Use of aqueous foams for the synthesis of gold nanoparticles of variable morphology

In this paper we describe the facile synthesis of gold nanocrystals of variable morphology using aqueous foam as a template. The aqueous foams are formed by bubbling an aqueous solution of AuCl4- ions electrostatically complexed with the surfactant cetyltrimethylammonium bromide (CTAB). The gold ions in the stable foam are then reduced by hydrazine vapours, this process leading to the formation of gold nanoparticles of spherical, flat plate and flake-like structures. The variation in morphology of the gold nanoparticles derived from the foam is believed to arise from the complex spatial structure of reaction sites in the foam. The foam-derived gold nanoparticles were analysed by UV-vis spectroscopy, X-ray diffraction, Fourier transform infrared spectroscopy and transmission electron microscopy.