Cobalt-Filled Apoferritin for Suspended Single-Walled Carbon Nanotube Growth with Narrow Diameter Distribution

Cobalt-filled apoferritin (Co−ferritin) was, for the first time, used as a wet catalyst for the synthesis of single-walled carbon nanotubes (SWNTs) with narrow diameter distribution. Co−ferritins were spin-coated and converted to cobalt nanoparticles by calcination. Using chemical vapor deposition, suspended networks of SWNTs were formed on pillar-structured substrates. The suspended SWNTs show narrow tube diameter distribution with a relatively good graphite structure. By virtue of the low diffusion coefficient of cobalt, Co−ferritin might be more useful for narrow diameter SWNTs growth than ferritins, which encase iron particles.