Theoretical study of the permeation of water through TiO₂ nanotubes using molecular dynamics simulation

Abstract

In this study, the theoretical structures of armchair (6, 6) and zigzag (12, 0) TiO₂ nanotubes (TiNTs) were constructed by rolling the (101) layer of an anatase TiO₂ crystal. The (101) layer was made using Materials Studio (MS) by cutting the cleave plane (101) of the anatase TiO₂ crystal. Based on these structures, the basic properties of TiO₂ nanotubes were investigated using MS. Molecular dynamics simulations were performed using the software NAMD to investigate the status and permeation of water through the TiO₂ nanotubes. Structure analysis shows that both the inner and outer walls of the structures were terminated with oxygen atoms. The thicknesses of single tube walls are smaller than that of a perfect triple layer (2.20 Å) in bulk anatase TiO₂. With regard to the bulk Ti–O bond length, the Ti–O bonds in the outer layer are elongated, and are shortened in the inner layer. Molecular dynamics simulation shows that the water molecules in the nanotubes move back and forth, as in one-dimensional Brownian motion. Moreover, the penetration properties of TiNTs are associated with their radii, with the TiNT with larger radii having better penetration properties. Thus, when used in drug delivery or filtration systems, armchair TiNT has a better effect than zigzag TiNT.

Keywords:

• TiO₂ nanotube
• molecular dynamics
• water permeation
• theoretical structure

Acknowledgements

Project No. CDJZR10230004 supported by the Fundamental Research Funds for the Central Universities.