Efficient dispersion and exfoliation of single-walled nanotubes in 3-aminopropyltriethoxysilane and its derivatives

A novel amine solvent, 3-aminopropyltriethoxysilane, has been used to disperse single-walled carbon nanotubes. Well-dispersed nanotubes in the form of small bundles coexist in the liquid phase with large nanotube aggregates. A mild centrifugation step can be used to remove the aggregates. By measurement of the absorbance before and after centrifugation as a function of concentration, the fraction of the dispersed nanotube phase can be estimated. As measured by atomic force microscopy, the mean bundle diameter tends to decrease with decreasing concentration and levels off below a concentration of ∼0.012 mg ml⁻¹. Individual nanotubes are always observed, whose population increases with decreasing concentration before saturating at a concentration of ∼0.012 mg ml⁻¹. The absolute number of individual nanotubes per volume of dispersion initially increases with decreasing concentration, and then reaches a peak at a concentration of ∼0.024 mg ml⁻¹. Further experimental results showed that nanotubes can also be effectively dispersed in a series of aminoalkoxylsilane derivatives. In the light of these findings, possible solvent–nanotube interaction mechanisms are discussed.