Quantifying the ultimate limit of plasmonic near-field enhancement

          The Paper of the Day describes the quantitative measurement of the ultimate limit of plasmonic near-field enhancement around silver (Ag) nanocavities. The researchers used a silver nanocube-on-mirror (NCOM) structure with a monolayer of MoS2 as the spacer to precisely control the nanogap distance. By optimizing the excitation and collection conditions, they were able to achieve a maximum surface-enhanced Raman scattering (SERS) enhancement factor of 4.27 × 10^10, corresponding to an averaged near-field enhancement of over 1200 times. This result represents the upper limit of plasmonic field enhancement in the visible and near-infrared region before the onset of quantum effects. The study provides important insights into the fundamental limits of light-matter interactions at the atomic scale.