Robust nanosponges soak up oil again and again
solids have been convincingly demonstrated, he said.
“The interactions happen as they grow, and the material comes out of the furnace as a solid,” Ajayan said. “People have made nanotube solids via post-growth processing but without proper covalent connections. The advantage here is that the material is directly created during growth and comes out as a cross-linked porous network.
“It’s easy for us to make nano building blocks, but getting to the macroscale has been tough,” he said. “The nanotubes have to connect either through some clever way of creating topological defects, or they have to be welded together.”
The release notes that when he was an undergraduate student of Ajayan’s at Rensselaer Polytechnic Institute, Hashim and his classmates discovered hints of a topological solution to the problem while participating in a National Science Foundation exchange program at the Institute of Scientific Research and Technology (IPICYT) in San Luis Potosí, Mexico. The paper’s co-author, Mauricio Terrones, a professor of physics, materials science and engineering at Penn State University with an appointment at Shinshu University, Japan, led a nanotechnology lab there.
“Our goal was to find a way to make three-dimensional networks of these carbon nanotubes that would form a macroscale fabric — a spongy block of nanotubes that would be big and thick enough to be used to clean up oil spills and to perform other tasks,” Terrones said. “We realized that the trick was adding boron — a chemical element next to carbon on the periodic table — because boron helps to trigger the interconnections of the material. To add the boron, we used very high temperatures and we then ‘knitted’ the substance into the nanotube fabric.”
The researchers have high hopes for the material’s environmental applications. “For oil spills, you would have to make large sheets of these or find a way to weld sheets together (a process Hashim continues to work on),” Ajayan said.
“Oil-spill remediation and environmental cleanup are just the beginning of how useful these new nanotube materials could be,” Terrones added. “For example, we could use these materials to make more efficient and lighter batteries. We could use them as scaffolds for bone-tissue regeneration.
We even could impregnate the nanotube sponge with polymers to fabricate robust and light composites for the automobile and plane industries.”
Hashim suggested his nanosponges may also work as membranes for filtration.
“I don’t think anybody has created anything like this before,” Ajayan said. “It’s a spectacular nanostructured sponge.”
The National Science Foundation and the Air Force Office of Scientific Research Project MURI program for the synthesis and characterization of 3-D carbon nanotube solid networks supported the research.
— Read more in Daniel P. Hashim et al., “Covalently bonded three-dimensional carbon nanotube solids via boron induced nanojunctions,” Scientific Reports 2, article no. 363 (13 April 2012) (doi:10.1038/srep00363)
