Cryo-TEM Imaging of Carbon Nanotube / Superacid Systems

The production of high-performance fibers, films, and composites from carbon nanotubes (CNTs) depends on the liquid-phase dispersion and processing of CNTs. However, CNTs are notorious for their low solubility in virtually all common solvents, because they naturally tend to form bundles and ropes due to van der Waals forces. In recent years we have explored the dissolution of carbon nanotubes in superacids, and have shown that such solutions can be processed into fibers and films. Here we utilize cryogenic-temperature transmission electron microscopy (cryo-TEM) to image nanotubes dispersed in chlorosulfonic acid and fuming sulfuric acid. Results indicate that nanotubes naturally dissolve as individuals in chlorosulfonic acid. To our knowledge, this is the first-ever imaging of any superacid solution, and these stunning images confirm that chlorosulfonic acid is a truly athermal solvent for CNTs, even for multi-walled CNTs and long (500 micron) CNTs.