Electronic Structure Controlling of Assembly and Optical Properties of TiO₂ Nanotube Arrays

First principles calculations are carried out to study the interaction between TiO₂ nanotubes. Two type tubes, the (9, 0) and (0, 6) tubes, with different separations and arrangements are studied in detail. Interactions between ions from neighboring nanotubes and contact angle between tubes could greatly affect the stability of nanotube arrays. The (0, 6) nanotubes tend to contact with each other owing to the attracting interactions between Ti and O ions from different tubes, while the (9, 0) nanotubes prefer to distribute separately due to the repulsion between oxygen ions in neighboring nanotubes. The atomic configurations in contact zone and the electronic structures are further studied to clarify the controlling mechanisms of the stability of TiO₂ nanotube arrays. Regulation of arrangement of TiO₂ nanotube arrays bring diverse electronic and optical properties.