Influences of compositions and ligands on photoluminescent properties of Eu(III) ions in composite europium complex/PMMA systems

Three kinds of europium complexes; Eu(phen)₂Cl₃(H₂O)₂, Eu(DN-bpy)phenCl₃(H₂O)₂ and Eu(DB-bpy)phenCl₃(H₂O)₂ (phen: 1,10-phenanthroline, DN-bpy: 4,4′-Dinonyl-2,2′-dipyridyl, DB-bpy: 4,4′-Di-tert-butyl-2,2′-dipyridyl) were prepared and then incorporated into polymethyl methacrylate (PMMA) matrix with different molar ratios of CO groups/Eu³⁺ ions. The final solid composites were formed by a self-assembly process among Eu³⁺ ion, the ligands and PMMA during the solvent evaporation process, and then the ligands re-coordinate to Eu(III). It was found that the ligands affect not only the emission properties of the pure complexes, but also the miscibility of the complexes and PMMA. More than one kind of symmetric sites of Eu³⁺ ions were formed in the composites due to the coordination of CO in PMMA to Eu³⁺ ions. The micro-environments of Eu(III) in the composites were changed with the compositions and the ligands, leading to the change in the crystalline structure, and consequently, the emission characteristics.     

A terbium (III) complex with triphenylamine-functionalized ligand for organic electroluminescent device

A novel ligand, 4-diphenylamino-benzoic acid (HDPAB), and the corresponding Tb (III) complex, Tb (DPAB)₃ which can be dissolved easily in organic solvents were synthesized and characterized. Organic electroluminescent (EL) device with a structure of indium tin oxide (ITO)/poly(N-vinylcarbazole) (PVK): Tb (DPAB)₃ (50 wt%, 80 nm)/1,3,5-tris-(N-phenylbenzimidazol-2-yl)benzene (TPBI) (30 nm)/tri(8-hydroxyquinoline)aluminum (AlQ) (20 nm)/LiF (1 nm)/Al (150 nm) in which Tb (DPAB)₃ acted as an emitter were fabricated. The maximum luminance of 230 cd m⁻² at 20 V and the maximum efficiency of 0.62 cd A⁻¹ were obtained due to the introduction of hole-transporting group, representing the best result to date among Tb (III) carboxylate complexes based EL devices. These results indicate that modifications of rare earth complexes are a promising way to improve the properties of EL devices.     

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.     

Synthesis, characterization and fluorescence studies of a novel europium complex based sensor

A novel europium(III) complex was synthesized using TTA (α-thenoyltrifluoroacetone) as the first ligand and H₂bpdc (2,2′-bipyridine-3,3′-dicarboxylate) as the second ligand. Elemental analysis, thermal analysis, IR and UV–vis spectrum and fluorescence spectrum of the europium(III) complex were carried out. A characteristic Eu³⁺ fluorescence emission was observed in ethanol–water (1:1) solution, indicating that the complex is stable in solution and the emission of Eu(III) ions was not influenced by the water molecules. The fluorescence emission of the complex was quenched completely by the Co²⁺ and Fe³⁺ ions, but the quenched emission was recovered in the presence of glycine. Moreover, the Eu³⁺ emission was very sensitive to pH, so the complex can be used as pH-dependent fluorescence probe or chemosensors.     

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.     

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.     

A novel Re(I) complex for electroluminescence application: synthesis, theoretical studies, photophysical and electroluminescent properties

