Optical Response and Light Propagation in Bimetallic Quantum Dot Ag@Au Core-shell Nanocomposite Embedded in Non-absorptive Host Medium

In this research work, optical and dispersion responses of bimetallic quantum dot Ag@Au core-shell nanostructures embedded in the non-absorptive host-medium, along with the propagation of slow and fast light waves through these structures, have been investigated. The local field enhancement factor, absorption coefficient, refractive index and group velocity were studied by engineering silver (Ag) as a core and gold (Au) as a shell. The study is based on the quasi-static approximation of classical electrodynamics for composite radii ranging from 6 to 10 nm. Within this quantum dot configuration, two sets of plasmonic resonances were observed in the visible spectral region, corresponding to the two interfaces of the core–shell geometry. The optical properties of the composite were found to depend on factors such as core size, shell thickness, overall composite size, filling factor, and the dielectric function of the host medium. The two plasmonic resonances become closer and more intense as the composite size decreases for a fixed core size, while they shift in opposite directions. Moreover, the resonance peak intensity decreases as the core size increases for a fixed composite size. For optimized core/composite dimensions, shell thickness, and other parameter values, these Ag@Au core–shell nanostructures are promising for diverse applications including photocatalysis, biomedicine, nano-optoelectronics, security technologies, and optical communication.