Europium Complex Eu Research Articles

Electrospinning Preparation and Photoluminescence Properties of Rare-Earth Complex/Polymer Composite Fibers

Composite fibers of poly(vinyl pyrrolidone) (PVP, Mw ≈ 1 300 000) and europium complex Eu(BA)3(TPPO)2 (BA =1-benzoylacetone; TPPO = triphenylphosphine oxide) with strong photoluminescence were prepared by electrospinning. Their luminescent properties were studied in comparison to that of the pure complex. The results indicate that due to decreased symmetry in the composites the excitation bands are split into two different components, peaking at ∼246 and ∼336 nm, respectively, while the ratio of the electronic dipole 5D0-7F2 transitions to the magnetic dipole 5D0-7F1 ones in the emission spectra becomes a little larger. The room temperature fluorescence lifetime for the 5D0 level becomes shorter due to increased radiative and nonradiative transition rates. The temperature dependence of photoluminescence was investigated under 325-nm excitation. It is interesting to observe that in the composite fiber the total emission intensity of the Eu3+ ions changes little below 150 K, while in the pure complex the in...

Modified photoluminescence properties of rare-earth complex/polymer composite fibers prepared by electrospinning

Efficiently luminescent composite fibers of poly (vinyl pyrrolidone) (Mw≈1300000) and europium complex Eu(TTA)3(TPPO)2 (TTA is thenoyltrifluoroacetone; TPPO is triphenylphosphine oxide) were prepared by electrospinning, with average diameters of 200–500nm and lengths of several tens of micrometers. Their photoluminescence properties were studied in comparison to the pure Eu(TTA)3(TPPO)2 complex. It was significant to observe that the thermal stability of photoluminescence in the composite fibers was improved considerably over the pure complex.

Effects of synergetic ligands on structure and fluorescence properties of Langmuir and Langmuir–Blodgett films containing Eu(TTA) 3nL

Effects of synergetic ligands of the europium complexes Eu(TTA) 3nL (Eu denotes the central ion Eu(III), TTA denotes the β-diketone ligand α-thenoyltrifluoroacetone, L denotes the synergetic ligands triophenylphosphine oxide, 1,10-phenanthroline, 2,2′-bipy and H 2O, respectively) on fluorescence properties and supermolecular structures of Langmuir and Langmuir–Blodgett films were studied. Experiments on the Langmuir trough showed that different supermolecular structures were formed for each complex with different synergetic ligands, in which aggregate structure was found at the air/subphase interface for Eu(TTA) 3Phen and multilayer structure for the other three complexes. This result is accordance with the R values calculated in terms of their fluorescence spectra. Fluorescence enhancement was found to be in an order of the relative emission intensity of the fluorescent LB films: I(Eu(TTA) 3(TPPO) 2) > I(Eu(TTA) 3Phen) > I(Eu(TTA) 3Bipy) > I(Eu(TTA) 3·2H 2O). Detailed analysis on the LB film containing Eu(TTA) 3(TPPO) 2 revealed that the LB film containing Eu(TTA) 3(TPPO) 2 not only have the strongest red light emit, the best monochromacity, good miscibility with arachidic acid (AA), but also have condensed structure, controllable nanometer-scale thickness and vertical uniformity.

Improved electroluminescent performances of europium-complex based devices by doping into electron-transporting/hole-blocking host

High-efficiency, pure red organic light-emitting devices were fabricated by doping a europium-complex Eu(DBM)3pyzphen (DBM=dibenzoylmethane, pyzphen=pyrazino[2,3-f][1,10]phenanthroline) into 4,7-diphenyl-1,10-phenanthroline as emission layer. A maximum current efficiency of 5.1cd∕A at the current density of 1.2mA∕cm2 and a maximum luminance of 1400cd∕m2 were obtained from a 25wt% Eu(DBM)3pyzphen doped device. High efficiencies were maintained at high current densities and high luminance. For example, at the current density of 10mA∕cm2, the efficiency reached 3.8cd∕A. It means that the efficiency roll-off, a major obstacle to the development of Eu-complex ogranic light-emitting devices, was greatly alleviated. The mechanisms behind the improvement are discussed.

