Members of Girl Scouts of the United States of America Troop 25080 came to Rice's Smalley Institute for Nanoscale Science and Technology to see how graphene -- a single-atom-thick sheet of the same material in pencil lead -- can be made from just about any carbon source, including food, insects and waste.
The cookie gambit started on a dare when chemist Tour mentioned at a meeting that his lab had produced graphene from table sugar.
"I said we could grow it from any carbon source -- for example, a Girl Scout cookie, because Girl Scout Cookies were being served at the time," Tour recalled. "So one of the people in the room said, 'Yes, please do it. ... Let's see that happen.'"
. Rice graduate students Gedeng Ruan, lead author of the paper, and Zhengzong Sun calculated that at the then-commercial rate for pristine graphene -- $250 for a two-inch square -- a box of traditional Girl Scout shortbread cookies could turn a $15 billion profit.
"That's a lot of cash!" said an amazed Sydney Shanahan, a member of the troop.
A sheet of graphene made from one box of shortbread cookies would cover nearly three football fields, Sun said.
The experiment was a whimsical way to make a serious point: that graphene -- touted as a miracle material for its toughness and conductivity since its discovery by Nobel Prize-winning scientists Andre Geim and Konstantin Novoselov in 2004 -- can be drawn from many sources.
To demonstrate, the researchers subsequently tested a range of materials, as reported in the new paper, including chocolate, grass, polystyrene plastic, insects (a cockroach leg) and even dog feces (compliments of lab manager Dustin James' miniature dachshund, Sid Vicious).
The process: the researchers were able to make high-quality graphene via carbon deposition on copper foil. In this process, the graphene forms on the opposite side of the foil as solid carbon sources decompose; the other residues are left on the original side. Typically, this happens in about 15 minutes in a furnace flowing with argon and hydrogen gas and turned up to 1,050 degrees Celsius.
Tour expects the cost of graphene to drop quickly as commercial interests develop methods to manufacture it in bulk.