The UK's National Physical Laboratory, along with a team of international scientists, have shown that when graphene is combined with particular polymers, its electrical properties can be precisely controlled by light and exploited in a new generation of optoelectronic devices.
The polymers keep memory of light and therefore the graphene device retains its modified properties until the memory is erased by heating. As a single-layer of sp-2 bonded carbon atoms graphene is the thinnest material known and yet one of the strongest ever tested. It is possible to engineer a super-sensitive sensor because when molecules land on the surface they alter the electrical characteristics in the immediate region.
The team of researchers included scientists from the U.K.'s National Physical Laboratory (NPL), the University of Copenhagen (Denmark), the University of California Berkeley (USA), Chalmers University of Technology (Sweden), Linkoping University (Sweden) and Lancaster University (UK).
In their paper Non-volatile Photo-Chemical Gating of an Epitaxial Graphene-Polymer Heterostructure published in the Journal of Advanced Materials, the team show that when graphene is coated with light-sensitive polymers its electrical properties can be controlled precisely and therefore exploited. At the same time the polymers protect the graphene from contamination.
Light-modified graphene chips have already been used at NPL in ultra-precision experiments to measure the quantum of the electrical resistance. In the future, similar polymers could be used to effectively 'translate' information from their surroundings and influence how graphene behaves. This effect could be exploited to develop robust reliable sensors for smoke, poisonous gases, or any targeted molecule.
Graphene does not have volume, only surface – its entire structure is exposed to its environment, and responds to any molecule that touches it. This makes it in principle a very exciting material for super-sensors capable of detecting single molecules of toxic gases. Polymers can make graphene respond to specific molecules and ignore all others at the same time, which also protects it from contamination.