Phase transition in confined water inside carbon nanotubes

In materials confined within nanometer channels in single-walled carbon nanotube (SWNT) bundles, interesting properties which are not observed in bulk materials are expected. In the present paper, we report an X-ray diffraction (XRD) study on water adsorption in SWNT bundles. It was found that a substantial amount of water is absorbed inside SWNTs at room temperature (RT). The desorption-adsorption of water molecules occurred reversibly above RT. We found that the liquid-like water is transformed into a new solid form, i.e., ice nanotubes, at 235 K.