Benzene- and anthracene-mediated assembly of gold nanoparticles at the liquid-liquid interface

The organization of gold nanoparticles at the liquid-liquid interface between the gold hydrosol and benzene as well as anthracene in chloroform is described. Vigorous stirring of the biphasic mixture results in almost complete transfer of the gold nanoparticles from the aqueous to the benzene phase and the subsequent assembly of the gold nanoparticles at the liquid-liquid interface. In the case of anthracene in chloroform, the gold nanoparticles assembled directly at the interface forming an extremely flexible membrane. The gold nanoparticle films formed at the interface in both cases could be transferred onto different solid supports and were analyzed by a host of techniques. The films show reasonable two-dimensional ordering of the gold nanoparticles over large length scales. It was observed that the benzene and anthracene molecules are strongly bound to the gold particle surface, presumably through cation-pi interactions between the aromatic molecules and nanoparticle surface-bound Au+ ions, thus opening up a hitherto unexplored avenue for the assembly of gold nanoparticles.