Ice Nanoribbons Confined in Uniaxially Distorted Carbon Nanotubes

2021 Fiscal Year Final Research Report

• Project/Area Number: 18K13518
• Research Category: Grant-in-Aid for Early-Career Scientists
• Allocation Type: Multi-year Fund
• Review Section: Basic Section 13040:Biophysics, chemical physics and soft matter physics-related
• Research Institution: Kanagawa University
• Principal Investigator: Kyakuno Haruka 神奈川大学, 工学部, 准教授 (10746788)
• Project Period (FY): 2018-04-01 – 2022-03-31
• Keywords: ナノ氷 / 水 / カーボンナノチューブ / ナノサイエンス / プロトン輸送 / 誘電体

Outline of Final Research Achievements

We investigated effects of the pore geometry on water properties inside single-walled carbon nanotubes (SWCNTs) by means of molecular dynamics simulations. SWCNTs were uniaxially compressed in a direction perpendicular to the SWCNT axis. It was found that a new form of ice, ice nanoribbon, forms when the shortened diameter of a SWCNT after the compression becomes less than about 0.9 nm. The protons of water molecules are ordered in the ice nanoribbons. It was demonstrated that dielectricity of an ice nanoribbon can be controlled by the number of ferroelectric water chains forming the nanoribbon. Proton transport properties through the ice nanoribbons were also examined. An excess proton diffused along edge water chains of the ice nanoribbon via the Grotthuss mechanism. These unusual physical properties are caused by finite widths of the ice nanoribbons perpendicular to the tube axis.

Free Research Field

物性物理学、ナノサイエンス

Academic Significance and Societal Importance of the Research Achievements

本研究では、SWCNTの空洞形状を変化させることにより、内包水の構造、ダイナミクス、誘電特性、プロトン輸送特性などを制御可能であることを示した。リボン状氷は、二次元氷を帯状に切り出したような構造であり、そのエッジ（端）では水分子の水素結合が遮断される。この端構造に由来して特異な物性を発現する。本研究の成果は、新たなナノ流体デバイス、プロトン伝導体、およびナノ誘電体デバイスの創製などに繋がることが期待される。