Inserting fullerene dimers into carbon nanotubes: Pushing the boundaries of molecular self-assembly

Carbon nanotubes can encapsulate several molecular species forming one-dimensional crystals. Using previously reported methods we produced directly-bonded, asymmetric C-60-C-70 dimers and oxygen-bridged dimers of the type C-60-O-C-60, We present here microscopic evidence of filling single-waited carbon nanotubes (SWNTs) with the above fullerene dimers. The most important filling constraint is found to be the nanotube size. SWNTs with diameters around 1.6 nm incorporate dimers; considerably more easily than SWNTs with smaller diameters. This kind of molecular self-assembly opens up the potential for using nanotubes and fullerenes for nanodevices