Synthesis and electroluminescent properties of a carbozole-functionalized europium(III) complex

A novel europium(III) complex, tris(dibenzoylmethanate){1-[9-hexyl-9H-carbazole]-2-(2-pyridyl)-benzimidazole}europium(III) [Eu(DBM)₃(CAR-PyBM)] functionalized by a carbozole fragment, was synthesized and used as emitting material in organic electroluminescent (EL) devices. Compared with the device based on an unfunctional Eu(III) complex, [Eu(DBM)₃HPyBM] (HPyBM=2-(2-pyridyl)benzimidazole), the EL performances of the device using [Eu(DBM)₃(CAR-PyBM)] as an emitter was significantly enhanced due to the improvement of hole-transporting ability. The maximum efficiency and luminance of red emission achieved from the device with the configuration of ITO/N,N′-diphenyl-N,N′-bis(3-methylphenyl)-1,1′-biphenyl-4,4′diamine (TPD, 50 nm)/ [Eu(DBM)₃(CAR-PyBM)] (30 nm)/1,3,5-tirs-(N-phenylbenzimidazol-2-yl)benzene (TPBI, 20 nm)/LiF (1.5 nm)/Al were 4.2 cd/A and 200 cd/m², respectively.     

Synthesis and photoluminescent properties of YVO4:Eu nano-crystal phosphor prepared by Pechini process

A sol-gel technique emphasizing the Pechini process has been employed for the preparation of nano-crystal Eu³⁺-doped YVO₄ phosphor. The precursor powders were heated at 800 °C for 3 h to obtain good crystallinity with better luminescence. XRD results indicate that the second phase is not presented when the Eu³⁺ ion concentration is increased up to 50 mol%. The absorption and photoluminescent (PL) studies indicated that the energy is absorbed first by the host and then transferred to the emitting level of the Eu³⁺ ions. Excitation at 318 nm in terms of Eu³⁺ concentrations in YVO₄ powders shows that the YVO₄ phosphors display bright red luminescence at about 618 nm belonging to the ⁵D₀→⁷F₂ electric dipole transition, and a weak band in the orange region of the ⁵D₀→⁷F₁ transition at 594 nm. In addition, the time-resolved ⁵D₀→⁷F₂ transition presents a single-exponential decay behavior, revealing the decay mechanism of the ⁵D₀→⁷F₂ transition is a single decay component between Eu³⁺ ions only. The saturation of the emission intensity excited by the CTS when the Eu³⁺ concentration is 10 mol%. The concentration quenching is active when the Eu³⁺ concentration is larger than 10 mol%, and the critical distance is about 5.75 Å.     

The photoluminescent properties of europium and terbium ions co-doped one-dimensional gadolinium orthophosphate nanorods and microcrystals

The europium/terbium ion-doped gadolinium orthophosphate nanorods and microcrystals phosphors were synthesized by the hydrothermal reaction and solid-phase reaction, respectively. The structures, morphologies, and luminescent behaviors were compared. The microcrystals can obtain higher quantum efficiency compared with nanorods because of the different structures (monoclinic and hexagonal). In the ultraviolet-visible region, the gadolinium ions absorbed energy then transferred to europium and terbium ions. The energy transfer from terbium to europium existed both in microcrystals and in nanorods, and it was confirmed that the energy transfer efficiency from terbium to europium in nanorods is higher than that in microcrystals.     

