title: Quasiphase Transition in a Single File of Water Molecules Encapsulated in (6,5) Carbon Nanotubes Observed by Temperature-Dependent Photoluminescence Spectroscopy.
abstract: Molecules confined inside single-walled carbon nanotubes (SWCNTs) behave quite differently from their bulk analogues. In this Letter we present temperature-dependent (4.2 K up to room temperature) photoluminescence (PL) spectra of water-filled and empty single-chirality (6,5) SWCNTs. Superimposed on a linear temperature-dependent PL spectral shift of the empty SWCNTs, an additional stepwise PL spectral shift of the water-filled SWCNTs is observed at ∼150  K. With the empty SWCNTs serving as an ideal reference system, we assign this shift to temperature-induced changes occurring in the single-file chain of water molecules encapsulated in the tubes. Our molecular dynamics simulations further support the occurrence of a quasiphase transition of the orientational order of the water dipoles in the single-file chain.
authors.affiliation: Center for Integrated Nanotechnologies, Materials Physics and Applications Division, Los Alamos National Laboratory, New Mexico 87545, USA.
authors.forename: Xuedan
authors.initials: X
authors.lastname: Ma
authors.affiliation: Experimental Condensed Matter Physics Laboratory, University of Antwerp, B-2610 Antwerp, Belgium.
authors.forename: Sofie
authors.initials: S
authors.lastname: Cambré
authors.affiliation: Experimental Condensed Matter Physics Laboratory, University of Antwerp, B-2610 Antwerp, Belgium.
authors.forename: Wim
authors.initials: W
authors.lastname: Wenseleers
authors.affiliation: Center for Integrated Nanotechnologies, Materials Physics and Applications Division, Los Alamos National Laboratory, New Mexico 87545, USA.
authors.forename: Stephen K
authors.initials: SK
authors.lastname: Doorn
authors.affiliation: Center for Integrated Nanotechnologies, Materials Physics and Applications Division, Los Alamos National Laboratory, New Mexico 87545, USA.
authors.forename: Han
authors.initials: H
authors.lastname: Htoon