Characterization of the wetting behavior of place exchanged mixed-monolayer-protected gold nanoparticles

Abstract

Mixed-monolayer-protected gold nanoparticles have been shown to have self assembling ligand shells. Given certain ligand concentrations, the NP shell can spontaneously form complex ordered domains with domain spacing as small as five angstroms. It has been proven that the solubility of NPs synthesized using a one step method is almost solely dependent on the corresponding ligand shell morphology. We have attempted to get a better understanding of the morphological differences between NPs synthesized in one step and those synthesized through place exchange by comparing their solubility characteristics. Both types NPs were functionalized using different concentrations two immiscible ligands. The place exchanged NPs almost certainly form a type of ripple shell morphology due to the presence of nonmonotonic solubility peaks in polar solvents at low hydrophilic ligand concentrations. Based on the solubility results, we conclude that the ligand shell morphology must be different for place exchanged and one step nanoparticles. The differences are most likely due to the mechanism by which place exchange populates the nanoparticles.