In this paper, we report a novel phosphorescent Re(I) complex of Re(CO)₃(ETCP)Br, where ETCP=1-ethyl-2-naphthalen -1-yl-1H-1,3,7,8-tetraaza-cyclopenta[l]phenanthrene, including its photophysical properties, geometric/electronic structures, electrochemical and thermal properties. Experimental data suggest that Re(CO)₃(ETCP)Br is a promising yellow emitter peaking at 540--nm with short excited state lifetime of ∼0.06 μs. Re(I) center localizes in a distorted octahedral field in Re(CO)₃(ETCP)Br and the emissive state of Re(CO)₃(ETCP)Br has metal-to-ligand-charge-transfer character, leading to the room-temperature phosphorescence. Further analysis reveals that Re(CO)₃(ETCP)Br has HOMO and LUMO energy levels at −6.03 V and −3.56 V, respectively, as well as its high thermal decomposition temperature of 377 °C. Using Re(CO)₃(ETCP)Br as a dopant, an electroluminescence peaking at 565-nm is realized, with a maximum luminance of 5900 cd/m² and a maximum current efficiency of 11.3 cd/A.     

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.     

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.     

Synthesis and luminescence properties of europium (III) complexes

Three types of europium complexes were synthesized by introducing benzoylacetone as the first ligand and 1, 10-phenanthroline, triphenylphosphine oxide, 2,2'-bipyridyl as the second ligand, respectively. The properties of above materials were characterized by infrared absorption spectra, UV-Vis absorption spectra and fluorescence spectra. Then, it was discussed that the different second ligands of europium complexes can affect their luminescence properties, and their intramolecular energy transfer models had been set up. The results indicated that ligands and complexes have a strong absorption of UV light and the three types of europium complexes exhibit characteristic luminescence of europium ion when excited by UV light. In addition, it is suggested that the fluorescence yield of europium complexes mostly depend on both the energy difference between the second ligand and the Eu3+ ion and the energy difference between the second ligand and the first ligand.     

Temperature dependence of the luminescence lifetime of a europium complex immobilized in different polymer matrices

The temperature dependence of the luminescence lifetime of temperature sensor films based on europium (III) thenoyltrifluoroacetonate (EuTTA) as sensor dye in various polymer matrices such as polystyrene (PS), polymethylmethacrylate (PMMA), polyurethane (PU) and model airplane dope was studied and compared. The luminescence lifetime of EuTTA was found to depend on the polymer matrix. The temperature sensitivity of lifetime was maximum for EuTTA-PS coating in the temperature range of 10-60 °C. The effect of concentration of the sensor dye in the polymer on the lifetime and temperature sensitivity was also studied.     

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.     

Synthesis and electroluminescent property of dinuclear aluminum 8-hydroxyquinoline complex

A new structural dinuclear aluminum 8-hydroxyquinoline complex (DAlq₃) with two aluminum chelate-center was designed and synthesized. It was assessed as light-emitting material in organic light-emitting device (OLED). The green light emission was observed in films and OLEDs. DAlq₃ has better electron mobility and also shows a higher electroluminescence (EL) efficiency than that of aluminum 8-hydroxyquinoline (Alq₃).     

铕与4-(4-吡啶甲酰基)苯甲酸配合物的合成与荧光性能研究

以Eu3+为中心离子,4-(4-吡啶甲酰基)苯甲酸(HPFBA)、1,10-菲罗啉(Phen)和三苯基氧膦(TPPO)为配体,合成了新型配合物Eu(PFBA)3(H2O)4,Eu(PFBA)3Phen(H2O)3和Eu(PFBA)3TPPO(H2O)3(PFBA=4-(4-吡啶甲酰基)苯甲酸根).红外光谱表明,形成配合...     

Samarium(III) picrate tetraethylene glycol complex: Photoluminescence study and active material in monolayer electroluminescent

