Modeling blue to UV upconversion in β-NaYF<sub>4</sub>:Tm<sup>3+</sup>

Villanueva-Delgado, Pedro; Krämer, Karl; Valiente, Rafael; Jong, Mathijs de; Meijerink, Andries

doi:10.1039/c6cp04347j

Cited by 40 publications

(50 citation statements)

References 38 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…This corresponds to a critical Förster radius of 9.2 Å for Er 3+ –Er 3+ cross-relaxation, a typical value for Förster transfer to a lanthanide acceptor. 42,51 For Er 3+ –Yb 3+ cross-relaxation we obtain 3.5 Å, somewhat shorter because of the energy mismatch for this pathway (Figure 3c). Alternatively, we can calculate a rate of 308 ms –1 for cross-relaxation from the green-emitting levels ( 2 H 11/2 and 4 S 3/2 ) to a nearest-neighbor Er 3+ ion or 1.0 ms –1 to a nearest-neighbor Yb 3+ ion, compared to a radiative decay rate of 1.6 ms –1 for NCs in toluene.…”

Section: Resultsmentioning

confidence: 85%

See 1 more Smart Citation

Quenching Pathways in NaYF₄:Er³⁺,Yb³⁺ Upconversion Nanocrystals

et al. 2018

Self Cite

View full text Add to dashboard Cite

Lanthanide-doped upconversion (UC) phosphors absorb low-energy infrared light and convert it into higher-energy visible light. Despite over 10 years of development, it has not been possible to synthesize nanocrystals (NCs) with UC efficiencies on a par with what can be achieved in bulk materials. To guide the design and realization of more efficient UC NCs, a better understanding is necessary of the loss pathways competing with UC. Here we study the excited-state dynamics of the workhorse UC material β-NaYF4 co-doped with Yb3+ and Er3+. For each of the energy levels involved in infrared-to-visible UC, we measure and model the competition between spontaneous emission, energy transfer between lanthanide ions, and other decay processes. An important quenching pathway is energy transfer to high-energy vibrations of solvent and/or ligand molecules surrounding the NCs, as evidenced by the effect of energy resonances between electronic transitions of the lanthanide ions and vibrations of the solvent molecules. We present a microscopic quantitative model for the quenching dynamics in UC NCs. It takes into account cross-relaxation at high lanthanide-doping concentration as well as Förster resonance energy transfer from lanthanide excited states to vibrational modes of molecules surrounding the UC NCs. Our model thereby provides insight in the inert-shell thickness required to prevent solvent quenching in NCs. Overall, the strongest contribution to reduced UC efficiencies in core–shell NCs comes from quenching of the near-infrared energy levels (Er3+: 4I11/2 and Yb3+: 2F5/2), which is likely due to vibrational coupling to OH– defects incorporated in the NCs during synthesis.

show abstract

Section: Resultsmentioning

confidence: 85%

“…49 This and other variations of and correlations between the rates of various UC steps can only be taken into account fully with a microscopic theoretical model that considers individual luminescent centers ( e . g ., Er 3+ and Yb 3+ ) explicitly, 51 as an alternative to the more common mean-field models. 35,52 …”

Section: Discussionmentioning

confidence: 99%

Quenching Pathways in NaYF₄:Er³⁺,Yb³⁺ Upconversion Nanocrystals

et al. 2018

Self Cite

View full text Add to dashboard Cite

show abstract

“…The core of all the nanoparticles under investigation contains an equivalent concentration of the sensitizer and activator ions and only the concentration of the Tb 3+ ions in the shell varies, to avoid the introduction of ulterior differences between the samples. The UCL mechanism of Yb 3+ , Tm 3+ co‐doped materials continues to be under investigation, as the population of the high‐energy states is disputed . Co‐doped materials with Tm 3+ and Yb 3+ undergo upconversion luminescence mainly through ETU.…”

Section: Resultsmentioning

confidence: 99%

Intrinsic Time‐Tunable Emissions in Core–Shell Upconverting Nanoparticle Systems

et al. 2019

View full text Add to dashboard Cite

Color‐tunable luminescence has been extensively investigated in upconverting nanoparticles for diverse applications, each exploiting emissions in different spectral regions. Manipulation of the emission wavelength is accomplished by varying the composition of the luminescent material or the characteristics of the excitation source. Herein, we propose core–shell β‐NaGdF4: Tm3+, Yb3+/β‐NaGdF4: Tb3+ nanoparticles as intrinsic time‐tunable luminescent materials. The time dependency of the emission wavelength only depends on the different decay time of the two emitters, without additional variation of the dopant concentration or pumping source. The time‐tunable emission was recorded with a commercially available camera. The dynamics of the emissions is thoroughly investigated, and we established that the energy transfer from the 1D2 excited state of Tm3+ ions to the higher energy excited states of Tb3+ ions to be the principal mechanism to the population of the 5D4 level for the Tb3+ ions.

show abstract

“…Some differences in the relative intensities of the Tm 3+ emission bands are observed for samples deposited on silicon and quartz substrates, in particular for the 1 D 2 → 3 F 4 and 1 G 4 → 3 H 6 emission transitions. Presently, this behavior cannot be easily rationalized, and it could be tentatively attributed to an effect of cross‐relaxation processes among the Tm 3+ ions, due to possible clustering of the lanthanide ions . Additional experiments using samples at different Tm 3+ concentration would be necessary in order to shed light on this issue.…”

