Optimized plasmonic configurations: adjacent and merging regimes between a symmetric couple of Au rod/shell nano-arrangements for LSPR sensing and spectroscopic purposes

In this work, we studied the optical properties and spectral response of a novel and practical plasmonic pair shape configuration of gold rod/shell nanoparticles theoretically and numerically. We investigated that proposed pairs that are acknowledged as dimers can be presented in various fashions to apply in numerous purposes. The effect of controlled structural and chemical modifications on the optical response and scattering efficiency of the configuration have been determined. Moreover, proposed pair of gold rod/shell nanocompositions in touching and nontouching regimes have been studied to provide weak and strong coupling of plasmon resonance modes. The confirmed geometrical parameters sizes for proposed composition of rod and shell have been determined as R rod = 60 nm, H rod = 35 nm, and R i(shell) = 80.5 nm, R o(shell) = 115.5 nm, H shell = 35 nm, respectively, which have been modified subtlety during examinations to obtain desired spectral results. Considering these quantities, we measured the shape factor of an isolated rod/shell configuration as exactly κ = 3.6. Also, we utilized same geometrical sizes in the dimer structure, and the effect of interparticle distance as a crucial factor in measuring the strength of resonance coupling have been analyzed numerically in the strong coupling regime, which is quantified as D ~ 2 nm. We showed that red and blue-shifts of LSPR can be detected based on the tuning of the proximity distance (interparticle distance) of the two arrangements pair. The influence of separation and merging distances on the plasmon resonance excitation and coupling intensity have been considered and examined numerically. Finally, the ultra-sensitivity of the proposed pair for molecular sensing and spectroscopy purposes have been elucidated based on the position of the peak of scattering intensity. Obtained results based on finite-difference time-domain method have proved that the proposed structure is a practical system in complex sensing and spectroscopy applications.