Hexagonally packed zinc oxide nanorod bundles on hydrotalcite sheets

Abstract

A hexagonal-shaped, hydrotalcite-like [Zn(II)_(1−x)Al(III)_x(OH)₂)]·mH₂O interface that is very effective in promoting the self-assembly of ZnO nanorods has been developed on aluminium-coated substrates in alkaline hydrothermal conditions. The growth of the hydrotalcite interface is due to the reaction between zinc and aluminium ions and it provides a surface of low interfacial energy for the heterogeneous growth of ZnO nanorods at supersaturation levels that do not sustain homogeneous nucleation. The ZnO nanorods self-assemble to form a tightly packed “nail-on-bed” hexagonal structure on the hydrotalcite template. The size of the nanorods can be controlled by controlling the pH of the solution. Delamination of the thin hydrotalcite template at high temperatures produces sheets of ZnO nanorod bundles. Oriented growth of ZnO nanorods can be achieved on a wide range of substrates mediated by the thin hydrotalcite-precoated interface. Stable electron field emission characteristics can be obtained from the ZnO nanorods at a turn-on voltage of 2.73 V µm⁻¹.