Anisotropic chemical reactivity of gold spheroids and nanorods

We observed anisotropic chemical reactivity of gold spheroids during cyanide dissolution and reaction with persulfate. Cyanide dissolution of 2-5 aspect ratio spheroids (with 12-30 run short axis) starts at the ends of the long axis and leads to intermediate lower aspect ratio spheroids and spheres. Persulfate converts the spheroids into spheres. In contrast, cyanide dissolution of 18 aspect ratio nanorods (with 16 run short axis) starts simultaneously at many sites and does not change the nanorod length throughout dissolution. Spheroids are thermally less stable than rods and slowly convert to spheres with time, and thus anisotropic chemical reactivity is presumably due to their lower stability.