study of surface-enhanced raman scattering of plasmonic coupled biomolecule: role of multi-layered nanosphere

In this communication, we study the surface enhanced raman scattering (sers) by a molecule which is adsorbed on a trilayer (ag@sio2@ag) spherical shaped metallic nanostructure. we have studied the plasmonic signature of the trilayer nanostructure under quasi-static approximation. the plasmonic response of trilayer nanostructures is analysed in terms of surface plasmon resonances and extinction efficiency which is a function of size, shape of core-shell material and thickness polarisability. the polarisability of trilayer nanostructure has been derived using t-matrix method and coupled it with the gersten-nitzan model to study the raman enhancement factor. the raman enhancement factor (r) has been studied under the influence of several parameters such as core-shell material, thickness, molecule distance and the surrounding media. the model developed here suggests strong relative amplification of the raman gain of biomolecule adsorbed on the surface of the nanogeometry. the trilayer metal nanostructure exhibits three plasmon resonance peaks in uv to visible range (raman spectroscopy range) which helps in detection of biological molecules into three different regimes. we have also compared the raman enhancement factor for trilayer, bilayer and single metal nanosphere and it was observed that the magnitude of raman gain factor, number of resonant peaks and its spectral bandwidth are different for different geometries.