Multipolar scattering and collective mode engineering in SiO₂@C core-shell nanoparticles and clusters

Area of Science:

• Nanophotonics
• Optical Metamaterials
• Dielectric Nanoparticles

Background:

• Multipolar resonance interactions in metal-free nanophotonic structures are underexplored.
• Understanding these resonances is key for optical sensing, photonics, and medical diagnostics.

Purpose of the Study:

• Investigate the impact of SiO₂ nanoparticle size, carbon shell thickness, and cluster topology on multipolar resonance excitation and evolution.
• Optimize SiO₂@C core-shell nanoparticles for enhanced scattering properties.

Main Methods:

• Utilized the finite-element method (FEM) in COMSOL Multiphysics for scattering simulations.
• Validated simulation results against Mie theory.
• Analyzed SiO₂@C core-shell nanoparticles and their clusters (dimers to heptamers).

Main Results:

• Optimal scattering observed for SiO₂ nanoparticles with a 200 nm radius.
• Carbon shell thickness (5-100 nm) modulated spectral shifts and enhanced electric dipole, magnetic dipole, and electric quadrupole modes.
• Magnetic quadrupole (MQ) mode emerged as the dominant scattering contributor, influenced by shell thickness.
• MQ mode intensified with increasing cluster size, but central particle inclusion in larger clusters caused destructive interference.

Conclusions:

• Particle arrangement and symmetry critically govern scattering in SiO₂@C nanoparticle clusters.
• Findings provide a framework for designing low-loss, spectrally tunable nanophotonic structures.
• Potential applications include dielectric metasurfaces and refractive-index sensing.