Graphene isolated with carbon dioxide

The findings from the research group of SungWoo Nam, assistant professor of mechanical science and engineering at the University of Illinois at Urbana-Champaign, are published in Journal of Materials Chemistry C.

Graphene is synthesised by using chemical vapour deposition onto a metal substrate – such as copper foil – but separating the material from its native metal substrate can be problematic.

The process typically involves either dissolving away the high-purity metal or delaminating it from the substrate, which require the use of harsh chemicals that leave stubborn residue.

The ultra-thin graphene also needs to be coated with a polymer support layer such as polycarbonate or PMMA (poly methyl methacrylate), which requires the use of toxic or carcinogenic solvents.

"In our case, we are using a biomass derived polymer, ethyl cellulose, for the coating," said Michael Cai Wang, Nam's PhD student and lead researcher on the project. "A common and inexpensive polymer often used as a food additive, ethyl cellulose is solvated in just ethanol. This not only makes our graphene transfer process more environmentally friendly, it is now also compatible with a variety of polymeric and soft biological materials such as common plastics and hydrogels that would otherwise not tolerate harsh solvents."