Abstract
In this paper, an interaction of metal nanoparticles that appears in the extinction spectra was investigated. The mutual coupling between the nanoparticles, the effect of size difference, and the interparticle separation in silver nanoparticle dimers are studied by computer discrete dipole approximation methods. The obtained results show that nanoparticle interaction results in the distinct collective modes, known as the low-energy bonding modes and the higher-energy antibounding modes. The spectral position of the modes is analyzed as a function of the ratio of interparticle distance to particle size that reduces the dependency on the particle size itself. The optical spectra of nanoparticles that form the fractal cluster were investigated. It was found that the number of spectral bands increase with the growth of the number of nanoparticles in the fractal cluster, which are described within the plasmon hybridization model.
Highlights
Metal nanoparticles have attracted a great attention due to their strong interaction with light
Calculation of extinction spectra of dipoles shows that the interaction between the nanoparticles, which depends on the distance between them, manifested in the appearance of two components (Fig. 1)
Analysis of the results shows that the ratio d = D/r is more universal because it minimizes the dependency on the nanoparticle radius r
Summary
Metal nanoparticles have attracted a great attention due to their strong interaction with light. In the presence of the oscillating electromagnetic field of the light, the free electrons of the metal nanoparticle undergo a collective coherent oscillation with respect to the positive metallic lattice [1]. This process is resonant at a particular frequency of the light and is called the localized surface plasmon resonance (LSPR) oscillation. In a single metal nanoparticle, frequency, strength, and quality of the LSPR depends on the size, geometry, the metal composition, and the refractive index of the local environment. In an assembly of metal nanoparticles with small interparticle distance compared to the size of particle, the LSPR is strongly affected by the near-field coupling of the individual particles [2]
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