Graphene Finds Environmental Use

Graphene has been hailed as a wonder product by materials engineers looking for faster circuits to replace silicon. Now a group at Brown University has discovered a new use for the oxidized form of these nanoscale carbon sheets: chemical barriers. A thin layer of graphene oxide, about 10 atoms thick, prevents most of the gaseous mercury from escaping from a closed glass container, the researchers found (Environ. Sci. Technol., DOI: 10.1021/es301377y).

Brown’s Robert Hurt and his colleagues had previously tested how much mercury escapes from crushed compact fluorescent light bulbs contained in plastic bags on the way to recycling. Most of the toxic heavy metal seeped out (Environ. Sci. Technol., DOI: 10.1021/es8004392). He thought lining bags with graphene might hold the mercury in.

Because making large sheets of pure graphene is difficult, Hurt’s graduate student Fei Guo made graphene oxide by exfoliating pure graphite. From a watery suspension, the researchers dried the graphene oxide to create a film atop a plastic sheet.

The team set this layered plastic-and-graphene barrier above a pool of mercury in a glass container. After air flowed across the surface of the barrier and out of the container, a vapor analyzer measured its mercury content.

The membrane blocked 90% of the mercury that a naked plastic sheet would have let through. That was better containment than was provided by other proposed barriers to mercury vapors, including a nanoclay-coated plastic layer that blocked only 29%. The researchers plan to make the graphene layer thinner and therefore cheaper. Hurt thinks the film could find several other uses, such as preventing the release of volatile organic compounds from fabrics into a room.