Atomically Precise Nanoclusters as SERS Probes.

Manna, Sujan; Bhasin, Anant O; Yadav, Vivek; Chowdhury, Soham; Duary, Subrata; Mondal, Samapti; Giri, Sajal Kumar; Base, Tomas et al. · Nano Lett · 2026

basic_science · Level V

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Abstract

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, [Ag<sub>17</sub>(<i>o</i><sub>1</sub>-carboranethiolate)<sub>12</sub>]<sup>3-</sup> (abbreviated as Ag<sub>17</sub>), by integrating it with plasmonic gold nanotriangles (Au NTs), forming an Ag<sub>17</sub>@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 × 10<sup>5</sup>, with ∼2 × 10<sup>2</sup> 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 Ag<sub>17</sub>@Au NT nanohybrid.