Structure-activity relationships in gold nanoparticle dimers and trimers for surface-enhanced Raman spectroscopy

Area of Science:

• Nanotechnology
• Spectroscopy
• Materials Science

Background:

• Understanding nanoparticle structure-activity relationships is crucial for surface-enhanced Raman spectroscopy (SERS).
• Plasmonic nanoantennas are vital components in SERS applications.
• Characterizing individual nanoantennas presents a significant challenge.

Purpose of the Study:

• To investigate the correlation between the structure and SERS activity of individual plasmonic nanoantennas.
• To determine the key structural parameters influencing SERS enhancement factors (EFs).
• To elucidate the role of "hot spots" in achieving maximum SERS signals.

Main Methods:

• Correlated transmission electron microscopy (TEM) for structural analysis.
• Dark-field Rayleigh scattering microscopy for optical properties.
• Surface-enhanced Raman scattering (SERS) microscopy for activity measurements.
• Finite element method (FEM) calculations for theoretical modeling.

Main Results:

• SERS enhancement factors (EFs) showed a narrow distribution across diverse nanoantenna structures.
• EFs were largely uncorrelated with aggregation state and localized surface plasmon resonance (LSPR) wavelength.
• Crucially, EFs were highly dependent on the size of the interparticle gap.

Conclusions:

• The formation of "hot spots" through subnanometer interparticle gaps or coalesced crevices is paramount for maximal SERS enhancement.
• Interparticle gap size is a more critical factor for SERS activity than aggregation state or LSPR wavelength.
• This study provides critical insights into designing efficient plasmonic nanoantennas for SERS.