Analysis of the surface plasmon resonance of a single core-shelled nanocomposite by surface integral equations

To investigate the interactions of an illuminating light with a single nanocomposite (a core-shelled nanoparticle) in the range of ultraviolet (UV) to near infrared (NIR), a set of new surface integral equations was derived from the Stratton-Chu formulation of Maxwell's equations for a two-dimensional TM-mode problem. These integral equations belong to Fredholm equations of the second kind. Using the boundary-element method (BEM), these equations are solved to obtain the surface components (the tangential magnetic field, the normal displacement field and the tangential electric field) along the multi-connected interfaces (host/shell and shell/core) simultaneously. Two main structures of the core-shelled nanocomposite are studied by BEM; one is a nanoparticle of metallic core (Au or Ag) with an oxide shell (SiO₂ or ZrO₂), and the other structure is a silica core (SiO₂) with a metallic shell (e.g. Au or Ag). The numerical results illustrate a red-shift effect on the surface plasmon resonance (SPR) of the former structure can be induced by covering a high-permittivity shell on a metallic nanoparticle. For the latter, the red shift of SPR is caused by thinning the thickness of the metallic shell. This is to say by tuning the compositions and the configurations of the nanocomposites, the peak position and the linewidth of the SPR can be manipulated on demand.