One-Pot Separation of Semiconducting Single-Walled Carbon Nanotubes and Their Enantiomer Recognition Based on Self-Organized Supramolecular Riboflavin (Vitamin B2) Motifs

Abstract

The development of a facile method to sort semiconducting single-walled carbon nanotubes (s-SWCNTs) and their enantiomer recognition are still great challenges. We here describe a finding that a commercially available, safe, and cost-effective hydrophobic riboflavin analogue (riboflavin tetrabutyrate; RTB) efficiently sorts only s-SWCNTs by a one-pot method (bath-type sonication for 30 min followed by ultracentrifugation) and recognizes their enantiomers (left- and right-handed s-SWCNTs). The solubilization behavior of the SWCNTs strongly depends on the concentration of RTB; namely, with the decrease in the concentration of RTB, the s-SWCNT (n,m)-chiral selective sorting efficiency is enhanced. When using RTB = ∼0.4 mM (SWCNTs = 1 mg/3 mL toluene), two (n,m) chiralities of the s-SWCNTs with (n,m) = (8,6) and (8,7) were efficiently sorted. Furthermore, when using RTB = 0.5–1 mM, the SWCNT enantiomer recognition was observed. In addition, the X-ray photoelectron spectroscopic study revealed that the adsorbed RTB molecules on the s-SWCNTs were readily removed by simple rinsing with acetone to provide adsorbent-free pure s-SWCNTs. On the basis of the experimentally obtained data using Raman, photoluminescence, and visible–near-IR absorption spectroscopy techniques and computational density functional theory (DFT) approaches, we have revealed a possible mechanism for this unique s-SWCNT selective sorting and their enantiomer recognition. The supramolecular orientation of RTB into the helical superlattice with its own chirality provides a mechanism for chirality recognition. The study demonstrates one-pot sorting of s-SWCNTs and their enantiomer recognition using a cost-effective, safe molecule. Such a study is important for s-SWCNT separation science and its application in nanoscience and engineering areas.

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