Surface-Enhanced Raman Scattering from Oleate-Stabilized Silver Colloids at a Liquid/Liquid Interface

Abstract

Oleate-stabilized silver colloids of 5-nm-diameter were adsorbed to a toluene/water interface, and surface enhanced Raman scattering (SERS) spectra from these colloids were measured under the total internal reflection (TIR) condition. From the observed spectra, we examined the states of oleate ions and toluene molecules on silver colloids at the liquid/liquid interfacial region. The TIR-SERS spectra of oleate ions showed stronger peaks of the carboxylate group and the ethylene group than those of alkyl chains. From these results, it was found that the oleate ions were adsorbed on the silver surface in two different ways at the liquid/liquid interface; the carboxylate group adsorbed in the organic phase side, while the ethylene group adsorbed in the aqueous phase side. The shifts of the toluene in the interfacial SERS spectra were identical to those of bulk toluene, though the relative intensities among the peaks were not same. This result suggested that the toluene was adsorbed with a weak interaction, but was significantly enhanced by the local electromagnetic field at the colloid surface.

In vivo human time-exposure study of orally dosed commercial silver nanoparticles

“…Although the observed peak position of the surface plasmon band is slightly larger than these previously reported, its position is still consistent with Mie theory predictions. This optical absorption strongly depends on particle size, extent of aggregation, 32 dielectric, and chemical properties of the milieu. 33 Small silver spherical nanoparticles (i.e., <20nm diameter) exhibit a single, narrow surface plasmon band inconsistent with experimental observations here.…”

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