Exploration of Bimetallic Au@Ag Core–Shell Nanocubes Dimers Supports Plasmonic Fano Resonances

We report a theoretical simulation of optical spectra of Au@Ag core/shell nanocubes dimers. The influence of the core/shell size ratio and the dimers separation gap on these spectra have been studied using boundary element method (BEM). The scattering sections of various core/shell size ratio (= 10 to 80%) with different separation gap (2 to 16 nm) have been numerically determined via Maxwell equations. We have examined the scattering sections along a wide wavelengths range, 250–1500 nm, in visible and IR domain. The edge lengths of 60, 80, 100, and 120 nm of the shell nanocubes have been considered. We revealed the formation of Fano resonance line shape through the investigation of the scattering section variation within the entire wavelengths. The Fano resonance line shape emerges with the variation of the gap between the dimer as well as of the core/shell size ratio. The trace of the Fano interference dip is slightly blue shifted and it is lost above gap separation equal 4 nm. The core/shell dimer with varied core/shell size ratio manipulate and image easily the trace of the Fano resonance dip up to core/shell size ratio equal 50% for gap separation above 4 nm. We demonstrate the important duality of the gap separation and core/shell ratio variation in designing Fano resonance interface. This has a potential effect on applications in non-linear optics, metamaterial, and tunable nanophotonic devices such as filters, wave-guiding, subwavelength optical imaging, chemical, and biological sensing.