Photoluminescence imaging of suspended single-walled carbon nanotubes.

Single-walled carbon nanotubes (SWNTs) suspended in air over trenches are imaged using their intrinsic near-infrared (NIR) photoluminescence (1.0-1.6 microm). Far-field emission from extended suspended lengths (approximately 50 microm) is both spatially and spectrally resolved, and SWNTs are classified based on the spatial uniformity of their emission intensity and emission wavelength. In a few cases, emission assigned to different (n,m) species is observed along the same suspended segment. Most SWNTs imaged on millisecond time scales show steady emission, but a few fluctuate and suffer a reduction of intensity. The quantum efficiency is dramatically higher than that in previous reports and is estimated at 7%, a value that is precise but subject to corrections because of assumptions about absorption and coherence.