《Dispersion of Single-Walled Carbon Nanotubes of Narrow Diameter Distribution》.pdfVIP

14454 J. Phys. Chem. B 2005, 109, 1445414460 Dispersion of Single-Walled Carbon Nanotubes of Narrow Diameter Distribution Yongqiang Tan and Daniel E. Resasco* School of Chemical, Biological and Materials Engineering, Uniersity of Oklahoma, 100 East Boyd Street, Norman, Oklahoma 73019 Recei ed: April 29, 2005; In Final Form: May 16, 2005 The dispersibility and bundle defoliation of single-walled carbon nanotubes (SWNTs) of small diameter ( 1 nm) have been evaluated on CoMoCAT samples with narrow distribution of diameters. As previously observed by photoluminescence and Raman spectroscopy, the CoMoCAT sample exhibits a uniquely narrow distribution of (n,m) structures that remains unchanged after different dispersion conditions. This narrow distribution allowed us to develop a method for quantifying the dispersability of the samples from their optical absorption spectra in terms of two ratios: the “resonance ratio” and the “normalized width.” The former is defined as the quotient of the resonant band area and its nonresonant background. The latter is defined as the ratio of the width of the band at half-height to the peak height on a spectrum that has been normalized at 900 nm, making this an intensive property, rather than varying with the path length. In this study of the CoMoCAT sample, we have used the S22 transition corresponding to the (6,5) nanotube to do these calculations, which is the most abundant species. These two ratios provide a quantitative tool to compare different dispersion parameters (time of sonication, degree of centrifugation, etc.) on the same type