Gold Nanostructures Formed in Ionic Clusters of Perfluorinated Ionomer

Gold nanoparticles and nanorods have been synthesized in the ionic cluster network of Nafion using a liquid-phase chemical impregnation/reduction process seemingly visualizing the phase-separated hydrated cluster network of Nafion. The spherical shape of the hydrated clusters is clearly seen by the replicated gold nanoparticles with diameters of 5-6 nm. The gold nanoparticles grow through the Nafion cluster network to form gold nanorods with diameters of 5-15 nm, which compare well to the previously reported small-angle X-ray scattering results. Tiny channels between adjacent spherical clusters are also observed, which expand to form a rod structure by a reorganization of ion exchange sites and an elastic deformation of Nafion polymer chains. The gold nanorods become interconnected in a cascadic feature, and a tripod-shaped nanorod structure is one of the most commonly observed structures of the replicated gold. Although further study should be performed, the synthesized gold may be used to visualize the hydrated cluster and the network structure of Nafion, which could be used as important information in identifying the morphology and ion transport phenomena of Nafion.