Highly efficient red electroluminescence from stacked organic light-emitting devices based on a europium complex

Stacked organic light-emitting devices (OLEDs) based on a europium complex Eu(TTA) 3(Tmphen) (TTA = thenoyltrifluoroacetone,Tmphen = 3,4,7,8-tetramethyl-1,10-phenanthroline) were fabricated. In this stacked OLEDs, Li:BCP/V 2O 5 was used the intermediate charge generation layer sandwiched between two identical emissive units consisting of TPD/CBP:DCJTB:Eu(TTA) 3(Tmphen)/BCP. As expected, the brightness and electroluminescent (EL) current efficiency were approximately enhanced by double times that of conventional single-unit devices. The stacked OLEDs showed the maximum luminance up to 3000 cd/m 2 at a current density of 190 mA/cm 2 and a current efficiency of 14.5 cd/A at a current density of 0.08 mA/cm 2. At the brightness of 100 cd/m 2, the current efficiency reached 10 cd/A at a current density of 1.6 mA/cm 2.

A NEW PHOSPHOR MADE BY A HIGHLY EMITTED EUROPIUM COMPLEX ADSORBED ON NANOSTRUCTURED TiO2 FILMS

Transparent mesoporous TiO 2 films consisting of uniform anatase particles have been deposited on glass slides by using sol-gel technique. A Europium complex Eu(TTA) 3 (bpy) , where the TTA ligand is β-diketonate thenoyltrifluoroacetonate and the bpy is 2,2-bipyridine, was formed on TiO 2 surface by physical adsorption of europium ions and successive formation of stable chelate complexes with TTA and bpy ligands. In this way a well dispersion of the complex has been achieved giving significant emission intensity. The excitation of the material in the UV region (374 nm) results in the emission of a nearly monochromatic light at 613 nm (5D0→7F2) via energy transfer from the excited organic ligands to europium emissive state.

Tuning the Triplet Energy Levels of Pyrazolone Ligands to Match the 5D0 Level of Europium(III)

Three pyrazolone-based ligands, namely 1-phenyl-3-methyl-4-(1-naphthoyl)-5-pyrazolone (HL1), 1-phenyl-3-methyl-4-(4-dimethylaminobenzoyl)-5-pyrazolone (HL2), and 1-phenyl-3-methyl-4-(4-cyanobenzoyl)-5-pyrazolone (HL3), were synthesized by introducing electron-poor or electron-rich aryl substituents at the 4-position of the pyrazolone ring. Their corresponding europium complexes Eu(LX)3(H2O)2 and Eu(LX)3(TPPO)(H2O) (X = 1-3) were characterized by photophysical studies. The characteristic Eu(III) emission of these complexes with at most 9.2 x 10(-3) of fluorescent quantum yield was observed at room temperature. The results show that the modification of ligands tunes the triplet energy levels of three pyrazolone-based ligands to match the 5D0 energy level of Eu3+ properly and improves the energy transfer efficiency from antenna to Eu3+, therefore enhancing the Eu(III) emission intensity. The highest energy transfer efficiency and probability of lanthanide emission of Eu(L1)3(H2O)2 are 35.1% and 2.6%, respectively, which opens up broad prospects for improving luminescent properties of Eu(III) complexes by the modification of ligands. Furthermore, the electroluminescent properties of Eu(L1)3(TPPO)(H2O) were also investigated.

The condition for electroplex emission from an europium complex doped poly( N-vinylcarbazole)

Spectral characteristics of photoluminescence (PL) and electroluminescence (EL) of poly( N-vinylcarbazole) (PVK) matrices doped with a novel europium complex Eu(aspirin) 3phen were investigated. A red-shift and broadening were observed in the EL spectra but not in the PL ones. However, neither red-shift nor broadening were observed in the EL spectra of PVK doped with a similar complex with the same ligand, terbium complex (Tb(aspirin) 3phen). This result suggests the formation of electroplexes in blend systems, which is likely due to inefficient energy transfer from host molecules to dopant molecules.

White Light Electroluminescence from a Dendritic Europium Complex

Abstract A novel dendritic europium complex Eu(TCPD)3(Phen) with carbazole units as the periphery has been prepared and the device ITO//NPB//CBP:Eu(TCPD)3(Phen)//BCP//Mg:Ag gave out white light with the CIE coordinate (0.333, 0.348) at 16.2 V and maximum external quantum efficiency of 1.1%.

