Actinide embedded nearly planar gold superatoms: structural properties and applications in surface-enhanced Raman scattering (SERS)

Planarity is a special property of superatoms, different from atoms. In this work, we predicted a series of nearly planar structures, An@Au₆ (An = Ac^-1, Th, Pa⁺¹) clusters, using density functional theory (DFT). Calculations of these actinide embedded clusters reveal a 10-electron (1s²1p⁴1d⁴) closed-shell singlet configuration. It is found that all An@Au₆ clusters are nearly or purely planar structures with only in-plane two-dimensional occupied superatomic molecular orbitals (SAMOs). In addition, applying them as surface-enhanced Raman scattering (SERS) substrates, the charge-transfer (CT) states at 677 nm (1d_metal-π₁^∗_pyridine) can lead to a SERS signal enhancement of 10⁴ for a pyridine-Th@Au₆ complex. Our research indicates that actinide embedded nearly planar superatomic clusters have unique optical properties and potential application value.