Carboxyl-tailed ionic liquid promoted aqueous dispersion of multi-walled carbon nanotubes

Abstract

The present work reports the dispersion of multiwalled carbon nanotubes (MWCNTs) in water using a short chain carboxyl-tailed ionic liquid (IL), 1-carboxymethyl-3-methyl imidazolium tetrafluoroborate ([cmmim][BF 4 ]), as an IL-based hydrophilic surfactant, instead of long-chain hydrophobic ILs. MWCNTs can be dispersed effectively in the aqueous solution of [cmmim][BF 4 ] due to their molecular structure, including one imidazolium ring head group and one carboxyl group with fewer hydrophobic chains. The resulting MWCNT suspensions are stable for more than a month, and no precipitation is observed. The transmission electron microscopy results showed that the structural integrity of MWCNTs did not deteriorate because of their dispersal in water. Ultraviolet–visible–near infrared spectral studies confirm the presence of IL molecules onto the surface of the MWCNTs. X-Ray photoelectron spectroscopy and Fourier transform Raman studies confirmed the cation–π or π–π interactions between the MWCNTs and IL molecules, which makes the suspension of MWCNTs more stable.