Metal-Dielectric Nanocavity for Real-Time Tracing Molecular Events with Temperature Feedback

Plasmonic nanoparticles coupled with metallic films forming nanometer scale cavities have recently emerged as a powerful tool for enhancement of light-matter interaction. Despite high efficiency for sensing and light emission, such nanocavities exhibit harmful and uncontrolled optical heating which limits the ranges of light intensities and working temperature. In contrast to plasmonic nanoparticles, all-dielectric counterparts possess low Ohmic losses, high temperature stability along with a strong temperature-dependent Raman response. Here, we demonstrate that a silicon nanoparticle coupled with a thin gold film can serve as a multifunctional metal-dielectric (hybrid) nanocavity operating up to 1200 K. Resonant interaction of light with such nanocavity enables molecular sensing, heat-induced molecular events (protein unfolding), and their real-time tracing with a nanoscale thermometry through the monitoring enhanced Raman scattering both from the nanoparticle and analyzed molecules. We model numerically the thermo-optical properties of the hybrid nanocavity and reveal two alternative regimes of operation - with and without strong optical heating while other functionalities are preserved. We believe that the concept of the multifunctional hybrid nanocavities holds great potential for diverse photochemical and photophysical applications.