Band-Gap Opening in Metallic Single-Walled Carbon Nanotubes by Encapsulation of an Organic Salt.

The encapsulation of viologen derivatives into metallic single-walled carbon nanotubes (SWNTs) results in the opening of a band gap, making the SWNTs semiconducting. Raman spectroscopy, thermogravimetric analysis, and aberration-corrected high-resolution transmission electron microscopy confirm the encapsulation process. Through the fabrication of field-effect transistor devices, the change of the electronic structure of the tubes from metallic to semiconducting upon the encapsulation is confirmed. The opening of a gap in the band structure of the tubes was not detected in supramolecular controls.