Bimetallic Au-Ag nanorod dimers as plasmonic biosensors

Abstract

Abstract Fano resonance, discovered by Italian-American physicist Ugo Fano, is a general wave phenomenon and is seen throughout many areas of engineering and physics. It is a kind of resonant scattering occurrence that results in an asymmetrical line shape. This unbalance is created due to interference between a resonant and a background scattering process. In the field of plasmonic nanostructures, Fano resonance has potential applications in bio-sensing and nonlinear optoelectronics. In this report, we study the Fano resonance in heterogeneous Au-Ag nanorod pairs (dimers). Finite Difference Time Domain (FDTD) method is used to solve Maxwell’s equations and calculate the absorption, scattering, and electric field spectrum in both near-field and far-field regions. The consequent Fano line-shape can be used to sense biologically interesting molecules such as a protein or a cell. Further electrodynamics characterization and calculations show that the resonance originates from the interference of a narrow quadrupolar and a wide quadrupolar plasmon mode of a nanorod.