Frequency- and polarization-dependent optical response of asymmetric spheroidal silver nanoparticles on dielectric substrate

Abstract

We report theoretical simulations of plasmonic near-field enhancement and polarization in a system consisting of an asymmetric spheroidal Ag nanoparticle on a smooth dielectric surface. Finite-difference time-domain (FDTD) simulations reveal resonant optical extinction bands whose near-field is concentrated at the metal-substrate contact point with intensity enhancement by a factor of 103 and predominant polarization along the normal to the surface. These features may help explain enhanced photo-catalytic activity observed for colloidal Au and Ag nanoparticles on titania substrates.Electron microscopy image of Ag-nanoparticles on titania and the used model for numerical FDTD simulations.(© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) Numerical simulations of plasmonic near-field enhancement at the interface between an asymmetric spheroidal nanoparticle and a smooth dielectric surface show dominant contribution from the light field polarized perpendicularly to the interface; for the incident light polarized parallel to it. The intensity enhancement factor can reach 1000. The enhancement of the field polarized across the interfaces is expected to facilitate photo-catalytic charge transport. © 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.