Process and characterization of macroporous periodic nanostructured zinc oxide via electrodeposition

Here we report a simple technique for the preparation of three-dimensional (3D) macroporous zinc oxide (ZnO) film (inverse opal) with periodic submicron spherical holes arranged in a close-packed structure. Polystyrene (PS) latex spheres of 200 nm diameter were first assembled on indium-tin-oxide (ITO) coated glass substrates using a vertical convective self-assembly method. The interstitial spaces between PS latex spheres were infiltrated with ZnO by galvanostatic cathodic deposition using simple aqueous zinc nitrate electrolyte maintained at 338 K. The 3D macroporous periodic ZnO film was obtained by heat treatment at 600 °C to remove the PS template. Field emission scanning electron microscopy revealed a well-formed, regular 3D periodic porous structure which consists of spherical holes arranged in a face-centered cubic (FCC) structure. These spherical holes have dimensions within the size disparity of the latex spheres used to form the initial opal template. UV–Vis reflection analysis proved the successful infiltration with the respective diffraction peaks observed for the PS template, ZnO–PS composite opal and inverse ZnO opal, indicating the existence of a photonic band gap (PBG) in these structures. This consistent with the calculated photonic (1 1 1) pseudo band gap. The efficient photoluminescence characteristic of the deposited ZnO film is also reported.