Preparation, characterization, and luminescence properties of novel hybrid material containing europium(III) complex covalently bonded to MCM-41

In this paper, a novel luminescent organic-inorganic hybrid material containing covalently bonded ternary europium complex in mesoporous silica MCM-41 has been successfully prepared by co-condensation of tetrethoxysilane (TEOS) and the modified ligand 2-phenyl-1H-imidazo[4,5-f][1,10]phen-3-(triethoxysilyl)propylcarbamate (PIP-Si) in the presence of cetyltrimethylammonium bromide (CTAB) surfactant as template. PIP-Si containing 1,10-phenanthroline covalently grafted to 3-(triethoxysilyl)propyl isocyanate is used not only as a precursor but also as the second ligand for Eu(TTA)₃·2H₂O (TTA: 2-thenoyltrifluoroacetate) complex to prepare a novel functionalized mesoporous material. The resulted mesoporous composite materials, which demonstrate strong characteristic emission lines of Eu³⁺⁵D₀-⁷F_J (J=0, 1, 2, 3, 4), were characterized by Fourier transform infrared (FT-IR), small-angle X-ray diffraction, excited-state decay analysis. Emission intensity of the Eu(III) complex covalently linked to MCM-41 (Eu-MCM-41) increases with the increasing irradiation time, demonstrating better photostability compared with both pure Eu(III) complex and physically incorporated sample.     

A red europium (III) ternary complex for InGaN-based light-emitting diode

One kind of europium (III) ternary complex was synthesized, and its photoluminescence properties were investigated. This complex exhibits broad excitation band in near-UV range, and strong red emission which is due to the ⁵D₀–⁷F_j transitions of Eu³⁺ ions. The luminescence quantum yield for the Eu³⁺ complex is 0.17. Thermogravimetric analysis confirms a high thermal stability of the complex with a decomposition temperature of 344 °C. All the characteristics indicate that the Eu³⁺ complex is a highly efficient red phosphor suitable to be excited by near UV light. An intense red light-emitting diode was fabricated by combining the europium (III) ternary complex with a ~395 nm-emitting InGaN chip.     

Europium(III) Concentration Effect on the Spectroscopic and Photoluminescent Properties of BaMoO4:Eu

BaMoO₄:Eu (BEMO) powders were synthesized by the polymeric precursor method (PPM), heat treated at 800 °C for 2 h in a heating rate of 5 °C/min and characterized by powder X-ray diffraction patterns (XRD), Fourier Transform Infra-Red (FTIR) and Raman spectroscopy, besides room temperature Photoluminescence (PL) measurements. The emission spectra of BEMO samples under excitation of 394 nm present the characteristic Eu³⁺ transitions. The relative intensities of the Eu³⁺ emissions increase as the concentration of this ion increases from 0.01 to 0.075 mol, but the luminescence is drastically quenched for the Ba_0.855Eu_0.145MoO₄ sample. The one exponential decay curves of the Eu^{3+ 5}D₀→⁷F₂ transition, λ _exc = 394 nm and λ _em = 614 nm, provided the decay times of around 0.54 ms for all samples. It was observed a broadening of the Bragg reflections and Raman bands when the Eu⁺³ concentration increases as a consequence of a more disordered material. The presence of MoO₃ and Eu₂Mo₂O₇ as additional phases in the BEMO samples where observed when the Eu³⁺ concentration was 14.5 mol%.     

Syntheses and electroluminescent properties of two europium ternary complexes Eu(DBM)3(PBO) and Eu(DBM)3(PBT)

Two europium complexes, Eu(DBM)₃(PBO) and Eu(DBM)₃(PBT) (DBM=dibenzoylmethanato, PBO=2-(2-pyridyl)benzoxazole, PBT=2-(2-pyridyl)benzothiazole), were prepared and used as emitting materials in organic electroluminescent (EL) devices. The devices with the structures ITO/TPD/Eu(DBM)₃(PBO) (or Eu(DBM)₃(PBT)/BCP/Alq₃/Mg:Ag/Ag emit red light originating from the europium complexes.     

Photoactive thin films of polycaprolactam doped with europium (III) complex using phenylalanine as ligand

A photoactive complex based on europium(III) using the amino acid phenylalanine as ligand was prepared and characterized. The obtained europium(III)/phenylalanine complex presents an effective energy transfer from ligands to the rare earth center. The observed photoluminescent behavior for europium(III)/phenylalanine complex was similar to the well known europium(III)/ acetyl-β-acetonate hydrate. New photoactive polyamide thin films were prepared using polycaprolactam as host of these complexes. The structural characterizations of the films were studied through Rutherford backscattering (RBS), Fourier transform infrared (FTIR) and Raman spectroscopies. The polyamide films doped with the amino acid and acetyl-β-acetonate rare earth complexes maintain the original photoluminescent behavior, narrow emission bands corresponding to transitions ⁵D₀ → ⁷F_0-4, which indicates that this polymer is an excellent host to these complexes.     

