Self‐Organized Arrays of SnO2 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 SnC2O4 on the Sn anode surface. The chemical composition of the surface SnO2 was established by Mössbauer spectroscopy and X‐ray photoemission spectroscopy (XPS). The growth direction of the SnO2 nanoplates was shown to be related to the orientation of the domains of the underlying polycrystalline yet oriented β‐Sn foil. The structured SnO2 surface is highly photoactive and generates superoxide radicals (O2·–) upon UV exposure resulting in a strong degradation of organic contaminants and a strong antimicrobial activity. Upon illumination the SnO2 coating exhibits a switchable amphiphilic behavior, which – in combination with its photoactivity – creates a self‐cleaning surface. Anodization of tin foils in buffered oxalic acid at low voltages leads to the formation of oriented layers of sub‐microsized SnO2 plates, whose orientation is related to the domains of the underlying polycrystalline, but oriented β‐Sn foil. Under UV illumination the structured SnO2 surface shows self‐cleaning behavior.