Abstract
Although the hollow icosahedral M12 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 Ag28Cu12(SR)24 to the template-maintained AuxAg28-xCu12(SR)24 and then to the template-transformed Au12CuyAg32-y(SR)30, the kernel evolution/collapse from "tetrahedral Ag4 + 4∗Ag3" to "tetrahedral Au4 + 4∗M3 (M = Au/Ag)" and then to "hollow icosahedral Au12" 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 M12 in this work, but also might be a very common approach in constructing metallic kernels of nanoclusters and nanoparticles (not limited to the M12 structure).