The standard and anomalous crystal-field spectra of Eu3+

Dual-Mode Nanoprobes Based on Lanthanide Doped Fluoride Nanoparticles Functionalized by Aryl Diazonium Salts for Fluorescence and SERS Bioimaging

The design of dual-mode fluorescence and Raman tags stimulates a growing interest in biomedical imaging and sensing applications as they offer the possibility to synergistically combine the versatility and velocity of fluorescence imaging with the specificity of Raman spectroscopy. Although lanthanide-doped fluoride nanoparticles (NPs) are among the most studied fluorescent nanoprobes, their use for the development of bimodal fluorescent-Raman probes has never been reported yet, to the best of the authors knowledge, probably due to the difficulty to functionalize them with Raman reporter groups. This gap is filled herein by proposing a fast and straightforward approach based on aryl diazonium salt chemistry to functionalize Eu3+ or Tb3+ doped CaF2 and LaF3 NPs by Raman scatters. The resulting surface-enhanced Raman spectroscopy (SERS)-encoded lanthanide-doped fluoride NPs retain their fluorescence labeling capacity and display efficient SERS activity for cell bioimaging. The potential of this new generation of bimodal nanoprobes is assessed through cell viability assays and intracellular fluorescence and Raman imaging, opening up unprecedented opportunities for biomedical applications.

A Photoluminescence Study of Eu3+, Tb3+, Ce3+ Emission in Doped Crystals of Strontium-Barium Fluoride Borate Solid Solution Ba4-xSr3+x(BO3)4-yF2+3y (BSBF)

The present study is aimed at unveiling the luminescence potential of Ba4-xSr3+x(BO3)4-yF2+3y (BSBF) crystals doped with Eu3+, Tb3+, and Ce3+. Owing to the incongruent melting character of the phase, the NaF compound was used as a solvent for BSBF crystal growth. The structure of BSBF: Eu3+ with Eu2O3 concentration of about 0.7(3) wt% was solved in the non-centrosymmetric point group P63mc. The presence of Eu2O3 in BSBF: Eu3+ leads to a shift of the absorption edge from 225 nm to 320 nm. The photoluminescence properties of the BSBF: Ce3+, BSBF: Tb3+, BSBF: Eu3+, and BSBF: Eu3+, Tb3+, Ce3+ crystals have been studied. The unusual feature of europium emission in BSBF is the intensively manifested 5D0→7F0 transition at about 574 nm, which is the strongest for BSBF: Eu3+ at 370 nm excitation and for BSBF: Eu3+, Tb3+, Ce3+ at 300 nm and 370 nm excitations. No evidence of Tb3+→Eu3+ energy transfer was found for BSBF: Eu3+, Tb3+, Ce3+. The PL spectra of BSBF: Eu3+ at 77 and 300 K are similar with CIE chromaticity coordinates of (0.617; 0.378) at 300 nm excitation and (0.634; 0.359) at 395 nm excitation and low correlated color temperature which implies application prospects in the field of lightning. Due to the high intensity of 5D0→7F0 Eu3+ transition at 370 nm excitation, the BSBF: Eu3+ emission is yellow-shifted.

A Comparative Study of Eu3+-Doped Sillenites: Bi12SiO20 (BSO) and Bi12GeO20 (BGO)

The spectroscopic properties of Eu³⁺-doped Bi₁₂SiO₂₀ (BSO) were investigated and compared with that of Eu³⁺-doped Bi₁₂GeO₂₀ (BGO). The emission properties and the absorption spectra have been measured at 10 K as well as at 300 K (room temperature). Luminescence was detected due to the direct excitation of the ⁵D₀ level of Eu³⁺, as well as through the excitation of the ⁵D₁ level. The Judd-Ofelt theoretical framework was used to compute the radiative lifetimes (τ) and the omega parameters (Ω_λ). The electric dipole transition probabilities, asymmetry ratios (R), along with the branching ratios (β) were also determined based on the obtained experimental data. The strongest detected luminescence belongs to the ⁵D₀ → ⁷F₀ transition observed at 578 nm, similar to the BGO sillenite. Reasons for the major presence of the ⁵D₀ → ⁷F₀ emission, theoretically forbidden by the Judd-Ofelt Theory, were investigated and compared with that of the BGO sillenite. Obtained results showed that the strong ⁵D₀ → ⁷F₀ line is also present in Eu:BSO, indicating that this is a feature of the entire sillenite family and not just Eu:BGO.

