Polymer nanowires or nanopores? Site selective filling of titania nanotubes with polypyrrole

Conducting polymer nanowires and nanopore arrays were formed by site selective filling of titania nanotubes with polypyrrole by electropolymerization using a surfactant electrolyte of dodecyl sulfate. The polymerization process can be controlled by modifications of the geometry and chemistry of a nanotubular titania framework in which the polymer is deposited to form either nanowires or nanopore arrays. The size of the polymer can be adjusted to ca. 13 nm and thus lies below the typical value of exciton-diffusion-length in organic photovoltaic systems. Aspect ratios of 200 with a length of 3000 nm can be reached for well-organized and mechanically stable polymer nanopore arrays. The preferential deposition of the polymer is discussed in view of the wetting behaviour of titania nanotubes.