not only the elevation of ion diffusion and adsorption lower the crystallite/solution interfacial energy and then the crystal nucleation barrier by increasing charge intensity, but also the production of H⁺ through oxidation of OH⁻ increases properly the degree of solution supersaturation near the substrate, and thus lowers the activation energy. Both the two processes do favor to rod growth. With increasing precursor concentration in this system, the average diameter and length of ZnO nanorods increase, leading to decreasing of optical transmittance. The maximum rod growth rate at given concentration of Zn²⁺ occurs at a specific temperature.