Role of ions in the colloidal synthesis of gold nanowires

Abstract

Gold nanocrystals of different shapes have been made by a wet chemical approach based on a two-step, seed-mediated synthesis. In this paper, we demonstrate a one-step synthetic method for achieving simple and systematic control over the shape of gold nanoparticles. Gold nanowires, which have been prepared by multi-step approaches, are produced in very high yield in this single-step technique. The width of the rods can be varied over a broader range compared to previously reported methods. Rectangle-, cube- or tetrapod-like gold nanocrystals can also be prepared in aqueous solution at room temperature. The formation of various shapes, in the presence of silver nitrate, requires bromide ion and alkylammonium surfactant ion of appropriate hydrocarbon tail length. The shape, dimension and yield of the nanocrystals depend on the nature and concentrations of the stabilizing cationic surfactants and other additives, such as salts, in addition to the reactants.