Core Values: Elucidating the Role of Seed Structure in the Synthesis of Symmetrically Branched Nanocrystals

Abstract

Branched metal nanoparticles often display unique physicochemical properties on account of their structures; however, most examples are asymmetric, with branches randomly distributed from the cores of the nanoparticles. This asymmetry can give rise to variable properties between samples. Here, we report the synthesis of symmetrically branched Au/Pd nanocrystals including five-branched pentapods with D(3h) symmetry, 24-branched nanocrystals with O(h) symmetry, 12-branched nanocrystals with T(d) symmetry, and eight-branched octopods and bowties with O(h) and D(4h) symmetry, respectively. These structures are achieved by seed-mediated co-reduction wherein the shapes of the seeds direct the number and symmetry patterns of the branches. Compositional boundaries exist at the interfaces between the seed and overgrowth metals to provide visualization via advanced electron microscopy of the relationships between seed structure and the symmetry of branched nanocrystals. Significantly, seed structure plays a definitive role in determining the final shape of convex metal nanocrystals, and the results presented here illustrate a similar relationship for branched nanocrystals and will enable the design of new architecturally distinct nanostructures.