Double active control of the plasmonic resonance of a gold nanoparticle array.

A two-fold active control of the plasmonic resonance of randomly distributed gold nanoparticles (GNPs) has been achieved. GNPs have been immobilized on an Indium Tin Oxide (ITO) coated glass substrate and then covered with a liquid crystalline compound. The system has been investigated by means of atomic force and scanning electron microscopy, revealing the presence of isolated and well distributed GNPs. The application of an external electric field to the sample has a two-fold consequence: the re-orientation of the hybrid-aligned liquid crystal layer and the formation of a carrier accumulation layer in the proximity of the ITO substrate. The refractive indices of both liquid crystal and accumulation layers are influenced by the applied field in a competitive way and produce a "dancing behavior" of the GNP's plasmonic resonance spectral position.