Structural, Spectroscopic, and Biological Characterization of Novel Rubidium(I) and Europium(III) Co-Doped Nano-Hydroxyapatite Materials and Their Potential Use in Regenerative Medicine

This research investigates hydrothermally synthesized hydroxyapatite nanoparticles doped with rubidium(I) and europium(III) ions. Investigation focused on establishing the influence of co-doped Eu³⁺ and Rb⁺ ions on hydroxyapatite lattice. Therefore, structural, and morphological properties were characterized via using X-ray powder diffraction (XRPD), infrared spectroscopy (FT-IR), and scanning electron microscopy (SEM), as well as transmission electron microscopy (TEM) techniques. Furthermore, this investigation evaluates the impact of various Rb⁺ ion doping concentrations on the distinct red emission of co-doped Eu³⁺ ions. Hence, luminescence properties of the obtained materials were evaluated by measuring emission excitation, emission spectra, and luminescence decays. As established by numerous studies, synthetic hydroxyapatite has excellent application in biomedical field, as it is fully biocompatible. Its biocompatible makes it highly useful in the biomedical field as a bone fracture filler or hydroxyapatite coated dental implant. By the incorporation of Eu³⁺ ions and Rb⁺ ions we established the impact these co-doped ions have on the biocompatibility of hydroxyapatite powders. Therefore, biocompatibility toward a ram's red blood cells was evaluated to exclude potential cytotoxic features of the synthesized compounds. Additionally, experimental in vitro bioactive properties of hydroxyapatite nanoparticles doped with Rb⁺ and Eu³⁺ ions were established using a mouse osteoblast model. These properties are discussed in detail as they contribute to a novel method in regenerative medicine.

Excitation-Dependent Photoluminescence of BaZrO3:Eu3+ Crystals

The elucidation of local structure, excitation-dependent spectroscopy, and defect engineering in lanthanide ion-doped phosphors was a focal point of research. In this work, we have studied Eu³⁺-doped BaZrO₃ (BZOE) submicron crystals that were synthesized by a molten salt method. The BZOE crystals show orange-red emission tunability under the host and dopant excitations at 279 nm and 395 nm, respectively, and the difference is determined in terms of the asymmetry ratio, Stark splitting, and intensity of the uncommon ⁵D₀ → ⁷F₀ transition. These distinct spectral features remain unaltered under different excitations for the BZOE crystals with Eu³⁺ concentrations of 0-10.0%. The 2.0% Eu³⁺-doped BZOE crystals display the best optical performance in terms of excitation/emission intensity, lifetime, and quantum yield. The X-ray absorption near the edge structure spectral data suggest europium, barium, and zirconium ions to be stabilized in +3, +2, and +4 oxidation states, respectively. The extended X-ray absorption fine structure spectral analysis confirms that, below 2.0% doping, the Eu³⁺ ions occupy the six-coordinated Zr⁴⁺ sites. This work gives complete information about the BZOE phosphor in terms of the dopant oxidation state, the local structure, the excitation-dependent photoluminescence (PL), the concentration-dependent PL, and the origin of PL. Such a complete photophysical analysis opens up a new pathway in perovskite research in the area of phosphors and scintillators with tunable properties.

A high-sensitivity rapid acquisition spectrometer for lanthanide(III) luminescence

Detecting luminescence beyond 750-800 nm becomes problematic as most conventional detectors are less sensitive in this range, and as simple corrections stops being accurate. Lanthanide luminescence occurs in narrow bands across the spectrum from 350-2000 nm. The most emissive lanthanide(III) ions have bands from 450 nm to 850 nm, some with additional bands in the NIR. Investigating the NIR bands are hard, but the difficulties start already at 700 nm. In general, the photon flux from lanthanide(III) emitters is not great, and the bands beyond 700 nm are very weak, we therefore decided to build a spectrometer based on cameras for microscopy with single-photon detection capabilities. This was found to allieviate all limitations and to allow for fast and efficient recording of luminescence spectra in the range from 450 to 950 nm. The spectrometer characteristics were investigated and the performance was benchmarked against two commercial spectrometers. We conclude that this spectrometer is ideal for investigating lanthanide luminescence, an all other emitters with emission in the target range.

