Synthesis of hierarchical hexagonal zinc oxide/zinc aluminium hydroxide heterostructures through epitaxial growth using microwave irradiation

Abstract

We present a simple, fast and reproducible method for synthesising zinc oxide (ZnO)/zinc aluminium hydroxide (ZnAl : LDH) hierarchical heterostructures with various secondary ZnO morphologies. ZnAl : LDHs, support materials, were synthesised by microwave irradiation at 95 °C for 20 min. Microwave-assisted secondary growth formed ZnO nanorod/ZnAl : LDH heterostructures through introducing the as-produced ZnAl : LDHs into the reaction solution. ZnO nanotube/ZnAl : LDH heterostructures were synthesised by aging the ZnO nanorod/ZnAl : LDH structures. 2D ZnO film/ZnAl : LDH sandwich-like heterostructures were formed by secondary ZnO growth in a citrate anion-containing solution. The secondary structures grew epitaxially and perpendicularly along the [0001] direction (c-axis orientation) on the ZnAl : LDH surfaces. On the basis of the results, we propose the mechanisms for the epitaxial growth of the various ZnO structures on the ZnAl : LDH surfaces.