Seed-Mediated Growth of ZnO Nanorods on Multiwalled Carbon Nanotubes

The heterostructures of ZnO nanorods on multiwalled carbon nanotubes (MWNTs) were fabricated by a seed-mediated growth method. First, the surfaces of the carbon nanotubes (CNTs) were coated in situ with mono-dispersed ZnO nanocrystals of about 7 nm by the reaction of zinc acetate and sodium hydroxide. These nanocrystals were then served as the seeds for further growth of ZnO nanorods. In the second step, ZnO nanorods were grown on MWNTs coated with ZnO nanocrystals in an aqueous solution of zinc nitrate and equimolar hexamethylenetetramine at 85 °C. Typically, the ZnO nanorods had the length of 300–600 nm and the diameter of 40–140 nm and took a random direction on the outside walls of MWNTs. The morphology of the ZnO nanorods was dependent on pH, reactant concentration, and growing time.