Engineered SERS substrates with multiscale signal enhancement: nanoparticle cluster arrays

Area of Science:

• Nanotechnology
• Plasmonics
• Spectroscopy

Background:

• Surface-enhanced Raman scattering (SERS) offers high sensitivity for molecular detection.
• Controlling nanoparticle arrangement is crucial for optimizing SERS performance.
• Nanoparticle cluster arrays (NCAs) present a promising platform for enhanced plasmonic coupling.

Purpose of the Study:

• To fabricate and characterize defined nanoparticle cluster arrays (NCAs) using template-guided self-assembly.
• To investigate the impact of cluster size (n) and inter-cluster separation (Lambda) on SERS signal enhancement.
• To demonstrate the application of NCAs for rapid bacterial species discrimination.

Main Methods:

• Fabrication of NCAs on a gold film using template-guided self-assembly.
• Systematic variation of nanoparticle number per cluster (n) and edge-to-edge separation (Lambda).
• Analysis of Rayleigh scattering spectra and SERS signal intensities.
• Testing SERS performance with small molecules and bacterial cells.

Main Results:

• Precise control over NCA structural parameters (1 < n < 20, 50 nm ≤ Lambda ≤ 1000 nm).
• Observed near-field coupling within clusters, saturating around n=4.
• Significant inter-cluster coupling effects on SERS for Lambda < 200 nm.
• Multiscale signal enhancement due to simultaneous inter- and intracluster coupling.
• Strong and reproducible SERS signals enabling rapid spectral discrimination of E. coli, B. cereus, and S. aureus.

Conclusions:

• NCAs fabricated via template-guided self-assembly provide tunable plasmonic properties.
• Near-field coupling plays a critical role in SERS enhancement within and between clusters.
• NCAs demonstrate potential for sensitive and rapid detection and differentiation of bacterial pathogens.