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3 June 2005 Spectroscopic analysis of the interaction of SWNT with simple organic molecules
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This paper shows the solublisation and de-bundling of SWNT with an aim to obtaining individual SWNT. By achieving this goal their theoretically proposed properties can be verified and their industrial potential realised. It is well documented that Single Wall Carbon Nanotubes (SWNTs) show varying degrees of solubility in a number of organic solvents. Solubility of SWNTs in toluene was found to be negligible. With toluene having such a poor affinity for SWNT it is clear that the solvent interaction with the SWNT is negligible. Therefore toluene is an ideal candidate for monitoring the improvements in the solubility of the SWNTs as a result of interaction with dye molecules such as terphenyl and anthracene. The suspensions formed are stable for periods greater than thirty-six months. Spectroscopic analysis clearly shows interaction and de-bundling of SWNT on addition of the 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 which gives further support to the notion of interaction. With the quenching in fluorescence of the dye molecules signifying interaction, a large range of concentrations were studied in order to quantify the degree of interaction between the SWNT and dye molecules. It was found at high concentrations such as 1 x 10-3 M, that both the dye molecules and SWNT formed aggregates. At lower concentrations such as 1 x 10-9 M for terphenyl and 1 x 10-6 M for anthracene, it was found that free dye and individual SWNT were interacting. Raman spectroscopy of the composites formed on interaction show vibrational modes that are not present in either the SWNTs or dye powders. It was found that both the dye and SWNTs had Infra Red (IR) active vibrational modes at the positions at which these new or unique Raman modes occur in the composite spectra. It is therefore thought that the new Raman modes in the composite samples are related to the IR modes. The Raman 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 de-bundling of the SWNT on interaction with the dye molecules.
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Theresa G. Hedderman, Sinead M. Keogh, Gordon Chambers, and Hugh J. Byrne "Spectroscopic analysis of the interaction of SWNT with simple organic molecules", Proc. SPIE 5826, Opto-Ireland 2005: Optical Sensing and Spectroscopy, (3 June 2005);

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