Energy Transfer in Bi- and Er-Codoped Y₂O₃ Nanocrystals: An Effective System for Rare Earth Fluorescence Enhancement

Abstract

The enhancement of the low absorption cross section and widening of the absorption range of the RE ions in the UV-blue region is still a challenge to develop optical systems with high performance. In this work we synthesized Bi- and Er-codoped Y2O3 nanocrystals by means of Pechini type sol-gel process. X-ray powder diffraction (XRPD) and transmission electron microscopy (TEM) were performed to evaluate the nanocrystalline particle size and phase. Photoluminescence investigation in the UV–vis and IR regions showed that the presence of Bi3+ ions promotes the strengthening of Er3+ emitter properties. In particular, an Er3+ sensitization process based on a broadband energy transfer mediated by the Bi3+ ions in the C2 site was evaluated, resulting in a wavelength spread for the photostimulation of the rare earth emissions in the visible and NIR range. We pointed out a resonant type via a dipole-dipole interaction as the most probable mechanism of energy transfer. Moreover, the critical distance between the Bi3+ and Er3+ ions was estimated to be of about 8.5 Å

Unprecedented Selenium and Lanthanide Simultaneously Bridging Selenotungstate Aggregates Stabilized by Four Tetra‐vacant Dawson‐like {Se2W14} Units

“…It can be clearly seen that all of the excitation spectra show a broad band in the range 210–260 nm derived from the 1 A 1g → 1 T 1u transitions of the O→W LMCT band of the tungsten‐oxygen cluster fragments as discussed above. In the range 390–500 nm in their excitation spectra, some excitation peaks assigned to the typical f–f transitions of Ln 3+ ions can be observed, that is, 7 F 4 → 5 D 3 (454 nm), 7 F 6 → 5 D 4 (475 nm) for 1 , 6 H 15/2 → 4 G 11/2 (428 nm), 6 H 15/2 → 4 I 15/2 (458 nm), 6 H 15/2 → 4 F 9/2 (479 nm) for 2 , 5 I 8 → 5 G 6 (443 nm), 5 I 8 → 5 F 3 (478 nm) for 3 , 4 I 15/2 → 4 F j (448 nm, 475 nm and 498 nm) for 4 , and 3 F 4 → 1 D 2 (447 nm) for 5 . Upon the excitation at 234 nm for 1 , 244 nm for 2 , 250 nm for 3 , 250 nm for 4 , and 230 nm for 5 from the oxygen‐to‐metal (O→W) charge‐transfer transitions, their emission spectra all exhibit the emission band attributed to the 3 T 1u → 1 A 1g transitions of tungsten‐oxygen cluster fragments in the range 400–500 nm and some emission peaks associated with the transitions of 5 D 4 → 7 F 6 (546 nm), 5 D 4 → 7 F 5 (583 nm), 5 D 4 → 7 F 4 (621 nm) for 1 , 4 F 9/2 → 6 H 13/2 (574 nm) for 2 , 5 F 4 + 5 S 2 → 5 I 8 (554 nm), 5 F 5 → 5 I 8 (656 nm) for 3 , 4 S 3/2 → 4 I 15/2 (556 nm) for 4 , and 1 D 2 → 3 F 4 (452 nm) for 5 of Ln 3+ ions.…”

“…5 F 3 (478 nm) for 3, 4 I 15/2 ! 4 F j (448 nm, 475 nm and 498 nm) for 4, [29] and 3 F 4 ! 1 D 2 (447 nm) for 5.…”

Energy transfer in color-tunable water-dispersible Tb–Eu codoped CaF2 nanocrystals

“…Therefore, while reserving for the future the development of fluorescence decay models, in the following we try to spread light on the nature of the observed energy transfer mechanism by means of studies based on the evolution of the donor emission intensity. The energy-transfer efficiency from Tb 3+ to Eu 3+ can be expressed by the following relation: 31,32 (1)…”

Multi‐phase glass‐ceramics containing CaF2: Er3+ and ZnAl2O4:Cr3+ nanocrystals for optical temperature sensing

“…The multi‐phase GC exhibits great advantages to realize both the FIR and fluorescence lifetime based thermometry methods for effective temperature sensing. At the same time, some experiments have shown that if both Ln 3+ and TM ions are doped into same host material then due to adverse energy transfers between the different active centers has resulted into quenching of the fluorescence . The typical host for Ln 3+ /TM ions is oxy‐fluoride GC, where Ln 3+ and TM ions could be partitioned into different host environments so as to suppress energy transfer between active ions and achieve high fluorescence efficiencies.…”