New nitrene functionalizations onto sidewalls of carbon nanotubes and their spectroscopic analysis

Abstract

The reactivity of p-toluenesulfonyl, methylsulfonyl and trimethylsilyl nitrene, derived from the corresponding azides, was studied towards single-walled carbon nanotubes (SWCNT) prepared by electric arc or HiPCO (High-pressure CO conversion) methods. The functionalized SWCNTs were analyzed by Raman, IR, and VIS/NIR spectroscopy. The spectroscopic results indicated that covalent modification of the SWCNTs was successful. While the IR measurements gave evidence of successful reaction in all studied cases, the Raman measurements indicated differences in the reactivity of the two tube types and between different nitrenes. VIS/NIR spectrum was measured for reaction with p-toluenesulfonyl azide and it indicated strong changes upon functionalization. In the reaction between p-toluenesulfonyl azide and SWCNTs, for tubes prepared by the electric arc method the Raman signal from the metallic tubes decreased while for HiPCO tubes an opposite effect was observed. For the reaction with p-toluenesulfonyl nitrene the changes in the Raman spectra induced by the reaction were substantial but for the other two nitrenes the changes were more modest. Therefore, control experiments were performed without heating the reactions mixtures and complementary IR analysis was performed for the samples. Based on the analysis, it can be concluded, that nitrenes provide a route for rich chemical modification of carbon nanotubes.