A Series of Carboxylic‐Functionalized Ionic Liquids and their Solubility for Lanthanide Oxides

Herein we report the synthesis of propanoic acid functionalized ionic liquids (ILs) with various lengths of alkyl chain on the imidazole ring. The synthesized propanoic acid functionalized ILs were used to dissolve Eu₂O₃ (or Tb₄O₇) due to the formation of europium(III) (or terbium(III)) carboxylate, aimed to get soft luminescent materials combining the properties of ILs and attractive luminescent properties of lanthanide ions. The luminescent behavior of Eu³⁺ and Tb³⁺ in the ILs were investigated by luminescence spectroscopy. The affect of the alkyl chain on the luminescent behavior (the asymmetry parameter (R), the lifetime of ⁵D₀, and the ⁵D₀ quantum efficiency) of Eu³⁺ has been discussed.     

Spectroscopic Investigation of the Europium(3+) Ion in a New ZnY4W3O16 Matrix

A new Zn and Eu tungstate was characterized by spectroscopic techniques. This tungstate, of the formula ZnEu₄W₃O₁₆, crystallized in the orthorhombic system and was synthesized by a solid‐state reaction. It melts incongruently at 1330°. The luminescent properties, including excitation and emission processes, luminescent dynamics, and local environments of the Eu³⁺ ions in ZnEu₄W₃O₁₆ and ZnY₄W₃O₁₆ : Eu³⁺ diluted phases (1, 5, and 10 mol‐% of Eu³⁺ ion) were studied basing on the f⁶‐intraconfigurational transitions in the 250–720 nm spectral range. The excitation spectra of this system (λ_em 615 and 470 nm) show broad bands with maxima at 265 and 315 nm related to the ligand‐to‐metal charge‐transfer (LMCT) states. The emission spectra under excitation at the O→W (265 nm) and O→Eu³⁺ (315 nm) LMCT states present the blue‐green emission bands. The emission of tungstate groups mainly originate from the charge‐transfer state of excited 2p orbitals of O^2? to the empty orbitals of the central W⁶⁺ ions. On the other hand, in the emission of the Eu³⁺ ions, both the charge transfer from O^2? to Eu³⁺ and the energy transfer from W⁶⁺ ions to Eu³⁺ are involved. The emission spectra under excitation at the ⁷F₀→⁵L₆ transition of the Eu³⁺ ion (394 nm) of ZnY₄W₃O₁₆ : Eu³⁺ diluted samples show narrow emission lines from the ⁵D₃, ⁵D₂, and ⁵D₁ emitting states. The effect of the active‐ion (Eu³⁺) concentration on the colorimetric characteristic of the emissions of the compound under investigation are presented.     

Tuning Mixed‐Valent Eu2+/Eu3+ in Strontium Formate Frameworks for Multichannel Photoluminescence

Cooperative performance of mixed‐valent Eu²⁺/Eu³⁺ in single‐compound phosphors offers significant advantages in color rendering and luminescence efficiency, but their synthesis is challenging because of Eu²⁺ oxidation. Using the tunable nature of the metal‐ion nodes in metal–organic frameworks (MOFs), we present an in situ reduction and crystallization route for preparing MOFs and doping Eu²⁺/Eu³⁺ with a controlled ratio. These materials exhibit rich photoluminescence, including intrinsic‐ and sensitized‐emissions of Eu²⁺ and Eu³⁺, and long‐lived luminescence from charge transfer. Color rendering can be easily achieved by fine‐tuning the valence states of Eu. A linear relation between temperature and the intensity ratio of Eu²⁺/Eu³⁺ emissions provides outstanding properties for applications as self‐calibrated luminescent thermometers with a wide working temperature range. Further incorporation of Tb³⁺ into the MOFs results in white light, utilizing all Eu²⁺,Tb³⁺, and Eu³⁺ emissions in a single crystalline lattice.     

