Rare Earth Eu Research Articles

Development of Novel Thermal Sprayed Hydroxyapatite-Rare Earth (HA-Re) Coatings for Potential Antimicrobial Applications in Orthopedics

Biofilm-associated infections and the lack of successful tissue integration of biomaterial surfaces are the two main barriers to the long-term service of implanted biomaterials. Development of novel biocompatible antimicrobial materials has provided insights into their potential biomedical applications. Many clinical studies have successfully proved that hydroxyapatite coating has excellent osteogenic activity but lacks antibacterial infection in the early stages after implantation. Rare earth (Re) elements have become promising antibacterial biocides and bone-forming effects. Antibacterial capacity of 14 rare earth elements (Eu, Gd, Ce, Nd, Y, La, Pr, Er, Sm, Ho, Tb, Yb, Lu, Dy) was assayed. The gadolinium (Gd) showed outstanding broad-spectrum antibacterial activity against both Gram-positive and Gram-positive bacteria. Here, we report Gd-HA coatings deposited on titanium (Ti) substrate by liquid thermal spraying. The grain size of Gd-HA decreased slightly after Gd3+ incorporation. The antibacterial properties of Gd-HA composite coatings were determined against Gram-negative pathogens Escherichia coli and Gram-positive pathogens Staphylococcus epidermidis. The anti-infection performances were assessed by examining bacteria adhesion and biofilm formation on the coatings. The in vitro cytotoxicity of the Gd-doped HA coatings was further measured on human osteoblast cell line by CCK-8 method. The thermal sprayed HA-Re composite coatings show improved antimicrobial and biocompatible properties and great applicable potential in orthopedics.

Luminescent europium(iii) complexes based on tridentate isoquinoline ligands with extremely high quantum yield

Synthesis and characterization of two new lanthanide Eu(iii) complexes based on tridentate isoquinoline ligands with high luminescence efficiency, extended excitation wavelength and good thermal stability.

Exceptionally high saturation magnetisation in Eu-doped magnetite stabilised by spin-orbit interaction.

The significance of the spin-orbit interaction is very well known in compounds containing heavier elements such as the rare-earth Eu ion. Here, through density functional calculations, we investigated the effect of the spin-orbit interaction on the magnetic ground state of Eu doped magnetite (Fe3O4:EuFe). By examining all possible spin alignments between Eu and magnetite's Fe, we demonstrate that Eu, which is most stable when doped at the tetrahedral site, adapts a spin almost opposite the substituted Fe. Consequently, because of smaller spin cancellation between the cations on the tetrahedral site (FeTet and EuTet) and the cations on the octahedral sites (FeOct), Fe3O4:EuFe exhibits a maximum saturation magnetisation of 9.451 μB per f.u. which is significantly larger than that of undoped magnetite (calculated to be 3.929 μB per f.u.). We further show that this large magnetisation persists through additional electron doping. However, additional hole doping, which may unintentionally occur in Fe deficient magnetite, can reduce the magnetisation to values smaller than that of the undoped magnetite. The results presented here can aid in designing highly efficient magnetically recoverable catalysts for which both magnetite and rare earth dopants are common materials.

Separation and solvent extraction of rare earth elements (Pr, Nd, Sm, Eu, Tb, and Er) using TBP and Cyanex 572 from a chloride medium

In this study, synergistic effect of Cyanex 572 mixed with TBP on the extraction and separation of six selected light, medium and heavy rare earth elements (REE), namely neodymium (Nd), praseodymium (Pr), samarium (Sm), europium (Eu), terbium (Tb), and erbium (Er), from the chloride medium was investigated. The results demonstrated that sole TBP is not a suitable extractant for the separation of the REEs from the chloride media. However, Cyanex 572 was identified as a suitable extractant for the separation of heavy REEs, Er, and Tb. At initial pH (pHi) of 1.5, the mixture of 25% TBP + 75% Cyanex 572 extracted about 70% and 85% of Er and Tb, respectively. The separation factor (SF) results of some couples were noteworthy: SFEr/Pr = 30.08, SFEr/Nd = 29.95, SFTb/Pr = 12.22, SFTb/Nd = 12.16, SFEr/Sm = 9.96. Furthermore, the extraction mechanism of these two heavy REEs was studied using slope analysis and Fourier transform infrared measurements (FT-IR). The results showed that Er and Tb were extracted as ErCl2R(HR)3TBP and TbCl2R(HR)3TBP complexes (presumably R and HR refers to Cyanex 572), respectively. The FT-IR spectra confirmed these obtained results qualitatively.

