Nanotwinned gold nanowires obtained by chemical synthesis

We demonstrate a facile method for synthesizing and isolating Au nanowires with a high density of twin boundary defects normal to the growth axis. In this process, oleylamine conveniently plays the role of the solvent, the reducing agent and the ligand. The geometry of the twin boundaries in the nanowires is in sharp contrast with the pentagonal twinning commonly observed in metal nanowires, and is of particular interest for its ultrahigh tensile strength. The nanostructure geometry and twin-twin average spacing were characterized using high-resolution electron microscopy, and the tensile strength of the nanowires was estimated in solution using a Ti ultrasonication probe. We present a model for explaining the role of the bulky ligand oleylamine in the formation of the twin boundaries that could be extended to include elastic terms in the ligand shell. Our work demonstrates that the use of bulky, asymmetric ligands can induce extensive formation of twin boundary defects that in turn control the mechanical properties at the nanoscale.