A protective cover a few atoms thick

Water permeation through a brick without (left) and with (right) “graphene paint” coating. Credit: Y. Su et al./ArXiv

Graphene, a single layer of carbon atoms arranged in hexagons, is seen by many as the holy Grail of this decade because of its amazing properties: strengths, conductivity, lightness as well as impermeability to liquid and gases. We already have graphene, what we miss is a way of producing it in industrial quantity at an affordable price. 

As researchers are working on this, variations of graphene are being studied, like graphine. Now researchers at the University of Manchester, led by Rahl Nair and Andre Geim (Nobel laureate for his studies on graphene), have found that graphene oxide can be used as a protective coating on a variety of materials. 
Graphene oxide can be produced in flakes. These can be layered onto a surface (basically any kind of surface, plastic, ceramics, metal, is ok for them to stick on). Whilst graphene is totally impermeable, flakes are not. They let molecules below a certain size pass through because there are little gaps among the flakes that are deposited on a surface. This would make them a good sieve and actually scientists are studying how to use them for purifying water. However, this makes them of little use when you want to have a protective surface.

What the team at Manchester University did was to find a way to close any nano pore resulting from the random deposition of the flakes. By using hydroiodic acid they have been able to create a surface that is completely impermeable. They demonstrated it by covering a bowl made of copper with this graphene oxide paint and pouring in it strongly corrosi acide with no impact on copper.

The flakes are just a few atoms thick (where flakes overlay one another, they are just one atom thick as a single flake) hence they are completely transparent.

One application, according to Yang Su, the first author of the paper where the researchers have announced their discovery, could be in the medical field. A protective layer of graphene flakes would make blisters totally impermeable prolonging the life of pills on the pharmacy shelf. Amazing how top notch technology finds application in something as common as a blister.

Author - Roberto Saracco

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