Functionalization of multi-walled carbon nanotubes: Direct proof of sidewall thiolation

We analyzed structural changes and clearly revealed position and character of newly attached, sulfur containing, functional groups. Multi-walled carbon nanotubes (MWCNTs) have been first exposed to harsh acid treatment to induce defects and oxygen containing hydroxyl and carboxyl groups. Such tubes were imaged by High Resolution Transmission Electron Microscopy (HRTEM) to visualize the structural changes that have occurred to due to extensive acid-treatment. Consequently the MWCNT were thiolated using P4S10 and we used Electron Energy Loss Spectroscopy (EELS) to characterize the changes and to visualize sulfur containing sites on the nanotubes due to sidewall functionalization. The determined sulfur content is 0.6%. We also present vibrational modes around 500 cm(-1). Such modes appears only on thiolated MWCNT and may be explained by creation of characteristic carbon-sulfur bonds. (c) 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.