Fig. 2. (a) TEM micrograph of the seeds with an average diameter of 3 nm. The HRTEM micrograph (inset) shows the single crystalline morphology of the seed, with an interplanar spacing characteristic of the {111} plane in FCC gold. (b and c) TEM and STEM micrographs of penta-twinned intermediate seeds isolated within the first instance of growth of the 6-branched stars. (d) High resolution STEM image of the selected area of (c) exhibiting a fivefold symmetry. (e) STEM image of a typical penta-twinned intermediate seed showing one five-fold symmetry and two four-fold symmetry defects, which correlates with the 3D construction of the decahedral morphology of the penta-twinned intermediate seeds. (f) Representation of spike growth from decahedral seeds. Top image: Schematic side view identifying the spike growth directions on seeds such as that shown in (e). Bottom image: Schematic top view representing five neighbouring facets. (g–i) TEM and HRTEM images of multiply twinned intermediate seeds isolated within the first instance of growth of the multibranched stars. Reprinted from ref. 38 with permission from the Royal Society of Chemistry.