Preparation and thermally promoted ripening of water-soluble gold nanoparticles stabilized by weakly physisorbed ligands.

Here, we report on a facile method for the preparation of an aqueous dispersion of 3.6 nm gold nanoparticles electrostatically stabilized by a weakly physisorbed ligand, namely, 4-(dimethylamino)pyridine (DMAP). The nature and extent of the interaction of this ligand with the surface of a gold nanoparticle has been examined. We also report on the thermally promoted ripening of these nanoparticles under mild conditions to yield a dispersion of 11.3 nm gold nanoparticles. The role of the weakly physisorbed DMAP ligand in facilitating thermally promoted ripening under mild conditions has also been examined.