We study the fluorescence properties of up-converting α-NaYF4:Er3+/Yb3+ 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 4S3/2→ 4I15/2 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 4F9/2→ 4I15/2 transition, which appears at 650 nm, we find the increase of emission intensity. Complementary measurement of fluorescence lifetimes of individual NaYF4:Er3+/Yb3+ nanocrystals reveals that plasmonic excitations in Au nanoparticles influence the dynamics of both emission band in erbium ions.
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