Design of silver nanoparticles with graphene coatings layers used for LSPR biosensor applications

Abstract A new hybrid graphene nanoplasmonic structure, using silver nanoparticles (AgNPs) coated with a graphene film and deposited on a substrate is proposed in this paper. The aim is to obtain a plasmonic response with high sensitivity for plasmonic biosensors. We show, through the calculation of absorption spectra, that the localized surface plasmon resonance (LSPR) obtained in the SiOx/AgNPs/Graphene nanostructure is very sensitive to variations in the thickness of the graphene and those of the refractive index of the detection medium. The study reveals a shift in plasmon resonance peaks resulting from the coupling between the AgNPs networks and the covering graphene layer. We obtained the red-shift of LSPR modes from 412 nm to 548 nm when the thickness of the graphene layer increases from 0.34 nm to 9 nm. We have shown that the increase in graphene thickness significantly affects the sensitivity of the device under study. An optimal sensitivity value is obtained for a graphene thickness of 9 nm, with a 304.60% gain in sensitivity value compared to the structure without graphene. These properties should enhance these nano-device and make them a preferred choice for biosensors applications, over other current biosensors.