Self-Organization of Nanosized Gold Particles

TLDR: In this paper, a quaternary ammonium bromide salt (R4N+Br-) is specifically adsorbed on the colloidal gold solutions through the formation of surface ion pairs, probably with the Br- ion attached to the Au surface.

Abstract: “Naked” colloidal gold solutions have been prepared in toluene using a two-phase system The phase-transfer reagent used, a quaternary ammonium bromide salt (R4N+Br-), is specifically adsorbed on the clusters through the formation of surface ion pairs, probably with the Br- ion attached to the Au surface The separation between clusters for two-dimensional structures is dependent on the chain length in R4N+ When more than one layer is present, the nanosized particles show unusual self-organization properties:  the occupancy of 2-fold saddle sites is preferred to that of 3-fold hollow sites, leading to linear and circular arrangements It is proposed that this is due to the balance between local electrostatic repulsion and dispersion forces between the particles