Phase transfer of aqueous gold colloidal particles capped with inclusion complexes of cyclodextrin and alkanethiol molecules into chloroform

Colloidal gold particles synthesized in water have been capped with octadec anethiol (ODT) molecules rendered water-soluble by threading with alpha -cy clodextrin (alpha -CD) molecules. Thereafter, the gold nanoparticles could be transferred into an organic solvent such as chloroform by vigorous shaki ng of a biphasic mixture of the alpha -CD-threaded ODT-stabilized gold hydr osol and: chloroform. The phase transfer of the gold : nanoparticles could be observed as a rapid transfer of color from the aqueous phase to the orga nic phase. During shaking of the biphasic mixture, it is believed that alph a -CD molecules are dislodged from the octadecanethiol molecules, rendering the gold particles hydrophobic and amenable to phase transfer. Transmissio n electron microscopy studies of films of the gold nanoparticles in chlorof orm formed by solvent evaporation indicate a uniform size distribution of t he nanoparticles and hexagonal close-packing of the particles in the film.