Template-Directed Formation of Hemispherical Cavities of Varying Depth and Diameter in a Silicate Matrix Prepared by the Sol−Gel Process

2-D ordered arrays of hemispherical cavities were formed in a sol−gel-derived silicate film on a glassy carbon electrode using polystyrene latex spheres as templates. The depth and the diameter of the cavities were varied over 1 order of magnitude by changing the diameter of the template and diluting the sol. Sulfate-stabilized polystyrene latex spheres ranging in size from 100 to 1000 nm were doped into a silica sol prepared from the hydrolysis and condensation of tetramethoxysilane, and the resultant solution was spin cast on a glassy carbon electrode. The 2-D ordered array of spheres in a thin silicate film was removed via soaking the film in chloroform. Scanning electron microscopy and atomic force microscopy (AFM) were used to image the films, and AFM with high-resolution TM tips was used measure the depth and diameter of the cavities. The cavities are open at the top and bottom and provide direct access to the underlying electrode surface as verified by cyclic voltammetry. Nanosized copper and polya...