Coupling of lattice, spin, and intraconfigurational excitations of Eu3+ in Eu2ZnIrO6

In Eu2ZnIrO6, effectively two atoms are active i.e. Ir is magnetically active, which results in complex magnetic ordering within the Ir sublattice at low temperature. On the other hand, although Eu is a van-vleck paramagnet, it is active in the electronic channels involving 4f 6 crystal-field split levels. Phonons, quanta of lattice vibration, involving vibration of atoms in the unit cell, are intimately coupled with both magnetic and electronic degrees of freedom (DoF). Here, we report a comprehensive study focusing on the phonons as well as intra-configurational excitations in double-perovskite Eu2ZnIrO6. Our studies reveal strong coupling of phonons with the underlying magnetic DoF reflected in the renormalization of the phonon self-energy parameters well above the spin-solid phase (TN ~ 12 K) till temperature as high as ~ 3TN, evidences broken spin rotational symmetry deep into the paramagnetic phase. In particular, all the observed first-order phonon modes show softening of varying degree below ~3TN, and low-frequency phonons become sharper, while the high-frequency phonons show broadening attributed to the additional available magnetic damping channels. We also observed a large number of high-energy modes, 39 in total, attributed to the electronic transitions between 4f-levels of the rare-earth Eu3+ ion and these modes shows anomalous temperature evolution as well as mixing of the crystal-field split levels attributed to the strong coupling of electronic and lattice DoF.

Carboniferous Magmatism in the Polar Urals

Dikes and sills of dolerites, essexite–dolerites, diorites, monzodiorites, and lamprophyres belonging to the Musyur (Malyi Khanmey) hypabyssal complex (Polar Urals) cut all Ordovician–Middle Devonian oceanic and island arc formations. Based on the geological data and previous isotope dating, the age of this complex is estimated from the end of the Late Devonian to the Early Triassic. The 40Ar/39Ar dating of hypabyssal magmatic bodies (various intrusive phases) of the Musyur complex was performed for the first time for the northern part of the Urals. The following 40Ar/39Ar ages were obtained: 349 ± 3, 347 ± 9, 339 ± 4, 334 ± 3, and 313 ± 10 Ma. They recorded the collision of the Polar Ural island-arc system with the continent of Arct–Laurussia (Arctida + Baltica + Laurentia), which led to the formation of the Carboniferous Early Ural Orogen. The prevailing northwestern (transversely to the supposed orogen) strike of most dikes in the Toupugol–Khanmeyshor area, predominantly the subduction zone geochemical features of the rocks (low and moderate TiO2 contents (0.7–2.1 wt %), P2O5 (0.1–0.8 wt %), enrichment in large-ion lithophile elements (Cs, Rb, Ba, Pb, Sr) compared to high-field-strength trace elements, the Ta–Nb minimum, and Pb and Th–U maxima), and the Early Carboniferous age estimates (349–334 Ma) lead to the conclusion that they probably formed in a syncollisional setting. The orthogonal northeastern (along the orogen axis) strike of some dikes (essexite–dolerites in more southerly regions), significantly higher concentrations of TiO2 (3.1–3.6 wt %), P2O5 (0.6–1.3 wt %), high-field-strength (Ta, Nb) and most rare earth elements (Eu, Gd, Tb, Dy, Y, Ho, Er, Tm, Yb, Lu), which are more typical for rift-related and intraplate igneous rocks, and their Late Carboniferous age (313 Ma) may testify to their emplacement in a post-collision setting.

