Lumps of graphite are sooty; its constituent layers of graphene, however, are transparent, a property that researchers have used in a liquid-crystal device. Kostya Novoselov at the University of Manchester, UK, and his co-workers have shown that an electrode made from a thin graphene film can switch a device from opaque to transparent.
Most optical display devices have indium tin oxide as the transparent conductor, but this compound is apt to degrade because its ions are mobile. Graphene films, by contrast, are chemically stable and strong. The researchers find that the films can be cheaply spray-deposited onto glass from a suspension in an organic solvent.