Large-scale ZnO inverse opal films fabricated by a sol-gel technique

We demonstrate that high-quality large-scale ZnO inverse opals can be fabricated by a simple sol-gel technique, comprising infiltration of polystyrene colloidal crystal films with zinc nitrate solution, drying and annealing at 300 degrees C. This simple method yields continuous films, which consist of inverse opal domains (up to several hundreds of mu m(2) in size), separated by small cracks filled with zinc oxide. Microradian X-ray diffraction was employed to verify the crystalline quality of ZnO inverse opals on the macroscale, revealing that the samples have a predominant face-centered cubic structure, and that the majority of domains have the same crystallographic orientation. The samples exhibit bright iridescence and possess photonic stop-bands in the visible to near-infrared spectrum. (C) 2009 Elsevier Ltd. All rights reserved.