Lanthanide (Eu, Tb, La)-Doped ZnO Nanoparticles Synthesized Using Whey as an Eco-Friendly Chelating Agent

Strategies for production and use of nanomaterials have rapidly moved towards safety and sustainability. Beyond these requirements, the novel routes must prove to be able to preserve and even improve the performance of the resulting nanomaterials. Increasing demand of high-performance nanomaterials is mostly related to electronic components, solar energy harvesting devices, pharmaceutical industries, biosensors, and photocatalysis. Among nanomaterials, Zinc oxide (ZnO) is of special interest, mainly due to its environmental compatibility and vast myriad of possibilities related to the tuning and the enhancement of ZnO properties. Doping plays a crucial role in this scenario. In this work we report and discuss the properties of undoped ZnO as well as lanthanide (Eu, Tb, and La)-doped ZnO nanoparticles obtained by using whey, a by-product of milk processing, as a chelating agent, without using citrate nor any other chelators. The route showed to be very effective and feasible for the affordable large-scale production of both pristine and doped ZnO nanoparticles in powder form.

Vacuum ultraviolet photoluminescence of NaMgF3:Sm and NaMgF3:Sm,Ce: Energy levels of the lanthanides in NaMgF3:Ln compounds

The luminescence properties of NaMgF₃:Sm and NaMgF₃:Ce,Sm were studied in the vacuum ultraviolet spectral region. Excitation bands corresponding to the charge transfer processes F^-→ Sm³⁺, O^2-→ Sm³⁺, and O^2-→ Ce³⁺, and the energy transfer processes Ce³⁺→ Sm³⁺and O^2-→ Sm³⁺, were observed. The energies of the Sm³⁺charge transfer transitions and the crystal field split Ce³⁺4f⁰5d¹transitions were used to construct a complete host referred binding energy diagram for the series of lanthanide-doped NaMgF₃:Ln compounds. We demonstrate that the optical and luminescence properties predicted by the binding energy diagram are in good agreement with those predicted by the binding energy diagram constructed via the alternative impurity-informed method, and all available experimental data regarding the NaMgF₃:Ln compounds. We demonstrate that NaMgF₃:Ln compounds are model systems for the study of charge trapping phenomena and divalent lanthanide luminescence. Ultimately, we validate that the impurity-informed method can be used to establish the energy levels of lanthanides in fluoride systems.

Self-referenced method for the Judd-Ofelt parametrisation of the Eu3+ excitation spectrum

Judd–Ofelt theory is a cornerstone of lanthanides’ spectroscopy given that it describes 4fⁿ emissions and absorptions of lanthanide ions using only three intensity parameters. A self-referenced technique for computing Judd–Ofelt intensity parameters from the excitation spectra of Eu³⁺-activated luminescent materials is presented in this study along with an explanation of the parametrisation procedure and free user-friendly web application. It uses the integrated intensities of the ⁷F₀ → ⁵D₂, ⁷F₀ → ⁵D₄, and ⁷F₀ → ⁵L₆ transitions in the excitation spectrum for estimation and the integrated intensity of the ⁷F₀ → ⁵D₁ magnetic dipole transition for calibration. This approach facilitates an effortless derivation of the Ω₆ intensity parameter, which is challenging to compute precisely by Krupke’s parametrisation of the emission spectrum and, therefore, often omitted in published research papers. Compared to the parametrisation of absorption spectra, the described method is more accurate, can be applied to any material form, and requires a single excitation spectrum.

Revealing Eu3+-doped yttrium pyrogermanate as a soft UV excitable phosphor: retaining the pros of the commercial phosphor and compensating for the cons

This article presents the synthesis of a single-phase red emitting Y2Ge2O7:Eu3+ soft-UV excitable phosphor with up to 10% Eu3+ content. Experimental and theoretical exploration has established its relative potential with respect to the commercial Y2O3:Eu3+ phosphor.