Electrospinning preparation and properties of NaGdF4:Eu3+ nanowires

Eu³⁺ doped NaGdF₄ (NaGdF₄:Eu³⁺) nanocrystals in hexagonal crystal phase were prepared by a polyol method, and the size and morphology controllable NaGdF₄:Eu³⁺/PVP nano-composite fibers were obtained through the electrospinning technique, and then the NaGdF₄:Eu³⁺ nanowires were obtained by followed annealing. By changing the ratio of PVP to NaGdF₄ as well as the calcination temperature, the optimal conditions for synthesizing the NaGdF₄ nanowires were obtained, and the structural properties of the synthesized sample were characterized by powder X-ray diffraction (XRD) patterns and field emission scanning electron micrographs (SEM) images. The luminescent properties of the NaGdF₄:Eu³⁺ nanocrystals and nanowires were also studied in this paper. We observed that the luminescent intensity of NaGdF₄:Eu³⁺ nanowires was greatly increased compared to the annealed NaGdF₄:Eu³⁺ nanocrystals at the same temperature.     

Photophysical Properties of Lanthanide (Eu3+, Tb3+) Hybrid Soft Gels of Double Functional Linker of Ionic Liquid–Modified Silane

Four kinds of luminescent hybrid soft gels have been assembled by introducing the lanthanide (Eu³⁺, Tb³⁺) tetrakis β‐diketonate into the covalently bonded imidazolium‐based silica through electrostatic interactions. Here, the imidazolium‐based silica matrices are prepared from imidazolium‐derived organotriethoxysilanes by the sol–gel process, in which the imidazolium cations are strongly anchored within the silica matrices while anions can still be exchanged following application for functionalization of lanthanide complexes. The photoluminescence measurements indicated that these hybrid soft gels exhibit characteristic red and green luminescence originating from the corresponding ternary lanthanide ions (Eu³⁺, Tb³⁺). Further investigation of photophysical properties reveals that these soft gels have inherited the outstanding luminescent properties from the lanthanide tetrakis β‐diketonate complexes such as strong luminescence intensities, long lifetimes and high luminescence quantum efficiencies.     

Synthesis and photoluminescence of single crystals europium ion-doped BaF2 cubic nanorods

In this work, we used the hydrothermal method to synthesize Eu³⁺ ion-doped cubic BaF₂ nanorods, which is a luminescent material. The clubbed structures were well crystallized and exhibited face-centred cubic structures, as indicated by powder X-ray diffraction, scanning electron microscopy, electron diffraction, and transmission electron microscopy. The luminescent properties were studied, and local symmetry surrounding Eu³⁺ ions and electronic transition processes included. The results indicated that Eu³⁺ occupied only one C_4ν site in nanorods.     

Divalent Europium Nanocrystals: Controllable Synthesis,Properties, and Applications

Magnetic and luminescent bifunctional divalent europium nanocrystals (Eu²⁺ NCs) are a promising class of novel advanced materials that have various applications in magneto‐optic devices, catalysis, bioimaging, and solar cells. In the past few decades, much work has been carried out to study the synthesis, properties, and applications of Eu²⁺ NCs. The aim of this Minireview is to present the progress in preparing Eu²⁺ NCs based on the reported research, by describing the advantages and disadvantages of the synthesis methods. The morphologies and size are controlled through adjusting the experimental conditions. Eu²⁺ NCs show superior magnetic and luminescence properties simultaneously. Self‐assembly and doping with other ions are important routes to improve their magnetic and luminescence properties. Their applications in magneto‐optic devices are discussed. Some difficulties and challenges in the fabrication of Eu²⁺ NCs are discussed, such as water‐soluble Eu²⁺ NCs and tunable luminescence in the whole visible region.     

