Effect of fluoride content and cleaning agent on the formation of self organized TiO2 nanotube arrays

Abstract

Titania nanotube arrays were synthesized by anodizing Ti foil in ethylene glycol (EG) containing ammonium fluoride (NH4F). The role of fluoride ion and the different cleaning agents were investigated. The morphology was observed via Field Emission Scanning Electron Microscopy (FESEM). A self-organized TiO2 nanotube with an average inner diameter of 110 nm and length of 9.5 μm was acquired by anodizing the foil at 60 V for 60 minutes. The presence of F- ions leads to chemical dissolution of Ti oxide layer. The chemical dissolution rate increased with increasing the fluoride content because more F- ion is available to attack the barrier layer. When the barrier layer gets thinner the oxidation rate will increase and thus formed the long tubes. Acetone and DI water were used as a cleaning agent. It was found that sample washed in acetone and ultrasonic for 1 minute, the precipitates like oxide layer formed onto surface of the nanotubes was successfully removed and revealed smooth and clean pores. Such clear opening enhanced the photocatalytic activity of methyl orange degradation because the diffusion of methyl orange takes place not only on the outer surface of TiO2 nanotube but also on the inner walls.