Probing the Crystal Structure and Formation Mechanism of Lanthanide-Doped Upconverting Nanocrystals

Hudry, Delphine; Abeykoon, A. M. Milinda; Dooryhée, E.; Nykypanchuk, Dmytro; Dickerson, James H.

doi:10.1021/acs.chemmater.6b04140

Cited by 28 publications

(24 citation statements)

References 50 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…As discussed in the Background section, our analysis of cross-relaxation requires knowledge of the Ln 3+ site structure in the lattice in order to determine the shell structure of acceptor sites surrounding each donor site. The crystal structure of hexagonal NaLnF 4 has been reported for several lanthanides, with some disagreement about the correct space group. − In the space group, P 6̅ there are two distinct sites, site 1 is occupied by a rare earth ion (Y 3+ , Yb 3+ , or Er 3+ ), and site 2 is occupied 50% by a rare earth and 50% by a sodium ion. As a result, with a statistical distribution, the donors are distributed as 2/3 in site 1 and 1/3 in site 2.…”

Section: Resultsmentioning

confidence: 99%

Cross-Relaxation from Er³⁺(²H_11/2,⁴S_3/2) and Er³⁺(²H_9/2) in β-NaYF₄:Yb,Er and Implications for Modeling Upconversion Dynamics

2019

View full text Add to dashboard Cite

We have implemented both the Dornauf− Heber (D−H) model and a brute force statistical (BFS) model to characterize the quenching by neighboring Er and Yb ions of the green and blue emitting states of Er in β-NaYF 4 :Yb,Er@NaYF 4 nanoparticles. Each of these models explicitly considers the radial distribution of Er and Yb acceptors around the two crystallographically distinct types of Er donor sites out to a user-specified donor−acceptor (D−A) cutoff distance, R a , beyond which the acceptor distribution is approximated as a spatial continuum. An algorithm is proposed for the BFS model, which makes it tractable to deal with the enormous number of possible acceptor distributions around the donor sites. The two models are compared for the convergence of fit values of critical energy-transfer distances, R 0 , as a function of the D−A cutoff distance, R a , for switching to the continuum approximation. The D−H model requires a much higher R a value (R a ≫ R 0 ) to achieve convergence compared to BFS, primarily because of the specific mathematical construct of the D−H model. The BFS model achieves convergence at R a ≈ R 0 , indicating that, on a purely physical basis, the continuum approximation is acceptable for D−A separations larger than the critical energy transfer distance. Both models do, however, ultimately converge to similar R 0 values. Our analysis shows that the green emission from Er ions, which have other Er ions occupying nearest neighbor sites, is almost completely quenched. In modeling upconversion, this subpopulation of Er ions should be treated as "dark" quenching sites for Yb 3+ ( 2 F 5/2 ) excitation. For an 18% Yb, 2% Er doping composition, approximately 10% of Er ions are "dark".

show abstract

Section: Resultsmentioning

confidence: 99%

Cross-Relaxation from Er³⁺(²H_11/2,⁴S_3/2) and Er³⁺(²H_9/2) in β-NaYF₄:Yb,Er and Implications for Modeling Upconversion Dynamics

2019

View full text Add to dashboard Cite

show abstract

“…For hexagonal NaGdF 4 :Yb,Er UCNs with the large-sized Gd 3+ ions, P6 was the optimal space group (Figure 2a). 36 In comparison, the P6 3 /m space group was the best to describe the structure of hexagonal NaYF 4 :Yb,Er UCNs with the small-sized Y 3+ ion. 37 By the use of PDF analysis, the local lattice distortion and dynamic nucleation and growth of UCNs 36 as well as the cation diffusion at the core−shell interface 38 can also be disclosed.…”

Section: Characterizations Of Local Structurementioning

confidence: 99%

Local Structure Engineering in Lanthanide-Doped Nanocrystals for Tunable Upconversion Emissions

2021

View full text Add to dashboard Cite

Upconversion emissions from lanthanide-doped nanocrystals have sparked extensive research interests in nanophotonics, biomedicine, photovoltaics, photocatalysis, etc. Rational modulation of upconversion emissions is highly desirable to meet the requirements of specific applications. Among the diverse developed methods, local structure engineering is fundamentally feasible, through which the upconversion emission intensity, selectivity, wavelength shift, and lifetime can be tuned effectively. The underlying mechanism of the local-structure-dependent upconversion emissions lies in the degree of parity hybridization and energy level splitting of lanthanide ions as well as the interionic energy transfer efficiency. Over the past few years, there has been significant progress in local-structure-engineered upconversion emissions. In this Perspective, we first introduce the principles of upconversion emissions and typical characterization methods for local structure. Subsequently, we summarize recent achievements in tuning of upconversion emissions through local structure engineering, including host composition adjustment, external field regulation, and interfacial strain management. Finally, we propose a few perspectives that should tackle the current bottlenecks. This Perspective is expected to deepen the understanding of local-structure-dependent upconversion emissions and arouse adequate attention to the engineering of local structure for desired properties of inorganic nanocrystals.

