Graphene, the 21st century's most promising new material, has acquired yet another entry in its burgeoning CV.
A team led by graphene co-discoverer Professor Sir Andrew Geim at the University of Manchester has demonstrated that thin films of graphene oxide are impermeable to most gases and liquids, but extremely permeable to water. The research was reported in Science on Friday.
The behaviour happens when graphene oxide sheets are stacked on top of each other to form a laminate. The researchers put such a film on top of a metal container containing various liquids and gases: even helium, a gas noted for its ability to pass through almost anything, was blocked. Water, however, evaporated out of the container.
"Helium gas is hard to stop. It slowly leaks even through a millimetre -thick window glass but our ultra-thin films completely block it. At the same time, water evaporates through them unimpeded. Materials cannot behave any stranger," Professor Geim said in a press release. "You cannot help wondering what else graphene has in store for us".
Graphene oxide is a sheet of ordinary graphene — carbon atoms linked in a hexagonal, single-atom plane — but with the addition of other molecules, such as hydroxyl, that adhere to the matrix but don't disrupt its structure.
The scientist who led the experimental work, Dr Rahul Nair, said: "Graphene oxide sheets arrange in such a way that between them there is room for exactly one layer of water molecules. They arrange themselves in one molecule thick sheets of ice which slide along the graphene surface with practically no friction. If another atom or molecule tries the same trick, it finds that graphene capillaries either shrink in low humidity or get clogged with water molecules."
The experimenters tried sealing a bottle of vodka with the graphene oxide membrane, and said that it got stronger over time, as the water evaporated but the alcohol was left behind.