Microstructural origin of peculiar spectra and excellent luminescence properties of Y10Ta4O25:Eu3+ with a fluorite-related structure

Y10Ta4O25:Eu3+ presents peculiar spectra and excellent red luminescence properties due to its special fluorite-related structure. The microstructure was characterized by the site-selective luminescence of Eu3+ activators.

Probing structural and photophysical features of Eu3+ activated NaCdPO4 orthophosphate phosphor

A series of Eu³⁺ doped NaCd_1-xPO₄: x Eu³⁺ (0 ≤ x ≤ 0.1) phosphors were synthesized and a systematic investigation of structural, morphological, optical and photophysical properties were carried out. Structural characteristics were analyzed both qualitatively as well as quantitatively to establish the phase purity, supported by FTIR and Raman spectroscopy methods. The valance state of the dopant, as well as surface elemental compositions were investigated by XPS technique. The optical characteristics were analyzed by employing UV-Visible DRS, which shows that the host bandgap is getting broadened upon doping as a result of the Burstein-Moss (BM) effect. Eu³⁺ doped phosphor exhibits emissions rich in red (617 nm) under suitable excitations at 393 nm while the optimal doping concentration was found to be around x = 0.06. The effective non-radiative transfer of energy from host to activator is governed by the dominant dipole-dipole transitions. The hypersensitive transition line ⁵D₀ → ⁷F₂ is observed owing to the induced electric dipole (ED) transition of Eu³⁺ centered at 617 nm. Local site symmetry has been analyzed to ascertain the environment around Eu³⁺ and presence of any non-equivalent cation sites. The concentration quenching effect of phosphors was explained on the basis of Dexter's theory and charge compensation mechanism. The Commission Internationale de l'Eclairage (CIE 1931) chromaticity coordinates for the prepared phosphors were estimated and found to lie in the red region of color space. The photoluminescence decay time was measured for the most intense emission line ⁵D₀ → ⁷F₂ at 617 nm under 393 nm excitation and the results indicate that Eu³⁺ activated NaCdPO₄ can be a suitable red phosphor for white LED using UV-LED chip owing to it's near UV-excitation characteristics.

The effect of lithium on structural and luminescence performance of tunable light-emitting nanophosphors for white LEDs

Li⁺ incorporated tunable Y₂O₃:Eu³⁺ red-emitting nanophosphors were synthesized using a wet chemical method. The effect of Li⁺ on structural and luminescence properties of the nanophosphors were studied in detail. The structural results exhibited that nanophosphors have a body-centered cubic (I) phase with point group symmetry m3̄. No additional impurity peaks were observed within the range of the XRD pattern due to the Li⁺ ion. FTIR spectra reveal the formation of the pure and crystalline structure of the nanophosphors. TEM results show the prepared nanophosphors were highly crystalline and polycrystalline in nature. PL studies show the highly enhanced emission band due to the flux effect, greatly improved crystallinity caused by the Li⁺ ion, and the different excitation wavelengths. The most intense luminescence band was observed at 612 nm for red emission ascribed to the ⁵D₀ → ⁷F₂ transition of Eu³⁺ ion upon 254, 393, and 465 nm excitations in the C_3i and C₂ symmetry site of Y₂O₃ respectively. The highly enhanced emission band was observed under excitation at 254 nm and is 6.9 and 3.67 times higher than the emission band excited at 393 and 466 nm, respectively. The average lifetime also varies with different concentrations of Li⁺ ions. The chromaticity color coordinates, CCT values, were tuned in the red region of the color space. Hence, the results indicate that the prepared nanophosphor can be used as a red component to construct the white light for light-emitting diode applications.

Li⁺ incorporated tunable Y₂O₃:Eu³⁺ red-emitting nanophosphors were synthesized using a wet chemical method.

