Synthesis of ZnO nanotubes and nanotube-nanorod hybrid hexagonal networks using a hexagonally close-packed colloidal monolayer template

Abstract

We present a new synthetic approach, via hydrothermal process with the use of polystyrene (PS) colloids, to fabricate vertically aligned, single crystalline ZnO nanotube arrays. Electron microscopy images revealed that single crystalline nanotubes with inner diameters of similar to 15-20 nm and wall thicknesses of similar to 10-15 nm were formed just below the PS colloids, whereas solid nanorods were grown in the absence of PS colloids. In addition, nanorods enclosing the PS colloids exhibited much faster growth rates than those on the area not covered with PS colloids. These results indicate that the introduction of PS colloids affected the formation and diffusion of adatoms. The growth behavior of ZnO crystals with regards to the PS colloids was exploited to convert the ZnO nanostructures from solid to nanotube-nanorod hybrid networks by introducing hexagonally close-packed PS colloidal monolayers. Moreover, we demonstrated further conversion to complete tubular forms by reducing the aperture size between adjacent PS colloids with thermal annealing.