title: Fast Water Relaxation through One-Dimensional Channels by Rapid Energy Transfer.
abstract: Water in carbon nanotubes is surrounded by hydrophobic carbon surfaces and shows anomalous structural and fast transport properties. However, the dynamics of water in hydrophobic nanospaces is only phenomenologically understood. In this study, water dynamics in hydrophobic carbon nanotubes is evaluated based on water relaxation using nuclear magnetic resonance spectroscopy and molecular dynamics simulations. Extremely fast relaxation (0.001 s) of water confined in carbon nanotubes of 1 nm in diameter on average is observed; the relaxation times of water confined in carbon nanotubes with an average diameter of 2 nm (0.40 s) is similar to that of bulk water (0.44 s). The extremely fast relaxation time of water confined in carbon nanotubes with an average diameter of 1 nm is a result of frequent energy transfer between water and carbon surfaces. Water relaxation in carbon nanotubes of average diameter 2 nm is slow because of the limited number of collisions between water molecules. The dynamics of interfacial water can therefore be controlled by varying the size of the hydrophobic nanospace.
authors.affiliation: Graduate School of Science, Chiba University, 1-33 Yayoi, Inage, Chiba, 263-8522, Japan.
authors.forename: Tomonori
authors.identifier: http://orcid.org/0000-0001-8207-3630
authors.initials: T
authors.lastname: Ohba
authors.affiliation: Institute for Materials Chemistry and Engineering, Kyushu University, 6-1 Kasuga-koen, Kasuga, Fukuoka, 816-8580, Japan.
authors.forename: Keiko
authors.initials: K
authors.lastname: Ideta
authors.affiliation: Institute for Materials Chemistry and Engineering, Kyushu University, 6-1 Kasuga-koen, Kasuga, Fukuoka, 816-8580, Japan.
authors.forename: Koichiro
authors.initials: K
authors.lastname: Hata
authors.affiliation: Institute for Materials Chemistry and Engineering, Kyushu University, 6-1 Kasuga-koen, Kasuga, Fukuoka, 816-8580, Japan.
authors.forename: Seong-Ho
authors.initials: SH
authors.lastname: Yoon
authors.affiliation: Institute for Materials Chemistry and Engineering, Kyushu University, 6-1 Kasuga-koen, Kasuga, Fukuoka, 816-8580, Japan.
authors.forename: Jin
authors.initials: J
authors.lastname: Miyawaki
authors.affiliation: Nanotube Research Center, National Institute of Advanced Industrial Science and Technology (AIST), 1-1-1 Higashi Tsukuba, Ibaraki, 305-8565, Japan.
authors.forename: Kenji
authors.initials: K
authors.lastname: Hata
keywords: NMR spectroscopy; molecular dynamics; nanostructures; nanotubes; water chemistry