The Penn team's research shows that single-layer-thick graphene can be reliably produced at normal pressures if the metal sheets are smooth enough.
"The fact that this is done at atmospheric pressure makes it possible to produce graphene at a lower cost and in a more flexible way," Luo, the study's lead author, said.
Whereas other methods involved meticulously preparing custom copper sheets in a costly process, Johnson's group used commercially available copper foil in their experiment.
"You could practically buy it at the hardware store," Johnson said.
Other methods make expensive custom copper sheets in an effort to get them as smooth as possible; defects in the surface cause the graphene to accumulate in unpredictable ways. Instead, Johnson's group "electropolished" their copper foil, a common industrial technique used in finishing silverware and surgical tools. The polished foil was smooth enough to produce single-layer graphene over 95% of its surface area.
Working with commercially available materials and chemical processes that are already widely used in manufacturing could lower the bar for commercial applications.
"The overall production system is simpler, less expensive, and more flexible" Luo said.
The most important simplification may be the ability to create graphene at ambient pressures, as it would take some potentially costly steps out of future graphene assembly lines.
"If you need to work in high vacuum, you need to worry about getting it into and out of a vacuum chamber without having a leak," Johnson said. "If you're working at atmospheric pressure, you can imagine electropolishing the copper, deposi
|Contact: Evan Lerner|
University of Pennsylvania