Abstract
The gap-induced plasmonic response of metallic nanoparticles drastically changes the near and far-field properties of nanoparticle antenna. Similar to a pair of metallic nanostructures, the two nanoparticles, with a dielectric core and silver shell in close proximity, exhibit multiple high energy plasmonic resonances at the short wavelength end of their optical spectrum. In this article, we have overwhelmingly investigated the disparity in the electric field of a core–shell dimer antenna when the gap between nanoparticles within the dimer becomes sub-nanometer in length. We used an electromagnetic planewave to excite the core–shell nanoparticles within the dimer. Frequency domain Finite Element Method (FEM) was employed for the numerical optical analysis of a dimer comprised of two silver-coated silica (SCS) nanoparticles in close proximity, using Computer Simulation Technology (CST) Microwave Studio. A modified Drude model has been used to predict the optical properties of the system with incorporating the size effects. The SCS dimer was numerically analyzed in the visible frequency band, and anomalies in near-field plasmonic coupling were investigated in detail. The inter-surface gap g between nanoparticles within the dimer varied in a range from 0.1 to 402 nm.
Highlights
Light-induced oscillation of conduction electrons within sub-wavelength regimes in metallic nanoparticles such as Ag and Au is usually termed as localized surface plasmon resonance (LSPR)
The plasmonic behavior of metal and core–shell nanoparticles has been utilized in many advanced technologies, e.g., imaging, sensing, and biomedical technologies [8]
In addition to the breakdown of the Ruler equation due to strong near-field coupling, there is an associated transition of electric field distribution which leads to the breeding of two plasmonic modes as the gap between nanoparticles approaches a nanometer or sub-nanometer level [20]
Summary
Light-induced oscillation of conduction electrons within sub-wavelength regimes in metallic nanoparticles such as Ag and Au is usually termed as localized surface plasmon resonance (LSPR). In addition to the breakdown of the Ruler equation due to strong near-field coupling, there is an associated transition of electric field distribution which leads to the breeding of two plasmonic modes as the gap between nanoparticles approaches a nanometer or sub-nanometer level [20]. These plasmonic modes strongly affect the major bonding dipolar mode between nanoparticles within the dimer.
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