Nanostructured surfaces
Nanotubing of TiO2 layers by anodization
Naiko L.V.1, Schurenko А.І.1, Steopkin V.І.1, Grinko D.А.1 DobrovolskiiА.М.1
1 Institute of Physics of the NAS of Ukraine. Prospect Nauki, 46, Kyiv-03039, Ukraine. 
E-mail: lilianajko@gmail.com

At present, nanotube coatings of titanium dioxide are quite promising due to the wide range of their applications. For example, TiO2 nanofilms and highly porous TiO2 layers are used in the manufacture of solar cells and LEDs, for cleaning air and water from pollution, but the most promising area of application is the medical industry, because titanium is the most biologically compatible among a wide variety of materials that, in spite of all their benefits, can cause strong inflammation and necrosis of cells.
In this research we have used the method of creating an oxide porous film on the surface of a titanium using an electrochemical anodizing on a titanium foil in electrolytes of various composition. The anodization was carried out at room temperature and various applied potential difference (from 30 to 70 V), followed by annealing at 430 С in the air. Anodizing time ranged from 10 minutes to 5 hours. Depending on the temperature and the applied potential, the obtained samples have different patterns of structure. Also, obtained electrochemical anodized samples have a well-ordered homogeneous structure with nanotubes that are parallel to each other and perpendicular to the foil surface. The thickness of the tube layer varies from 1 to 30 m, the diameter of the nanotubes - from 30 to 70 nm, depending on the anodizing conditions.
The obtained samples were explored before and after annealing using electron microscopy and Raman spectroscopy. Based on the spectra obtained before and after annealing, we can approve the following: before the annealing, there are lines that correspond to amorphous titanium dioxide and a line of organic impurities. But after annealing, there are only lines that correspond to the anatase form of titanium dioxide. This is an extremely good result, which proves the necessity of annealing the samples to obtain a particularly pure anatase form of titanium dioxide. And this result also gives wide opportunities for the use of electrochemically obtained and annealed TiO2 nanotube arrays in medical applications.