Investigation of the quasi-liquid nature of nano-water films on solids and pioneering science and technology of phenomena occurring in nano-water films

2021 Fiscal Year Final Research Report

• Project/Area Number: 20K20359
• Project/Area Number (Other): 18H05343 (2018-2019)
• Research Category: Grant-in-Aid for Challenging Research (Pioneering)
• Allocation Type: Multi-year Fund (2020); Single-year Grants (2018-2019)
• Review Section: Medium-sized Section 28:Nano/micro science and related fields
• Research Institution: Kanazawa University
• Principal Investigator: Arai Toyoko 金沢大学, 数物科学系, 教授 (20250235)
• Project Period (FY): 2018-06-29 – 2022-03-31
• Keywords: ナノ水膜 / 水固体界面 / 周波数変調原子間力顕微鏡

Outline of Final Research Achievements

A few nanometers thick water film adsorbed on a solid surface from atmospheric water vapor has different properties from the bulk water (liquid phase). This water film was named “nanometer-thick water film”. Using frequency modulation atomic force microscopy (FM-AFM), we successfully obtained images of the nanometer-thick water film/solid interface. Inside the thinner nanometer-thick water film, the hydration layer spacing is narrower, the mobilities of water molecules and ions are lower, and then the dissolution-deposition reactions that frequently occur at the normal saturated solution/solid interface are suppressed. However, when the KBr crystal surface covered by the nanometer-thick water film is pressed with an FM-AFM tip, KBr dissolves atom by atom and instantly deposits at the same location when the pressure is removed. We found mechanical catalytic effects that occur only in the nanometer-thick water film.

Free Research Field

表面科学

Academic Significance and Societal Importance of the Research Achievements

大気中には水蒸気が含まれ、多くの固体表面には水が吸着している。固体表面上の水膜は、種々の表面反応を促進させたり失活させたりし、時には邪魔者とされてきた。大気中の水蒸気から固体表面上に吸着したナノ水膜は、水（液相）とも異なる性質を持つ。本研究では、ナノ水膜の準液体性を研究し、さらにその特異性を活用するナノ水膜内の科学技術の開拓をめざした。FM-AFM探針による力学的触媒作用により、原子レベルの反応制御ができる可能性を示した。原子レベルの液中反応を誘起してナノ構造を創成するなど、資源利用効率の向上を通じて社会の持続可能性向上に寄与することが期待される。