The effect of dispersant on defects in length-separated single-wall carbon nanotubes measured by Raman spectroscopy
The fluorescence quantum yield of single-wall carbon nanotubes (SWCNTs) in solution depends dramatically on dispersant. To evaluate the role of defects in this dependence, we compare Raman spectra from aqueous suspensions of SWCNTs dispersed using either ss-DNA adsorption or deoxycholate-surfactant encapsulation. For each dispersion method we examine length-separated fractions ranging from approximately (50 to 1000) nm. The intensity ratio of the disorder-induced Raman D-band to the G′-band scales inversely with length, consistent with predominately end cap defect sites. The comparable length-dependent D/G′ for each dispersion scheme excludes defects as a possible explanation for the lower fluorescence in DNA versus deoxycholate dispersions.