  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.
