Controllable structure phases and tunable freezing zones of water confined in multi-walled carbon nanotube capillaries

• Published in: Journal of molecular liquids 2024-06, Vol.403, p.124837, Article 124837
• Main Authors: Pu, Yangyang, Zhao, Wenhui, Liu, Yuan
• Format: Article
• Language: English
• Subjects: Ice nanotube; Nano-confined water; One-dimensional ice; Phase transition
• ISSN: 0167-7322
• DOI: 10.1016/j.molliq.2024.124837

•It demonstrates water can be spontaneously drawn into the multi-walled carbon nanotube (MWCNT) capillaries and can be transformed into ice nanotubes (INTs) through first-order liquid–solid phase transition based on molecular dynamics simulations.•The INT structures formed in the gaps of MWCNT can be controlled by tuning the inter-wall spacings of the MWCNT, Flat-square-walled INTs and puckered-rhombic-walled INTs will separately be formed with the inter-wall spacings of 6.66 and 8.61 Å, respectively.•The freezing zones of water confined in MWCNTs are tunable, e.g. water confined in MWCNTs with the inter-wall spacings of 6.66 Å, the freezing will occur zone by zone and can be controlled by the temperature. One-dimensional nanoconfined water exhibits rich structure phases. The freezing behavior of water confined in single-walled carbon nanotubes has been studied by both experimental measurements and theoretical simulations, however, it lacks of studying the freezing behavior of water confined in multi-walled carbon nanotubes (MWCNTs). Herein, we investigated the freezing behavior of water confined in MWCNTs using molecular dynamics simulations. Flat-square-walled ice nanotubes (FSW-INTs) were formed in the gaps with the inter-wall spacing of 6.66 Å, while, puckered-rhombic-walled ice nanotubes (PRW-INTs) were observed in the gaps with the inter-wall spacing of 8.61 Å. Then, the INT structures formed among the inter-wall gaps of MWCNTs can be controlled by tuning the inter-wall spacings of MWCNTs. Specifically, various groups of FSW-INTs and/or PRW-INTs were designed to form by using MWCNTs with the inter-wall spacing of 6.66 and/or 8.61 Å. In addition, it was found that water could be frozen in a simultaneous way or be frozen in a zone-by-zone form by tuning the inter-wall spacings of the MWCNTs due to the freezing temperatures of INTs are related with their diameters. The study will provide deep insights into the freezing behavior of water in MWCNTs.