Preparation and properties of titania nanotube arrays by anodization method

Titania (TiO2) nanotube arrays were prepared by the anodization method. The cathode was titanium (Ti) sheets and anode was platinum (Pt). The electrolytes were mixtures of ethylene glycol (EG), ammonium fluoride (NH4F) and deionized water (DI water) that contained different concentrations of silver ions. The dopants were varied, and included 1.0 mM, 1.5 mM, and 2.0 mM of silver nitrate (AgNO3). The preparation of electrolytes included stirring and aging. The anodizing voltage was set to 50 V and the process was carried out for 2 h. The titanium foils were anodized at room temperature. The nanotube arrays were crystallized by annealing at 450 C for 2 h. The morphology, structure, and optical properties of the prepared nanotubes were characterized by scanning electron microscopy (SEM). X-ray diffraction (XRD), and UV-vis spectroscopy (UV-vis) respectively. It was found that the structures of the TiO2 nanotubes obtained from the stirred and aged electrolyte solutions and the electrolyte solutions with added silver ions were similar. When the concentration of AgNO3 increased, the TiO2 nanotube arrays cracked and were not well-arranged. The optical bandgaps of TiO2 nanotubes obtained from the stirred electrolyte solutions were 2.52-2.75 eV, which were less than those of the aged electrolyte solutions.