Sidewall functionalization of single-walled carbon nanotubes through CF 4 plasma treatment and subsequent reaction with aliphatic amines L. Valentini * , D. Puglia, I. Armentano, J.M. Kenny Materials Engineering Center, Universita ` di Perugia, INSTM, UdR Perugia, 05100 Terni, Italy Received 30 September 2004; in final form 12 January 2005 Abstract Single-walled carbon nanotubes (SWNTs) with aliphatic amines covalently attached to their side walls have been prepared start- ing from fluorinated SWNTs (F-SWNTs) obtained by CF 4 plasma treatment. TEM images showed the practical use of sidewall fluo- rination of SWNTs to achieve unroping of them while infrared and thermogravimetric measurements demonstrated the obtained sidewall fluorination of the tubes. Amino-sidewall functionalization of SWNTs have been then obtained at room temperature by fluorine displacement reactions of F-SWNTs with amines. This work demonstrates the practical use of plasma fluorination to achieve functionalization and unroping of SWNTs as well as yields sidewall amino-functionalized nanotube precursors for the prep- aration of thermosettings-SWNTs polymer materials. Ó 2005 Elsevier B.V. All rights reserved. 1. Introduction Recently, a number of research groups have focused on the functionalization of carbon nanotubes, and espe- cially single-walled carbon nanotubes (SWNTs) with various organic, inorganic, and organometallic struc- tures using covalent approach [1–6]. The primary focus of many of these studies has concentrated on improving the solubility properties of nanotubes and dispersion in polymer matrices [7–9]. On this regard a strategy for SWNTs functionalization involves the use of sidewall reactions such as fluorination with elemental fluorine [7–11]. This covalent functionalization strategy have opened up a wide range of chemistry that can be per- formed on the sidewalls of carbon nanotubes, allowing chemists to control the properties of these nanoscale materials. In previous works, the fluorination of carbon nanotubes was obtained through elemental fluorine or gaseous mixture of BrF 3 and Br 2 [7–12]. It was demon- strated how the functionalization of carbon nanotubes using fluorine gas decreases the conductivity with increasing doping content, and the wettability improves, remarkably, which is of technological importance [11]. However, the disintegration of the nanotube walls at high doping content and the total defluorination of the tubes caused by the temperature, limits their applica- tions [13–15]. Moreover the subsequent amino-function- alization of fluoronanotubes obtained with the methods reported above was obtained at elevated temperatures (70–170 °C) in the presence of a catalyst [7]. Here, we propose for the first time, at our best knowl- edge, an approach of plasma treatment of the surface of SWNTs by first covalently attaching fluorine and then exposing the obtained fluorinated SWNTs (F-SWNTs) to polymerization initiators at room temperature with- out the catalyst. In particular, we have done a systematic study on the structural transformation of SWNTs in- duced by plasma fluorination. It was observed as after CF 4 plasma treatment the bundles of pristine SWNTs 0009-2614/$ - see front matter Ó 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.cplett.2005.01.042 * Corresponding author. Fax: +39 074 449 2925. E-mail address: mic@unipg.it (L. Valentini). www.elsevier.com/locate/cplett Chemical Physics Letters 403 (2005) 385–389