Evaluation of Interfacial Structure and Interaction between Alkylamine-Modified Ag and Organic Solvent via Molecular Dynamics Simulations

Controlling the dispersion stability of surface-modified nanoparticles in suspensions is essential for their successful industrial application. However, the structures and interactions at the interface between the surface-modified nanoparticles and organic solvents remain poorly understood. In this study, the effects of the surface coverage and solvent species on the interfacial structure and interactions between the dodecylamine-modified Ag slab and organic solvents were investigated using all-atom molecular dynamics simulations. Toluene and methanol were selected as typical nonpolar and polar solvents, respectively. At higher surface coverages, the ligand exhibited more ordered and oriented structures. In toluene (a good solvent for dodecylamine-modified Ag), more ligands extended toward the solvent phase and more solvent molecules penetrated the ligand layer compared to methanol (a poor solvent for dodecylamine-modified Ag). As a result, the interaction between the solvent and the alkyl chain of the ligand for toluene was stronger than that for methanol. The degree of penetration and the interaction in both solvent systems varied with the surface coverage, showing a maximum in penetration and a minimum in interaction energy at 50% coverage. These findings provide insights into the design of ligands to improve the dispersion stability of surface-modified nanoparticles in organic solvents.