Photoluminescence Characterization of Silicon NanoparticlesHybridized Europium Complex

A europium complex Eu (DBM)3 TPPO (Eu tris(benzoylmethide)-(triphenylphosphine oxide)) and silicon nanoparticles have beenhybridized. The hybridization can evidently change thephotoluminescence (PL) characteristics of the Eu complex in thefollowing aspects: under an excitation of 390 nm, the intensity of thePL peak at 611 nm due to the 5D0–7F2 transition of theEu3+ ions has been increased by 30%, and the integrated PLintensity in the visible range has been increased by nearly 3 times; thePL excitation efficiency beyond 440 nm has been improved evidently; thepeak in the PL excitation spectrum shifts from 408 to 388 nm, and thePL decay time decreases from 2.07 to 0.96 μs. The experimental resultsindicate that in the PL process, the photoexcited energy may transferfrom the silicon nanoparticles to the Eu3+ ions.

Studies on photoluminescent properties of Eu(III) ions in composite europium complex/polymer systems

Europium complex Eu(DB-bpy)phenCl 3(H 2O) 2 ( phen: 1,10-phenanthroline, DB-bpy: 4,4′-di- tert-butyl-2,2′-dipyridyl) was doped in poly(methyl methacrylate) (PMMA) and poly(vinyl pyrrolidone) (PVP). The composite systems with various molar ratios of C O groups/Eu 3+ ions were characterized by photoluminescent (PL) spectroscopy, X-ray diffractometry (XRD) and luminescent lifetime measurements. It was found that Eu 3+ ions have more than one kind of symmetrical sites in Eu/PMMA composites and the PL spectra of Eu(III) change with the compositions. However, the composites of Eu/PVP with different molar ratios show similar PL spectra, indicating different influence of matrices on luminescent properties.

Distinct composite structure and properties of Eu(phen)2Cl3(H2O)2 in poly(methyl methacrylate) and polyvinylpyrrolidone

The luminescent europium complex Eu(phen)2 Cl3(H2O)2 (phen refers to 1,10-phenanthroline) was doped in poly(methyl methacrylate) (PMMA) and polyvinylpyrrolidone (PVP), respectively. The formed composite systems with different molar ratios of CO groups in polymers and Eu ions were characterized by X-ray diffractometry (XRD), FTIR, and photoluminescent (PL) spectroscopy and lifetime measurement. The XRD diffractograms show that the composites of PMMA/Eu(phen)2Cl3(H2O)2 and PVP/Eu (phen)2Cl3(H2O)2 have crystalline and amorphous structures, respectively, arising from different interactions between the polymers and the complex, as revealed by FTIR spectra. This leads to distinct luminescent characteristics arising from the 5D07FJ transitions of Eu(III) ion (J = 0–4). For the composite systems of PMMA/complex, the characteristics of the emission lines change with decreasing molar ratios of CO/Eu and approach that of the pure complex; whereas the composite systems of PVP/complex have similar spectral features, regardless of the molar ratios, differing from that of the pure complex. The polymer matrices have a substantial influence on the structure and properties of the composites. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 3524–3530, 2004

Efficient red organic light-emitting devices based on a europium complex

An efficient organic light-emitting device using a trivalent europium (Eu) complex Eu(Tmphen)(TTA)3 (TTA=thenoyltrifluoroacetone, Tmphen=3,4,7,8-tetramethyl-1,10-phenanthroline) as the dopant emitter was fabricated. The devices were a multilayer structure of indium tin oxide/N,N-diphenyl-N,N-bis(3-methylphenyl)-1,1-biphenyl-4,4-diamine (40 nm)/ Eu complex:4,4-N,N-dicarbazole-biphenyl (1%, 30 nm)/2,9-dimethyl,4,7-diphenyl-1,10phenanthroline (20 nm)/AlQ (30 nm)/LiF (1 nm)/Al (100 nm). A pure red light with a peak of 612 nm and a half bandwidth of 3 nm, which is the characteristic emission of trivalent europium ion, was observed. The devices show the maximum luminance up to 800 cd/m2, an external quantum efficiency of 4.3%, current efficiency of 4.7 cd/A, and power efficiency of 1.6 lm/W. At the brightness of 100 cd/m2, the quantum efficiency reaches 2.2% (2.3 cd/A).

