Multi-dimensional control of surfactant-guided assemblies of quantum gold particles

The controlled assembly of monodispersed Au NPs (gold nanoparticles) into multi-dimensional 1D, 2D, and 3D structures by using ionic and nonionic surfactants was reported. Au NPs, prepared by a wet chemical method based on the reduction of a gold precursor, were stabilized using a protective layer of citrate anions at the particles' surface, and could be then further modified using a variety of surfactants. Trisodium citrate was used as reducing agent and stabilizer, since it provides a high zeta-potential for the prevention of aggregation of the Au NPs. A series of long chain ionic ammonium salts, imidazolium salts, and nonionic primary amines as exchange surfactants for the initial citrate stabilizer were used in order to multi-dimensionally assemble monodispersed Au NPs. The monodispersed citrate-coated Au NPs exhibit the well-known LSPR band at 520 nm, which undergoes a larger shift for C _xImida and ODA aggregates.