Controlled fluorescence manipulation by core-shell multilayer of spherical gold nanoparticles: Theoretical and experimental evaluation

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• Multilayer core-shell AuNPs obtained by polyelectrolytes deposition on the gold core. • Coupling range between AuNPs and emitter molecules located at different distances. • Gradual enhancement of fluorescence emission as a function of distance from AuNPs. In this paper, we investigate the coupling between spherical gold nanoparticles (AuNPs) and various emitters located at different distances from the plasmonic surface by the finite-difference time-domain (FDTD) method followed by experimental validation of the results. Specifically, the dependence of the excitation, radiative and non-radiative decay rates on the Au core-emitter distance have been evaluated in the case of a core-shell hybrid system based on a 70 nm diameter spherical AuNP coated with polyelectrolyte (PE) layers. We have distinguished enhancement or quenching in the presence of the Au core by simply manipulating the overlap of the plasmonic response of AuNPs and emitter dipole (i.e. Atto 390, Atto 532, and Atto 633) and the distance between them. Later, the simulated enhancement of the fluorophore emission of Atto 633 in the Förster radius was experimentally validated by measurements performed on colloidal multilayer core-shell AuNPs. This hybrid plasmonic system was experimentally obtained using the layer-by-layer assembly of PE which act as dielectric spacers to precisely tune the distance between the Au core and surrounding fluorescent molecules. In conclusion, the development of such composite nanostructures with integrated fluorescent molecules enables their use as efficient nanoscopic light sources.