Interparticle Coupling Effects on Plasmon Resonances of Nanogold Particles

The collaborative oscillation of conductive electrons in metal nanoparticles results in a surface plasmon resonance that makes them useful for various applications including biolabeling. We investigate the coupling between pairs of elliptical metal particles by simulations and experiments. The results demonstrate that the resonant wavelength peak of two interacting particles is red-shifted from that of a single particle because of near-field coupling. It is also found that the shift decays approximately exponentially with increasing particle spacing and become negligible when the gap between the two particles exceeds about 2.5 times the particle short-axis length. Noble metal nanoparticles, usually of Ag or Au, are well known for their strong interactions with visible light through the resonant excitations of the collective oscillations of the conduction electrons within the particles. As a result, local electromagnetic fields near the particle can be many orders of magnitude higher than the incident fields, and the incident light around the resonant-peak wavelength is scattered very strongly. This local-field enhancement and strong scattering have been proven to be very unique for biomolecular

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