Wavelength-tailored enhancement of Raman scattering on a resonant plasmonic lattice

Abstract

Routine single-molecule analysis using surface-enhanced Raman scattering (SERS) is still out of reach using conventional substrates based on corrugated metallic surfaces. Tailoring the substrate to a specific excitation wavelength is an effective way to improve the SERS enhancement factor. Here, we present a comprehensive theoretical and experimental study of wavelength-tailored SERS substrates with improved sensitivity, exploiting the surface lattice resonance (SLR) in a plasmonic lattice comprised of assembled Ag nanoparticles. We tuned the SLR close to 532 nm and evaluated its effect on SERS. We found that SLR-based substrates had 10 times overall higher sensitivity and 100 times higher sensitivity at the target wavelength compared to non-tuned counterparts. Furthermore, we compared monomer and tetramer unit cell cases and found that the combined effect of tuned SLR and hot spots further improves the enhancement factor more than 400 times over a substrate with a random layer of nanoparticles.