Structural, optical and thermal studies of Eu ions in lithium fluoroborate glasses

Borate glasses doped with trivalent europium were prepared by the conventional melt quenching technique, in the chemical composition of (49.99-x)B₂O₃ + 25Li₂O + 25LiF+xEu₂O₃ by varying the concentration of the rare earth ion in the order 0.01, 0.1, 1, 2 and 3 wt% and their structural, luminescence and thermal behavior have been reported. The XRD and FTIR spectra reveal the glass structure and the functional groups. The UV–VIS, luminescence spectra and lifetime of the Eu³⁺ ions were measured. The local site symmetry around the Eu³⁺ ions were evaluated through the luminescence intensity ratio (R) of the ⁵D₀ → ⁷F₂ to ⁵D₀ → ⁷F₁ transitions. Optical measurements have been carried out to explore the optical properties such as bonding parameters, Judd–Ofelt parameters, stimulated emission cross-section, transition probability, branching ratio, radiative lifetime, etc. The lifetime measurements of the ⁵D₀ level as a function of the concentration of Eu³⁺ ion have been found and is comparable to other reported for Eu³⁺ doped borate, phosphate glasses and higher than that for the tellurite glasses. The thermal properties such as glass transition, crystallization and melting temperatures of the Eu³⁺ glasses were studied through the DSC traces in the temperature range of 30−1200 °C at a heating rate of 10 °C per minute. The change in optical properties with the variation of Eu³⁺ ion concentration have been discussed and compared with similar results.     

Photophysical Properties of Metal Ion Functionalized NaY Zeolite

A series of luminescent ion exchanged zeolite are synthesized by introducing various ions into NaY zeolite. Monometal ion (Eu³⁺, Tb³⁺, Ce³⁺, Y³⁺, Zn²⁺, Cd²⁺, Cu²⁺) exchanged zeolite, rare‐earth ion (Eu³⁺, Tb³⁺, Ce³⁺) exchanged zeolite modified with Y³⁺ and rare‐earth ion (Eu³⁺, Tb³⁺, Ce³⁺) exchanged zeolite modified with Zn²⁺ are discussed here. The resulting materials are characterized by Fourier transform infrared spectrum radiometer (FTIR), XRD, scanning electronic microscope (SEM), PLE, PL and luminescence lifetime measurements. The photoluminescence spectrum of NaY indicates that emission band of host matrix exhibits a blueshift of about 70 nm after monometal ion exchange process. The results show that transition metal ion exchanged zeolites possess a similar emission band due to dominant host luminescence. A variety of luminescence phenomenon of rare‐earth ion broadens the application of zeolite as a luminescent host. The Eu³⁺ ion exchanged zeolite shows white light luminescence with a great application value and Ce³⁺ exchanged zeolite steadily exhibits its characteristic luminescence in ultraviolet region no matter in monometal ion exchanged zeolite or bimetal ions exchanged zeolite.     

Luminescence properties of sol-gel derived silica gels doped and undoped with RE-complexes(RE=Eu,Tb)

The luminescence properties of silica gels and silica gels doped with two rare earth complexes,Eu(TTA)3 and Tb(o-CBA)3 (TTA=thenoyltrifluocetate,o-CBA=o-chlorobenzoic acid) are reported and discussed.Pure silica gels show a blue luminescence,and the maximum excitation and emission wavelengths depend strongly on the solvents used.Both of the studied rare earth complexes exhibit the characteristic emissions of the rare earth ions in silica gels,i.e.,Eu3+5 Do→7 FJ(J=0,1,2,3,4),Tb3+5D4→7FJ(J=3,4,5,6) transitions.Compared with the pure RE-complexes powder,the silica gels doped with RE-complexes show fewer emission lines of the rare earth ions.Furthermore the rare earth ion (Tb3+) presents a longer lifetime (1346μs) in silica gel doped with Tb(o-CBA)3 than in pure Tb(o-CBA)3 powder (744μs).The reasons responsible for these results are discussed in the context.     

