Solvent Effects on the Adsorption of Polyvinylpyrrolidone on Ag Surfaces

The shape-control mechanism in metal nanocrystal syntheses relies heavily on the adsorption of structure-directing agents or capping molecules on metal surfaces. The solvent environment can influence the thermodynamics of adsorption and consequently influence the nanocrystal’s morphology. Here, we examine the effect of ethylene glycol solvent on the adsorption thermodynamics of polyvinylpyrrolidone (PVP) on Ag surfaces, where we use molecular dynamics simulation to calculate the binding free energy and entropy change due to adsorption. This interface is commonly observed in the solution-phase synthesis of Ag nanocrystals. Our calculations show that (a) solvent lowers the binding free energies of the adsorbing molecules, and (b) adsorption of PVP is entropically favorable in solvent due to the displacement of adsorbed solvent molecules by the binding PVP molecule. Our study underscores the importance of explicitly including solvent in theoretical models for molecular adsorption.