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Graphene: super-strong, super-thin, and super-conductive

27/01/2012

Graphene grasps helium as water escapes

Material adds selective permeability to superpowers

Adam Duckett

RESEARCHERS have found that graphene-based membranes, impermeable to helium, readily allow water to pass through them – an odd property that hints at a new class of industrial separation techniques.

Graphene is characterised by superlatives. It is the world’s thinnest and strongest material, and conducts heat and electricity better than any other.

The list of interesting properties has increased again, after researchers at the UK’s University of Manchester sealed a metal container with a film of graphene oxide. They were unable to detect air or any other gas including helium leaking through but when they added water however, it freely evaporated through at such a speed that the rate was the same whether the container was sealed or wide open.

“Just for a laugh, we sealed a bottle of vodka with our membranes and found that the distilled solution became stronger and stronger with time,” adds physics researcher Rahul Nair.

“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,” Nair explains.

Despite this the researchers do not offer any immediate ideas for practical applications.

However, researcher Andre Geim says: “The properties are so unusual that it is hard to imagine that they cannot find some use in the design of filtration, separation or barrier membranes and for selective removal of water.”

Science doi: 10.1126/science.1211694