Highly Efficient and Air‐Stable Lanthanide EuII Complex: New Emitter in Organic Light Emitting Diodes

AbstractLuminescent EuII complexes with a characteristic 5d–4f transition have potential applications in many fields. However, their instability in ambient conditions impedes further exploration and application. Herein, we report two new EuII complexes, bis[hydrotris(3‐trifluoromethylpyrazolyl)borate]europium(II) (Eu‐1) and bis[hydrotris(3‐methylpyrazolyl)borate]europium(II) (Eu‐2). Intriguingly, the blue emissive Eu‐1 showed high air stability arising from fluorine protection and close molecular packing, as maintaining a photoluminescence quantum yield (PLQY) of 91 % (initial 96 %) upon exposure to air over 2200 hours. While the orange emissive Eu‐2 showed a maximum luminance of 30620 cd m−2, and a maximum external quantum efficiency (EQE) of 6.5 %, corresponding to an exciton utilization efficiency around 100 % in organic light‐emitting diodes (OLEDs). These results could inspire further research on stable and efficient EuII complexes and their application in OLEDs.

Synthesis and Luminescence Investigation of Eu3+ Doped Ca2KZn2V3O12 Phosphors: A Potential Material for WLEDs Applications

A series of white light emitting Ca2KZn2–xV3O12:xEu3+ (x = 0.1, 0.2, 0.3, 0.4 and 0.5) phosphor samples were successfully synthesized by the traditional solid-state reaction method. The powder X-ray diffraction (XRD) patterns of the as-prepared sample reveal the high degree of crystallinity of the cubical structure with $$Ia\overline{3}d$$ space group and without any other phase formation. Fourier transform infrared (FTIR) spectra confirmed the occurrence of characteristic vibrational bands of garnet vanadate. The optical diffuse reflectance spectra consisting of broad band absorption in the ultraviolet (UV) region and the sharp absorption in the visible region were ascribing to the charge transfer between ligand–metal in the VO4 tetrahedral group and Eu3+ ions. Under the UV and near-UV excitation wavelengths, the broad band emission and the sharp emission were ascribing to the host material charge transfer of the VO4 tetrahedral group and f-f transitions of the rare-earth Eu3+ ions respectively. Ultimately, through the doping concentration optimization, a high Color Rendering Index (CRI) and excellent Correlated Color Temperature (CCT) were achieved with cool white emission. Therefore, the contribution of Ca2KZn1.8Eu0.2V3O12 phosphor was significant to phosphor-converted white light emitting device (WLEDs) excited with near ultraviolet.

B-site Y3+ assisted charge compensation strategy to synthesize Eu3+ doped Ruddlesden-Popper Ca2SnO4 perovskite and photoluminescence properties

The rare-earth doped phosphors are widely used in luminous applications. As necessary activators, the involved rare-earth ions are quite low in amount. This may lead to the unsuccessful incorporation or existence of secondary impurity, which, in turn, causes the incorrect interpretations in photoluminescence (PL) origins and mechanisms, e.g. in Eu3+doped Ruddlesden-Popper Ca2SnO4 perovskite. In this work, we adopted a B-site Y3+ assisted charge compensation strategy to dope A-site rare earth Eu3+ cations into Ca2SnO4 in order to obtain the pure-phase red-emission phosphors. The Ca2-xEuxSn1-yYyO4 (x = y = 0.01–0.05) phosphors were synthesized via the one-step solid-state reaction. The careful and systematic XRD measurements reveal that only Eu3+ doping cannot give pure-phase Ca2-xEuxSnO4, while the combination with B-site Y3+ assistance enables achieving pure-phase Ca2-xEuxSn1-yYyO4, which crystallize in an orthorhombic Pbam structure. The STEM-EDX and XPS characterizations indicate the uniform distribution of dopants in the matrix and B-site Y3+ plays a charge compensation role and assists the A-site Eu3+ doping. The charge transfer state (CTS) presenting the energy transfer from matrix to dopants (O2--Eu3+) in excitation spectra was observed with the center at around 275 nm. This excitation wavelength can give the strongest emission signals, i.e. the overall warm-reddish emission. The comprehensive structure and PL/FT-IR/UV spectroscopy analyses indicate that Eu3+ ions substitute for Ca2+ ions at a low symmetric position, and the electric-dipole transition (5D0→7F2) is dominant, giving rise to the stronger emission at 617 nm. The optimal PL emission is achieved at doping level x = 0.03, beyond which the concentration quenching occurs, with an origin of electric dipole-dipole interaction of Eu3+ responsible.

