A carbon nanotube sponge that can soak up（吸收） oil in water with unparalleled（无比的） efficiency has been developed with help from computational simulations performed at the Department of Energy's (DOE's) Oak Ridge¹ National Laboratory. Carbon nanotubes, which consist of atom-thick sheets of carbon rolled into cylinders², have captured scientific attention in recent decades because of their high strength, potential high conductivity and light weight. But producing nanotubes in bulk for specialized³ applications was often limited by difficulties in controlling the growth process as well as dispersing⁴（分散的） and sorting the produced nanotubes.

ORNL's Bobby Sumpter was part of a multi-institutional research team that set out to grow large clumps⁵ of nanotubes by selectively substituting boron atoms into the otherwise pure carbon lattice. Sumpter and Vincent Meunier, now of Rensselaer Polytechnic⁶ Institute, conducted simulations on supercomputers, including Jaguar⁷ at ORNL's Leadership Computing⁸ 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（弯曲） 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" junctions⁹ 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 axis¹⁰."

Further experiments showed the team's material, which is visible to the human eye, is extremely efficient at absorbing oil in contaminated seawater because it attracts oil and repels¹¹ water.