OS is a supervisor of the whole work, the results of which are presented in

this article. MB supervised the experiments performed by IH. All authors read and approved the final manuscript.”
“Background Noble metal nanoparticles are under intense scientific and applied attention because of their unique optical properties [1]. Incident light which is in resonance with the collective electronic oscillations near the surface of metal nanoparticles causes the so-called localized surface plasmon resonance. It results in strong concentration of light energy and electric field in the subwavelength nanoscale region near the particle. The strong local field causes an increase in the efficiency of light absorption, scattering, and fluorescence [2]. Metal-enhanced fluorescence MCC950 price as a branch of nano-optics was formed on the one hand from the needs of fluorescent sensing of minute amounts of matter [2, 3] and on the other hand from fundamental interest to the control of light energy on the nanoscale and inducing of coherent plasmons with low damping [4]. Effective coupling of plasmons with fluorescent light is actual also for the fluorescent Selleck HDAC inhibitor glasses [5, 6] and active optical waveguides [7]. Trivalent rare earth (RE) ions, which are popular due to their efficient narrow-band photostable fluorescence, are of special interest as subjects for plasmonic

enhancement. It is because C188-9 in vivo their absorption cross sections as well as radiative decay rate are both very low compared to other emitters, such as dye molecules. There are a few studies suggesting local plasmonic enhancement of RE fluorescence Urocanase induced by noble metal nanodopant in sol-gel-derived optical materials, such as silica glasses and active fibers in the visible

[5, 6] and infrared [7] spectral ranges. Yet, the preparation of such samples requires specific methods for dispersion of metal particles in the host media, avoiding their aggregation and oxidation, especially for the silver nanoparticles [6, 8]. As far as we know, detected local enhancement of fluorescence intensity in the RE-doped sol-gel materials does not exceed two to three times [5–7]. Plasmonic resonance in small metal particles (approximately 5 to 20 nm) mainly causes a waste of the incident light energy as heat and do not contribute significantly to fluorescence enhancement. In contrast, plasmonic resonance in bigger nanoparticles (>50 nm) results in a stronger light scattering, which could support fluorescence more essentially in the resonance spectral range [3]. However, the synthesis of such bigger nanoparticles with uniform size is not an easy task. Hereby, we propose to utilize silica-gold core-shell nanoparticles described earlier by Pham et al. [9] for the enhancement of RE3+ fluorescence.