Gilded nanoparticles for plasmonically enhanced fluorescence in TiO₂:Sm³⁺ sol-gel films

Silica-gold core-shell nanoparticles were used for plasmonic enhancement of rare earth fluorescence in sol-gel-derived TiO₂:Sm³⁺ films. Local enhancement of Sm³⁺ fluorescence in the vicinity of separate gilded nanoparticles was revealed by a combination of dark field microscopy and fluorescence spectroscopy techniques. An intensity enhancement of Sm³⁺ fluorescence varies from 2.5 to 10 times depending on the used direct (visible) or indirect (ultraviolet) excitations. Analysis of fluorescence lifetimes suggests that the locally stronger fluorescence occurs because of higher plasmon-coupled direct absorption of exciting light by the Sm³⁺ ions or due to plasmon-assisted non-radiative energy transfer from the excitons of TiO₂ host to the rare earth ions.