Optical Investigation of Eu3+ Doped Bi12GeO20 (BGO) Crystals

The spectroscopic properties of Eu3+ doped Bi12GeO20 (BGO) sillenite bulk crystals that were grown by the low-thermal-gradient Czochralski technique (LTG Cz) were investigated. The absorption spectra and the emission properties have been measured at room temperature (300 K) and at 10 K. Luminescence was observed both due to the direct Eu3+ ion excitation, as well as under UV excitation due to the energy transfer between Bi3+ and Eu3+ ions. Bi3+ → Eu3+ energy transfer mechanisms in Eu3+:BGO doped host were investigated. The Ωλ parameters, as well as radiative lifetimes, were calculated based upon the Judd-Ofelt formalism. The branching ratios and electric dipole transition probabilities were also determined, based upon the obtained experimental results. Luminescence has been observed from the 5D0,1,2 levels of Eu3+, with emissions from the 5D0 level being the strongest. The strongest observed luminescence band corresponds to the 5D0 → 7F0 transition at 578.7 nm. Reasons for the strong presence of the theoretically forbidden 5D0 → 7F0 emission were investigated.

Simultaneous tuning of optical and electrical properties in a multifunctional LiNbO3 matrix upon doping with Eu3+ ions

Combined photoluminescence (PL) and dielectric studies have been carried out on both undoped and Eu³⁺ doped LiNbO₃ compounds for their potential application in optical–electrical integration for the first time. Special focus has been given to simultaneously tuning both these physical properties. A PL study reveals that the blank compound is a blue emitting material, while upon doping with Eu³⁺ ions, the emitting color can be tuned from blue to red upon changing the excitation wavelength. Interestingly, the electrical property measurement of this ferroelectric compound showed that upon doping with Eu³⁺ ions, the remnant polarization was increased significantly. Density Functional Theory (DFT) based calculations were carried out to explain both the optical and electrical properties. It has been found that different defect centers are responsible for the bluish host emission while Eu³⁺ ions are energetically preferred to occupy the Nb site and gives rise to red emission. The DFT based results also showed that Eu³⁺ ions induced more distortion into the nearby Nb-site, which is responsible for enhancement of the remnant polarization. Stark-splitting patterns in the PL study also showed that the point symmetry of LiNbO₃ upon Eu³⁺ doping changes from C_6v to D₃, which indicates that the structure becomes less symmetric. Overall, the study presents a novel approach to designing multifunctional materials for optical–electrical integration application and to tuning their physical properties simultaneously in the desired range.

PL and dielectric studies have been carried out on LiNbO₃ and Eu³⁺:LiNbO₃ compounds with a special focus on simultaneous tuning of optical and electrical properties for their potential application in optical–electrical integration.

Photoluminescence control and abnormal Eu3+ orange emission in Ln3+ (Ln3+ = Ce3+, Eu3+)-doped oxyapatite-type phosphors

Controllable photoluminescence adjustment of Ce³⁺/Eu³⁺-doped phosphors.

Photochromic and luminescent switchable iodoargentate hybrids directed by solvated lanthanide cations

A series of photochromic and luminescent switchable iodoargentate hybrids have been constructed by using solvated lanthanide cations as SDAs.

Luminescent behavior of Eu3+ doped BaHfO3 perovskite ceramic under UV radiation

In this paper, luminescent properties of Europium trivalent ion in the matrix with unbalanced charge of barium hafnate under UV radiation, with special emphasis on the ⁵D₀ → ⁷F₀ transition are reported. The synthesis was conducted by the hydrothermal route at 200 °C with a reaction time of 90 min using chlorides as raw materials. In order to determinate the luminescent quenching concentration, the samples were doped with different amounts of Europium trivalent ions being the sample doped with 1 and 3% at of Eu³⁺ which shows the highest luminescent emission. X-ray diffraction analysis showed that the material crystallize in the cubic perovskite structure with space group Pm-3m. The Energy Dispersive Spectroscopy (EDS) shows there are not elements other those that Ba, Hf, O and Eu in the synthesized material. Photoluminescent emission spectra show peaks of emission associated with the ⁵D₀ → ⁷F_J (J = 0,1,2,3,4) transitions, characteristics of europium ion. The ⁵D₀ → ⁷F₀ transition centered at 580 nm showed an unusual great intensity when it was excited with the wavelength associated with the charge transfer band (272 nm). Finally the decay time was measured in the ⁵D₀ → ⁷F_J (J = 0,1,2,3,4) transitions using the sample doped with Eu³⁺ (3% at).