Preparation and characterization of luminescent cubic MCM-48 impregnated with an Eu 3+ β-diketonate complex

We report on the preparation of luminescent silica mesoporous molecular sieves (MCM-48) activated by the europium complex Eu(DBM) 3 · 2H 2O (where DBM=dibenzoylmethane), using a simple wet impregnation method. Different concentrations of Eu(DBM) 3 · 2H 2O were introduced into the MCM-48 cubic structure, and the resulting samples were washed with ethanol for different times. UV–Vis absorption measurements and thermogravimetric analysis were used to estimate the amount of Eu complex that has been incorporated within the pores of the MCM-48 host. The various samples were characterized by X-ray powder diffraction (XRD), infrared spectroscopy, diffuse reflectance (DR) and fluorescence measurements. The results reveal that Eu complexes have been successfully introduced into the pores of MCM-48 without disrupting the structure. All the impregnated MCM-48 materials show the typical red luminescence of Eu 3+ when excited with a UV lamp. Shifts of the absorption maxima were observed in the DR and fluorescence excitation spectra and will be discussed in relation with guest-host interactions between the organic complex and the silica matrix. The decay profiles of the europium luminescence in the different samples were also measured and discussed.

Synthesis of New Europium Complexes and Their Application in Electroluminescent Devices

AbstractSeveral substituted phenanthrolines (L = pyrazino[2,3‐f][1,10]phenanthroline (PyPhen), 2‐methylpyrazino[2,3‐f][1,10]phenanthroline (MPP), dipyrido[3,2‐a:2′,3′‐c]phenazine (DPPz), 11‐methyldipyrido[3,2‐a:2′,3′‐c]phenazine (MDPz), 11,12‐dimethyldipyrido[3,2‐a:2′,3′‐c]phenazine (DDPz), and benzo[i]dipyrido[3,2‐a:2,3‐c]phenazine (BDPz)) were successfully prepared and europium complexes Eu(TTA)3L (Eu‐L) based on these ligands were synthesized from EuCl3, 2‐thenoyltrifluoroacetone (TTA) and L in good yields. Irradiation at the absorption band between 320–390 nm of all these europium complexes, except Eu‐BDPz, in solution or in the solid state leads to the emission of a sharp red band at ∼ 612 nm, a characteristic Eu3+ emission due to the transition 5D0 → 7F2. No emission from the ligands was found. The result indicates that complete energy transfer from the ligand to the center Eu3+ ion occurs for these europium complexes. In contrast, the photoluminescence spectrum of Eu‐BDPz exhibits a strong emission at around 550 nm from the coordinated BDPz ligand and a weak emission at 612 nm from the central europium ion. Incomplete energy transfer from the ligand to the central Eu3+ ion was observed for the first time. Several electroluminescent devices (A–I) using Eu‐PyPhen, Eu‐MPP, Eu‐DPPz, and Eu‐DDPz as dopant emitters with the device configuration: TPD or NPB (50 nm)/Eu:CBP (1.7–7 %, 30 nm)/BCP (20–30 nm)/Alq (25–35 nm) (where TPD: 4,4′‐bis[N‐(p‐tolyl)‐N‐phenylamino]biphenyl; NPB: 4,4′‐bis[1‐naphthylphenylamino]biphenyl; CBP: 4,4′‐N,N′‐dicarbazole biphenyl; BCP: 2,9‐dimethyl‐4,7‐diphenyl‐1,10‐phenanthroline; Alq: tris[8‐hydroxyquinoline]aluminum) were fabricated. Some of these devices emit saturated red light and are the only europium complex‐based devices that show a brightness of more than 1000 cd m–2.

