Adsorption of surface-active compounds with the skeleton molecular structure from dimethylsulfoxide solutions on carbon nanotubes

Abstract

The adsorption of adamantane, adamantanol, thiocamphor, and sodium cryptate on electrodes of single-walled carbon nanotubes (SWNT) from dimethylsulfoxide (DMSO) solutions is studied by measuring the differential capacitance (C) vs. potential (E) dependences and cyclic voltammograms. In the tested systems, the high surface activity of these surfactants is observed to result in a noticeable increase in the C of such electrodes in the range of 0.2 ≤ E ≤ −(0.9−1.1) V (SCE). As in the case of aqueous solutions, this experimental fact is explained by the appearance of the so-called Rehbinder effect (the adsorption-induced decrease in the strength), which, in this particular case, consists in a decrease in the surface energy of a solid with the formation of adsorption layers on the side surfaces of SWNTs combined into bundles to afford the partial splitting of these bundles and, as a consequence, the increase in the nanotube surface accessible to the electrolyte. At the same time, the obtained results suggest that for the adsorption of surfactants from nonaqueous solvents (in contrast to aqueous), the interaction between solvent and adsorbate molecules may become important.