Formation mechanism of H2Ti3O7 nanotubes.

Formation mechanism of H2Ti3O7 nanotubes by single-step reaction of crystalline TiO2 and NaOH has been investigated via transmission electron microscopy examinations of series specimens with different reaction times and extensive ab initio calculations. It was found that the growth mechanism includes several steps. Crystalline TiO2 reacts with NaOH, forming a highly disordered phase, which recrystallized into some H2Ti3O7 thin plates. H-deficiency on the top surface leads to an asymmetrical environment for the surface Ti3O2-7 layer. The calculations of the surface tension, elastic strain energy, interlayer coupling energy, and Coulomb force indicated that the asymmetrical environment is the principal driving force of the cleavage of the single sheets of H2Ti3O7 from the plates and the formation of the multiwall spiral nanotubes.

[1]  D. Vanderbilt,et al.  Soft self-consistent pseudopotentials in a generalized eigenvalue formalism. , 1990, Physical review. B, Condensed matter.

[2]  S. Andersson,et al.  The crystal structure of Na2Ti3O7 , 1961 .

[3]  S. Iijima.  Helical microtubules of graphitic carbon , 1991, Nature.

[4]  P. Davies,et al.  The soft chemical synthesis of TiO2 (B) from layered titanates , 1992 .

[5]  O. Schmidt,et al.  Nanotechnology: Thin solid films roll up into nanotubes , 2001, Nature.

[6]  T. Arias,et al.  Iterative minimization techniques for ab initio total energy calculations: molecular dynamics and co , 1992 .

[7]  H. Monkhorst,et al.  SPECIAL POINTS FOR BRILLOUIN-ZONE INTEGRATIONS , 1976 .

[8]  Qing Chen,et al.  Trititanate nanotubes made via a single alkali treatment , 2002 .

[9]  X. B. Zhang,et al.  A Formation Mechanism for Catalytically Grown Helix-Shaped Graphite Nanotubes , 1994, Science.

[10]  S. H. Vosko,et al.  Accurate spin-dependent electron liquid correlation energies for local spin density calculations: a critical analysis , 1980 .

[11]  J. Nørskov,et al.  Improved adsorption energetics within density-functional theory using revised Perdew-Burke-Ernzerhof functionals , 1999 .

[12]  N. Hamada,et al.  Energetics of carbon nano-tubes , 1992 .

[13]  Timothy Hughbanks,et al.  Structural-electronic relationships in inorganic solids: powder neutron diffraction studies of the rutile and anatase polymorphs of titanium dioxide at 15 and 295 K , 1987 .

[14]  L. Pauling.  THE STRUCTURE OF THE CHLORITES. , 1930, Proceedings of the National Academy of Sciences of the United States of America.

[15]  Harris.  Simplified method for calculating the energy of weakly interacting fragments. , 1985, Physical review. B, Condensed matter.