Europium complex as a highly efficient red emitter in electroluminescent devices

Several devices using a europium complex Eu(TTA)3(DPPz)(TTA=2-thenoyltrifluoroacetonate, DPPz=dipyrido[3,2-a:2′,3′-c]phenazine) as dopant emitter were fabricated. The performances of these devices are among the best reported for devices incorporating a europium complex as a red emitter. One such device with structure TPD (50 nm)/Eu:CBP (4.5%, 30 nm)/BCP (30 nm)/Alq (25 nm) exhibits an external quantum efficiency 2.1%, current efficiency 4.4 cd/A, power efficiency 2.1 lm/W, and brightness 1670 cd/m2.

Enhanced electroluminescent efficiency from spin-coated europium(III) organic light-emitting device

Devices containing the europium complex Eu(TTFA) 3(phen) were fabricated by spin-coating. The complex was doped into poly(9-vinylcarbazole) (PVK) along with (4- tert-butylphenyl)biphenyloxadiazole (PBD) as electron-transporting material. Addition of an evaporated layer of 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (bathocuproine, BCP) forming a two-layer device structure between indium-tin oxide (ITO) and Ca:Al electrodes gave enhanced brightness and efficiency. A device 3 wt.% Eu(TTFA) 3(phen):32 wt.% PBD:PVK with a BCP hole-blocking layer gave Eu emission with a maximum luminance of 417 cd m −2 at 25 V and 175 mA cm −2.

Electroluminescence of a novel europium complex

Electroluminescent devices using a ternary europium complex Eu(DBM) 3(hhpy) 2 (dibenzoylmethane, DBM; hexahydro pyridine, hhpy) as an emitting layer, poly(vinyl-carbazole) (PVK) as a hole-transporting material and tris-(8-hydroxyquinoline) aluminum (Alq 3) as an electron-transporting material have been fabricated. When only using Eu(DBM) 3(hhpy) 2 as the emitting layer, luminance of 2.52 cd/m 2 with pure Eu 3+ EL emissions from devices is achieved. Introducing a hole transporting material PVK and an electron transporting material 2-(4-biphenylyl)-5-(4- tert-butylphenyl)-1,3,4-oxidiazole (PBD) in the emitting layer, luminance of 100 cd/m 2 is achieved, and the eletroluminescence efficiency is enhanced by about two orders of magnitude.

Electrochemical and NMR spectroscopic investigations of the influence of the probe molecule Eu(fod) 3 on the permeability of lipid membranes to ions

Investigating the action of the fluorinated europium complex Eu(fod) 3 on lipid membranes we found that the complex facilitates the ion transfer through the membrane. Electric measurements on planar lipid membranes showed that the membrane conductivity increases considerably by insertion of the complex into the membrane. The increase in the conductivity was only obtained if both layers of the membrane were modified with the complex. 1H NMR spectroscopic studies using DOPC liposomes gave information about the location of the modifier complex in the lipid membrane. From chemical shift effects we concluded that the complex resides in the choline head group region of the membrane and also in the membrane interior near the –CC– lipid double bond, but not in the center of the bilayer. For understanding of the mentioned conductivity effect we assume that the europium complex induces defects of yet unknown structure in the lipid matrix which provide paths for the ion transfer through the membrane. As appropriate measurements revealed, these paths seem to conduct cations predominantly. Investigating the current–voltage behavior of the modified lipid membranes in dependence on the ion concentration we obtained different shaped current–voltage curves. Calculation showed that a model with only one energy barrier inside the membrane is unable to describe these curves kinetically. However, by assuming two energy barriers – one barrier in each membrane lipid layer – the observed curve can be described satisfactorily.

Voltage-dependent recombination region movement in organic light-emitting diodes (OLEDs) based on a europium complex-doped polymer

The europium complex Eu (bphse) 3(ClO 4) 3 was dissolved in chloroform and doped into poly(N-Vinylcarbazole) (PVK). The doped polymer was sandwiched between a hole transport layer of poly(p-phenylene vinylene) (PPV) and an electron transport layer tris (8-hydroxy quinoline) aluminium (Alq 3) by spin coating, to form a three-layer organic light-emitting device. The observed electroluminescence of the devices varied from green to orange with applied voltage and the different electroluminescence (EL) spectra were recorded. The results of our experiments indicate that the recombination region of holes and electrons in the devices moves from the Alq 3 layer towards the PVK : Eu layer with increasing applied electric field.