Solubilization of SWNTs with organic dye molecules

Single Wall Carbon Nanotubes (SWNTs) are insoluble in most organic solvents, such as toluene. Improvements in the solubility of the SWNTs are, however, seen as a result of interaction with dye molecules such as terphenyl and anthracene. The suspensions formed are stable for periods greater than 24 months. Spectroscopic analysis clearly shows interaction between the SWNTs and dye molecules. The fluorescence of the dye molecules is quenched on interaction with SWNTs, and, in the case of terphenyl, the spectrum is red shifted. Raman spectroscopy of the composites shows vibrations that are not present in either the SWNTs or dye powders. At the position at which these unique Raman peaks occur in the composite spectra, it was found that both the dye and SWNTs had infrared (IR) active vibrations at these wavenumbers. It is therefore thought that the new Raman peaks in the composite samples are possible IR modes that become Raman active on interaction between the dyes and SWNTs. The Radial Breathing Modes (RBMs) give detail as to how diameter selective the dye samples are when compared to the pristine SWNT modes. Red shifting of the RBMs for both composite spectra was observed. It is believed that such a result is due to the debundling of the tubes on interaction with the dye molecules.