Temperature-Induced Structural Transformations in Undoped and Eu3+-Doped Ruddlesden-Popper Phases Sr2SnO4 and Sr3Sn2O7: Relation to the Impedance and Luminescence Behaviors

We report that luminescence of Eu³⁺ ion incorporated into Ruddlesden-Popper phases allows monitoring phase transition in powders (instead of single crystals), in a time-efficient manner (compared to neutron diffraction), and importantly, with greater sensitivity than previous methods. Crystal structure and dielectric response of undoped and 0.5%Eu³⁺-doped Sr₃Sn₂O₇ ceramics were studied as a function of temperature over the temperature range of 300-800 K. The luminescence studies of 0.5%Eu³⁺-doped Sr₂SnO₄ and Sr₃Sn₂O₇ samples were performed in the temperature range of 80-500 K. These results were compared with the respective dependences for the undoped compounds. The structural transformations in 0.5%Eu³⁺-doped Sr₃Sn₂O₇ were found at 390 and 740 K. The former is associated with the isostructural atomic rearrangement that resulted in a negative thermal expansion along two of three orthorhombic crystallographic axes, while the latter corresponds to the structural transition from the orthorhombic Amam phase to the tetragonal I4/mmm one. A similar temperature behavior with the structural transformations in the same temperature ranges was observed in undoped Sr₃Sn₂O₇, although the values of lattice parameters of the Eu³⁺-doped and undoped compounds were found to be slightly different indicating an incorporation of europium in the crystal lattice. A dielectric anomaly associated with a structural phase transition was observed in Sr₃Sn₂O₇ at 390 K. Optical measurements performed over a wide temperature range demonstrated a clear correlation between structural transformations in Eu³⁺-doped Sr₂SnO₄ and Sr₃Sn₂O₇ and the temperature anomalies of their luminescence spectra, suggesting the efficacy of this method for the determination of subtle phase transformations.

Site preference for luminescent activator ions in doped fluoroperovskite RbZnF3

With the dual objective of investigating the site preferences of larger sized activator ions and to append luminescence property to the perovskite structured RbZnF₃, doping of manganese(II), cerium(III), europium(III) and terbium(III) ions (5 mol%) was carried out. Although cubic symmetry of RbZnF₃ was preserved for all the doped samples, site preference of rare-earth ions for the A-site Rb⁺ leading to an inverse perovskite arrangement has been noticed from careful analysis of lattice parameters from refinement of powder X-ray diffraction data. Undoped RbZnF₃ exhibited rod-like morphology in the transmission electron microscopic image. In addition to an intense band around 230 nm assignable to the charge transfer from ZnF₃^- to Rb⁺, typical transitions of respective dopant ions were observed in their UV-visible spectra. The doped samples showed luminescence in blue, green and red regions and time decay experiments suggested uniform dispersion of them without any clustering effect. The lower phonon energy of RbZnF₃ matrix by virtue of the presence of heavier rubidium at the A-site together with its doping with rare-earth ions resulting in an inverse perovskite like arrangement could favour their utility in various practical applications.

Role of Synthesis Method on Luminescence Properties of Europium(II, III) Ions in β-Ca2SiO4: Probing Local Site and Structure

The europium ion probes the symmetry disorder in the crystal structure, although the distortion due to charge compensation in the case of aliovalent dopant remains interesting, especially preparation involves low and high temperatures. This work studies the preparation of the β-Ca₂SiO₄ (from here on C₂S) particle from Pechini (C₂SP) and hydrothermal (C₂SH) methods, and its luminescence variance upon doping with Eu²⁺ and Eu³⁺ ions. The blue shift of the charge-transfer band (CTB) in the excitation spectra indicates a larger Eu³⁺-O^2- distance in Eu³⁺ doped C₂SH. The changes in vibrational frequencies due to stretching and bending vibrations in the FTIR and the Raman spectra and binding energy shift in the XPS analysis confirmed the distorted SiO₄^4- tetrahedra in C₂SH. The high hydrothermal temperature and pressure produce distortion, which leads to symmetry lowering although doping of aliovalent ion may slightly change the position of the Ca atoms. The increasing asymmetry ratio value from C₂SP to C₂SH clearly indicates that the europium ion stabilized in a more distorted geometry. It is also supported by Judd-Ofelt analysis. The concentration quenching and site-occupancy of Eu³⁺ ions in two nonequivalent sites of C₂S were discussed. The charge state and concentration of europium ions in C₂SP and C₂SH were determined using X-ray photoelectron spectroscopy measurements. The C₂S particles were studied by X-ray powder diffraction, FTIR, Raman, BET surface area, TGA/DTA, electron microscopy, XPS, and luminescence spectroscopy. The impact of citrate ion on the morphology and particle size of C₂SH has been hypothesized on the basis of the microscopy images. This study provides insights that are needed for further understanding the structure of C₂S and thereby improves the applications in optical and biomedical areas and cement hydration.

