Nano-thick-dielectric encapsulation effects on the refractive index sensitivities of Ag plane-nanosphere-cluster sensors

The nano-thick-dielectric encapsulation effects on the bulk and local refractive index sensitivity behaviors of Ag plane-nanosphere-cluster sensors (including nanosphere monomers, dimers, trimer chains and trimer equilateral triangles, four kinds of normally encountered nanoparticles in experiments) have been numerically investigated by finite element method (FEM). The encapsulation is revealed to decrease the quadratic magnitude of the refractive index responses of their peak wavelengths of localized surface plasmon resonances (LSPR), while it does not violate such quadratic response natures. Its effect on their capabilities of surface enhanced Raman scattering (SERS) behaviors is discussed too. It is demonstrated to provide an efficient type of SERS substrate for plasmonic sensing and detections, which improves the stability of the concerned nanoparticles, and not diminish their SERS signals, in agreement well with experiments under the same nanostructure parameters. This work holds great promise for further designing SERS-based sensing/detecting substrates and sensors/detectors.