Atomically Precise Nanoclusters as SERS Probes

Atomically precise nanoclusters (NCs) exhibit molecule-like fingerprints, yet their Raman response is usually buried under intense luminescence. Herein, we report the use of surface-enhanced Raman spectroscopy (SERS) to probe the molecular nature of the stable eight-electron silver NC, [Ag17(o1-carboranethiolate)12]3– (abbreviated as Ag17), by integrating it with plasmonic gold nanotriangles (Au NTs), forming an Ag17@Au NT nanohybrid. This is the first demonstration of an atomically precise NC functioning as a stable next-generation Raman probe under harsh laser conditions. Synergistic electromagnetic (EM) and chemical enhancement (CE) mechanisms yield an overall enhancement factor of up to ∼6 × 105, with ∼2 × 102 attributed to CE, consistent with time-dependent density functional theory (TDDFT) calculations. TDDFT reproduces the observed spectra and reveals low-lying hybrid charge-transfer excited states, underpinning the CE pathway. Plasmonic confinement and charge transfer cooperatively amplify the Raman scattering of the Ag–Ag bonds and carborane framework at the nanoscale junctions of the Ag17@Au NT nanohybrid.