Influence of Crystal Structure on the Fluorescence Emission of Eu³⁺:LaOF Nanocrystals

Abstract

Optical transitions of Eu(3+)-doped LaOF nanocrystals with tetragonal and rhombohedral structures were studied experimentally using laser spectroscopic method. Fluorescence emissions from 5D1 and 5D0 of Eu3+ in LaOF nanocrystals were detected by exciting the sample with a 532 nm pulsed laser, and the influence of local symmetry on the fluorescence emission of doped ions was observed. The specific crystalline phase as well as the local symmetry on the fluorescence emission was investigated in both the frequency domain and time domain. It was found that Eu3+ ions doped in the tetragonal crystal structure present more efficient fluorescence emission, which was explained by lower symmetric distribution of local field at the doped ions.

Interpretation of europium(III) spectra

“…The delay is measured as a phase shift, which can be used to calculate the decay time. Although frequencydomain measurements are often used in fluorescence spectroscopy of organic molecules, only few studies have been devoted to frequency-domain measurements on europium(III) compounds [752][753][754][755][756].…”

Fluorescence enhancement of Ln3+ doped nanoparticles

“…The forced electric dipole transition from 5 D 0 to 7 F 2 is very sensitive to the local crystal field and site symmetry. Experimental observation showed that the overall fluorescence intensity obtained from Eu 3 + :LaOF nanocrystals with tetragonal crystal structure is about 20 times greater than that observed from those with hexagonal crystal structure [65] (Fig. 3).…”

“…For hexagonal LaOF nanoparticles, the La 3+ ion having C 3V symmetry is directly coordinated with four oxygen ions and four fluorine ions [65]. The corresponding bond lengths are 2.4200Å for four La-F bonds and 2.5800Å for four La-O.…”

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

“…Ln-doped NCs show unique luminescent properties, such as large anti-Stokes shift, long excited state lifetimes, and narrow luminescence band widths [6,7]. Several strategies have been proposed for improving their luminescence efficiency including the introduction of co-dopant ions/sensitizers, surface modification of nanoparticles (NPs), local symmetry and interaction adjustment [8][9][10][11][12], and other strategies for increasing the luminescence emission efficiency of Ln-doped NCs [2,4,5].…”