Ionic liquids plus microwave irradiation: a general methodology for the retro-functionalization of single-walled carbon nanotubes

One of the most important objectives nowadays in the field of chemical modification of carbon nanotubes (CNTs) is to control the degree of functionalization, since excessive modification can disrupt the π-conjugated system and adversely affect their useful properties. Covalent functionalization is one of the most common methods for the modification of single-walled carbon nanotubes (SWCNTs). However, only a few examples have appeared in the last few years regarding the control of the functionalization degree and the reversibility of the reaction. We present here an approach for the retro-functionalization of SWCNTs which could be applied to different types of covalent functionalizations, allowing the restoration of the π-conjugated structure. The process is performed through the combination of ionic liquids plus microwave irradiation and it is applicable to the retro-arylation and retro-cycloaddition reactions on SWCNTs. The successful retro-functionalization is monitored by Raman spectroscopy, thermogravimetric analysis and UV-Vis-NIR spectroscopy.