Dispersion of arc-discharged single-walled carbon nanotubes using the natural α-amino acid derivative N-dodecanoyl leucinate

Abstract

The natural α-amino acid derivate N-dodecanoyl leucinate was synthesized via Schotten-Baumann reaction and alkali treatment, and was applied to the dispersion of arc-discharged single-walled carbon nanotubes (SWNTs). Optical absorption and Raman scattering spectra as well as AFM observation confirmed the effective individualization and selective dispersion of SWNTs. Moreover, charge transfer from N-dodecanoyl leucinate to SWNTs was evidenced by FT-IR and Raman scattering spectroscopic analyses. We believe that the formation of a charge transfer complex between dispersants and SWNTs is responsible for the effective individualization of SWNTs, and that the charge transfer from dispersants to SWNTs (or from SWNTs to dispersants) is crucial for selective dispersion of semiconducting (or metallic) SWNTs.

Scheme 1. The synthesis procedures of N-dodecanoyl leucinate.

Fig. 1. The vis-NIR spectra of the primarily purified (red curve) and the sodium N-dodecanoyl leucinate dispersed (black curve) SWNTs.

Fig. 2. The typical AFM image of the sodium N-dodecanoyl leucinate dispersed SWNTs.

Fig. 3. The typical TEM image of the sodium N-dodecanoyl leucinate dispersed SWNTs.

Fig. 4. The normalized Raman spectra of the primarily purified (black curve) and the sodium N-dodecanoyl leucinate dispersed (red curve) SWNTs in the ranges of 120–230 cm⁻¹ (a) and 1200–1800 cm⁻¹ (b), respectively.

Fig. 5. FT-IR spectra of N-dodecanoyl leucinate (black curve) and the N-dodecanoyl leucinate dispersed SWNTs (red curve).