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 μm). Far-field emission from extended suspended lengths (∼50 μm) 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.