Monodisperse icosahedral Ag, Au, and Pd nanoparticles: size control strategy and superlattice formation

This paper reports the synthesis and self-assembly of monodisperse icosahedral Ag, Au, and Pd nanoparticles with tunable sizes. Ag nanoparticles were first prepared by a modified polyol method. The as-synthesized Ag nanoparticles were all icosahedral multiply twinned particles (MTPs) with notable size variations. The variability was reduced to less than 5% after a digestive ripening post treatment. The nearly monodisperse Ag nanoparticles were then used in replacement reactions with Au and Pd precursors to produce monodisperse icosahedral Au and Pd nanoparticles. The size of the monodisperse icosahedral Ag, Au, and Pd nanoparticles could also be increased thereafter by seed-mediated growth. The closely matched geometrical attributes of these icosahedral nanoparticles allowed them to easily self-assemble into 3-D superlattices either in the solution phase or on a solid substrate.