Luminescence properties of nano and bulk ZnWO4: Eu3+ phosphors for solid state lighting applications

Rare earth Eu3+ doped ZnWO4 bulk and nanophosphors were synthesized using solid state and hydrothermal reaction methods. Structural, morphological and microstructural characterizations of the as prepared phosphors were done by using X-ray diffractometer (XRD), Fourier transform infrared spectroscopy (FTIR), Field emission scanning electron microscope (FESEM) and High resolution transmission electron microscope (HRTEM). Their optical properties such as photoluminescence (PL) emission, thermal quenching and lifetime decay were investigated at 394 nm near UV excitation with respect to dimension which shows better outcome for the nanophosphor than the bulk one. The nanophosphors display homogeneous particles with much smaller dimension compared to the bulk phosphors which in turn intensifies the red emission and also increases the thermal stability.

Distribution, sources and ecological risk of trace elements and polycyclic aromatic hydrocarbons in sediments from a polluted urban river in central Bangladesh

To assess the spatial and layer-wise distributions of 26 elements (Na, Al, Mg, K, Ca, Sc, Ti, V, Cr, Mn, Fe, Sb, Co, Ba, Zn, Rb, Cs, La, Ce, Sm, Eu, Yb, Ta, Hf, Th and U) as well as the spatial distributions of polycyclic aromatic hydrocarbons (PAHs) in a polluted urban river (Turag, Bangladesh), benthic sediment samples from 11 different sampling stations were analyzed. Concentrations of Ti, Cr, Mn, Zn, Rb and Cs ranged from 2330 to 5490, 23–116, 186–4298, 34–7345, 77–186 and 2.19–12.0 μg.g−1(dw), respectively, whereas concentrations of ∑PAHs ranged from 45.8 to 1901 with an average value of 432 μg.kg−1(dw) in surface sediments. Geo-accumulation index, enrichment factor and pollution load index were used to assess the contamination level. Among the 26 elements, Zn is identified as the major elemental contaminant which shows significant layer-wise variations (RSDs: 21.7–221 %) at all sampling sites. Similarly, Cr, Mn, Ti, V, Fe and Co show layer-wise variation in some specific sampling sites which invokes variable contamination flux over the industrialization and/or urbanization period. Principal component analysis (PCA) and correlation study ascertained several anthropogenic sources for heavy metal contaminations. Although rare earth elements (La, Ce, Sm, Eu and Yb) seem to have crustal origin, their layer-wise variations are assumed to represent the sediment response toward the pollution load. Integrated study based on the diagnostic ratios and PCA depicted that pyrolytic origins mostly govern the PAHs distributions. Sediments quality guidelines (SQGs) indicated that the highest potential ecological risks occurred for Zn and fluorene at some specific sampling sites.

Photoluminescence and temperature sensing of lanthanide Eu3+ and transition metal Mn4+ dual-doped antimoniate phosphor through site-beneficial occupation

