Highly ordered nanocavity as photonic-plasmonic-polaritonic resonator for single molecule miRNA SERS detection

Abstract

Strong light-matter coupling between molecules and electromagnetic field lead to the formation of hybrid polaritonic states for surface enhanced Raman scattering (SERS) detection. However, owing to the inefficient interaction between zero-point fluctuations of photons/plasmons and molecular electronic transitions, the Raman enhancement is limited in relative low levels. Here, we propose and fabricate a TiO_x/Cu_2-xSe/R6G nanocavity based photonic-plasmonic-polaritonic resonator for single molecular SERS detection. Through precisely matching the energy levels of illuminated photon, generated plasmon, and molecular polariton, an extremely high Raman enhancement factor of 2.6 × 10⁹ is implemented. The rationally designed SERS substrate allows sensitive detection of miRNA-21 in single molecular level with a detection limit of 1.58 aM. The hybrid SERS mechanism both from electromagnetic and chemical perspectives in this photonic-plasmonic-polaritonic resonance strategy provides insight into polaritonic semiconductor systems, thus paving the way for new experimental possibilities in light-matter hybrids.