On Eu3+ luminescence in the hexagonal NaYF4 phase

Zakaria, Driss; Fournier, M.T.; Mahiou, Rachid; Cousseins, J.C.

doi:10.1016/0925-8388(92)90687-5

Cited by 22 publications

(11 citation statements)

References 9 publications

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“…The Stark levels of the 5 D 1 state of europium in NaYF 4 are separated by these small energies, typically ∼10 cm –1 . 37 For this reason, 10 nm NaYF 4 :Eu 3+ NCs are ideal to obtain further insight in the presence of phonon bottleneck effects in Ln-doped NCs. Figure 5a shows emission spectra of bulk NaYF 4 :Eu 3+ (0.3%) recorded in the temperature range between 4.2 and 44 K while exciting into the 5 D 2 level of Eu 3+ at 465.2 nm (21 496 cm –1 ) with a pulsed laser (peak intensity is 42 kW/cm 2 ).…”

Section: Resultsmentioning

confidence: 99%

“…The Stark levels of the 5 D 1 state of europium in NaYF 4 are separated by these small energies, typically ∼10 cm −1 . 37 For this reason, 10 nm NaYF 4 :Eu 3+ NCs are ideal to obtain further insight in the presence of phonon bottleneck effects in Ln-doped NCs.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

“…The positions of these emission lines agree reasonably well with the 19 013, 19 055, and 19 076 cm −1 previously reported in literature. 34,37 The energy gap between the 5 D 1 (1) level and the 5 D 1 (2) and 5 D 1 (3) levels are 10 and 32 cm −1 , respectively, which makes this system ideal to investigate the presence of the phonon bottleneck in Ln-doped NCs.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

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The Role of a Phonon Bottleneck in Relaxation Processes for Ln-Doped NaYF₄ Nanocrystals

et al. 2018

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The localized inner 4f shell transitions of lanthanide ions are largely independent of the local surroundings. The luminescence properties of Ln3+ ions doped into nanocrystals (NCs) are therefore similar to those in bulk crystals. Quantum size effects, responsible for the unique size-dependent luminescence of semiconductor NCs, are generally assumed not to influence the optical properties of Ln3+-doped insulator NCs. However, phonon confinement effects have been reported to hamper relaxation between closely spaced Stark levels in Ln3+-doped NCs. At cryogenic temperatures emission and excitation from higher Stark levels was observed for Ln3+ ions in NCs only and were explained by a cutoff in the acoustic phonon spectrum. Relaxation would be inhibited as no resonant low energy (long wavelength) acoustic phonon modes can exist in nanometer sized crystals, and this prevents relaxation by direct phonon emission between closely spaced Stark levels. This phenomenon is known as a phonon bottleneck. Here, we investigate the role of phonon confinement in Ln-doped NCs. High resolution emission spectra at temperatures down to 2.2 K are reported for various Ln3+ ions (Er3+, Yb3+, Eu3+) doped into monodisperse 10 nm NaYF4 NCs and compared with spectra for bulk (microcrystalline) material. Contrary to previous reports, we find no evidence for phonon bottleneck effects in the emission spectra. Emission from closely spaced higher Stark levels is observed only at high excitation powers and is explained by laser heating. The present results indicate that previously reported effects in NCs may not be caused by phonon confinement.

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Section: Resultsmentioning

confidence: 99%

Section: ■ Results and Discussionmentioning

confidence: 99%

Section: ■ Results and Discussionmentioning

confidence: 99%

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The Role of a Phonon Bottleneck in Relaxation Processes for Ln-Doped NaYF₄ Nanocrystals

et al. 2018

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“…The absence of the Eu 3+ -O 2-CT band in europium(III)-doped fluoride compounds can be used as an indication that no oxygen is built in the fluoride matrix and thus as a method for determination of the purity of fluoride compounds [251]. A strong charge-transfer band due to oxygen impurities was present in the reflection spectrum of NaEuF 4 [252]. Of course, such a charge-transfer band is also present in oxyfluorides, such as YOF:Eu 3+ [530,531].…”

Section: Transitions To Higher Energy Levelsmentioning

confidence: 96%

Interpretation of europium(III) spectra

Binnemans

2015

Coordination Chemistry Reviews

2,364

108

1,912

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“…[17] Colloidal solutions as well as powders of NaGdF 4 nanocrystals doped with 20 % of Yb 3+ and 2 % of Er 3+ display upconversion emission upon excitation with 975 nm light, [17] similar to NaYF 4 : Yb 3+ ,Er 3+ nanocrystals. [18][19][20] In addition, the optical properties of NaYF 4 : Eu 3+ nanocrystals have been investigated by the group of Mahiou et al [21] The synthesis of the cubic phase [18,22,23] as well as of the hexagonal phase of NaYF 4 and NaGdF 4 nanocrystals have been published in the literature. [22,[24][25][26][27][28] However, different temperatures have been employed to obtain each phase.…”

Section: Introductionmentioning

confidence: 99%

Crystal Phase Control of Luminescing α‐NaGdF₄:Eu³⁺and β‐NaGdF₄:Eu³⁺ Nanocrystals

Ptáček

Schäfer

Kömpe

et al. 2007

Adv Funct Materials

165

105

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NaGdF4:Eu3+, NaEuF4, and NaGdF4 nanocrystals were synthesized in the high‐boiling coordinating solvent N‐(2‐hydroxyethyl)‐ethylenediamine (HEEDA). Phase pure nanomaterials, crystallizing either in the cubic α‐phase or the hexagonal β‐phase, were obtained by adjusting one reaction parameter only, i.e., the molar ratio between metal and fluoride ions in the synthesis. The hexagonal β‐phase is formed, if this molar ratio is close to stoichiometric, whereas the cubic α‐phase is obtained in the presence of excess metal ions. The optical properties of the Eu3+ doped samples are different for the two crystal phases. The results indicate an increased number of oxygen impurities close to Eu3+ ions, if excess metal ions are used in the synthesis.

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On Eu3+ luminescence in the hexagonal NaYF4 phase

Cited by 22 publications

References 9 publications

The Role of a Phonon Bottleneck in Relaxation Processes for Ln-Doped NaYF₄ Nanocrystals

The Role of a Phonon Bottleneck in Relaxation Processes for Ln-Doped NaYF₄ Nanocrystals

Interpretation of europium(III) spectra

Crystal Phase Control of Luminescing α‐NaGdF₄:Eu³⁺and β‐NaGdF₄:Eu³⁺ Nanocrystals

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On Eu3+ luminescence in the hexagonal NaYF4 phase

Cited by 22 publications

References 9 publications

The Role of a Phonon Bottleneck in Relaxation Processes for Ln-Doped NaYF4 Nanocrystals

The Role of a Phonon Bottleneck in Relaxation Processes for Ln-Doped NaYF4 Nanocrystals

Interpretation of europium(III) spectra

Crystal Phase Control of Luminescing α‐NaGdF4:Eu3+and β‐NaGdF4:Eu3+ Nanocrystals

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Product

Resources

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The Role of a Phonon Bottleneck in Relaxation Processes for Ln-Doped NaYF₄ Nanocrystals

The Role of a Phonon Bottleneck in Relaxation Processes for Ln-Doped NaYF₄ Nanocrystals

Crystal Phase Control of Luminescing α‐NaGdF₄:Eu³⁺and β‐NaGdF₄:Eu³⁺ Nanocrystals