Luminescence Enhancement Mechanism of Lanthanide-Doped Hybrid Nanostructures Decorated by Silver Nanocrystals

Abstract

Hybrid nanostructures composed of rare earth iondoped lanthanum trifluoride nanocrystals deposited on silica nanospheres (LaF 3 :Yb 3+ , Er 3+ @SiO 2 ) and decorated with varying quantities of silver nanoparticles (Ag NPs) were synthesized using a simple strategy. Down and upconversion luminescence spectra were recorded. The luminescence dynamics were also recorded following excitation with a 532-nm pulse. Silver loading was found to have a significant effect both on the luminescence intensity and the luminescence decay rate, with the samples with the lowest silver content showing reduced luminescence intensity over silver-free samples, while the samples with large levels of silver loading showed significant luminescence enhancement. The results were successfully (and quantitatively) interpreted in terms of the competition between surface plasmon-induced field enhancement mediated by the Ag nanoparticles and nonradiative energy transfer from the luminescent ions to Ag nanoparticles. By combining the measured luminescence intensity with the luminescence decay rate determined from the dynamics measurements, and with the measured surface plasmon absorption spectra, one could obtain a quantitative and self-consistent understanding of the observed dependence of the green 4 S 3/2 → 4 I 15/2 (~540 nm) and red 4 F 9/2 → 4 I 15/2 (~650) emission bands on the Ag NP metal loading.

Recent Progress on Plasmon-Enhanced Fluorescence

“…Furthermore, a gold pyramid pattern was also introduced to enhance the rate of resonant energy transfer from Yb 3+ to Er 3+ ions, and sixfold enhancement of the UCNP(β-NaYF 4 :Yb 3+ /Er 3+ ) was obtained [117]. Zheng studied the robust DC and UC luminescence enhancement in lanthanide ions residing on silica hybrid nanostructures (LaF 3 :Yb 3+ , Er 3+ @SiO 2 ) decorated with varying quantities of AgNPs [118]. By using an appropriate model for the fluorescence enhancement and the simultaneous quenching effects induced by the introduction of the plasmonic metallic nanostructure, the luminescence enhancement as a function of AgNPs loading with the rates of luminescence buildup and decay are observed.…”

Unique adjustable UC luminescence pattern and directional radiation of peculiar-shaped NaYF4: Yb3+/Er3+ microcrystal particle

“…As shown in the Fig. 3(G), characteristic emission bands in spectra are mainly at 654 nm, 540 nm and 520 nm, which correspond to transitions of 4 F 9/2  →  4 I 15/2 , 4 S 3/2  →  4 I 15/2 and 2 H 11/2  →  4 I 15/2 of Er 3+ in the particle, respectively 25 . Very weak emission at 411 nm is resulted from the transition of 2 H 9/2  →  4 I 15/2 .…”

Photon Upconversion for Photovoltaics and Photocatalysis: A Critical Review

“…Indeed, the spatial organization as well as the relative distance and orientation of plasmonic antennas and upconverting NCs is currently better controlled for nondispersible nanostructures compared to dispersible ones. Nondispersible plasmonic structures mostly rely on patterned − and unpatterned plasmonic films, − as well as porous metal films, − but also in conjunction with opal-structured photonic crystals. , A large variety of dispersible plasmonic nanostructures have also been reported (e.g., upconverting NCs decorated with plasmonic NPs, plasmonic NPs decorated with upconverting NCs, the growth of plasmonic shells on upconverting NCs, or the growth of Ln-doped shells on plasmonic NPs), ,− but to date many lead to only limited enhancement or quenching. This is due to the difficulty in precisely controlling important structural properties such as (i) spatial organization, (ii) tunable interparticle distance, and (iii) directionality of dispersible plasmonic structures.…”