A series of Eu(III) emitters with a novel triphenylamine-derived beta-diketone ligand

In this paper, a series of Eu(III)complexes with a novel triphenylamine-derived beta-diketone ligand are synthesized. Systematical research reveals that these Eu(III) complexes take an occasional antenna mechanism by transferring energy between singlet state of ligand and central Eu(III), which leads to much shortened excited state lifetimes of the corresponding Eu(III) complexes.     

Structural and luminescence studies of trivalent europium complexes with pentaethylene glycol and 18-crown-6 ligands in the presence of picrate anion

Two new isostructural complexes of europium picrate (Eu-Pic) with pentaethylene glycol (EO5) and 18-crown-6 (18C6) ligands formed complexes of molecular formula [Eu(Pic)₂(18C6)]⁺(Pic)⁻I and [Eu(Pic)₂(EO5)]⁺(Pic)⁻II have been isolated and characterised. Compound I showed 10-coordination number through six oxygen atoms from the 18C6 ligand and two bidentate picrate anions. Meanwhile, compound II exhibited 9-coordination number via six oxygen atoms from EO5 ligand, two oxygen atoms from a bidentate and one oxygen atom from monodentate picrate anions. Photoluminescence (PL) spectra of the solid-state europium complexes display sharp lines which are assigned to ⁵D₀→⁷F_0-4 and ⁵D₁→⁷F_1,2,4 transitions. No emission of polyether ligands is observed, indicating that the energy transfer from the polyether ligands to the Eu³⁺ ion is quite efficient. The PL spectra of [Eu(Pic)₂(OH₂)₆]⁺(Pic)⁻·6H₂O III, [Eu(NO₃)₃(OH₂)₃]·(18C6) IV, [Eu(NO₃)₃·6H₂O] V and Eu₂O₃VI are also observed. Compounds I-IV exhibited high Ω₂ intensity parameter values, namely 16.93, 10.23, 17.10 and 12.35 (in units of 10⁻²⁰ cm²), respectively. These relatively high values reflect the hypersensitive behaviour of the ⁵D₀→⁷F₂ transition and indicate that the Eu³⁺ ion is located in a highly polarisable chemical environment.     

Investigation of the influence of silver and tin on the luminescence of trivalent europium ions in glass

Europium-doped aluminophosphate glasses prepared by the melt-quenching technique have been studied by photoluminescence (PL) and X-ray photoelectron spectroscopy (XPS). The effects of silver and tin doping, and of further thermal processing on Eu³⁺ ions luminescence have been assessed. For the glass system containing only europium, Eu³⁺ PL observed under UV excitation is suggested to occur through energy transfer from the excited glass host. After silver and tin doping, an enhanced UV excited Eu³⁺ PL has been indicated to occur essentially due to radiative energy transfer from isolated Ag⁺ ions and/or two fold-coordinated Sn centers. Since thermal processing of the material leads to a quenching effect on Eu³⁺ PL and Ag nanoparticles (NPs) formation due to reduction of silver ions by tin, XPS was employed in order to investigate the possibility for Eu³⁺→Eu²⁺ reduction during HT as a potential source of the PL decrease. The data points towards Ag NPs as main responsible for the observed weakening of Eu³⁺ PL.     

