Study of Surface Enhanced Raman Scattering of Single Molecule Adsorbed on the Surface of Metal Nanogeometries: Electrostatic Approach

In this paper, we have studied the surface enhanced raman scattering (SERS) from a molecule adsorbed on coated and non-coated spherical shape metallic nanoparticles. We have accounted for the nonlocal dielectric response from the metal nanoshell by using a phenomenological model based on quasi-static domain. The calculation of the enhancement factor has been done keeping the outer radius of the shell fixed. The modal developed here suggests strong enhancement of the Raman signal due to plasmonic coupling effect of a nanostructure with a biological cell. This facilitates the detection of some particular biological cell for example cancer cell. The basic principle involves amplification of the Raman signal that carries characteristic signature of the cell using coupled resonance system of cell and nanostructure. We have also compared the two cases of coated and non-coated nanospheres to analyse the SERS enhancement factor, surface plasmon resonance (SPR) and extinction efficiency which results that the coated geometry shows better response over the non-coated. The parameters such as material, size, thickness of the shell, and molecule distance from the surface of nanogeometry have been optimized to achieve Raman enhancement signal of maximum signal strength. It has been concluded that a small particle size of 20 nm for Ag at shell thickness 12 nm shows greater enhanced Raman characteristics. The enhancement factor of the order of 1012 for core-shell (SiO2@Ag) system shows a lot of future prospects and applications that can be achieved using such a plasmonically coupled resonance system.