Capillary Effects, Wetting Behavior and Photo-induced Tube Filling of TiO(2) Nanotube Layers

The present work addresses effects associated with the electrolyte penetration kinetics into TiO(2) nanotube layers. In particular, it is shown that the electrolyte uptake kinetics affects the magnitude of the measured photoresponse. We demonstrate that for aqueous electrolytes the penetration of the electrolyte into a TiO(2) nanotubular layer is comparably slow and may take up to several hours. The electrolyte uptake kinetics can significantly be accelerated by UV illumination. We ascribe this to a light-induced change in the wetting properties on the inside of the TiO(2) nanotube surface. This effect can be exploited to achieve photo-induced filling of the nanotubes by a secondary material.