Spectral engineering of LaF3:Ce3+ nanoparticles: The role of Ce3+ in surface sites

Abstract

Due to the high surface-to-volume ratio, luminescence centers on the surface have relative dominance in the overall spectral response of nanoparticles. The luminescence of LaF3:Ce3+ nanoparticles was investigated in the spectral and temporal domains with a particular focus on the role of Ce3+ on the surface. These nanoparticles present two luminescence bands at 4.10eV and 4.37 eV attributed to Ce3+ transitions from the 5d level to the spin-orbit split 4f ground levels F-2(5/2) and F-2(7/2), in addition to a low-energy band at 3.62 eV that has been attributed to Ce3+ ions residing in perturbed sites. The growth of up to three undoped shells, ca. 0.9 nm thick each, around the core promoted a progressive enhancement of luminescence output, concomitant with an increase in the fluorescence lifetime due to the weakening of energy transfer through multipolar interaction between Ce3+ in the core and quenching defects on the surface. Also, the growth of the first shell led to a decrease in the relative intensity of the low-energy band and a 0.23 eV shift to higher energies. These results were interpreted as being due to the existence of two types of perturbed sites, one on the surface that is eliminated by the growth of the first shell, and another within the volume of the nanoparticle, similar to observations in bulk single crystals. This work demonstrates how surface engineering can affect and control the luminescence behavior of this nanomaterial. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.3700343

The energy transfer mechanism in Ce,Tb co-doped LaF3 nanoparticles

“…The decay curve for singly doped LaF:Ce 1 mol% was processed in the same way as for the co-doped samples, but with only a single-exponential function, and the lifetime was found to be 29 ns for the 287 nm emission and 31 ns for the 301 nm emission. These values are similar to the lifetime reported for smaller Ce-doped LaF 3 nanoparticles coated with undoped LaF 3 shells [18]. The decay time was slightly longer for the longer wavelength emission, as has been reported for Ce doped NaCaPO 4 [19].…”

Electrospinning synthesis and photoluminescence properties of one-dimensional LuBO3 :Ln3+ (Ln = Tb, Eu) nanofibers

“…The porous structures will generate some surface defects, which cause luminescence quenching effect. Recently, some reports indicated that the luminescence properties of LaF 3 :Ce 3+ nanoparticles are related to the energy transfer through multipolar interaction between Ce 3+ in the core and quenching defects on the surface . Similarly, we suppose that the surface effect of nanofibers, as well as the anisotropy and space dimensionality, will lead to the most Tb 3+ ions residing on the surface, and the energy transfer between adjacent Tb 3+ ions on the surface is intensified, which can block luminescence quenching effect.…”

“…As the Tb 3þ doping concentration increases from 1 to 5%, the excitation and emission intensities of nanofibers increase gradually. It can be observed from where I 0 is the initial emission intensity at t ¼ 0, and t is the in the core and quenching defects on the surface [29]. Similarly, we suppose that the surface effect of nanofibers, as well as the anisotropy and space dimensionality, will lead to the most Tb 3þ ions residing on the surface, and the energy transfer between adjacent Tb 3þ ions on the surface is intensified, which can block luminescence quenching effect.…”

RE-Based Inorganic-Crystal Nanofibers Produced by Electrospinning for Photonic Applications

“…In fact, Ce 3+ ions are usually exploited for their very large absorption and emission features in the UV and visible regions but they also have a strong interaction with the crystalline lattice and this leads to large energy losses inside the material. Moreover, the exact location of these bands is strongly host-dependent and their properties are well-studied both in bulk and nanocrystalline hosts [115]. In nano fiber morphology, Ce 3+ optical properties have been studied either as single dopant in TiO 2 [67], YAG [77,78] and ZnO [21] or in conjunction with Tb 3+ in LaPO 4 [52], YAG [74] and Y 2 SiO 5 [85].…”