A reasonable approach for the generation of hollow icosahedral kernels in metal nanoclusters.

Although the hollow icosahedral M kernel has been extensively observed in metal nanoclusters, its origin remains a mystery. Here we report a reasonable avenue for the generation of the hollow icosahedron: the kernel collapse from several small nano-building blocks to an integrated hollow icosahedron. On the basis of the Au alloying processes from AgCu(SR) to the template-maintained AuAgCu(SR) and then to the template-transformed AuCuAg(SR), the kernel evolution/collapse from "tetrahedral Ag + 4Ag" to "tetrahedral Au + 4M (M = Au/Ag)" and then to "hollow icosahedral Au" is mapped out. Significantly, the "kernel collapse" from small-sized nano-building blocks to large-sized nanostructures not only unveils the formation of hollow icosahedral M in this work, but also might be a very common approach in constructing metallic kernels of nanoclusters and nanoparticles (not limited to the M structure).