show abstract

“…Hexagonal lattice parameters were a = b = 5.915 Å and c = 3.496 Å, i.e. experimental ones [33]. The atomic positions were relaxed within the a-b plane, while the positions along c were kept fixed to the experimentally observed values [33].…”

Section: Theorymentioning

confidence: 99%

“…experimental ones [33]. The atomic positions were relaxed within the a-b plane, while the positions along c were kept fixed to the experimentally observed values [33]. Hexagonal 6×6×8 meshes corresponding to 288 k-points in the full Brillouin zone were used for structural optimization as well as for the calculation of dynamical matrices on a 2×2×2 hexagonal mesh.…”

Section: Theorymentioning

confidence: 99%

Phonon density of states in lanthanide-based nanocrystals

Hudry

Heid

et al. 2020

Phys. Rev. B

Self Cite

View full text Add to dashboard Cite

We report a combined inelastic neutron and X-ray scattering study of the phonon density of states of the nano-and microcrystalline lanthanide-based materials NaY0.8Yb0.18Er0.02F4 and NaGd0.8Yb0.18Er0.02F4. While large (20 nm) nanocrystals display the same vibrational spectra as their microcrystalline counterparts, we find an enhanced phonon density of states at low energies, E ≤ 15 meV, in ultra-small (5 nm) NaGd0.8Yb0.18Er0.02F4 nanocrystals which we assign to an increased relative spectral weight of surface phonon modes. Based on our observations for ultra-small nanocrystals, we rationalize that an increase of the phonon density of states in large nanocrystals due to surface phonons is too small to be observed in the current measurements. The experimental approach described in this report constitutes the first step toward the rationalization of size effects on the modification of the absolute upconversion quantum yield of upconverting nanocrystals.

show abstract

Probing the Crystal Structure and Formation Mechanism of Lanthanide-Doped Upconverting Nanocrystals

Abstract: Probing the crystal structure and formation mechanism of lanthanide-doped upconverting nanocrystals.

Cited by 28 publications

References 50 publications

Cross-Relaxation from Er³⁺(²H_11/2,⁴S_3/2) and Er³⁺(²H_9/2) in β-NaYF₄:Yb,Er and Implications for Modeling Upconversion Dynamics

Cross-Relaxation from Er³⁺(²H_11/2,⁴S_3/2) and Er³⁺(²H_9/2) in β-NaYF₄:Yb,Er and Implications for Modeling Upconversion Dynamics

Local Structure Engineering in Lanthanide-Doped Nanocrystals for Tunable Upconversion Emissions

Phonon density of states in lanthanide-based nanocrystals

Contact Info

Product

Resources

About

Probing the Crystal Structure and Formation Mechanism of Lanthanide-Doped Upconverting Nanocrystals

Abstract: Probing the crystal structure and formation mechanism of lanthanide-doped upconverting nanocrystals.

Cited by 28 publications

References 50 publications

Cross-Relaxation from Er3+(2H11/2,4S3/2) and Er3+(2H9/2) in β-NaYF4:Yb,Er and Implications for Modeling Upconversion Dynamics

Cross-Relaxation from Er3+(2H11/2,4S3/2) and Er3+(2H9/2) in β-NaYF4:Yb,Er and Implications for Modeling Upconversion Dynamics

Local Structure Engineering in Lanthanide-Doped Nanocrystals for Tunable Upconversion Emissions

Phonon density of states in lanthanide-based nanocrystals

Contact Info

Product

Resources

About

Cross-Relaxation from Er³⁺(²H_11/2,⁴S_3/2) and Er³⁺(²H_9/2) in β-NaYF₄:Yb,Er and Implications for Modeling Upconversion Dynamics

Cross-Relaxation from Er³⁺(²H_11/2,⁴S_3/2) and Er³⁺(²H_9/2) in β-NaYF₄:Yb,Er and Implications for Modeling Upconversion Dynamics