Water and Ice in Graphene Nanovessels*

Studying water behavior in nano-enclosures is of particular interest but requires fine spectroscopic probes with sub-micrometer resolution. Graphene liquid cells (GLCs) which feature two closely-spaced sheets of graphene wrapped around hydrated samples, facilitate high-resolution transmission electron microscopy (TEM) and electron energy-loss spectroscopy (EELS) measurements of water and ice encased tightly in hydrophobic graphene nanovessels. We perform TEM and EELS measurements in GLCs maintained at either 25^oC or -165^oC to examine the nanoscale arrangement of water and ice molecules with sub-eV energy resolution. Simultaneous quantification of water and ice thickness leads to the conclusion that H-bonding strengthens under increased confinement. The present results offer new insight on water molecule arrangement under high-confinement conditions.