When aluminum is anodized in a suitable oxidizing acid, a two dimensional hexagonal network of quasi-periodic Al2O3 cells with uniform tubular pores is formed. The structure consists of a close packed array of columnar hexagonal cells, each containing a central pore normal to the substrate surface. At the bottom of each nanopore is a very thin layer of aluminum oxide, an electrical insulating material, separating the body of the pore from the conducting metal aluminum substrate.