Enhancement of water solubility of single-walled carbon nanotubes by formation of host-guest complexes of cyclodextrins with various guest molecules

Solubilization of single-walled carbon nanotubes (SWNTs) by physical adsorption of cyclodextrins (CDs), guest molecules, and host-guest complexes was investigated. As guest compounds, sodium adamantanecarboxylate (AdCNa), sodium dodecylbenzenesulfonate (SDBS), sodium ursodeoxycholate (UdCNa), sodium ferrocenecarboxylate (FeCNa), and TritonX-405 were employed. As host compounds, alpha-, beta-, and gamma-cyclodextrins (alpha-, -beta, and gamma-CDs) were used. By using CDs as a solubilizing agent, SWNTs were insoluble in aqueous media. In the presence of AdCNa and FeCNa, solubility of SWNTs was dramatically increased by formation of host-guest complex with beta- or gamma-CDs. By using SDBS-CD complexes, solubility of SWNTs was also enhanced compared to only guest molecules. On the other hand, solubility of SWNTs was decreased by formation of host-guest complexes of UdCNa and TritonX-405 with CDs. Formation of host-guest complex mostly resulted in enhancement of water solubility of SWNTs.