Molecular dynamics simulations of surfactant adsorption on carbon nanotubes intended for biomedical applications

Carbon nanotubes (CNTs) are allotropes of carbon with hollow, long structures, having diameters on the nanometer scale. They can be described as rolled-up graphene layers. During the last years, they have been increasingly used in the fields of pharmacy and biomedicine. However, due to their high hydrophobicity, they cannot be easily handled in most solvents of biological interest. To this end, different surfactants have been used to improve their dispersion in aqueous media. In the present work, we investigated the adsorption behavior of two surfactants, sodium dodecyl sulfate (SDS) and sodium dodecyl benzene sulfonate (SDBS), at different concentrations on a CNT surface by classical molecular dynamics (MD) simulations. Our results are presented in terms of distance between surfactant molecules and CNT surfaces, radial distribution functions and interaction energies. In all the models simulated in this work, a strong interaction of both surfactants with the CNT surface is observed, as it is demonstrated by decreasing distances between the surfactants and the CNT during simulation time, the shape of their radial distribution functions, as well as favorable adsorption processes from an energetic point of view.