Influence of the CTAB surfactant layer on optical properties of single metallic nanospheres.

We evaluate experimentally and theoretically the role of the residual ligands and ambient environment refractive index in the optical response of a single spherical gold nanoparticle on a substrate and demonstrate the changes in the near- and far-field properties of its hybridized modes in the presence of the cetyltrimethylammonium bromide (CTAB) layer. Particularly, we show that the conventional bilayer scheme for CTAB is not relevant for colloidal nanoparticles deposited on a substrate. We show that this CTAB layer considerably changes the amplitude and localization of the confinement of the electric field, which is of prime importance in the design of plasmonic complex systems coupled to emitters. Moreover, we numerically study the influence of the CTAB layer on the modification of sensitivity of plasmonic resonances of a gold nanopshere to local refractive index changes.