Li2O-Ln2O3-SiO2:Eu3+,Bi3+体系的结构

采用ｓｏｌ－ｇｅｌ法合成了系列发光体Ｌｉ２Ｏ－Ｌｎ２Ｏ３－ＳｉＯ２：Ｅｕ＾３＾＋，Ｂｉ＾３＾＋，并确定了发光体的物相结构。当Ｌｎ＾３＾＋＝Ｙ＾３＾＋和Ｌｎ＾３＾＋＝Ｌａ＾３＾＋时，紫外光激发下Ｅｕ＾３＾＋的发射分别以红光和橙光为主，只存在一种Ｅｕ＾３＾＋发光中心；Ｌｎ＾３＾＋＝Ｇｄ＾３＾＋时，至少存在两种Ｅｕ＾３＾＋发光中心和两种Ｂｉ＾３＾＋发光中心（共掺杂Ｅｕ＾３＾＋，Ｂｉ＾３＾＋的吸收和发射所     

Improved luminescent behavior of YVO4:Eu3+ ceramic phosphors by Li contents

Crystalline phase and surface morphology of phosphors are important factors to determine luminescent characteristics. Li-doped YVO₄:Eu³⁺ ceramic samples were prepared by a solid state reaction method. The Li⁺ concentration was varied from 1 to 3 wt% to improve crystallinity and surface morphology of ceramics. Influence of Li doping on luminescent properties of YVO₄:Eu³⁺ ceramics has been investigated. Photoluminescence spectra have been measured at room temperature using a luminescence spectrometer and excitation by a broadband incoherent ultraviolet light source with an excitation wavelength of 325 nm. The emitted radiation was dominated by a red emission peak at 620 nm radiated from the ⁵D₀ → ⁷F₂ transition of Eu³⁺ ions. As Li⁺ ion content increases from 0 to 2 wt%, the photoluminescence (PL) brightness improved. The brightness of 2 wt% Li-doped YVO₄:Eu³⁺ ceramic was increased by a factor of 1.43 in comparison with that of YVO₄:Eu³⁺ ceramic. The enhanced luminescence resulted not only from the improved crystallinity but also from the enhanced surface roughness. The luminescent intensity and surface roughness exhibited similar behavior as a function of Li⁺ ion concentration.     

有序介孔Al2O3∶RE3+的制备及Gd3+对Eu3+的能量传递

以P123为表面活性剂,异丙醇铝为铝源,用简易溶胶-凝胶法,获得了单掺和双掺Gd3+,Eu3+的介孔氧化铝组装体。用广角X-射线衍射仪(WAXD)进行了物相分析;小角X-射线衍射仪(SAXD)、比表面仪进行了孔结构分析和形貌表征;研究了组装体的发光性能并发现Gd3+对Eu3+有能量传递作用,并分析了能量传递过程。     

Hydrothermal homogeneous urea precipitation of hexagonal YBO3:Eu nanocrystals with improved luminescent properties

Well-crystallized YBO₃:Eu³⁺ nanocrystals were prepared by a mild hydrothermal method in the presence of urea, and a pure hexagonal phase could be obtained at a low temperature of 200°C only. The photoluminescence spectra showed a remarkable improvement on the chromaticity as well as the luminescent intensity, compared with the samples synthesized by solid-state reaction (SR). The effects of the synthesis temperature, urea concentration, and the doping concentration of Eu³⁺ on the crystallization and luminescent properties were investigated. The results showed that both high temperature and low urea concentration were favorable to the formation of YBO₃:Eu³⁺, and the ratio of red emission (⁵D₀→⁷F₂) to orange emission (⁵D₀→⁷F₁) increased with decreasing the synthesis temperature and the urea concentration. Furthermore, the samples exhibited a higher quenching concentration of Eu³⁺ in comparison with those prepared by the SR, which was beneficial to further enhancing the luminescent intensity. These synthesis-dependent phenomena were analyzed, and possible explanations were proposed.     

