title: Photoluminescence measurements and molecular dynamics simulations of water adsorption on the hydrophobic surface of a carbon nanotube in water vapor.
abstract: Hydrophilicity or hydrophobicity is a macroscopic property of the surface, and its atomic scale understanding has not been established. We have studied adsorption of water molecules on the "hydrophobic" carbon nanotube surface at room temperature in water vapor. Based on optical measurements of individual single-walled carbon nanotubes suspended between micropillars in water vapor together with molecular dynamics simulations, we found that water molecules form a stable adsorption layer of 1-2 ML thickness on the nanotube surface and they show rapid adsorption and desorption transition at a critical pressure. This adsorption layer is created by lateral hydrogen bonding of water molecules confined in the weak van der Waals potential of the surface. In spite of hydrophobic hydration, carbon nanotubes exhibit hydrophobicity macroscopically.
authors.affiliation: Department of Physics, Tokyo University of Science, Shinjuku, Tokyo 162-8601, Japan.
authors.forename: Yoshikazu
authors.initials: Y
authors.lastname: Homma
authors.affiliation: Department of Mechanical Engineering, The University of Tokyo, Bunkyo, Tokyo 113-8656, Japan.
authors.forename: Shohei
authors.initials: S
authors.lastname: Chiashi
authors.affiliation: Department of Liberal Arts, Faculty of Engineering and Department of Electrical Engineering, Graduate School of Engineering, Tokyo University of Science, Chiyoda, Tokyo 102-0073, Japan.
authors.forename: Takahiro
authors.initials: T
authors.lastname: Yamamoto
authors.affiliation: Department of Physics, Tokyo University of Science, Shinjuku, Tokyo 162-8601, Japan.
authors.forename: Kaname
authors.initials: K
authors.lastname: Kono
authors.affiliation: Department of Physics, Tokyo University of Science, Shinjuku, Tokyo 162-8601, Japan.
authors.forename: Daiki
authors.initials: D
authors.lastname: Matsumoto
authors.affiliation: Department of Physics, Tokyo University of Science, Shinjuku, Tokyo 162-8601, Japan.
authors.forename: Junpei
authors.initials: J
authors.lastname: Shitaba
authors.affiliation: Department of Physics, Tokyo University of Science, Shinjuku, Tokyo 162-8601, Japan.
authors.forename: Shintaroh
authors.initials: S
authors.lastname: Sato