Enhancement of Light Transmission through Silver Nanoparticles

This article reports experiments showing that the transmittance of silver nanoparticles on ZrO2-coated silica substrates is enhanced by functionalization of the silver surface with a self-assembled monolayer of perfluorodecanethiol. The transmittance can become surprisingly higher than that of the oxide substrate over a wide wavelength range (300-680 nm). The maximum of transmittance can even reach that of the naked silica. This enhancement is against what is expected from the usual modification of the extinction cross-section of noble metal nanoparticles upon coating with a dielectric shell. Large decrease of both reflectance and absorptance are related to the increase of transmittance. Conversely, the transmittance of silver nanoparticles on silica substrates, without ZrO2, decreases upon silver functionalization, in a classical way. An effective medium description of the fiinctionalized silver nanoparticles is presented. This approach, still to be improved, reveals the major role of the interferences of light in the nanoparticle films, in the phenomenon of transmittance enhancement. The respective effects of light scattering by the nanoparticles, of the silver functionalization and of ZrO2 are discussed.