Anisotropic growth of one-dimensional silver rod-needle and plate-belt heteronanostructures induced by twins and hcp phase.

In this paper, we report a one-step, high-yield synthesis of one-dimensional Ag heteronanostructures in aqueous solution. Besides the usual fcc phase of Ag, the heteronanostructures also contain a rare hcp (4H polytypic) phase, which favors asymmetrical growth. The rod-needle heteronanostructures (RNHSs) and plate-belt heteronanostructures (PBHSs) are formed through two different mechanisms. For RNHSs, the 4H and fcc phases coexist but have different densities in different segments, while for PBHSs, the fcc and 4H crystal structures exist in plate and belt segments, respectively. Condition-sensitive coexisting phase preferences can be applied as a new way of controlling the shape and thus the properties of Ag nanostructures.