Phase transfer of gold nanoparticles across a water/oil interface by stoichiometric ion-pair formation on particle surfaces

The transfer of surface-modified gold nanoparticles across a water/toluene interface was demonstrated. Stoichiometric ion-pair formation between carbo xylate anions on particle surfaces and tetraoctylammonium cations brought a bout the phase transfer, and was revealed by transmission electron microsco py (TEM), IR, UV-vis absorption, and energy dispersive X-ray (EDX) spectros copies. A surface structure of the transferred gold nanoparticles was also presented. During the nanoparticle transfer from water into an organic phas e, an improvement in the dispersibility and a slight decrease in the averag e diameter were observed (3.6 -> 2.9 nm) accompanied by a slight narrowing in the size distribution (standard deviation: 0.80 -> 0.54 nm). The phenome na could lead to a new methodology for size and/or dispersibility selection s.