Optical Properties of Lanthanide Doped Hybrid Organic-Inorganic Materials

Sol-gel matrices have been investigated for some years as potential matrices for rare earth luminescence. Sm³⁺, Eu³⁺, Dy³⁺, Er³⁺ and Tm³⁺ optical properties in siloxane-zirconium hybrid matrices prepared at room temperature have been investigated. Even if luminescence efficiency is governed by non-radiative relaxation linked to hydroxyl groups, in these matrices, rare earth fluorescence is always observed but lifetimes and quantum yields are dependent on the elaboration procedure. Eu³⁺ is used as a probe of the local surrounding around the dopant and the emission and decay profiles measurements in rare earth doped and undoped matrices are presented.     

Synthesis,Persistent Luminescence,and Thermoluminescence Properties of Yellow Sr3SiO5:Eu2+,RE3+ (RE=Ce,Nd, Dy,Ho, Er,Tm, Yb) and Orange‐Red Sr3−xBaxSiO5:Eu2+, Dy3+ Phosphor

Sunlight‐excitable orange or red persistent oxide phosphors with excellent performance are still in great need. Herein, an intense orange‐red Sr_3?xBa_xSiO₅:Eu²⁺,Dy³⁺ persistent luminescence phosphor was successfully developed by a two‐step design strategy. The XRD patterns, photoluminescence excitation and emission spectra, and the thermoluminescence spectra were investigated in detail. By adding non‐equivalent trivalent rare earth co‐dopants to introduce foreign trapping centers, the persistent luminescence performance of Eu²⁺ in Sr₃SiO₅ was significantly modified. The yellow persistent emission intensity of Eu²⁺ was greatly enhanced by a factor of 4.5 in Sr₃SiO₅:Eu²⁺,Nd³⁺ compared with the previously reported Sr₃SiO₅:Eu²⁺, Dy³⁺. Furthermore, Sr ions were replaced with equivalent Ba to give Sr_3?xBa_xSiO₅:Eu²⁺,Dy³⁺ phosphor, which shows yellow‐to‐orange‐red tunable persistent emissions from λ=570 to 591 nm as x is increased from 0 to 0.6. Additionally, the persistent emission intensity of Eu²⁺ is significantly improved by a factor of 2.7 in Sr_3?xBa_xSiO₅:Eu²⁺,Dy³⁺ (x=0.2) compared with Sr₃SiO₅:Eu²⁺,Dy³⁺. A possible mechanism for enhanced and tunable persistent luminescence behavior of Eu²⁺ in Sr_3?xBa_xSiO₅:Eu²⁺,RE³⁺ (RE=rare earth) is also proposed and discussed.     

Visible and near-IR luminescence via energy transfer in rare earth doped mesoporous titania thin films with nanocrystalline walls

Selected photoluminescence in the wavelength range of 600-1540 nm is generated by energy transfer from a light-gathering mesostructured host lattice to an appropriate rare earth ion. The mesoporous titania thin films, which have a well-ordered pore structure and two-phase walls made of amorphous titania and TiO₂ nanocrystallites, were doped with up to 8 mol% lanthanide ions, and the ordered structure of the material was preserved. Exciting the titania in its band gap results in energy transfer and it is possible to observe photoluminescence from the crystal field states of the rare earth ions. This process is successful for certain rare earth ions (Sm³⁺, Eu³⁺, Yb³⁺, Nd³⁺, Er³⁺) and not for others (Tb³⁺, Tm³⁺). A mechanism has been proposed to explain this phenomenon, which involves energy transfer through surface states on titania nanocrystals to matching electronic states on the rare earth ions.     

在空气下制备掺二价稀土的硼酸盐及二价稀土离子(RE2+=Sm,Eu,Tm,Yb)的光谱特征

本文讨论了Sm²⁺、Eu²⁺、Tm²⁺、Yb²⁺等二价稀土离子的光谱特征,特别是在一些含四面体硼酸根的硼酸盐如SrB₄O₇、SrB₆O₁₀和BaB₈O₁₃中它们的光谱性质。当以三价稀土离子取代化合物中的二价碱土离子时,利用不等价取代而产生的缺陷所带的电荷,可在高温的空气下使上述的稀土离子还     

Study on the energy transfer between UO_2~(2 ) and Eu~(3 ) in sol-gel derived titania matrix by luminescence spectroscopy

The TiO2 gel doped with UO22 and Eu3 has been prepared by a sol-gel method. The quenching of the UO22 emission by Eu3 and the energy transfer from the excited state of UO22 to the ground state of Eu3 have been investigated. The energy transfer has been studied by the measurement of luminescence lifetime τ, calculations of energy transfer efficiency ηET and energy transfer rate WET. The experimental results indicated that the quenching is combined static and dynamic mechanism, but the static mechanism is dominant.     

