The role of twinning in shape evolution of anisotropic noble metal nanostructures

Nanotechnology provides the ability to engineer the properties of materials by controlling their size and shape. Among the most interesting nanostructures are anisotropic noble metal nanocrystals such as nanorods and nanowires. Nevertheless, the production of such crystals in a controlled fashion remains as a challenging task, and many available colloidal techniques produce a mixture of morphologies. In cases where high yields of a particular anisotropic structure have been produced, the growth mechanism has been primarily explained in terms of the presence of surfactants or capping agents that regulate the growth of the crystal in a particular direction. However, the growth mechanism should also consider nucleation and kinetics, and not only thermodynamics or physical restrictions imposed by the surface stabilizing agent. In this work, we present several examples of anisotropic noble metal nanocrystals obtained by different methods. Finally, the important role of twinning in determining the habit of the final morphology is discussed.