Highly Functionalized and Soluble Multiwalled Carbon Nanotubes by Reductive Alkylation and Arylation: The Billups Reaction

Single-walled carbon nanotubes (SWNTs) have been directly sidewall functionalized with a variety of organic addends, which renders them organic soluble or water soluble, depending on the precise functionalities used. However, multiwalled carbon nanotubes (MWNTs) are generally less reactive toward organic group functionalizations. Here, we demonstrate the formation of heavily functionalized MWNTs using the Billups reaction, which is a method of reductive alkylation or arylation (using lithium or sodium) of nanotubes in liquid ammonia. The resulting functionalized MWNTs can be soluble in either water or organic solvents. Raman spectroscopy and high-resolution transmission electron microscopy verify the high degrees of sidewall addends on the MWNTs. Making MWNTs soluble can be critical for efficient composite applications.