The fluorescence quantum yield of single-wall carbon nanotubes in solution depended markedly upon dispersants. To evaluate the role of defects in this dependence, Raman spectra from aqueous suspensions of single-walled carbon nanotubes were compared using either ss-DNA adsorption or deoxycholate-surfactant encapsulation. For each dispersion method, length-separated fractions ranging from some 50 to 1000nm were examined. The intensity ratio of the disorder-induced Raman D-band to the G′-band scaled inversely with length; consistent with predominately end-cap defect sites. The comparable length-dependent D/G′ for each dispersion scheme excluded defects as a possible explanation for the lower fluorescence in DNA versus deoxycholate dispersions.

The Effect of Dispersant on Defects in Length-Separated Single-Wall Carbon Nanotubes Measured by Raman Spectroscopy. J.R.Simpson, J.A.Fagan, M.L.Becker, E.K.Hobbie, A.R.Hight Walker: Carbon, 2009, 47[14], 3238-41