Section: Values Of the A‐axis Parameters Of The Caf2:yb3+ Er3+ Filmsmentioning

confidence: 99%

Nanostructured CaF₂:Ln³⁺ (Ln³⁺ = Yb³⁺/Er³⁺, Yb³⁺/Tm³⁺) Thin Films: MOCVD Fabrication and Their Upconversion Properties

Pellegrino

Cortelletti

Pedroni

et al. 2017

Adv Materials Inter

View full text Add to dashboard Cite

it possible to collect the radiation energy outside the absorption range of the photoactive material (usually silicon) by shifting its energy to a more suitable optical region. In addition, rare-earth doped CaF 2 compounds are promising luminescent materials as phosphors and in technological applications as micro-and nanoscale thermometry for microelectronics and for biomedical assays. [4,[16][17][18] A comment deserves the CaF 2 structure, also in view of similar ionic size of the trivalent lanthanide ions, inserted as dopants, and the Ca 2+ ion. Calcium fluoride has the typical fluorite structure, following the name (fluorite) of the mineral form of CaF 2 , which is a simple cubic arrangement of anions with 50% cubic sites filled with Ca 2+ . Thus, in this structure, calcium is eight coordinated by fluoride ions, a coordination environment suitable for the lanthanide ions, being eight one of the most common coordination number for lanthanides. [19] Most of the above-mentioned applications require the calcium fluoride material in the form of thin films. Several studies are available on the deposition of CaF 2 thin films using physical vapor deposition techniques, such as sputtering, [20,21] electron beam evaporation, [22] pulsed laser deposition, [23,24] and molecular beam epitaxy. [25,26] Calcium fluoride films have also been deposited through sol-gel chemical routes using spin coating [27] or dip coating. [28] Among the chemical vapor deposition approaches, atomic layer deposition has been applied to the deposition of CaF 2 films. [29] Nevertheless, even though various deposition methods have been applied to the fabrication of CaF 2 films, a more versatile, easily scalable, fast, and industrially appealing approach is highly desirable.The metal organic chemical vapor deposition (MOCVD) has the potential advantage of being a very reliable and reproducible method for the fast production of films with high uniformity degree in both thickness and composition over large areas. In addition, note that in the case of potential integration of these layers in photovoltaic cell production, plasma-enhanced CVD is the most common fabrication method for thin film Si-based cells. [30] Calcium fluoride represents one of the most efficient hosts for up-conversion or down-conversion emissions. A simple metal organic chemical vapor deposition approach is applied to the fabrication of CaF 2 nanostructured thin films using the fluorinated "second-generation" β-diketonate compound Ca (hfa) 2 •diglyme•H 2 O as a Ca-F single-source precursor. The versatility of the process is demonstrated for the fabrication of up-converting Yb/Er or Yb/Tm codoped CaF 2 films on Si, quartz, and glass substrates. The Ln(hfa) 3 •diglyme (Ln = Tm, Er, Yb) precursors are used as sources of the doping ions. Structural, morphological, and compositional characterization of the films shows the formation of polycrystalline CaF 2 films with a very uniform surface and suitable doping. In fact, an appropriate tuning of the mixture composition, i.e., the Ca:Ln ...

show abstract

Modeling blue to UV upconversion in β-NaYF₄:Tm³⁺

Cited by 40 publications

References 38 publications

Quenching Pathways in NaYF₄:Er³⁺,Yb³⁺ Upconversion Nanocrystals

Quenching Pathways in NaYF₄:Er³⁺,Yb³⁺ Upconversion Nanocrystals

Intrinsic Time‐Tunable Emissions in Core–Shell Upconverting Nanoparticle Systems

Nanostructured CaF₂:Ln³⁺ (Ln³⁺ = Yb³⁺/Er³⁺, Yb³⁺/Tm³⁺) Thin Films: MOCVD Fabrication and Their Upconversion Properties

Contact Info

Product

Resources

About

Modeling blue to UV upconversion in β-NaYF4:Tm3+

Cited by 40 publications

References 38 publications

Quenching Pathways in NaYF4:Er3+,Yb3+ Upconversion Nanocrystals

Quenching Pathways in NaYF4:Er3+,Yb3+ Upconversion Nanocrystals

Intrinsic Time‐Tunable Emissions in Core–Shell Upconverting Nanoparticle Systems

Nanostructured CaF2:Ln3+ (Ln3+ = Yb3+/Er3+, Yb3+/Tm3+) Thin Films: MOCVD Fabrication and Their Upconversion Properties

Contact Info

Product

Resources

About

Modeling blue to UV upconversion in β-NaYF₄:Tm³⁺

Quenching Pathways in NaYF₄:Er³⁺,Yb³⁺ Upconversion Nanocrystals

Quenching Pathways in NaYF₄:Er³⁺,Yb³⁺ Upconversion Nanocrystals

Nanostructured CaF₂:Ln³⁺ (Ln³⁺ = Yb³⁺/Er³⁺, Yb³⁺/Tm³⁺) Thin Films: MOCVD Fabrication and Their Upconversion Properties