Exploration of the Atomic Pathway of Seed-Mediated Growth from Icosahedral [Au 25 (SR) 18 ] - to Bi-Icosahedral Au 38 (SR) 24 and Au 44 (SR) 26 Clusters Based on the 2 e - Hopping Mechanism.

Size growth is ubiquitous in the gold nanocluster synthesis. However, the atomic-level mechanism of seed-mediated growth of gold clusters remains mysterious. In this study, the seed-mediated growth pathway from the icosahedral [Au 25 (SR) 18 ] - cluster to the bi-icosahedral Au 38 (SR) 24 and Au 44 (SR) 26 clusters is studied based on the two-electron (2 e - ) hopping mechanism. First, atomic structures of three key intermediate clusters, [Au 29 (SR) 20 ] - , [Au 33 (SR) 22 ] - , and Au 41 (SR) 25 , are predicted based on the 2 e - -unit decomposition strategy. The theoretically simulated UV-Vis spectra based on the predicted structure model of [Au 29 (SR) 20 ] - and [Au 33 (SR) 22 ] - matched well with the experimental curves reported previously. Based on the predicted intermediate cluster structures, the size growth pathway from the eight-electron (8 e - ) [Au 25 (SR) 18 ] - cluster to 14-electron (14 e - ) Au 38 (SR) 24 and 18-electron (18 e - ) Au 44 (SR) 26 clusters is determined. In the step of formation of bi-icosahedral Au 38 (SR) 24 from icosahedral [Au 25 (SR) 18 ] - , two Au 4 units are first formed. The third 2 e - hopping step results in formation of an icosahedron unit. The present studies offered new insights into the formation and size conversion mechanism of ligand-protected gold nanoclusters containing icosahedral cores.