The direct addition of cyclic groups to carbon nanotubes is possible using a combination of pressure and a chromium catalyst
Single-walled carbon nanotubes (SWNTs) are particularly difficult to process and manipulate. Therefore, their unique mechanical, electronic and optical properties remain somewhat under-exploited. Functionalization, or the addition of molecular side groups, is one way of changing the properties of SWNTs in order to overcome these problems.
Now, researchers in France have found a new method to add cyclic groups to the outside of SWNTs. Charles Mioskowski, Eric Doris and co-workers1 used the Diels-Alder reaction, which is used in organic chemistry to make carbon rings, to functionalize SWNTs. After reacting nanotubes with a chromium complex, they were combined with several different organic molecules under high pressure. It was found that a combination of chromium and 1.3 GPa pressure was necessary for the Diels-Alder reaction to proceed. In addition, only certain electron-rich organic molecules were capable of forming carbon rings on the SWNTs.
The reaction products were characterized using Raman and ultraviolet–visible–near-infrared spectroscopy to ensure that the rest of the SWNT structure remained intact. Unlike a previous Diels-Alder method for modifying SWNTs, this one does not require the nanotubes to have been previously functionalized and primed to react.
References
Ménard-Moyon, C., Dumas, F., Doris, E. & Mioskowski, C. Functionalization of single-wall carbon nanotubes by tandem high-pressure/Cr(CO)6 activation of Diels-Alder cycloaddition. J. Am. Chem. Soc. 10.1021/ja065698g (2006).
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Mantoura, S. Pressure to perform. Nature Nanotech (2006). https://doi.org/10.1038/nnano.2006.144
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DOI: https://doi.org/10.1038/nnano.2006.144
