PLAYING with explosives has ever been a thrill for chemists 鈥� and now they have a new excuse to do it. The debris of a violent reaction, similar to the industrial process that creates artificial diamonds, has proved to be a rich source of carbon nanotubes. These curious carbon structures look like rolls of atomic-scale chicken wire and have oddly diverse applications, ranging from reinforcing materials to quantum computing.
Zhenping Zhu and colleagues at the Institute of Coal Chemistry in Taiyuan, China, describe the explosions in Chemical Communications (DOI: 10.1039/b207166e). They ignited a mixture of paraffin and picric acid, a common explosive, to produce a mini-fireball that reached temperatures of 900 掳C. The resulting shock wave generated pressures as high as 400 atmospheres. The paraffin and picric acid molecules decomposed and their carbon atoms rearranged themselves into nanotubes, with the help of a cobalt catalyst.
That delicate nanotubes can grow in such violent conditions was first discovered by Edwin Kroke and colleagues at the Technical University of Darmstadt in Germany, in 1999. But nanotubes made up only 5 per cent of the solid material left behind after Kroke鈥檚 reaction cooled. In Zhu鈥檚 method, the paraffin acts as an extra carbon source, and the team reckon that 80 per cent of the detritus from their explosion is tubular.
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Zhu is hopeful the high yield will tempt industry to adopt his method. But Malcolm Green of the Inorganic Chemistry Laboratories at the University of Oxford points out that there are simpler ways to make nanotubes. 鈥淣o one ever makes anything by explosion if there is a peaceful way to do it,鈥� he says.