Atomically Precise Nanoclusters as SERS Probes

Area of Science:

• Nanomaterials Science
• Spectroscopy
• Computational Chemistry

Background:

• Atomically precise nanoclusters (NCs) possess molecule-like properties but suffer from weak Raman signals obscured by luminescence.
• Developing sensitive probes for NC characterization is crucial for understanding their unique behaviors.

Purpose of the Study:

• To utilize surface-enhanced Raman spectroscopy (SERS) to investigate the molecular characteristics of a stable eight-electron silver NC, [Ag₁₇(o₁-carboranethiolate)₁₂]^3- (Ag₁₇).
• To create a robust nanohybrid system for advanced Raman probing under demanding experimental conditions.

Main Methods:

• Integration of Ag₁₇ NCs with plasmonic gold nanotriangles (Au NTs) to form Ag₁₇@Au NT nanohybrids.
• Application of SERS to detect and analyze the Raman signals of the nanohybrid.
• Time-dependent density functional theory (TDDFT) calculations to elucidate enhancement mechanisms and spectral features.

Main Results:

• The Ag₁₇@Au NT nanohybrid demonstrated stable and sensitive Raman probing capabilities, even under harsh laser irradiation.
• An overall enhancement factor of up to ~6 × 10⁵ was achieved, with chemical enhancement contributing ~2 × 10².
• TDDFT calculations successfully reproduced experimental spectra and identified low-lying hybrid charge-transfer excited states responsible for chemical enhancement.

Conclusions:

• The Ag₁₇@Au NT nanohybrid represents a significant advancement in using atomically precise NCs as next-generation Raman probes.
• Synergistic electromagnetic and chemical enhancement mechanisms, driven by plasmonic confinement and charge transfer, significantly amplify Raman scattering.
• This work provides a powerful platform for probing the molecular nature of NCs and related nanoscale materials.