A mononuclear Sm(III) complex involving Pic and EO4 (where Pic=picrate anion and EO4=tetraethylene glycol) has been studied. It shows a bright-orange emission when used as active material in a monolayer electroluminescent device of ITO/EO4-Sm-Pic/Al. The crystal structure of the complex consists of [Sm(Pic)₂(H₂O)(EO4)]⁺ cation and [Pic]⁻ anion. The Sm(III) ion is coordinated with nine oxygen atoms from one EO4 ligand in a pentadentate mode, two Pic anions each in bidentate and monodentate modes, and one water molecule. Both the terminal alcohol groups of the acyclic EO4 ligand were involved in the O-H…O hydrogen bonding by infinite one-dimensional (1D) chain within a symmetry direction [0 1 0]. The photoluminescence (PL) spectrum of the thin film shows the typical spectral features of the Sm(III) ion (⁴G_5/2→⁶H_7/2 transitions). The root-mean-square (rms) of the roughness of thin film is 30.605 nm and indicates that the formation of the monolayer electroluminescent device is not uniform and retains a high crystallinity. Typical semiconductor current-voltage (I-V) property was also observed in this device with threshold and turn voltages of 2.8 and 6.2 V, respectively. The [Sm(Pic)₂(H₂O)(EO4)](Pic)·H₂O complex can be applied as a luminescent center in OLED for bright-orange emission.     

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 copper(I) complexes with electron donor/acceptor embedded ligands: Synthesis, photophysical and electroluminescent properties

In this paper, we report the synthesis of four diimine ligands incorporated with an electron donor/acceptor, as well as their corresponding Cu(I) complexes with bis(2-(diphenylphosphanyl)phenyl) ether as an ancillary ligand, resulting in four phosphorescent Cu(I) complexes. Their crystal structures as well as photophysical and thermal properties are discussed in detail. Experimental data and theoretical calculations confirm that electron donor moieties and limited conjugation system may self-restrict geometry relaxation in excited states, leading to narrowed and blue-shifted emission bands. On the other hand, electron acceptor moieties and large coplanar conjugation system are ineffective in restricting geometry relaxation, leading to broadened and red-shifted emission bands. However, the introduction of electron donors compromises thermal stability of Cu(I) complexes. We also explore one of the Cu(I) complexes as a dopant for electroluminescence application, and a maximum luminance of 680 cd/m² peaking at 620 nm is achieved.     

Luminescence and magnetic properties of europium(III) carboxylatodibenzoylmethanates

This paper reports on the results of an investigation of the luminescence and magnetic properties of europium(III) carboxylates, which are determined by the structure of the Stark and Zeeman sublevels. It has been established that the energy splittings λ_lum between the ⁷ F ₀ ground level and the ⁷ F ₁ term in the luminescence spectra of these compounds well correlate with the energy splittings λ_magn obtained from magnetochemical measurements.     

新型稀土铕配合物Eu(o-BBA)3(phen)电致发光研究

研究了一种新的稀土配合物邻苯甲酰苯甲酸-1,10-菲咯啉-铕(Eu(o-BBA)3(phen))的电致发光特性.采用不同的电子传输层材料,制备了多种结构的有机电致发光器件及有机无机复合器件.比较了单层电致发光器件A:ITO/PVK:Eu/Al与有机无机复合器件B:ITO/PVK:Eu/ZnS/Al发光性能的不同.分析了采用无机半导体材料ZnS作为电子传输层的优点.研究结果表明采用无机的电子传输层,能有效地避免激基复合物的形成,提高器件的亮度同时保持稀土离子发光的色纯性.     

Photophysical properties of novel organic europium (III) complexes

Based on fluorescence and absorbance spectroscopy, the photophysical properties and mechanisms of novel organic europium (III) complexes in the case of different concentration in ethanol solution and solid flour were studied at room temperature. It was found that the complex absorption spectra are mainly due to the Phenanthroline ligand, gradually exhibit saturated absorption from shortwave to long wave with the concentration increased, and stretch and broaden to long wave. And four characteristic peaks of the fluorescence spectra are all emission spectra of Eu3+ in the complex, and the strongest emission wavelength was 617 nm corresponding to the (5)D0-->(7)F2 transition of Eu2+. And then, it is presented that the perturbation of acetanil ligand changes the parity state of Eu3+ energy field, resulting in the increase of (5)D0-->(7)F2 transition probability, making phenanthroline transfer its energy absorbed to Eu3+, and inducing 617nm strong emission of fluorescence peak.