Synthesis and characterization of monodisperse spherical SiO2@RE2O3 (RE=rare earth elements) and SiO2@Gd2O3:Ln (Ln=Eu, Tb, Dy, Sm, Er, Ho) particles with core-shell structure

Spherical SiO₂ particles have been coated with rare earth oxide layers by a Pechini sol-gel process, leading to the formation of core-shell structured SiO₂@RE₂O₃ (RE=rare earth elements) and SiO₂@Gd₂O₃:Ln³⁺ (Ln=Eu, Tb, Dy, Sm, Er, Ho) particles. X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), photoluminescence (PL), and cathodoluminescence spectra as well as lifetimes were used to characterize the resulting SiO₂@RE₂O₃ (RE=rare earth elements) and SiO₂@Gd₂O₃:Ln³⁺ (Eu³⁺, Tb³⁺, Dy³⁺, Sm³⁺, Er³⁺, Ho³⁺) samples. The obtained core-shell phosphors have perfect spherical shape with narrow size distribution (average size ca. 380 nm), smooth surface and non-agglomeration. The thickness of shells could be easily controlled by changing the number of deposition cycles (40 nm for two deposition cycles). Under the excitation of ultraviolet, the Ln³⁺ ion mainly shows its characteristic emissions in the core-shell particles from Gd₂O₃:Ln³⁺ (Eu³⁺, Tb³⁺, Sm³⁺, Dy³⁺, Er³⁺, Ho³⁺) shells.     

Novel bifunctional lanthanide‐centered nanophosphors for latent fingerprint detection and anti‐counterfeiting applications

Production of hybrid organic/inorganic complexes such as lanthanide phosphors in the nanodomain for human fingerprint visualization and anti‐counterfeiting ink under biocompatible UVA and blue light has not yet been studied that thoroughly. This paper presents the preparation of novel, bifunctional, green and red nanophosphors based on Eu³⁺ and Tb³⁺ complexes with quinolinone ligand (H₂L). They have been prepared and characterized for latent fingerprint detection and anti‐counterfeiting ink applications. The analytical data confirm that the ligand acts in a monoanionic bidentate manner through OO donor sites, forming mononuclear complexes, formulated as [Ln(HL)₃(C₂H₅OH)₃] (Ln = Eu³⁺ or Tb³⁺; L = 1‐ethyl‐4‐hydroxy‐3‐(nitroacetyl)quinolin‐2‐(1H)‐one). The Eu³⁺ and Tb³⁺ complexes have nanospherical morphologies with average particle sizes of 17 and 5 nm, respectively. Pure red and green photoluminescence with long lifetime values has been obtained from the Eu³⁺ and Tb³⁺ complexes, respectively, under non‐harmful UVA and blue illumination. Latent fingerprint details, including their characteristic three levels, have been clearly identified from various forensic (non‐porous, semi‐porous, highly fluorescent porous) substrates using red (Eu³⁺) and green (Tb³⁺) nanophosphors. The green nanophosphor powder has a greater capability for visualizing latent fingerprints from highly fluorescent porous surfaces as compared to the red one. Both nanophosphor complexes have been used to develop luminescent ink for anti‐counterfeiting applications.     

