| Abstract
| - In this report, procedures are discussed for the enrichment of single-walled carbon nanotube(SWNT) types by simple filtration of the functionalized SWNTs through silica gel. This separation usesnanotube sidewall functionalization employing two different strategies. In the first approach, a crude mixtureof metallic and semiconducting SWNTs was heavily functionalized with 4-tert-butylphenyl addends to impartsolubility to the entire sample of SWNTs. Two major polarity fractions were rapidly filtered through silicagel, with the solvent being removed in vacuo, heated to 700 °C to remove the addends, and analyzedspectroscopically. The second approach uses two different aryldiazonium salts (one with a polar graftinggroup and one nonpolar), appended selectively onto the different SWNTs by means of titration and monitoringby UV analysis throughout the functionalization process. The different addends accentuate the polaritydifferences between the band-gap-based types permitting their partial separation on silica gel. Thermaltreatment regenerated pristine SWNTs in enriched fractions. The processed samples were analyzed andcharacterized by Raman spectroscopy. A controlled functionalization method using 4-fluorophenyl and4-iodophenyl addends was performed, and XPS analyses yielded data on the degree of functionalizationneeded to affect the van Hove singularities in the UV/vis/NIR spectra. Finally, we demonstrate that relativepeak intensity changes in Raman spectra can be caused by morphological changes in SWNT bundlingbased on differing flocculation or deposition methods. Therefore a misleading impression of separationscan result, underscoring the care needed in assessing efficacies in SWNT enrichment and the prerequisiteuse of multiple excitation wavelengths and similar flocculation or deposition methods in comparativeanalyses.
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