铕(Ⅲ)-4-乙烯基吡啶共聚物稀土高分子配合物的合成及其光物理行为的研究

以4-乙烯基吡啶（4VP）与甲基丙烯酸甲酯（MMA）的共聚物为配体，并以邻菲洛啉（Phen)及2，2′-联吡啶（Bipy)小分子配体协同反应，与Eu(Ⅲ）配位，合成了稀土高分子配合物；通过FTIR表征了配合物的结构；通过紫外光谱与荧光光谱的测定，较充分地研究了稀土高分子配合物光致发光的光物理过程，实验结果表明，4-乙烯基吡啶共聚物通过吡啶环上的氮原子与稀土离子可直接配位；小分子配体的协同配位，可使稀土离子配位数趋于满足，且由于小分子配体能有效地加强能量吸收及分子内的能量传递，大大增强了配合物的荧光强度。     

Eu3+配合物掺杂聚合物的制备与光谱性能研究

以噻吩甲酰三氟丙酮(2-thenoyltrifluoroacetone , TTFA), 六氟乙酰丙酮(hexafluoro- acetylacetone, HFA)和甲基联苯甲酰(dibenzoylmethide, DBM) 分别为配体合成了Eu3+的三种β-二酮类配合物Eu(TTFA)3、Eu(HFA)3和 Eu(DBM)3,以及掺杂这三种配合物的聚合物（聚甲基丙烯酸甲酯,PMMA）,并用分光光度计对它们的荧光光谱特性进行了分析研究.结果表明,三种配合物中Eu(TTFA)3荧光强度最强,并分析了其原因,发现能级匹配、配体取代基、配体结构对称性等均对配合物发光效率有重要的影响.通过比对,证明了TTFA是Eu3+发红色荧光的优良配体.进一步研究还发现,Eu(TTFA)3掺杂PMMA中稀土离子的荧光强度和荧光寿命均随掺杂浓度（质量分数为0.08～0.5）的增加而增大.     

Synthesis and photophysical properties of novel polymeric Eu(III) complex with bicoordination ligand

A novel complex of Eu(III) with bicoordination ligand: 4,4′-bis[2-(2′-pyridyl) benzimidazol-yl]-biphenyl (Bmbp) has been synthesized. The structure of the ligand was characterized by ¹H NMR, FT-IR and UV-vis; Eu(III) complex was characterized by FT-IR, UV-vis, elemental analysis, conductivity measurements and gel-permeation chromatography (GPC). The luminescence properties were investigated by UV-vis and fluorescence spectra. The experimental results show that the complex contain more than one Eu(III) ion, the emission at 614 nm from the ⁵D₀→⁷F₂ electronic dipole transition is large enhanced, and the complex is excellent energy transfer from ligand to Eu³⁺in the solid state. Thermal property measurement and analysis show that it has a good thermal stability.     

The co-luminescence effect of a europium (III)-lanthanum (III)-gatifloxacin-sodium dodecylbenzene sulfonate system and its application for the determination of trace amount of europium (III)

A novel co-luminescence system based on the formation of a complex between europium (III) (Eu³⁺) and gatifloxacin (GFLX) in sodium dodecylbenzene sulfonate (SDBS) micelle solution containing lanthanum (III) (La³⁺) has been developed for the determination of Eu³⁺. The experimental results show that the complex formed by Eu³⁺ and GFLX here can emit the characteristic luminescence of Eu³⁺. With the addition of La³⁺, the luminescence intensity of the system was enhanced about 7-fold compared with that without La³⁺. Under the optimal conditions, the luminescence intensity exhibits an excellent linear relationship with Eu³⁺ concentration in the range of 1.0×10⁻¹⁰-5.0×10⁻⁸ mol L⁻¹. The correlation coefficient (r) is 0.9998, and the detection limit (3σ) is 7.0×10⁻¹⁴ mol L⁻¹. A test method with satisfactory accuracy based on this system was applied to determine trace amounts of Eu³⁺ in rare earth samples. In addition, the detailed luminescence mechanism of this system was investigated by analyzing the ultraviolet absorption spectra, surface tension, fluorescence polarization, quantum yield, and the number of water molecules in the first coordination sphere of the Eu³⁺ complex.     

