A new ion exchange behavior of protonated titanate nanotubes after deprotonation and the study on their morphology and optical properties

After the deprotonation of protonated titanate nanotubes (H2Ti3O7), we observed a novel ion exchange behavior on them. In the past literatures, protonated titanate nanotubes prepared via hydrothermal method have been reported with a poor exchangeability which may due to the chemical bonding of interlayer protons to nearby oxygen atoms. However, in this experiment under alkali environment (pH > 10), protonated titanate nanotubes exhibited a vast ion exchange capacity toward [Co(NH3)6]2+. This interesting phenomenon is contrary to the past reports which found protonated titanate nanotubes hardly could be ionexchanged by objective cations. This paper proves the deprotonation process on H2Ti3O7 nanotubes sufficiently facilitates the diffusion of metal complex cations into protonated titanate nanotubes and significantly changes their ion exchange capacity. As a consequence of cabalt intercalting via ion exchange, the tube wall of H2Ti3O7 nanotubes is observed to get loosened. Additionally, the exciton concentrations corresponding to the nanotube surface states are discussed in the paper.