Sandwich optoplasmonic hybrid structure for surface enhanced Raman spectroscopy

Combined with photonic microstructure and plasmonic nanostructure, the optoplasmonic hybrid structure with fantastic optical properties attracts lots of attentions in recent years. With the help of light enrichment by dielectric photonic microenvironment, the embedded plasmonic nanoantennas generate much greater electromagnetic field enhancement at surface for light harvesting compared to conventional plasmonic nanostructures. In this work, a sandwich optoplasmonic hybrid structure is developed for surface enhanced Raman spectroscopy (SERS) detection, which is consisted of polymethyl methacrylate (PMMA) microspheres array, self-assembled Ag nanoparticles (AgNPs) film and SiO₂ microsphere (PMMA@AgNPs@SiO₂). The SERS spectra collected on this optoplasmonic substrate point out it has high sensitivity with limit of detection (LOD) at 10 fM. The experimental data demonstrate both the PMMA microarray and SiO₂ microsphere play important roles in enrichment of light illuminating at AgNPs for SERS detection, which is confirmed by the simulated electric field distributions. This sandwich optoplasmonic hybrid structure not only enlarges research field of surface plasmon, but also provides a novel SERS subtract for sensitive analysis in chem/bio-field.