Critical size for metallization in core-derived epitaxial growth of thiolate-protected gold nanoclusters studied through Au171(SR)65 and Au207(SR)80 assembly

The structural design and metallization mechanism of large gold nanoclusters remain fundamental challenges in nanocluster science. Here we show a “core-derived epitaxial growth” strategy, in which intercross-sharing Au19 and vertex-sharing Au25 cores serve as initial templates to construct two larger clusters, Au171(SR)65 and Au207(SR)80. Density functional theory calculations confirm their high structural stability. Electronic structure analysis reveals discrete energy levels between -12 eV and 2 eV, dominated by gold atomic orbitals, indicating retained molecular-state character. Although both clusters exhibit narrow bandgaps, Au171(SR)65 lacks a surface plasmon resonance peak and shows weaker electron delocalization, confirming its molecular nature. Au207(SR)80, by contrast, displays a weak plasmon-like peak at 531 nm, suggesting only incipient metallic behavior. This work presents a new route for constructing large gold clusters and underscores the decisive role of core assembly patterns in governing the critical transition to metallicity, providing valuable insights into quantum confinement and metallic evolution in gold nanoclusters. Icosahedral structures influence the formation of thiolate-protected gold nanoclusters (RS-AuNCs), but whether different sharing modes of these units can lead to multi-shell large-sized clusters remains underexplored. Here, the authors propose a core-derived epitaxial growth strategy based on the structural characteristics of isolated icosahedral cores in Au133(SR)52, Au138(SR)48, and Au144(SR)60 clusters, showing that two giant gold clusters, Au171(SR)65 and Au207(SR)80, can be constructed by using intercross-sharing Au19 and vertex-sharing Au25 as the initial cores.