Clusters-based silver nanorings: An active substrate for surface-enhanced Raman scattering.

Area of Science:

• Plasmonics and Nanomaterials
• Spectroscopy and Sensing

Background:

• Plasmonic nanostructures, especially irregular silver (Ag) nanorings, show promise for surface-enhanced Raman scattering (SERS) spectroscopy.
• Understanding the relationship between nanostructure morphology and SERS performance is crucial for developing advanced sensing platforms.

Purpose of the Study:

• To fabricate and characterize cluster-based Ag nanorings as SERS-active substrates.
• To investigate the impact of localized electromagnetic (EM) near-field distributions within nanorings on SERS enhancement.
• To correlate simulated EM near-field distributions with experimentally observed SERS enhancements.

Main Methods:

• Fabrication of cluster-based silver nanorings.
• Characterization using high-resolution field emission scanning electron microscopy (FESEM).
• SERS measurements using Rhodamine 6G (R6G) as a Raman-active dye.
• Finite difference time domain (FDTD) simulations to model EM near-field distributions under varying interparticle gap conditions and incident polarizations.

Main Results:

• The fabricated Ag nanorings exhibited unique cluster arrangements, neither discontinuous nor linear.
• SERS enhancement factors as high as 2.1 × 10^4 were achieved.
• FDTD simulations revealed strong correlations between interparticle gaps, incident polarization, and localized EM near-field distributions, explaining SERS enhancements.

Conclusions:

• Cluster-based Ag nanorings are effective SERS-active substrates with significant enhancement capabilities.
• This work provides the first exploration of localized EM near-field effects within nanoring segments using SERS.
• The findings offer a pathway towards cost-effective SERS substrates and a deeper understanding of SERS enhancement mechanisms.