Controlling the Growth of Au on Icosahedral Seeds of Pd by Manipulating the Reduction Kinetics

This article reports a systematic study of how Au atoms nucleate and grow on Pd icosahedral seeds with a multiply twinned structure. By manipulating the reduction kinetics, we obtained Pd-Au bimetallic nanocrystals with two distinct shapes and structures. Specifically, Pd@Au core-shell icosahedra were formed when a relatively fast reduction rate was used for the HAuCl₄ precursor. At a slow reduction rate, in contrast, the nucleation and growth of Au atoms were mainly confined to one of the vertices of a Pd icosahedral seed, resulting in the formation of a Au icosahedron by sharing five adjacent faces with the Pd seed. The same growth pattern was observed for Pd icosahedral seeds with both sizes of 32 and 20 nm. We have also investigated the effects of other kinetic parameters, including the concentration of reducing agent and reaction temperature, on the growth pathway undertaken by the Au atoms. We believe that the mechanistic insights obtained from this study can be extended to other systems, including the involvement of different metals and/or seeds with different morphologies.