Last week we looked at the development of “hydrate-phobic” surfaces that could assist in the containment of oil leaks in deep water. Now, by adding boron to carbon while growing nanotubes, researchers have developed a nanosponge with the ability to absorb oil spilled in water. Remarkably, the material is able to achieve this feat repeatedly and is also electrically conductive and can be manipulated with magnets.

While multiwalled carbon nanotubes grown on a substrate via chemical vapor disposition form standing up without any real connections to their neighbors, the researchers found that adding a dash of boron to the nanotube production process puts kinks and elbows into them as they grow and promotes the formation of covalent bonds. This gives the nanosponges, which are 99% air, an elastic property that is retained even after 10,000 compressions in the lab.

The sponges are both superhydrophobic - meaning they repel water allowing them to float extremely well – and oleophilic – meaning they have a strong affinity for oils. These dual properties give the material the ability to soak up oil floating on the surface of water. The potential for the material in soaking up oil spills at sea is obvious. But the material has the added ability to be used repeatedly so, after soaking up oil, it could be wrung out and reused. The oil can also be burned off while in the sponge, which can then be reused again.

"These samples can be made pretty large and can be easily scaled up,” says Rice graduate student Daniel Hashim, holding a half-inch square block of billions of nanotubes. “They’re super-low density, so the available volume is large. That’s why the uptake of oil can be so high.” Hashim says the sponges can absorb more than a hundred times their weight in oil. He is working on ways to weld large sheets of the nanosponges together so they could be used to mop up oil spills.

However, the researchers believe environmental cleanup applications are just the tip of the iceberg for the material. “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,” says Mauricio Terrones, a professor of physics, materials science and engineering at Penn State University. Hashim adds that the nanosponges could also be used as membranes for filtration applications.

Researchers from Rice University and Penn State University developed the material, working with colleagues in labs around the U.S., and in Spain, Belgium and Japan. Hashim is lead author of the paper detailing the discovery, which appears online in Nature’s open-access journal Scientific Reports.

Hashim shows off some of the nanosponge’s remarkable properties in the following video.

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