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

Abstract

We present a systematic study of the effects of surfactants in the separation of single-walled carbon nanotubes (SWNTs) by density gradient ultracentrifugation (DGU). Through analysis of the buoyant densities, layer positions, and optical absorbance spectra of SWNT separations using the bile salt sodium deoxycholate (DOC) and the anionic salt sodium dodecyl sulfate (SDS), we clarify the roles and interactions of these two surfactants in yielding different DGU outcomes. The separation mechanism described here can also help in designing new DGU experiments by qualitatively predicting outcomes of different starting recipes, improving the efficacy of DGU and simplifying post-DGU fractionation.

Carbon nanotubes for ultrafast fibre lasers

“…Therefore, another reason to apply two surfactants simultaneously is the different reactions for CNT [160]. In [161], two different types of the solution consisting of sodium deoxycholate (DOC) and sodium dodecyl sulfate (SDS) were examined. The DOC with a higher reactivity [160] determines the initial structure of the surfactant-CNT molecule, whereas SDS molecules incorporate into the vacant space in between the DOC molecules ( Figure 4).…”

“…However, small-diameter nanotubes have a stronger interaction with DOC compared to SDS. Hence, the additional wrapping by SDS increases the buoyant density, and smalldiameter CNTs travel downwards the suspension [161].…”

Enhanced critical heat flux with single-walled carbon nanotubes bonded on metal surfaces

“…The diameter and length of SWCNTs were approximately 0.8-1.2 nm and 0.1-1.4 lm, respectively, although the individual lengths may have varied depending on the sonication time. The density-gradient ultracentrifugation was used to separate SWCNTs by the subtle difference of densities at 30,000 rpm, and the upper portion of the solution in well-dispersed solution was only decanted [35] (Fig. 1(a)).…”

High Precision Fractionator for Use with Density Gradient Ultracentrifugation

“…Several refinements have improved the resolution of the DGU layering process in separating SWCNTs, including the use of tailored density profiles, the addition of co-surfactants, and careful adjustment of surfactant concentrations. 1,3,[11][12]15 However, the extraction of highly resolved layers without crosscontamination from nearby layers requires specialized and precise fractionation methods.…”

“…Currently available methods for DGU fractionation include aspiration by syringes or micropipettes (possibly mounted to vertical translation stages); [11][12]15 controlled drainage after puncture of tube bottom; 16 slow upward displacement fractionation involving puncture of the centrifuge tube and careful injection of a chase solution; 1,13,[17][18][19] and piston gradient fractionation 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 3 in which the tube contents are slowly forced through the hole of a lowered rubber piston. 1,6,9,[20][21] In our experience, these approaches do not provide the fractionation convenience and performance needed to realize the separation potential of SWCNT DGU processing.…”