Plasmon-assisted aggregation and spectral modification of the layered rhodamine 6G molecules

Abstract

Rhodamine, a wide-used laser dye, is well-studied in the form of solution. Contrary to that, information on the properties of rhodamine in the thin film form is limited. Even less is known about modification of structural and optical properties of the rhodamine thin films in presence of the plasmonic nanoparticles. In this contribution we report on the results of experimental investigation of the rhodamine thin films doped with silver and gold nanoparticles supporting localized surface plasmon resonances. The nanoparticles were obtained on the quartz surfaces via physical vapor deposition. Then, part of the samples was covered up by the thin polymer film doped by rhodamine molecules using spin-coating technique. At the surfaces of other part of the samples the rhodamine thin films of different thicknesses were fabricated. In the near field of plasmonic nanoparticles, absorption and fluorescence spectra of the samples were enhanced and red-shifted. This enhancement was rationalized by the near fields effect and slight reduction of the decay time of the molecules. A new absorption and fluorescent band of rhodamine molecules which was red-shifted, is associated to J-aggregates formation and their fluorescence enhancement.