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Institutes/ Institute of Biology and Technology Saclay (iBiTec-S)/ News/ Scientific news/ Separation of metallic and semiconducting carbon nanotubes
Friday July 21 2006

Separation of metallic and semiconducting carbon nanotubes

J. Am. Chem. Soc.(2006) 128: 6552-6553
CEA
Researchers in the Department of Molecular Labelling and Bio-organic Chemistry (DBJC, Saclay) have developed a new method for the selective functionalisation of carbon nanotubes.


Nanotubes are cylindrical structures formed by rolled-up graphite sheets. The tubes are micrometres in length and of the order of a nanometre in diameter. They are used in electronics for their high electron carrying capacity, in the manufacture of novel materials (nanotubes are a hundred times stronger than steel and six times lighter) and in biomedical applications. These structures are pure carbon, but they occur as a mixture of tubes with metallic and semi-conducting properties. However, many applications require samples of nanotubes with homogeneous electronic properties. But no method currently exists for making either type of nanotube on its own. Consequently the only way to obtain pure samples of one electronic type is by separation.

The SMMCB has developed a gentle method for functionalising carbon nanotubes. The process is used to construct hybrid materials by covalent grafting of various groups on the nanotube surface. More importantly, by adjusting the operating conditions this reaction can be made selective towards semi-conducting nanotubes, which are thus preferentially functionalised. In this way the non-functionalised metallic nanotubes are rendered chemically different from the functionalised semiconducting nanotubes. The two sorts of nanotubes can now be separated: the functionalised semiconducting ones are soluble in certain solvents, while the metallic ones remain insoluble. Selective functionalisation thus makes it possible to separate metallic and semiconducting nanotubes.