Evolution of standing mesochannels on porous anodic alumina substrates with designed conical holes.

We report the formation of standing mesochannels simply by spin-coating a precursor solution onto a PAA (porous anodic alumina) substrate with designed conical holes, utilizing exactly the same precursors and reaction conditions that form two-dimensional (2D) hexagonal mesoporous SBA-15-type films. When the aspect ratios of the conical holes are lower, the sponge-like mesopores are generated within the conical holes. Such a formation of sponge-like mesostructures truly acts as a trigger for the evolution of perpendicularly oriented and tilted mesochannels. On the other hand, when the PAA substrates with high-aspect cones are used, the mesochannels are stacked like a doughnut within the conical holes, which leads to parallel orientations of the mesochannels in the continuous film region.