Scalar Relativistic Density Functional Theoretical Investigation of Higher Complexation Ability of Substituted 1,10‐Phenanthroline over Bipyridine Towards Am3+/Eu3+ Ions

The better selectivity of Am³⁺ over Eu³⁺ ion with N‐based CyMe4‐BTPhen compared to CyMe4‐BTBP for experimentally observed [ML₂(NO₃)]²⁺ complexes was demonstrated using scalar relativistic DFT in conjunction with Born‐Haber thermodynamic cycle and COSMO solvation model. The calculated free energy of extraction, ΔG_ext reveals strong dependence on the hydration free energies of Am³⁺ and Eu³⁺ ions and week dependence to the difference in Gibbs free energy of solvation of the ligand or metal‐ligand complexes. Further, for the first time, we have computed the effect of co‐anion species ([M(NO₃)₅]^2–) on ΔG_ext of Am³⁺ and Eu³⁺ ions with CyMe4‐BTPhen and CyMe4‐BTBP, which adds a positive contribution and thus reduces the ΔG_ext. The calculated values of ΔΔΔG_ext (= ΔΔG_ext,L1 – ΔΔG_ext,L2, ΔΔG_ext = ΔG_ext,M1 – ΔG_ext,M2) can be used to avoid the very sensitive metal ion solvation energy, effect of co‐anionic species and thus provides a robust approach to determine the selectivity between two metal ions towards different competitive ligands. The natural population analysis (NPA), molecular orbital analysis, Mayer bond order analysis, and bond character analysis using Bader's quantum theory of atoms in molecules indicates slightly more covalency for complexes of Am³⁺ ion that are correlated to the experiental selectvity of Am³⁺ ion over Eu³⁺ ion and hence might be useful in the design and development of next generation extractants.     

Strong f‐f Excitation and Bright Red Emission in Cd4Gd1‐xEuxO(BO3)3 (0≤x≤1): Near‐UV LED Pumped Red Phosphor with Low Thermal Quenching

Searching efficient red phosphors under near‐UV or blue light excitation is practically important to improve the current white light‐emitting diodes (WLEDs). Eu²⁺‐ and Mn⁴⁺‐based red phosphors have been extensively studied. Here we proposed that Eu³⁺ is also a promising activator when it resides on a noncentrosymmetric coordination site. We proved that Cd₄GdO(BO₃)₃ is a good host, which has a significantly distorted coordination for Eu³⁺. A careful crystallographic study was performed on the solid solutions of Cd₄Gd_1‐xEu_xO(BO₃)₃ (0≤x≤1) by Rietveld refinements. The as‐doped Eu³⁺ cations locate at the Gd³⁺ site and are well separated by CdO₈, CdO₆ and BO₃ groups; thus, only a slight concentration quenching was observed at ≈80 atom % Eu³⁺. Most importantly, the parity‐forbidden law of 4f‐4f transitions for Eu³⁺ are severely depressed, thus the absorptions at ≈393 and ≈465 nm are remarkable. Cd₄Gd_0.2Eu_0.8O(BO₃)₃ can be pumped by a 395 nm LED chip to give a bright red emission, and when mixed with other commercial blue and green phosphors, it can emit the proper white light (0.3657, 0.3613) with a suitable R_a≈87 and correlated colour temperature ≈4326 K. In‐situ photoluminescence study indicated the low thermal quenching of these borate phosphors, especially under 465 nm excitation. Our case proves the practicability to develop near‐UV excited red phosphors in rare‐earth‐containing borates.     

Calorimetric investigations of luminescent films polycarbonate (PC) doped with europium complex [Eu(TTA)<Subscript>3</Subscript>(H<Subscript>2</Subscript>O)<Subscript>2</Subscript>]

Polymers doped with rare earth complexes are advantaged in film production for many applications in the luminescent field. In this luminescent polycarbonate (PC) films doped with diaquatris(thenoyltrifluoroacetonate)europium(III) complex [Eu(TTA)₃(H₂O)₂] were prepared and their calorimetric and luminescent properties in the solid state are reported. The thermal behavior was investigated by utilization of differential scanning calorimetry (DSC) and thermogravimetry (TG). Due of the addition of rare earth [Eu(TTA)₃(H₂O)₂] into PC matrix, changes were observed in the thermal behavior concerning the glass transition and thermal stability. Characteristic broadened narrow bands arising from the ⁵D₀ → ⁷F_J transitions (J = 4−0) of Eu³⁺ ion indicate the incorporation of the Eu³⁺ ions in the polymer. The luminescent films show enhancement emission intensity with an increase of rare earth concentration in polymeric matrix accompanied by decrease in thermal stability.     

