Optical Properties of Assembled Single-Walled Carbon Nanotube Gels

A macroscopic system of single-walled carbon nanotubes (SWNTs) created by a novel DNA/protein complex-assisted assembly is investigated. Due to a point-like nature of connectors, the resulting SWNT aerogel represents a network of self-suspended nanotubes with a record-low density of less than 0.75 mg?cm-3. The assembly method and low density enable a direct comparison of optical properties of nanotubes in solvent and air to surfactant solubilized nanotubes. Optical properties of SWNT gels are investigated using optical absorption, photoluminescence, and Raman spectroscopy. Gelled nanotubes in water and in the low-energy regime behave similar to solubilized nanotubes. In contrast, the photoluminescence of SWNT aerogels exhibits a previously unobserved peak at 1.3 eV that corresponds to a phonon-assisted recombination of photoexcited charges. This new emission pathway is the result of the unique nature of self-suspended nanotubes in aerogel and a reduced phonon decay.