The Effects of Lengths of Flavin Surfactant N -10-Alkyl Side Chains on Promoting Dispersion of a High-Purity and Diameter-Selective Single-Walled Nanotube.

Flavin with defined helical self-assembly helps to understand chemical designs for obtaining high-purity semiconducting ( s )-single-walled carbon nanotubes (SWNT) in a diameter ( d t )-selective manner for high-end applications. In this study, flavins containing 8, 12, 16, and 20 n -alkyl chains were synthesized, and their single/tandem effects on d t -selective s -SWNT dispersibility were investigated at isomolarity. Flavins with n -dodecyl and longer chain lengths (FC12, FC16, and FC20) act as good surfactants for stable SWNT dispersions whereas n -octyl flavin (FC8) exhibits poor dispersibility owing to the lack of SWNT buoyancy. When used with small- d t SWNT, FC8 displays chirality-selective SWNT dispersion. This behavior, along with various flavin helical motifs, prompts the development of criteria for 'side chain length ( l S )' required for stable and d t -selective SWNT dispersion, which also explains l S -dependent d t -enrichment behavior. Moreover, SWNT dispersions with flavins with dodecyl and longer l S exhibit increased metallic ( m )-SWNT, background absorption-contributing carbonaceous impurities (CIs) and preferential selectivity of s -SWNT with slightly larger d t . The increased CIs that affect the SWNT quantum yield were attributed to a solubility parameter. Furthermore, the effects of flavin l S , sonication bath temperature, centrifugal speed, and surfactant concentration on SWNT purity and s -/ m -SWNT ratio were investigated. A tandem FC8/FC12 provides fine-tuning of d t -selective SWNT dispersion, wherein the FC8 ratio governs the tendency towards smaller d t . Kinetic and thermodynamic assemblies of tandem flavins result in different sorting behaviors in which wide d t -tunability was demonstrated using kinetic assembly. This study highlights the importance of appropriate side chain length and other extrinsic parameters to obtain d t -selective or high-purity s -SWNT.