Appropriate PEG compounds for dispersion of single wall carbon nanohorns in salted aqueous solution

Aiming at improving the dispersion state of single wall carbon nanohorns (SWNHs) in highly salted aqueous environment for potential biological applications, we compared the dispersion ability of different PEG-based dispersants in this work. We have found that ceramide-conjugated poly(ethylene glycol) (CPEG) dispersed SWNHs better than phospholipid-conjugated PEG (DPEG) in both water and phosphate buffer saline (PBS), which was evidenced by the measurements of particle sizes and dispersion stability. The large zeta potentials, according to the high surface charges, did not fully explain the high dispersion ability of CPEG for SWNHs. We propose that the more neutral linker group between alkyl and PEG chains in CPEG, in contrast to the charged phosphoethanolamino group in DPEG, resulted in the larger number of CPEG molecules attaching on SWNHs, and those PEG molecules enhanced the dispersion of SWNHs in water and PBS. In addition, for the first time we reported the adverse effect of the amino terminal group of PEG chain on the dispersion ability, compared with the methyl terminal group.