Due to the special properties of carbon nanotubes (CNT) including size, huge surface area and high cellular uptake, they are important in drug delivery and separation. On the other hand, oleuropein (oleu), according to the pharmaceutical properties such as anti-cancer, anti-inflammatory, anti-microbial and anti-hypertensive has attracted many attentions. In this study, we investigated adsorption of oleuropein at two positions inside and outside of the different types of single-walled carbon nanotubes including the chiral, zigzag and armchair with different diameter. According to radial distribution functions graph and the amount of Lennard-Jones energy between oleuropein and nanotubes, oleuropein is adsorbed on all nanotubes. Interaction between CNT and oleu is stronger on the inner surface rather than the outer surface. The strongest interaction belongs to inner surface with a diameter of 1.3 Å. Chirality of nanotubes has no effect on interaction energy between CNT and oleu. However, interaction between CNT and oleu on the inner surface becomes weaker with increasing the diameter of CNT but this interaction on the outer surface of CNT does not change significantly. The strong interaction of the oleuropein adsorbed on the outer surface of the nanotubes with solvent leads to improve the solubility of the nanotubes.

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