A new type of charge compensating mechanism in Ca5(PO4)3F:Eu phosphor

The X-ray powder diffraction, reflectance, photoluminescence, photoluminescence excitation and ESR spectra of Ca₅(PO₄)₃F:Eu³⁺ phosphor have been studied. Three distinct variants of calcium substitutional Eu³⁺-sites have been observed in this host and the charge compensating species related to each of these sites has been identified. It is noted that the host related trace impurities those have prospects of acting as charge compensator, and the reaction environment that exists during the preparation of the material, greatly influence the preferential substitution of different Ca²⁺-sites by the Eu³⁺ ions. It is also noted that the charge compensating species in a suitable case, takes part in the photophysical process of luminescence of the Eu³⁺.     

The Role of Ligand Topology in the Decomplexation of Luminescent Lanthanide Complexes by Dipicolinic Acid

In this study, we present the aqueous solution behavior of two luminescent lanthanide antenna complexes (Eu³⁺? 1 , Dy³⁺? 9 ) with different ligand topologies in the presence of dipicolinic acid (DPA, pyridine‐2,6‐dicarboxylic acid). Macrocyclic (1,4,7,10‐tetraazacyclododecane‐1,4,7‐triacetic acid, DO3A, 9 ) and acyclic (1,4,7‐triazaheptane‐1,1,7,7‐tetraacetic acid, DTTA, 1 ) ligands have been selected to form a ratiometric pair in which Dy³⁺? 9 acts as a reference and Eu³⁺? 1 acts as a probe for the recognition of DPA. The pair of luminescent complexes in water reveals the capability to work as a DPA luminescent sensor. The change of emission intensity of Eu³⁺ indicates the occurrence of a new sensitization path for the lanthanide cation through excitation of DPA. NMR evidence implies the presence of free 1 and mass spectrometry shows the formation of emitting [EuDPA₂]^? as a result of a ligand exchange reaction.     

Energy transfer and heat-treatment effect of photoluminescence in Eu-doped TbPO4 nanowires

We have successfully synthesized Eu³⁺-doped TbPO₄ nanowires, which are orderly organized to form bundle-like structure. A thermal treatment up to 600 °C does not modify the size, shape and structure of as-synthesized sample. Due to the energy overlap between Tb³⁺ and Eu³⁺, an efficient energy transfer occurs from Tb³⁺ to Eu³⁺. The effects of Eu³⁺ concentration and thermal treatment on the luminescent properties of Eu³⁺ are investigated. The increase of Eu³⁺ concentration leads to the increase of the energy transfer efficiency from Tb³⁺ to Eu³⁺, but also enhances the probability of the interaction between neighboring Eu³⁺, which results in the concentration quenching. With the heat-treatment, the luminescence of Eu³⁺ presents an obvious increase, but almost no change for the luminescence of Tb³⁺. This difference is explained based on the TGA, DTA, and fluorescent decay dynamics analyses.     

Towards the development of Eu(III) luminescent switching/sensing in water-permeable hydrogels

The synthesis of the Eu(III) complex 1.Eu and photophysical studies of this complex in solution are described. In water, the Eu(III) luminescence was ‘switched on’ in the presence of H⁺, with large enhancements in the Eu(III) luminescence. The complex was then incorporated into poly[methylmethacrylate-co-2-(hydroxyethylmethacrylate)]-based hydrogels and the luminescent properties of the resulting polymeric films were investigated using confocal laser-scanning microscopy as well as using steady-state luminescence. The luminescence was shown to be ‘switched on’ in the soft material after adjusting the pH of the solution in which the 1.Eu-incorporated film was immersed from alkaline to acid.     

Influence of the Matrix in the Optical Response of Organic-Inorganic Hybrid Materials Doped with Europium(III)

Eu³⁺-doped siloxane-oxide hybrid nanocomposites have been prepared by hydrolysis and condensation of diethoxydimethylsilane (DEDMS) and different metallic alkoxides, M(OR) _n with M = Ti, Zr, Al and Ta. The luminescent properties of Eu³⁺ have been used to study the environment of the rare earth ion within the matrices. Emission spectra shows that the surrounding of the Eu³⁺ varies with the matrix composition and depends on the nature of the metal introduced as cross-linking agent. In addition, decay curves have been performed and they show different lifetime values for each system. Among the systems under investigation, the one with tantalum presents the most anisotropic surrounding and the lowest coordination number for the rare earth ion, and the one with aluminium, which shows the most symmetrical surrounding, presents a small lifetime value, probably due to the tendency of Al³⁺cation to attract and retain hydroxyl groups, responsible for luminescence quenching.     