For a long time, rare-earth ion-doped phosphors have been widely used in temperature sensing because of their excellent light-emitting properties. However, most of the rare earth elements are relatively rare and expensive, so the transition group elements that are economical and easy to obtain have been favored by researchers. This paper presents a new type of phosphor doped with rare earth ion and transition metal for optical temperature measurement. In recent years, Mn4+-doped phosphors have attracted wide attention because of their strong deep red light-emitting properties. La2LiSbO6 provides a good host environment for Mn4+ and Eu3+ due to its unique crystal structure. In this paper, a series of La2LiSbO6 phosphors singly doped with Mn4+ and Eu3+, and co-doped with Eu3+/Mn4+ were synthesized. The crystal phases and optical properties of these materials were characterized and analyzed in detail. We specifically studied the temperature dependence of the fluorescence intensity of the optimized La2LiSbO6: Eu3+, Mn4+ phosphors at 303K–523K. The experimental results prove that the thermal responses of Mn4+ and Eu3+ are different. With increasing temperature, the thermal quenching of the Mn4+ fluorescence intensity is much faster than that of Eu3+, so the temperature characteristics can be explored by the fluorescence intensity ratio (FIR) of Eu3+ to Mn4+. At 523 K, its maximum relative sensitivity and maximum absolute sensitivity can reach 0.891% K−1 and 0.000264 K-1, respectively. Our experimental analysis shows that La2LiSbO6:Eu3+/Mn4+ phosphors have relatively high temperature sensitivity and have potential application prospects in the field of high temperature sensing.

Effect of Molten Salt on Synthesis and Luminescence Properties of YVO4:Eu3+ Red Phosphors

Red phosphors YVO4:Eu3+ with high efficiency photoluminescence have been successfully synthesized using the molten salt synthesis (MSS) method, in which (Mg(NO3)2 ⋅ 6H2O, Ca(NO3)2 ⋅ 4H2O, Sr(NO3)2, and Ba(NO3)2) were used as the molten salt. These phosphors were characterized by powder X‑ray diffraction (XRD), scanning electron microscopy (SEM), and photoluminescence (PL). The results indicated that all phosphors showed rare earth Eu3+ ion characteristic emissions in the YVO4 host. The influence of adding molten salt on photoluminescence properties of YVO4:Eu3+ phosphors has been discussed. The red/orange (R/O) intensity ratio 5D0–7F2 to 5D0–7F1 values of Eu3+ of phosphors doped with different molten salts decreases in the order of Mg, Ca, Ba, Sr, which indicates that the red color of the light emitted by the material prepared using Mg(NO3)2 ⋅ 6H2O is the most pure. The most pure red light could be achieved from YVO4:Eu3+ phosphor with chromaticity coordinates of (0.64, 0.34) under excitation at 275 nm.

Luminescence and temperature sensing abilities of zincate phosphors co-doped bismuth Bi3+ and lanthanide Eu3+/Sm3+

We proposed the FIR method-based optical materials involving dual luminescent centers of Bi3+ and lanthanide (Ln): Eu3+/Sm3+. Resulted from the f-f characteristic transition of Eu3+, the tunable color region changing from cyan to jacinth with the augment of Eu3+/Bi3+ ratio exists . Owing to Bi3+ being susceptive to crystal surroundings, and asymmetric crystal sites of Sm3+ in the host, phenomena respectively involving redshift and energy level splitting occur. In addition, benefiting from the unshielded 3d orbitals, the thermal quenching of Bi3+ ion occurs through energy-level crossing relaxation (ELCR), while the heating quenching of Ln3+ ions takes place due to the shielded 4f orbitals via multi-phonon deexcitation (MPD). Considering the symmetric crystal environment, stronger sensitivity compared with Sm3+ ion to the outer environment due to its smaller value of thermal activation energy and the weaker crystal field than CAZO:Bi3+,Sm3+, a more excellent temperature sensing sensitivity is excepted by applying Eu3+ as the temperature-detecting signal.

Eu3+ and Dy3+-activated LaAlO3 phosphor for solid-state lighting

Rare earth Eu3+ and Dy3+-activated LaAlO3 phosphor were prepared by wet chemical method. The prepared phosphors were characterized by, X-ray diffraction(XRD) for phase purity, scanning electron microscopy (SEM) for morphology and photoluminescence (PL) emission and excitation spectra. SEM analysis does not reveal the crystal structure; however, it shows that the prepared phosphor has irregular morphology with particle size in micron range. Under both 395 nm and 466 nm excitation, LaAlO3:Eu3+ phosphor shows emission at 593 nm and 614 nm. LaAlO3:Dy3+ phosphor shows emission at 484 nm and 575 nm when excited by wavelength of 351 nm. The synthesized phosphors have mercury-free excitation, and therefore, prepared phosphor might be applicable in environmental-friendly solid-state lighting.