CaWO4:xEu3+,ySm3+,zLi+红色荧光粉的制备及光学性能

采用微波固相法制备了CaWO₄：xEu³⁺,ySm³⁺,zLi⁺红色荧光粉。测量样品的XRD图、激发谱、发射谱及发光衰减曲线,研究并分析了Eu³⁺、Sm³⁺、Li⁺的掺杂浓度,对样品微结构、光致发光特性、能量传递及能级寿命的影响。结果表明,Eu³⁺、Sm³⁺、Li⁺掺杂并未引起合成粉体改变晶相,仍为CaWO₄单一四方晶系结构。Eu³⁺、Sm³⁺共掺样品中,Sm³⁺掺杂为3%时,Sm³⁺对Eu³⁺的能量传递最有效。Li⁺掺杂起到了助熔剂和敏化剂的作用,使样品发光更强。在394 nm激发下,与CaWO₄：3%Eu³⁺样品比较,3%Eu³⁺、3%Sm³⁺共掺CaWO₄及3%Eu³⁺、3%Sm³⁺、1%Li⁺共掺CaWO₄样品的发光分别增强2倍及2.4倍。同一激发波长下,单掺Eu³⁺样品寿命最短,Sm³⁺、Eu³⁺共掺样品随Sm³⁺浓度增加,寿命先减小后增加,且掺杂了Li⁺的样品比不掺Li⁺的样品⁵D₀能级寿命有所增加。     

铕(III)对伴清蛋白溶液构象的影响

用TNS疏水探针研究了脱铁伴清蛋白(apoOTf)和不同形式的铕伴清蛋白(Eu_N-OTf, Eu₂-OTf)的表面疏水暴露程度, 依次为apoOTf＞Eu_N-OTf＞Eu₂-OTf, 表明Eu^3＋与脱铁伴清蛋白N端结合引起蛋白构象变化大, 与C端结合引起蛋白构象变化小. 此外, 由盐酸胍对3种蛋白变性实验, 发现Eu^3＋与脱铁伴清蛋白的结合稳定了蛋白的结构, 稳定性依次为apoOTf＜Eu_N-OTf＜Eu₂-OTf. 离子强度效应也充分表明3种蛋白内部疏水基团相互作用依apoOTf＜Eu_N-OTf＜Eu₂-OTf顺序增大, 稳定性也依次增大. 本研究对进一步探讨Eu^3＋的生物效应提供理论依据.     

Fluoridhaltige Gäste in Alumosilicaten: Tetrafluoroborate in dem Sodalithen Na8Al6Si6O24(BF4)2

In the course of investigations on optical properties resulting from the interaction of fluorides with alumosilicate host materials and rare earth guests, a well defined BF₄^– ion wasfound to be incorporated within the sodalite of composition Na₈Al₆Si₆O₂₄(BF₄)₂. The resulting cubic molecular structure, which was determined by Rietveld methods (space group P4 n, a = 906.91 pm, wRp = 0.045, Rp = 0.027), contains one anion in each sodalite cage and is, contrarily to expectations, thermally stable. NMR spectroscopic investigations indicated a fast rotatory motion of the BF₄^– tetrahedra at room temperature and agreed with the tetrahedral BF₄^– ions found in IR and Raman spectra. Preliminary attempts to obtain a luminescent material by incorporation of Eu³⁺ through aqueous ion exchange only yielded low rare earth concentrations, giving rise to characteristic red emission lines at 581 nm (⁵D₀ → ⁷F₁) and 615 nm (⁵D₀ → ⁷F₂) in a 1:2 intensity ratio. The material unexpectedly exhibited a strong broad band emission at 520 nm after calcination under Ar, which is attributed to the formation of an Eu²⁺ species. Further calcination under air partially reestablished the Eu³⁺ emission.     