Exploitation of Eu3+ red luminescence through order–disorder structural transitions in lanthanide stannate pyrochlores for warm white LED applications

The structural transition from an ordered pyrochlore to a fluorite-type structure in Ln_2.85YSnNbO_10.5:0.15Eu³⁺ (Ln = La, Gd, Y, and Lu) provides a gateway for exploiting Eu³⁺ red luminescence for warm white LED applications.

Iodoargentates from clusters to 1D chains and 2D layers induced by solvated lanthanide complex cations: syntheses, crystal structures, and photoluminescence properties

Lanthanide(iii) iodoargentates [Ln(DMSO)₈]₄Ag₂₂I₃₄·2H₂O (Ln = La (1), Ce (2)), [Ln(DMSO)₈]Ag₇I₁₀(Ln = Eu (3), Tb (4), Dy (5)), and [Yb(DMSO)₇]Ag₅I₈(6) were synthesized by a diffusion method.

Structural Diversity of Three Pyrazoyl-Carboxyl Bifunctional Ligand-Based Metal-Organic Frameworks: Luminescence and Magnetic Properties

Three metal-organic frameworks (MOFs), [Cd(Hpzbpdc)(H₂ O)]⋅H₂ O (1), [Mn₂ (Hpzbpdc)₂ (dmf)₂ ] (2), and [H₂ N(CH₃ )₂ ]_0.5 [Eu(Hpzbpdc)_1.5 (HCOO)_0.5 (dmf)_0.5 ]⋅DMF⋅0.5 H₂ O (3) (H₃ pzbpdc=4'-(2 H-pyrazol-3-yl)biphenyl-3,5-dicarboxylic acid), have been solvothermally synthesized from one pyrazoyl-carboxyl bifunctional ligand and characterized by single-crystal structures. The H₃ pzbpdc ligand in 1-3 displays various coordination modes through the pyrazoyl and carboxyl groups. Both 1 and 3 contain dinuclear cluster building units and reveal a four-connected gismondine (gis) zeolite 3D framework and a 2D grid layer structure, respectively. Compound 1 shows blue luminescence, compound 3 reveals red luminescence that arises from efficient energy transfer from the organic ligand to the europium(III) ion, and compound 2 reveals an uncommon (3,8)-connected tfz-d; UO₃ net with a rare Mn₄ (COO)₆ cluster and shows antiferromagnetic interactions between the manganese(II) ions.

Hard-and-soft phosphinoxide receptors for f-element binding: structure and photophysical properties of europium(iii) complexes

New phosphinoyl-based tetradentate heterocycles and their phosphorescent Eu(iii) complexes prepared and characterized.

Red phosphor based on Eu3+-isoelectronically doped Ba2SiO4 obtained via sol–gel route for solid state lightning

Ba₂SiO₄:Eu³⁺ red phosphor with high quantum efficiency synthesized via sol–gel route as a candidate to white LEDs component is introduced. An approach for the 0–0 Eu³⁺ transition anomalous emission due to Eu³⁺–O²⁻ associates is also provided.

Site-selective Eu3+ luminescence in Sr2ScLi(B2O5)2

Unit cell of Sr₂ScLi(B₂O₅)₂ borate.

