Self-organized TiO₂ nanotubes with controlled dimensions by anodic oxidation

The effect of ammonium fluoride (NH₄F) concentration on the dimensions (length, diameter, and wall thickness) of the self-organized nanotube arrays has been investigated. Results show that varying the concentration of NH₄F exerts a strong effect on changing the dimensions of the as-grown nanotube arrays. The length of the nanotube arrays increases gradually by increasing the concentration up to a maximum length at a concentration of 1.00 wt%, after which the length decreases slightly with the increase in NH₄F concentration. It was also observed that the diameter and wall thickness of the nanotube arrays vary with the change in concentration of NH₄F, where the diameter was found to alter between 80 and 140 nm, and the wall thickness decreases by increasing the NH₄F concentration. These results indicate that it is possible to entirely control the dimensions of the nanotube arrays, by tailoring the concentration of NH₄F besides the anodization time and voltage.