Self‐Organized Arrays of SnO 2 Microplates with Photocatalytic and Antimicrobial Properties

Porous anodic metal oxides have been widely used for the development of various functional nanostructures. So far, these self‐organized pore structures were prepared as hexagonal arrangements of nanopores, which have become a popular template system for the fabrication of functional nanostructures. Here we report a new oxalic acid‐based anodization process for long‐range ordered arrays of submicrometer tin dioxide plates at low applied voltages in buffered solution, which prevents the precipitation of SnC 2 O 4 on the Sn anode surface. The chemical composition of the surface SnO 2 was established by Mössbauer spectroscopy and X‐ray photoemission spectroscopy (XPS). The growth direction of the SnO 2 nanoplates was shown to be related to the orientation of the domains of the underlying polycrystalline yet oriented β‐Sn foil. The structured SnO 2 surface is highly photoactive and generates superoxide radicals (O 2 · – ) upon UV exposure resulting in a strong degradation of organic contaminants and a strong antimicrobial activity. Upon illumination the SnO 2 coating exhibits a switchable amphiphilic behavior, which – in combination with its photoactivity – creates a self‐cleaning surface.