Why host to dopant energy transfer is absent in the MgAl2O4:Eu3+ spinel? And exploring Eu3+ site distribution and local symmetry through its photoluminescence: interplay of experiment and theory

Local site occupancy of Eu³⁺ in combustion synthesized MgAl₂O₄ spinel and host → Eu³⁺ energy transfer dynamics is investigated using photoluminescence and DFT calculations.

On peculiarities of Eu3+ and Eu2+ luminescence in Sr2GeO4 host

Powders of Sr₂GeO₄:Eu were prepared in air or forming gas and were investigated for their luminescent properties in the 20–300 K range of temperatures, and as much as eight emitting sites of Eu³⁺ and just one of Eu²⁺ were found.

The effect of vanadium substitution on photoluminescent properties of KSrLa(PO4)x(VO4)2−x:Eu3+ phosphors, a new variant of phosphovanadates

In the KSrLa_1−y(PO₄)_x(VO₄)_2−x:yEu³⁺ system, luminescence properties of Eu³⁺ can be enhanced via substitution of phosphate with vanadate.

Versatile properties of CaGd₂ZnO₅:Eu³⁺ nanophosphor: its compatibility for lighting and optical display applications

Red color-emitting CaGd2ZnO5:Eu(3+) (CGZO:Eu(3+)) nanophosphors were synthesized by a facile sol-gel process. The structural and luminescent properties of these phosphors were investigated as a function of annealing temperature and Eu(3+) ion concentration. The orthorhombic phase was confirmed at different annealing temperatures, showing an irregular morphology within the nanoscale range. Photoluminescence (PL) excitation spectra of CGZO:Eu(3+) showed host absorption band (HAB), charge transfer band (CTB), and intense f-f transitions of Eu(3+) in the violet and blue wavelength regions. The CTB intensity increased and the HAB intensity decreased with increasing annealing temperature or Eu(3+) ion concentration. The CGZO:Eu(3+) exhibited a strong absorption in the blue region as compared to the CTB and had a superior property compared to available commercial phosphors. This feature facilitates the fabrication of high color rendering index white light-emitting diodes for display systems. In PL spectra, an intense red emission was observed due to the hypersensitive (5)D0→(7)F2 transition with good asymmetry ratio and chromaticity coordinates. Optimized annealing temperature and concentration of Eu(3+) ions were observed for CGZO host lattice based on the 466 nm excitation wavelength. The cathodoluminescent properties were also similar to the PL results.

Combustion synthesized tetragonal ZrO2: Eu(3+) nanophosphors: structural and photoluminescence studies

Novel crystalline tetragonal ZrO2: Eu(3+) phosphors were prepared by a facile and efficient low temperature solution combustion method at 400±10 °C using oxalyl dihydrazide (ODH) as fuel. The powder X-ray diffraction patterns and Rietveld confinement of as formed ZrO2: Eu(3+) (1-11 mol%) confirmed the presence of body centered tetragonal phase. The crystallite size estimated from Scherrer's and W-H plots was found to be in the range of 7-17 nm. These results were in good agreement with transmission electron microscopy studies. The calculated microstrain in most of the planes indicated the presence of tensile stress along various planes of the particles. The observed space group (P42/nmc) revealed the presence of cations in the 2b positions (0.75, 0.25, 0.25) and the anions in the 4d positions (0.25, 0.25, 0.45). The optical band gap energies estimated from Wood and Tauc's relation was found to be in the range 4.3-4.7 eV. Photoluminescence (PL) emission was recorded under 394 and 464 nm excitation shows an intense emission peak at 605 nm along with other emission peaks at 537, 592, 605 and 713 nm. These emission peaks were attributed to the transition of (5)D0→(7)FJ (J=0, 1, 2, 3) of Eu(3+) ions. The high ratio of Intensity of ((5)D0→(7)F2) and ((5)D0→(7)F1) infers that Eu(3+) occupies sites with a low symmetry and without an inversion center. CIE color coordinates indicated the red regions which could meet the needs of illumination devices.

Two series of reactant's ratio-dependent lanthanide organic frameworks derived from nicotinic acid N-oxide and oxalate: synthesis, crystal structures and luminescence properties

Two series of Ln-MOFs of different structures and consequently different chemo-physical properties were obtained by simply controlling the reactant's ratio.