Localized Surface Plasmon Resonance of Ag-SiO2 Core–Shell Nanowire Tetramers

Ag@SiO₂ polymer structure model is established with the assistance of COMSOL software. The effects of SiO₂-free layer configuration and different SiO₂ thickness on the electric field distribution, absorption spectrum, and far-field radiation in the gap of different Ag nanostructures were calculated the simulation results demonstrate that the Ag@SiO₂ polymer structure exhibits two plasmon resonance modes: low energy and high energy. With an increase in SiO₂ thickness, the high energy mode is redshifted, while the low energy mode is blue shifted, and the peak of the absorption spectrum changes with the thickness of the SiO₂ layer. The alteration of the tetramer configuration enables the attainment of an octupole resonance mode, giving rise to a novel resonance absorption peak within the wavelength range of 400 to 500 nm. The maximum peak offset observed is 82 nm, a phenomenon that results in the broadening of the polymer's absorption spectrum range. This development provides a solid theoretical foundation for high-wavelength resonance coupling.