A Hierarchical Anodic Aluminum Oxide Template.

Anodic aluminum oxide (AAO) templates are widely used for the development of various functional nanomaterials due to their highly ordered and tunable porous structures. Here, we report a new hierarchical AAO (hAAO) template with the hexagonally ordered unit cells and the radially distributed nanochannels. It is formed by integrating the self-assembled polystyrene microsphere template into the AAO fabrication process and rationalized in terms of mechanical stress and electric-field-induced oxide dissolution. The back side of the hAAO template resembles a moth-eye-like nanoarray, which shows good hydrophobicity. A variety of radial nanopillar arrays and moth-eye-like nanoarrays are fabricated by a series of materials and synthesis techniques employing the hAAO template. These unique nanoarrays demonstrate many physicochemical properties that are distinct from those obtained from the conventional AAO template.