"If nanotubes can live up to all their predicted promise, then we believe that we have a method for making analogous materials for a fraction of the cost," Mack said.
Nanotubes are pure carbon sheets in a tubular form, capped at each end. Viculis and Mack's carbon nanoscrolls are also pure carbon but the sheets are curled up, without the caps on the ends, potentially allowing access to significant additional surface area. While nanotubes are normally made at high temperatures, nanoscrolls can be produced at room temperature.
"Our method involves scrolling sheets of graphite, which could give us a much higher surface area," Viculis said.
"If we can access the entire surface area on both sides of the carbon sheets -- unlike with carbon nanotubes, where only the outside surface is accessible -- then we could adsorb twice the amount of hydrogen -- an enormous increase," Mack said, "improving on hydrogen storage for fuel (an alternative to fossil fuels)."
"Nanoscrolls can be made by a relatively inexpensive and scalable process at low temperatures," Mack said. "Our starting materials are just graphite and potassium metal. The idea is beautiful in its simplicity."
"Carbon surfaces are known to adsorb hydrogen. A difficulty with using hydrogen as a fuel source for cars, instead of gas, is obtaining a material capable of storing enough hydrogen to make the approach feasible," Viculis said.
"Carbon nanoscrolls could make pollution-free, hydrogen-powered cars better than they would otherwise be," said Kaner, the third co-author on the Science paper. "This research is a good start. We have a long way to go. For this approach to work well, we need to get down to individual carbon layers, and we are not there yet. On average, the nanoscrolls are 40 layers thick. We have not yet realized the full surface area or all the properties we are after. The challenge is to reduce the nanoscrolls to individual layers. We have many good leads, and have started new collaborations."
The research may lead to numerous applications.
"For electronic applications, nanotubes may work well," Kaner said. "For applications where high surface area is important -- such as hydrogen storage, or energy storage in super-capacitors -- these nanoscrolls may be better."
Other possible applications for nanoscrolls, Kaner said, include lightweight but strong materials for planes and cars, and improved graphite-based tennis rackets and golf clubs.
Kaner, Viculis and Mack are collaborating on mechanical properties and applications with H. Thomas Hahn, UCLA's Raytheon Professor of Manufacturing Engineering, and chair of the UCLA Department of Mechanical and Aerospace Engineering.
"We see this research as a jumping-off point," Viculis said. "We believe it will give people ideas. Colleagues are finding us for collaborations, in engineering as well as chemistry."
Viculis, Mack and Kaner, who have been working on this project together for more than two years, have continued to make significant progress even in the time since they submitted the Science paper.
The research is funded by the National Science Foundation, the Office of Naval Research, the Air Force Office of Scientific Research and UCLA's Academic Senate.