Adsorption mechanism of oleic acid on the surface of aluminum nanoparticle: ReaxFF molecular dynamics simulation and experimental study

Abstract

The adsorption mechanism of oleic acid(OA) on the surface of aluminum(Al) nanoparticle was studied using ReaxFF molecular dynamics simulation. A surface-oxidized Al nanoparticle was constructed to simulate the single-molecule and multi-molecule adsorption processes of OA on the surface of Al nanoparticle. It was found that single OA molecule adsorbed on the surface of the Al nanoparticles through its –COOH group to form a carboxylate structure, thereby forming a chemical adsorption monolayer on the surface of Al nanoparticle. During the multi-molecule adsorption process, the chemical adsorption layer will become denser with the increase of initial density of OA in the system. When the initial density is large enough, excess OA molecules were adsorbed outside the chemical adsorption layer by physical adsorption and form a chemical-physical bilayer adsorption structure on the surface of the particles. The simulation results were verified by the adsorption layer thickness determined with XPS and the bonding structure detected with FTIR. The adsorption mechanism of OA on the surface of Al nanoparticle was found to changes from a chemical monolayer adsorption to a chemical-physical bilayer adsorption with the increase of OA concentration.