Separation of gadolinium and europium from chloride media by the solvent extraction technique

Abstract Obtaining rare earth elements (REE) is a complicated task, due mainly to the difficulty of separating and purifying them. Solvent extraction is the most widely used technique for separating REE, and the most common extractants used are organophosphorus acids. The low selectivity of this technique leads to the need for a high number of extraction cells. To increase the selectivity and separation and avoid the practice of saponification of the extractant, the use of complexing agents has been studied, such as low-molecular-weight and biodegradable weak organic acids. The objective of this research was to study the separation of the rare earth elements Gd and Eu by the solvent extraction technique using the organophosphonic extractant 2-ethylhexyl phosphonic acid mono-2-ethylhexyl ester (P507). Assays were performed using non-saponified and saponified P507 extractant and adding lactic acid to the aqueous phase prior to extraction. Experimental factorial planning was used to study the effect on the extraction and separation of the Eu and Gd of the variables extractant concentration, initial feed pH, saponification degree, and lactic acid concentration. The greatest Gd extractions were obtained when lactic acid was added to the feed solution. Also, saponification of the extractant and lactic acid addition improved the Gd/Eu separation. The number of stages required to extract Gd using McCabe-Thiele diagrams was estimated, whether or not the solution was conditioned with lactic acid. The largest extraction percentage was obtained by adding lactic acid in a continuous counter-current extraction assay, achieving 94% Gd extraction.

Sensitized Mechanoluminescence Design toward Mechanically Induced Intense Red Emission from Transparent Polymer Films

Mechanoresponsive polymers with intense red emission are highly desirable in view of the strong penetrability and high resolution of red luminescence. Herein we introduce the sensitized luminescence of rare-earth Eu(III) complexes into the mechanochemiluminescence from polymeric dioxetane in a covalent way. By controlling the energy-transfer process from mechanically broken dioxetane to the Eu(III) center, bright red emission from transparent poly(methyl acrylate) films was achieved for the first time. Importantly, mechanoluminescence sensitivity is greatly improved, enabling the location and timing of bond scission with high resolution. A sensitive stretchable device with the polymer film as an emissive layer was fabricated by a facile surface-engineering method, which can emit patterned red light upon deformation. This sensitized mechanoluminescence design thus expands the useful space of luminescent stress probes.

Conductive transparent (InGa)2O3 film as host for rare earth Eu

We have investigated the optical and electrical properties of (InGa)2O3:Eu films. We have demonstrated the obtained (InGa)2O3:Eu films have conductive transparent properties, and they can be used as a host for rare earth Eu. The (InGa)2O3:Eu films are of a (111) oriented cubic structure, as revealed by both x-ray diffraction and Raman spectroscopy measurements. The (InGa)2O3:Eu films show high transmittance of over 70% in the visible wavelength range and low resistivity ranging from 2.8 × 10−3 Ω cm to 2.1 × 10−2 Ω cm, depending on the Ga content. The intensity of main Eu3+ emission peaks upon excitation at 488 nm at room temperature increased with an increase in the Ga content. The enlarged bandgap as well as the decreased local symmetry of the cubic structure should be responsible for the enhanced Eu3+ emission. The results suggested that (InGa)2O3:Eu films can be very good candidates for light-emitting devices that can be driven electrically.

Effect of Rare-earth Variable-valence Element Eu doping on Thermoelectric Property of BiCuSeO

Effect of Rare-earth Variable-valence Element Eu doping on Thermoelectric Property of BiCuSeO

Air stable and efficient rare earth Eu(ii) hydro-tris(pyrazolyl)borate complexes with tunable emission colors

Eu(ii) complexes with high air stability and tunable emission colors were synthesized and characterized.