Molecular mechanics calculations were carried out to model the oleate molecule (OLM) adsorption on silver nanoparticle surface. Eight OLM solutions in different solvents on the given Ag(111) surface were chosen to present the adsorption system. The energy minimizations of all systems were performed with full atomic representation model. A series of relative adsorption energies for two different adsorbing modes of OLM, via double bond or carboxylate group, were calculated and compared in the presence of water or isooctane. Results show that the OLM is stable on the Ag surface as a stabilizer either in polar or nonpolar solvents. The favorable adsorption mode of OLM was transformed with changing solvent polarity from the double bond anchoring in the water to the carboxylate group anchoring in the isooctane solvent. Furthermore, the computed vibrational frequencies of these two stable systems and isolated pure Na oleate and Ag oleate components were basically agreed with the experimental values of IR spectroscopy, providing a better understanding of molecular adsorption nature on metal surface.

Key words: molecular modeling, oleate, molecular mechanics, adsorption