A Theoretical Explanation for the Existence of Certain Maxima in the Visible Spectrum Pattern of Wave Scattering from Spherical Metal-Dielectric-Janus Nanoparticles Based on Surface Plasmon Excitation

Abstract

In this research, within the visible frequency band region, the scattering phenomenon of plane electromagnetic waves from two-piece nano-spheres, consisting of metal-dielectric (spherical metal-dielectric Janus nanoparticles), will be investigated theoretically. Mie’s theory, which addresses wave scattering from spherical structures, and the point-matching method for solving field equations, are the two main mathematical tools utilized in this work. Simulations have been conducted for objects with several dual combinations of metal-dielectric materials, such as Gold metal paired with dielectrics like Alumina, PVC, Teflon, and Rexolite. This investigation also extends to objects incorporating Silver metal. The diagrams depicting the variations of the scattering cross-section versus wave frequency have been presented. It will be demonstrated that, at certain frequencies, the diagrams of the scattering cross-section exhibit peaks. These peaks indicate the state in which the densities of surface plasmon dipoles at the metal-dielectric boundary have the most significant and optimal response to the presence of an electromagnetic wave. Since the maxima in the scattering cross-section diagram occur at specific frequencies within the visible region, they can be attributed as a reason for the dominant color observed in colloidal solutions containing spherical metal-dielectric Janus nanoparticles.