Microwave-Assisted Regeneration of Single-Walled Carbon Nanotubes from Carbon Fragments

Direct growth of chirality-controlled single-walled carbon nanotubes (SWNTs) with metal catalyst free strategy, like cloning or epitaxial growth, has suffered from the low efficiency. The underlying problem is the activation of seed edge. Here an unexpectedly efficient microwave-assisted pathway to regenerate SWNTs from carbon fragments on SiO₂ /Si substrate is demonstrated via Raman spectroscopy and atomic force microscope (AFM) characterization. In this attempt, microwave irradiation provides fast heating to remove polar groups bonded to carbon nanotubes and reduce the spontaneous closure of tubes' open ends. The survived SWNT and carbon fragments connected to it after plasma treatment are simply microwaved and then they serve as the template for regeneration. Scanning electron microscope and AFM characterizations indicate that the efficiency of the regeneration can reach 100%. And the regenerated SWNT has been proved without any change in chirality compared to the original SWNT. Electrical measurements on regenerated carbon nanotube films indicate 1 and 2 times increase in on/off ratio and on-state current respectively than original carbon nanotube films obtained from solution-phase separation, confirming the improvement of SWNT's quality. The microwave-assisted regeneration is found to be highly effective and would be applied to improve the cloning efficiency of carbon nanotubes potentially.