Band-gap shift transition in the photoluminescence of single-walled carbon nanotubes

Photoluminescence (PL) from single-walled carbon nanotubes suspended in free space is shown to persist to high temperatures, at least to 425 degrees C. A new transition is identified, shifting the optical band gap. This transition is abrupt, is hysteretic, depends simply on the PL emission energy, and is affected by the gas atmosphere. A model is proposed to explain the transition, connecting changes in the PL to the environment.