Metallic single‐wall carbon nanotubes separated by density gradient ultracentrifugation

Abstract

A density gradient ultracentrifugation (DGU) technique recently applied for separation of single-wall carbon nanotubes (SWNTs) over diameter also appeared to be efficient for the nanotube separation according to their electronic structure. In this work we used DGU for extraction of a highly metallic (>97 wt%) nanotube fraction from a raw soot of arc-discharge SWNTs. The process parameters (the surfactant type and concentration, the treatment time, the approach to the gradient formation) have been optimized. A variation of surfactant concentration allowed obtaining the highly metallic nanotube fractions with different dominant diameter distribution resulting in the ''blue'' or ''green'' top fractions. Sodium taurodeoxycholate (TDOC) was efficiently used for DGU separation of raw, non-purified SWNTs. The fractions have been studied with the UV-Vis-NIR absorption and Raman spectroscopy.Photograph of the SWNT solution after DGU.

Separation and optical identification of semiconducting and metallic single‐walled carbon nanotubes

“…This regime was achieved with the following concentrations of polymers and surfactants at 25 °C represented in the Table . For estimation of semiconducting nanotubes concentration in the fraction we used method, described in , which consists in subtracting the background in absorbance spectra and comparing the ratio between S 22 and M 11 peaks in the parent suspension and the separated one. The optical absorption spectrum corresponding to the semiconducting nanotube suspension obtained with the below mentioned parameters is presented in the Fig.…”

Optical Features of Vapor‐Phase Epitaxial Re‐Grown Long Semiconducting Single‐Walled Carbon Nanotubes

“…We assigned all the features in the absorption spectra to S 11 , S 22 , S 33 excitonic transitions of semiconducting nanotubes evaluated from PLE map. By fitting the optical absorption spectrum (Figure S1, Supporting Information) using common procedures we show that the sorting purity of the obtained semiconducting SWCNT seeds is high and estimate the quantity of residual metallic nanotubes to be below optical quantification limits, roughly less than 1% …”

Tunable separation of single-walled carbon nanotubes by dual-surfactant density gradient ultracentrifugation

“…Direct synthesis of homogeneous SWNTs is of course the most desirable solution, but this is not yet possible using current production methods. Various post-production separation methods, however, have been developed over the last few years to obtain small amounts of SWNTs with a specific chirality or electronic type [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20]. Of all these techniques, the density gradient ultracentrifugation (DGU) method, adapted to SWNTs by Arnold et al [6,7], is considered one of the most promising and effective for achieving good SWNT selectivity not only by electronic type [7,[11][12][13][14] but also by diameter [6,7,[15][16][17][18][19][20] and even chirality [6,7,[18][19][20].…”