Graphene Ice Sandwich...

Square ice between two graphene sheets as seen in a transmission electron microscope. High-contrast dark spots are oxygen atoms that indicate positions of water molecules. Hydrogen atoms yield too little contrast to be resolved even by the state-of-the-art TEM. The top right inset shows a magnified image of a small area in the centre of the ice crystal. Credit: University of Ulm, Germany

Topics: Carbon Nanotubes, Graphene, Nanotechnology, Nanostructures

Researchers in the UK, Germany and China say they have observed a new type of frozen water in the form of square ice sandwiched between sheets of graphene. The ice films, which are less than 1 nm thick, have a completely different symmetry to that of normal ice – which has a hexagonal structure. This ice should also exist inside certain other types of nanostructures, such as carbon nanotubes, and could help explain why water moves unusually in these materials – a result that could have implications for developing more efficient filtration, desalination and distillation technologies.

"The new phase of ice forms at room temperature, well above the 'normal' freezing temperature of water," explain team leaders Irina Grigorieva and Andre Geim of the University of Manchester in the UK. "Apart from finding this new phase – not something that happens every day – our result will allow us to better understand the counterintuitive behaviour of water inside nanochannels, such as ultrafast permeation though graphene oxide membranes."

Nanotech Web: Square ice forms in graphene sandwich, Belle Dumé, contributing editor at nanotechweb.org