The luminescence of mercury-like ions in and the crystal structure of SrLaBO4

The crystal structure of SrLaBO₄ contains triangular borate groups. The luminescence of mercury-like ions (Sn²⁺, Sb³⁺, Tl⁺, Pb²⁺, Bi³⁺) in this host lattice is characterized by a large Stokes shift. The Pb²⁺ is a very efficient activator at room temperature. The luminescent properties are discussed in terms of earlier models related to an off-center position of the metal ion. The emission of Eu³⁺ shows that the crystal structure has a disordered nature and confirms an off-center position. Energy transfer from Pb²⁺ to Eu³⁺ and Tb³⁺ was studied and found to be inefficient.     

Mono(di)nuclear Europium(III) Complexes of Macrobi(tri)cyclic Cryptands Derived from Diazatetralactams as Luminophores in Aqueous Solution

To increase the excellent light-emitting properties of the Eu³⁺ ion, macrobicyclic and macrotricyclic ligands 7 – 10 , incorporating a 18-membered tetralactam ring (acting as a lanthanide binding site) and a sensitizer group (2,2′-bipyridine or 2,2′-bipyridine 1,1′-dioxide moiety), were synthesized. The mononuclear and dinuclear europium cryptates derived from these ligands were isolated and characterized. Their luminescent properties and those of the corresponding cryptates containing a phenanthroline group (see 11 and 12 ) were examined in H₂O and D₂O solutions at 77 and 300 K. It results that the tetralactam moiety plays a major role in the efficient shielding of the complexed Eu³⁺ ion from the water environment. The cryptands incorporating the bipyridine unit are the most promising labels according to their photophysical properties (excitation maxima, emission decay lifetime, relative luminescent yield). In contrast with literature data, introduction of N-oxide groups in the bipyridine chromophore weakens the luminescence properties of the cryptate.     

Small amount of water induced preparation of several morphologies for InBO3:Eu3+ phosphor via a facile boric acid flux method and their luminescent properties

Four kinds of morphologies for InBO₃:Eu³⁺ phosphor have been prepared via a facile boric acid flux method only by adjusting the small amount of added water. The prepared samples have been characterized by XRD, FT-IR, and SEM. It was found that the size and morphology of the samples could be effectively controlled by adjusting reaction temperature, reaction time, especially the small amount of added water, which plays an extremely critical role in the controlling morphology. The possible growth mechanisms for microsphere and flower-like morphologies were further discussed on the basis of time-dependent experiments. Furthermore, the luminescence properties of prepared InBO₃:Eu³⁺ samples have been investigated by photoluminescence (PL) spectra. The results show that the InBO₃:Eu³⁺ phosphors show strong orange emissions under ultraviolet excitation at 237 nm. The monodisperse microsphere sample possesses the highest PL intensity among above four morphologies, which can be used as a potential orange luminescent material.     

Properties of barium chlorophosphate (apatite) luminophors activated by divalent europium

A series of powder materials of barium and calcium chlorophosphate activated by divalent europium have been prepared. These luminophors are isomorphous representatives of the hexagonal chlorapatites (Ba, Ca, Mg)₁₀(PO₄)₆Cl₂. In addition to x-ray diffractograms, excitation and emission spectra of luminescence have been studied at room and low temperatures (T ∽ 4 K). An increasing calcium content affects the luminescence properties of the solid solutions by changing the crystal field acting upon the Eu²⁺ ion. The appearance of a new low-temperature emission band with higher Ca²⁺ content indicates that the Eu²⁺ ions substitute on two different barium sites thus forming two types of luminescent centres. The luminescence arises from transitions between 4f⁶5d and 4f⁷ configurations of Eu²⁺.