Self-assembled monolayer silver nanoparticles: Fano resonance and SERS application

Abstract

Plasmonic response of noble metal nanoparticle are of fundamental interest in nanophotonic applications, such as photocatalysis, information storage, sensing, optical switches, and nonlinear optics. We comprehensively investigate the Fano resonance and SERS (surface–enhanced Raman scattering) application of self–assembled monolayer silver nanoparticles using commercial FDTD (finite difference time domain) solver, cartesian multipole decompositions method, two coupled oscillators model and experiments. We found that the higher–energy antibonding mode is not only from the antibonding dipole–dipole mode (ADD), but also from the antibonding quadrupole–quadrupole mode (AQQ) and the hybridized magnetic mode when the particle size is relatively large in homodimer, as for the heterodimer, the case will change even more. The effects of dimer gap and size are discussed in details. A two coupled oscillators model is used to illustrate the mechanism of the Fano resonance, and the energy storage as a function of radiation loss and intrinsic loss in the plasmonic system is qualitatively evaluated, which is directly related to the near–field enhancement. Finally, SERS (surface–enhanced Raman scattering) experiments are carried out to meet the numerical results, and the SERS performance is also investigated and given.