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Fluorination of Carbon Nanotubes in CF4 Plasma

Alexandre Felten 1Jean-Jacques Pireaux 1Jacques Ghijsen 1Robert L. Johnson 2Caroline M. Whelan 3Xiaoxing Ke 4Gustaaf Van Tendeloo 4Carla Bittencourt 5

1. University of Namur, Laboratoire Interdisciplinaire de Spectroscopie Electronique (LISE), 61 rue de Bruxelles, Namur 5000, Belgium
2. University of Hamburg, Institute for Experimental Physics, Luruper Chausse 149, Hamburg D-22761, Germany
3. IMEC, Kapeldreef 75, Leuven B-3001, Belgium
4. University of Antwerp, EMAT, Groenenborgerlaan 171, Antwerp B-2020, Belgium
5. University of Mons-Hainaut, LCIA (UMH), Mons 7000, Belgium


CNTs have been proposed as building blocks for advanced materials such as reinforced polymer and metal matrices, because they exhibit either metallic or semiconducting properties and are quite unique in terms of their chemical and thermal stability, strength and elasticity. However, the relatively low reactivity of the CNT-surface presents a challenge for their integration into complex material assemblies. Our approach is to activate their surface by grafting functional groups that improve their interaction with other materials including polymers and metals.
Fluorination of CNTs has proved to yield high utility products that can be used directly or as precursor for other derivatives. Typically, this is accomplished by immersing the nanotubes in appropriate chemical solutions or exposing them to vapours at high temperatures. Fluorine gas generally results in high reaction rates and deep penetration into carbon related materials. The imprecise control of the fluorination depth makes it difficult to accomplish treatment limited to sidewall functionalization. Conversely, plasma treatment has the potential to limit fluorination to the CNT surface.
In this study MWCNTs were exposed to CF4 rf-plasma and the resulting impact on CNT electronic structure investigated using X-ray and UV photoelectron spectroscopy. XPS showed that plasma treatment effectively grafts fluorine atoms at the CNT surface. The fluorine atomic concentration and the nature of the C-F bond (semi-ionic or covalent) can be tuned by varying the plasma conditions. UPS confirms that the valence electronic states are altered by the grafting of fluorine atoms. Characterization with high resolution-TEM reveals that while the plasma treatment does not induce significant etching impact on the CNT surface, it increases the number of active sites for gold cluster formation. Dispersion characteristics found for CF4-functionalized-MWCNTs will be discussed in terms of fluorine concentration at the CNT surface.


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Presentation: Poster at E-MRS Fall Meeting 2008, Symposium F, by Jacques Ghijsen
See On-line Journal of E-MRS Fall Meeting 2008

Submitted: 2008-05-18 17:10
Revised:   2009-06-07 00:48