Energy Transfer between Tb³⁺ and Eu³⁺ in LaPO₄: Pulsed versus Switched‐off Continuous Wave Excitation

Abstract

The energy transfer (ET) between Tb 3+ and Eu 3+ is investigated experimentally and with available theoretical models in the regime of high Tb 3+ concentrations in ≈30 nm LaPO 4 nanoparticles at room temperature. The ET efficiency approaches 100% even for lightly Eu 3+ ‐doped materials. The major conclusion from the use of pulsed laser excitation and switched‐off continuous wave laser diode excitation is that the energy migration between Tb 3+ ions, situated on La 3+ sites with ≈4 Å separation, is not fast. The quenching of Tb 3+ emission in singly doped LaPO 4 only reduces the luminescence lifetime by ≈50% in heavily doped samples. Various theoretical models are applied to simulate the luminescence decays of Tb 3+ and Tb 3+ , Eu 3+ ‐doped LaPO 4 samples of various concentrations and the transfer mechanism is identified as forced electric dipole at each ion.

Host Differential Sensitization toward Color/Lifetime‐Tuned Lanthanide Coordination Polymers for Optical Multiplexing

“…The results show that only the Y‐T model can well fit the decay curves of Tb 3+ (Figure 2 f) and simultaneously the obtained physical parameters are meaningful (Table S10). It indicates that the slow EM process between donor Tb 3+ plays a leading role in Tb 3+ ‐Sm 3+ ET dynamics and similar phenomenon is also observed in Tb 3+ , Eu 3+ doped LaPO 4 nanocrystals [40] . Moreover, the main Tb 3+ ‐Sm 3+ ET mechanism is electric dipole‐dipole (EDD) interaction, the microparameter C DA for Tb 3+ ‐Sm 3+ ET process is ≈7.203×10 −52 m 6 s −1 and the microparameter C DD for Tb 3+ ‐Tb 3+ EM process is ≈3.134×10 −54 m 6 s −1 .…”

“…As shown in Figure S9, the luminescence decay curves of donor Tb 3+ ions gradually drop faster and the corresponding lifetime values decrease from ≈588 to ≈301 μs with the increase of Eu 3+ ions, which confirm the depopulation of Tb 3+ excited states by CRET process from Tb 3+ to Eu 3+ ions. Furthermore, it's well studied that the main mechanism of Tb 3+ ‐Eu 3+ CRET process is electric dipole‐dipole (EDD) interaction and the dominant CRET channel is [ 5 D 4 (Tb 3+ ), 7 F 0, 1 (Eu 3+ ) → 7 F 4 (Tb 3+ ), 5 D 0 (Eu 3+ )] (Figure S10) [38–40] . As for Tb x Sm z ‐BTC ( x =0.70, z =0–0.10) samples, under the host excitation the green emission of “sounding” Tb 3+ is dominant while that of “silent” Sm 3+ is negligible (Figure 2 e), which results from the differential sensitization effect of host.…”

“…It indicates that the slow EM process between donor Tb 3+ plays al eading role in Tb 3+ -Sm 3+ ET dynamics and similar phenomenon is also observed in Tb 3+ ,E u 3+ doped LaPO 4 nanocrystals. [40] Moreover,t he main Tb 3+ -Sm 3+ ET mechanism is electric dipole-dipole (EDD) interaction, the microparameter C DA for Tb 3+ -Sm 3+ ET process is % 7.203 10 À52 m 6 s À1 and the microparameter C DD for Tb 3+ -Tb 3+ EM process is % 3.134 10 À54 m 6 s À1 .S ee Figure S13…”

Mechanistic Insight into Energy‐Transfer Dynamics and Color Tunability of Na4CaSi3O9:Tb3+,Eu3+ for Warm White LEDs

“…Considering that the energy difference between spin-allowed and spin-forbidden 4f-5d transitions of Tb 3 + is usually 1.0 eV, [14] bands Ca nd Dc an be assigned to Tb 3 + spin-forbidden 4f-5d J excitations with its5 d electrons in the high-spin (HS) state. The excitation peaks from 300 to 400 nm are assigned to 7 inset. Upon 376 nm excitation,t he sample demonstrates intense green light emission,s uggesting its potential application as ag reen light phosphor in WLED devices.…”

“…[5] More importantly,T b 3 + can serve as a sensitizer to widen the Eu 3 + absorption through ET,f urther enhancing the luminescent intensity of Eu 3 + . [6,7] However,i ti si mperative to elucidate the ET mechanism through theoretical analysis.…”