We have studied photophysical properties of individual single-wall carbon nanotubes (SWNTs) and SWNT aggregates in colloidal suspensions using fluorescence microscopy, -spectroscopy and time-correlated single photon counting. The results suggest that SWNT aggregates, formed by addition of a divalent salt to a monomer SWNT suspension, have an open structure with a density of ≈12SWNTsμm−3. We also find a sizable spectral red-shift of 16nm, line-broadening of 23nm and reduced PL lifetimes in coagulated structures, independent of aggregate size for the range of structures studied here. Such changes may be used as fingerprint of SWNT aggregate formation in similar environments.
Photoluminescence microscopy and spectroscopy of individualized and aggregated single-wall carbon nanotubes - ScienceDirect