Synthesis and characterization of core-shell europium(III)-silica nanoparticles

Luminescent core-shell europium(III)-silica nanoparticles were prepared using europium(III) chelate core structure and polyvinylpyrrolidone synthesis strategy for silica shell. Europium(III):naphtoyltrifluoroacetone:trioctylphosphineoxide complex was spontaneously agglomerated from organic solvent to water. Polyvinylpyrrolidone was adsorbed onto the core structure and stable silica shell was synthesized using tetraethylorthosilicate. Nanosized particles with a diameter of 71 ± 5 nm and 11 nm shell thickness were obtained with fluorescence decay rate of 517 μs and excitation and emission wavelengths of 334 and 614 nm, respectively.     

Ligand-to-metal charge-transfer quenching of the Eu(D1) state in europium-doped tris(2,2,6,6-tetramethyl-3,5-heptanedionato)gadolinium (III)

Rate constants for the decay of the Eu³⁺(⁵D₁) state in dilute Eu³⁺-doped tris(2,2,6,6-tetramethyl-3,5-heptanedionato)gadolinium(III) are reported for a temperature range 50-315 K. A temperature-independent contribution of 1.3×10⁶ s⁻¹ is attributed to carbonyl mediated ⁵D₁→⁵D₀ relaxation. A temperature-dependent contribution, that has been parameterized as k_CT=Ae^−E_a/kT with E_a=2540±140 cm⁻¹ and A=1.3×10¹² s⁻¹ is attributed to quenching of ⁵D₁ by a low-lying ligand-to-metal charge-transfer state (CTS). The height of the activation barrier, E_a, relative to the previously reported height for charge-transfer quenching of the Eu³⁺(⁵D₀) state in the pure europium analog (J. Phys. Chem. 100 (1996) 9216) is discussed in terms of mechanistic implications. Specifically, these data strongly suggest that quenching of ⁵D₁ by the charge-transfer state is mediated by the ⁵D₀ state with a novel, indirect mechanism.     

Study of Structural and Photoluminescent Properties of Ca8Eu2(PO4)6O2

In this work it is presented for the first time the nanostructured hydroxyapatites doped with 0.5, 1.0 and 2.0 wt% of Eu³⁺ prepared at room temperature by the mechanical alloying technique. X-ray diffraction powder (XRD), infrared (IR) and Raman scattering spectroscopy, scanning electron microscopy (SEM), microhardness measurements as well as luminescent data of Eu³⁺ were used to investigate the structural and optical properties of these nanomaterials. The electrical and dielectrical analyses were used with the intention of having a better comprehension about the electromagnetic fields in pure and doped hydroxyapatites.     

Hydrothermal preparation and photoluminescent properties of MgAl2O4: Eu spinel nanocrystals

Nanoplates of the MgAl₂O₄ spinel doped with Eu³⁺ ions were prepared by a microwave assisted hydrothermal method. Structural properties of the precursor calcined at 700 and 1000 ^oC powders were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). According to the obtained XRD patterns the formation of single-phase spinels after calcination was confirmed. The average spinel particle size was determined to be 11 nm after calcination at 700 °C and it increased up to 14 nm after calcination at 1000 °C. The photoluminescent properties of prepared powders with different Eu³⁺ ion concentrations (0-5% mol) were investigated using excitation and emission spectroscopy at room and low temperatures (77 K).     

Improvement in mechanical and optical properties of vapour chopped vacuum evaporated PANI/PMMA composite thin film

PANI/PMMA composite was synthesized by emulsion polymerization pathway and the composite thin film was obtained by vacuum evaporation. The effect of vapour chopping and varying PMMA concentration was also studied. The FTIR spectra showed that the PANI/PMMA composite thin film deposited as a short chain oligomers. Increase in transmittance and decrease in refractive index was obtained with increasing concentration of PMMA, which further increased the adhesion and decreased intrinsic stress. The vapour chopping improved its optical as well as mechanical properties and produced smoother surface morphology. Increase of PMMA made the film more amorphous and does not change its band gap.