Super-Radiant SERS Enhancement by Plasmonic Particle Gratings.

Despite recent developments, surface-enhanced Raman spectroscopy (SERS) applications face challenges in achieving both high sensitivity and uniform Raman signals over a large area. Using the directional self-assembly of plasmonic nanoparticles in lattice structures, we show how one can increase the SERS signal 43-fold over randomly aligned gold nanoparticles without relying on the photoluminescence of Rhodamine 6G. For this study, we have chosen the lattice constant for an off-resonant case that matches the lattice resonance and super-radiant plasmon mode along the particle chain. Supported by electromagnetic simulations, we systematically analyze the radiative components of the plasmon modes by varying the particle size while keeping the lattice periodicity constant. We perform polarization-dependent SERS measurements and compare them with other standard SERS excitation wavelengths. Using the self-assembled plasmonic particle lattice, we have developed an effective SERS substrate that provides a significantly higher signal with 73% less surface coverage. This colloidal approach enables the cost-effective and scalable fabrication of highly sensitive, uniform, and polarization-dependent SERS substrates.