Modified dispersion of functionalized multi-walled carbon nanotubes in acetonitrile

The dispersion of hydroxylated multi-walled carbon nanotubes was modified in non-protic acetonitrile solvent using a treatment by ethanol. The dispersion was examined by photoluminescence and Rayleigh-scattering methods. In spite of well known very low solubility of nanotubes, present results showed presence of nanotube dimers in the solution with considerable concentration. Applying a qualitative model, Delta H = -46.6 +/- 12 kJ/mol and Delta S = -29.9 +/- 7 J/K mol enthalpy and entropy changes were obtained during formation of nanotube dimers. This highly negative entropy term is of great importance for the deposition of carbon nanotubes by liquid phase epitaxy to enlarge the surface coverage. (C) 2010 Elsevier B.V. All rights reserved.