Ring formation from the direct floating catalytic chemical vapor deposition

Rings of single-walled carbon nanotubes (SWNTs) with a high yield of 30–50% have been fabricated through a floating catalytic chemical vapor deposition (FCCVD) method. The SWNT rings, which were characterized as the self-looping nanotube coils, feature a relative small diameter of 100–300 nm and a thin thickness of 1–8 nm.The high yield of the SWNT rings has been ascribed to the unique experimental configuration which could favor the as-synthesized straight SWNTs to bend freely and easily to form the coil-shaped structures. The technique presented here may advance the new understanding to bulk-prepare the nanotube rings.