Alkali metal intercalated titanate nanotubes: A vibrational spectroscopy study

Alkali metal (Li+, Na+, K+) intercalated titanate nanotubes have been studied by vibrational spectroscopy (Raman and FT-infrared), X-ray diffraction, and electron microscopy. The vibrational spectroscopic data shown that the most affected vibrational mode is that related to Ti-O bond whose oxygen is not shared among the TiO6 units of the framework structure. A correlation between vibrational frequency shifts and intercalated metal was found, thus showing that vibrational spectroscopy is very useful for probing metal intercalated titanate nanotubes. Our results provide good evidences that the structure of titanate layers in titanate nanotube, a subject of long debate in the literature, is similar to trititanates (like Na2Ti3O7).