Nanotube 'sponge' has potential in oil spill cleanup

A carbon nanotube sponge that can soak up oil in water with unparalleled efficiency has been developed with help from computational simulations performed at the Department of Energy's (DOE's) Oak Ridge National Laboratory.

Carbon nanotubes, which consist of atom-thick sheets of carbon rolled into cylinders, have captured scientific attention in recent decades because of their high strength, potential high conductivity and light weight. But producing nanotubes in bulk for specialised applications was often limited by difficulties in controlling the growth process as well as dispersing and sorting the produced nanotubes.

ORNL's Bobby Sumpter was part of a multi-institutional research team that set out to grow large clumps of nanotubes by selectively substituting boron atoms into the otherwise pure carbon lattice. Sumpter and Vincent Meunier, now of Rensselaer Polytechnic Institute, conducted simulations on supercomputers, including Jaguar at ORNL's Leadership Computing Facility, to understand how the addition of boron would affect the carbon nanotube structure.

"Any time you put a different atom inside the hexagonal carbon lattice, which is a chicken wire-like network, you disrupt that network because those atoms don't necessarily want to be part of the chicken wire structure," Sumpter said. "Boron has a different number of valence electrons, which results in curvature changes that trigger a different type of growth."

Simulations and lab experiments showed that the addition of boron atoms encouraged the formation of so-called "elbow" junctions that help the nanotubes grow into a 3-D network. The team's results are published in Nature Scientific Reports.

"Instead of a forest of straight tubes, you create an interconnected, woven sponge-like material," Sumpter said. "Because it is interconnected, it becomes three-dimensionally strong, instead of only one-dimensionally strong along the tube axis."