We studied physical properties of hybrid nanostructures consisting of α-NaYF<sub>4</sub>:Tm<sup>3+</sup>/Yb<sup>3+</sup> nanocrystals coupled to
single silver nanowires. By using confocal fluorescence microscope we observed much higher intensity of the upconversion
emission form nanocrystals placed in the vicinity of nanowires as compared to isolated ones. At the
same time Fluorescence Life-time Imaging Microscopy demonstrates shortening of the fluorescence decays times
for metal-coupled nanocrystals. We conclude that plasmon-enhanced emission rates are mainly responsible for
enhanced up-conversion efficiency.
We study the fluorescence properties of up-converting α-NaYF<sub>4</sub>:Er<sup>3+</sup>/Yb<sup>3+</sup> nanocrystals (NCs) in the presence of spherical Au nanoparticles. The effects of plasmon excitations in the Au nanoparticles were studied using scanning confocal fluorescence microscope. The results show that the <sup>4</sup>S<sub>3/2</sub>→ <sup>4</sup>I<sub>15/2</sub> transition in erbium ions, which appears at 540 nm, resonant with the plasmon band of the Au nanoparticles, is efficiently quenched. In contrast, in the case of <sup>4</sup>F<sub>9/2</sub>→ <sup>4</sup>I<sub>15/2</sub> transition, which appears at 650 nm, we find the increase of emission intensity. Complementary measurement of fluorescence lifetimes of individual NaYF<sub>4</sub>:Er<sup>3+</sup>/Yb<sup>3+</sup> nanocrystals reveals that plasmonic excitations in Au nanoparticles influence the dynamics of both emission band in erbium ions.