Using soda water as the electrolyte, chemical vapor deposition synthesized graphene via under-etching delamination. Source: University of Illinois Fizzy carbonated water is no longer just for your favorite adult beverage.

Researchers at the University of Illinois at Urbana-Champaign have discovered a new use for the soda—manufacturing graphene.

As graphene popularity grows, the ability to produce the material quickly and at a high quality is incredibly important. This method is a cleaner and more environmentally-friendly way to isolate graphene using carbon dioxide (CO2) in the form of carbonic acid as the electrolyte solution, researchers say.

Graphene is synthesized by using chemical vapor deposition onto a metal substrate, typically copper foil. One difficult aspect of this is how to separate this atomically thin material from its native metal substrate for integration into useful devices. This involves either dissolving away the metal or delaminating it from the substrate—using harsh chemicals that leave residue. The ultra-thin graphene then needs to be coated with a polymer support layer such as polycarbonate (PMMA), which required the use of toxic and carcinogenic solvents.

"In our case, we are using a bio-mass derived polymer, ethyl cellulose, for the coating," says Michael Cai Wang, a PhD student at University of Illinois. "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."

After the graphene is transferred, the carbonic acid evaporates as carbon dioxide and water, eliminating the need for further rinsing. This process saves both water and time by not having to repeat the duplicate rinsing process, researchers say.

"Graphene is just starting to mature from the laboratory and into commercial applications," Wang says. "Once you start large-scale manufacturing, workers' health is also a major consideration, another benefit of our greener process."

The full research can be found in the Journal of Materials Chemistry C.