Synthesis and luminescence resonance energy transfer based on noble metal nanoparticles and the NaYF₄:Tb³⁺ shell.

A core-shell hybrid nanostructure was prepared by combining NaYF4 doped with the lanthanide dopant Tb(3+) as shell layer materials and noble metal nanoparticles (Au and Ag) as cores. For the core-shell system, the luminescence resonance energy transfer (LRET) was demonstrated, in which noble metal nanoparticles as fluorescence quenchers can absorb the emission energy of the α-NaYF4:Tb(3+) donor. The morphology, structure, composition and properties of the as-prepared samples were characterized by X-ray powder diffraction (XRD), transmission electron microscopy (TEM), energy dispersive spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), UV-Vis absorption and photoluminescence (PL) spectroscopy, respectively. In the Au/Ag@NaYF4:Tb(3+) system, it is observed that the plasmonic absorption bands of gold or silver nanoparticles overlap with the emission bands of (5)D4→(7)F(j) (j = 6, 5) transition of the Tb(3+) ions, and the emission intensity of the (5)D4→(7)F5 transition is clearly attenuated. The photoluminescence decay curve measurements show that the lifetimes of the (5)D4→(7)F6 and (5)D4→(7)F5 transitions of Tb(3+) are slightly decreased in the presence of gold or silver cores. The quenching efficiency of the gold and silver nanoparticles implies that the efficiency of energy transfer is highly dependent on the extent of spectral overlap in the LRET system.