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Hydrogen in chemical vapour deposited carbon nanotubes: an active site for functionalization

Titus, E.T. ; Cabral, G.C. ; Mendes, J. C. ; Coelho, M.C.C. ; P. Ramesh Babu, P.R.B. ; Blau, W.J.B. ; Misra, D.S.M.

Journal of Nanoscience and Nanotechnology Vol. 8, Nº 8, pp. 4017 - 4022, August, 2008.

ISSN (print): 1533-4880
ISSN (online):

Journal Impact Factor: 1,435 (in 2009)

Digital Object Identifier: 10.1166/jnn.2008.AN34

The presence of hydrogen in as-grown carbon nanotubes (CNTs) synthesized by microwave plasma (MP) chemical vapour deposition (CVD) technique is demonstrated. Our results showed that the MPCVD, as-grown CNTs were hydrogenated consisting of C—H bonds; whereas, the tubes synthesized by arc discharge consisted of non-hydrogenated multi-walled CNTs. Fourier transform infrared spectroscopy (FTIR) and micro-Raman spectroscopy techniques were used to detect C—H bonding in the as-grown CNTs. The effective functionalization of as-grown hydrogenated CNTs grown using a microwave CVD process is first time demonstrated by laser assisted CVD process. It was found that the laser-assisted CVD process resulted in the termination of hydrogen and the oxidation of as-grown CNT structure leading to the carboxylic group attachment. The FTIR results show the presence of —OH and C=O bonds in the functionalized samples. However, the non-hydrogenated CNTs could not be effectively functionalized by the same process, probably due to the fact that it did not contain active sites pre-requisite for functionalization, as did the CVD grown samples. The functionalization of CVD grown tubes is believed to take place at the 'active' hydrogen-terminated sites on the CNT surfaces.