Possibility of non-radiative plasmonic support for the excitons was recently Selumetinib mouse demonstrated in the case of plasmonically improved photocatalysis [12]. Plasmonic support of Förster resonance energy transfer for quantum dot’s fluorescence was described in [13]. Table 1 Lifetimes of fluorescence for the TiO 2 :Sm 3+ film doped with gilded nanoparticles, λ exc   = 355 nm Place on the sample τ 1,μs τ 2, μs τ 3, μs τ, μs Bright spot 1 2.4 25 156 103 Bright spot 2 6.5 48 299 147 Bright spot 3 10.5 78 294 202 Spot 1

on the background 4.1 35.3 225 138 Spot 2 on the background 7.4 50 220 137 Excitation by green light, λ exc = 532 nm, results in direct excitation of Sm3+ and also yields a fluorescence spectrum consisting of the four bands. But check details in this case, the bands are broader and almost featureless (Figure 5). It means that different ensemble of Sm3+ ions is excited in this case. The absence of spectral features suggests that those Sm ions

are situated in less ordered TiO2 environment [14]. In spite of the exclusion of excitonic influence at such excitation, we detected still 2.5 times enhancement of fluorescence in the vicinity of gilded nanoparticles (Figure 5). Under 532 nm excitation, the Stokes shift of the fluorescence emission is very small [15]. So, both excitation and emission can be influenced by plasmons. Figure 5 Micro-luminescence spectra of TiO 2 :Sm 3+ films doped with gilded nanoparticles: (1) bright spot, (2) background ( λ exc   = 532 nm). 8-Bromo-cAMP Fluorescence lifetimes at 532 nm excitation were measured in the time-gated mode on a FLIM in the spectral range of 580 to 660 nm. Obtained fluorescence decay is also multiexponential because different Sm3+ centers situate in TiO2 environment with different local surroundings. Numerical values of the lifetimes are similar to those presented in Table 1. Because of the insignificant changes in the lifetimes of Sm3+ fluorescence, we suppose that through the detected 2.5 times enhancement in the intensity of fluorescence

could be caused mainly by plasmon-enhanced direct absorption of exciting light by Sm3+ ions near the gilded nanoparticles. Conclusions Silica-gold core-shell nanoparticles were synthesized and successfully adjusted for the incorporation into TiO2:Sm3+ films. Prospective capabilities of these particles for the local plasmonic enhancement of rare earth fluorescence are demonstrated. Detected locally strong Sm3+ fluorescence is connected more with local increase in light absorption and energy transfer than with changes in radiative decay rates since fluorescent lifetimes are not changed significantly. Detected enhancement of fluorescence can be based both on the plasmonic enhancement of direct light absorption by Sm3+ ions and on profitable plasmonic support of energy transfer from exciton to rare earth ions in the case of the indirect excitation.