Fabrication of Vertically Oriented TiO2 Nanotube Arrays Using Ethylene Glycol

Titanium dioxide, due to its specific semiconductive properties, has been a highly investigated material for a variety of applications including gas sensors, hydrogen generation by water photoelectrolysis, photocatalysis, dye-sensitized solar cells and purification of water and air [1,2]. Highly ordered vertically oriented TiO2 nanotube arrays fabricated by potentiostatic anodization constitute a material architecture that offers a large internal surface area without a concomitant decrease in geometric and structural order. In contrast to random nanoparticle systems where slow electron diffusion typically limits device performance, the precisely oriented nature of the crystalline (after annealing) nanotube arrays makes them excellent electron percolation pathways for vectorial charge transfer between interfaces [3]. As initially reported by Zwilling and co-workers in 1999, the first generation titania nanotube arrays fabricated by anodization using an aqueous HF-based electrolyte could be grown to a length of about 500 nm. Successful approach to increase the tube length is using non-aqueous electrolytes. Fabrication of TiO2 nanotube arrays up to 6 μm in length using of polar organic electrolytes reported by Patrik Schmuki et al [4].In the present work we explore the formation of self-organized TiO2 nanotube arrays in ethylene glycol based electrolytes containing small amounts of fluoride ions in order to maximize the aspect ratio of the nanotubes. For this we investigate the morphology dependence on the applied potential, concentration of fluoride ions and time.