Anomalous Freezing of Low Dimensional Water Confined in Graphene Nanowrinkles

TL;DR

This study develops a novel method to confine water molecules in nanodimensional graphene wrinkles and monitors their phase transitions using cryogenic Raman spectroscopy, supported by molecular dynamics simulations.

Contribution

A new technique for permanently trapping water in graphene nanowrinkles and analyzing its phase behavior with sensitive spectroscopic methods.

Findings

Successfully confined water below a graphene monolayer in nanometric wrinkles.

Detected phase changes of confined water as a function of temperature.

Supported experimental results with molecular dynamics simulations.

Abstract

Various properties of water are affected by confinement as the space-filling of the water molecules is very different from bulk water. In our study, we challenged the creation of a stable system in which water molecules are permanently locked in nanodimensional graphene traps. For that purpose, we developed a technique, nitrocellulose-assisted transfer of graphene grown by chemical vapor deposition, which enables capturing of the water molecules below an atomically thin graphene membrane structured into a net of regular wrinkles with a lateral dimension of about 4 nm. After successfully confining water molecules below a graphene monolayer, we employed cryogenic Raman spectroscopy to monitor the phase changes of the confined water as a function of the temperature. In our experiment system, the graphene monolayer structured into a net of fine wrinkles plays a dual role: (i) it enables water confinement and (ii) serves as an extremely sensitive probe for phase transitions involving water via graphene-based spectroscopic monitoring of the underlying water structure. Experimental findings were supported with classical and path integral molecular dynamics simulations carried out on our experimental system.