Hydrothermal synthesis, physical characterization and photoluminescence of homologous-SBA-15 fabricated with Eu

Two series of Eu³⁺-doped homologous-SBA-15 materials (abbreviated as MPTMS-SBA-15: Eu³⁺ and CTMS-SBA-15: Eu³⁺) have been synthesized by a hydrolysis-controlled technology, in which two novel silane crosslinking reagents (3-(methacryloyloxy) propyltrimethoxysilane (MPTMS) and 3-(chloropropyl) trimethoxysilane (CTMS)) are used as silicate precursor instead of traditional tetraethoxysilane (TEOS). It can be found that the different silicate precursors with different functional groups have influence on the physical properties of the corresponding homologous materials. In comparison to the pure SBA-15, the BET surface area and pore size of the modified mesoporous materials have been changed. Finally, the characteristic luminescence is observed for the ⁵D₀ → ⁷F_J (J = 0, 1, 2) transition of Eu³⁺ ion, suggesting that these kind of homologous-SBA-15 materials are potential host for the luminescence of Eu³⁺, whose excitation energy can be quenched by Eu³⁺ to some extent.     

A few remarks on the simulation and use of crystal field energy level schemes of the rare earth ions

The usefulness of the simulation of the energy level schemes of the trivalent rare earth (R³⁺) ions in the prediction of the properties of the rare earth compounds is demonstrated for a few selected cases emphasizing the connection between different spectroscopic and magnetic properties of the R³⁺ ions. The importance of the calculated energy level schemes in the UV-VUV range in interpreting complicated spectra and designing new phosphors by energy transfer and quantum cutting is described. In the absence of direct measurements, the calculated energy level values can be very useful. The possibilities to interpret the magnetic properties of the R³⁺ (and R²⁺) ions are described by using the wave functions of the energy levels obtained from the energy level simulations. As a fine example, it is shown how the amount of an Eu²⁺ impurity can be obtained from the calculation of the paramagnetic susceptibility as a function of temperature. The problems involved in the simulation of the ⁷F_J crystal field energy level scheme of the Eu³⁺ ion are highlighted by using a comparison between the extensive literature data and calculated level schemes.     

Ambient‐Pressure Stabilization of β‐GdB3O6 by Doping with Bi3+ and Color‐Tunable Emissions by Co‐Doping with Tb3+ and Eu3+: The First Photoluminescence Study of a High‐Pressure Polymorph

Rare‐earth borates are good candidates for optical applications. To date, however, the high‐pressure/high‐temperature technique has produced a large number of novel borates with optical properties that have rarely been investigated due to the severe problem of substantial defects. We targeted the high‐pressure polymorph of β‐GdB₃O₆ and synthesized three solid solutions of β‐Gd_0.75−x Bi_0.25Tb_x B₃O₆ (0≤x ≤0.75), β‐Gd_0.75−y Bi_0.25Eu_y B₃O₆ (0≤y ≤0.75), and β‐Gd_0.50−z Bi_0.25Tb_0.25Eu_z B₃O₆ (0≤z ≤0.05) by using typical solid‐state reactions at 820 °C. Here, the function of Bi³⁺ is to stabilize the high‐pressure phase by lowering the synthetic temperature and being the sensitizer to promote the green and red emissions of Tb³⁺ and Eu³⁺. The multiple energy transfer paths were investigated by using lifetime decay experiments and photoluminescent spectra, and both efficiency and mechanism were determined. Eventually, color‐tunable and white emissions were achieved by rational doping of Bi³⁺, Tb³⁺, and Eu³⁺ into β‐GdB₃O₆, that is, the CIE chromaticity coordinate for β‐Gd_0.44Bi_0.25Tb_0.30Eu_0.01B₃O₆ is (0.318, 0.365) with a correlated color temperature of 6101 K.     

Valence and environment of rare earth ions in CaAl2O4:Eu,R persistent luminescence materials

The existence of the different R²⁺/R³⁺/R^IV (R: rare earth) ions as well as the modifications in the structural environment around the dopant and co-dopants in CaAl₂O₄:Eu²⁺,R³⁺ persistent luminescence materials was studied by L_III edge X-ray Absorption Near Edge Structure (XANES) and Extended X-ray Absorption Fine Structure (EXAFS) measurements at Hamburger Synchrotronstrahlungslabor (HASYLAB) at Deutsches Elektronen-Synchrotron (DESY) (Hamburg, Germany). The measurements were carried out at 10 and 296 K for selected rare earth (co-)dopants (Eu²⁺; Ce³⁺, Nd³⁺, Sm³⁺, and Yb³⁺).