Luminescent properties of PP and LDPE films and rods doped with the Eu(III)‐La(III) complex

The work is devoted to luminescent properties of trivalent lanthanide complexes dispersed in thermoplastic host matrices. Polyethylene films and polypropylene‐rods, both doped with these complexes, were manufactured using an extrusion technique. Two kinds of dopants were used: Eu(III)‐thenoyltrifluoroacetone‐1,10‐phenanthroline complex (1) and Eu(III)‐La(III)‐1,10‐phenanthroline complex (2). Absorption, excitation, emission spectra and lifetime of luminescence were studied. The impact of the polymer matrix on the emission spectra was investigated. Emission spectra of the films were studied at room and helium temperatures. Time‐of‐flight secondary ion mass spectrometry (TOF‐SIMS) surface mapping showed that in the Eu(III)‐La(III) complex europium forms islands (clusters) with a dimension of 1 µm, whereas lanthanum was dispersed more uniformly in the polymer matrix. Dependence of emission intensity on the excitation was determined. Copyright © 2006 John Wiley & Sons, Ltd.     

Synthesis and characterization of a Eu-containing polymer precursor featuring thenoyltrifluoroacetone and 5-acrylamido-1,10-phenanthroline

A polymerizable ligand, 5-acrylamido-1,10-phenanthroline (L), was synthesized. Its Eu(III) complex with 2-thenoyltrifluoroacetone (HTTA) was prepared and characterized by elemental analysis, IR, MS, and ¹H NMR spectra. The photophysical properties of the complex were studied in detail by using UV, luminescence spectra, luminescence lifetime and quantum yield. The complex shows a remarkable luminescence quantum yield at room temperature (40.1%) upon ligand excitation and a long ⁵D₀ lifetime (590 μs), which makes it not only a promising light-conversion molecular device but also an excellent luminescent polymer precursor.     

Photokinetics of gas phase europium(III) chelated with hexafluoroacetylacetonate

The europium chelate salt, triethylammonium tetrakis-hexafluoroacetylacetone europium(III), was evaporated into the gas phase and the luminescence properties of the gas phase material were examined. The rate of decay of luminescence of the gas phase europium chelate was observed to increase with temperature. An activation energy of 2650 cm⁻¹ was measured for the barrier to non-radiative decay from the ⁵D₀ state. The quantum yield for formation of the ⁵D₀ state showed a slight temperature dependence at temperatures above 220°C.     

Luminescence studies of europium chelates with increasing benzene ring substituents ligand-doped polymer

The luminescence properties of four europium chelates with increasing benzene ring substituents ligand in poly(methylmethacrylate) (PMMA) have been investigated by fluorescence emission spectra and lifetime measurements. According to the fluorescence emission spectra, the Judd-Ofelt parameters Omega2, Omega4 of europium chelates-doped PMMA have been calculated and the radiative properties were also presented. It showed that the increase of benzene ring substituents in ligand can increase the metastable state lifetime tau(m), the luminescence quantum yield eta and the stimulated emission cross-section sigma of 5D0-->7F2 transition.     

Solution Chemistry of Europium(III) Aqua Ion at Micromolar Concentrations as Probed by Direct Excitation Luminescence Spectroscopy

Direct excitation europium(III) luminescence spectroscopy is used to study the speciation of aqueous europium(III) ions at micromolar concentrations and near neutral pH. The pH and concentration dependence of the europium(III) ⁷F₀→⁵D₀ excitation peak is consistent with the formation of both mononuclear and dinuclear europium(III) hydroxide complexes at pH 6.5. Luminescence intensity and lifetime quenching studies in the presence of Nd^III at pH 5.0 and 6.5 support the formation of a dinuclear complex at pH 6.5. Steady state excitation and time‐resolved luminescence spectroscopy are consistent with the formation of innersphere nitrate and fluoride complexes, but outersphere perchlorate and chloride complexes at pH 6.5 and 5.0.     

Synthesis, optophysical and electrochemical properties of bipolar-transporting europium(III) complexes with carbazole and oxadiazole units

A series of bipolar-transporting europium(III) complexes containing carbazole and oxadiazole units were synthesized and characterized. Two intense UV absorption bands at around 286 nm and 352 nm, and sharply red emissions peaked at 614 nm were observed for these europium complexes in dichloromethane. Importantly, the bipolar-transporting europium(III) complexes exhibited higher thermal stability, more intense UV absorption at 286 nm and twofold increased photoluminescent quantum yield compared to the reported red chromophore of tri(dibenzoylmethane) (1,10-phenanthroline) europium(III).     

Listening to Lanthanide Complexes: Determination of the Intrinsic Luminescence Quantum Yield by Nonradiative Relaxation

The photophysical properties of lanthanide complexes have been studied extensively; however, fundamental parameters such as the intrinsic quantum yield as well as radiative and nonradiative decay rates are difficult or even impossible to measure experimentally. Herein, a photoacoustic (PA) method is proposed to determine the intrinsic quantum yield of lanthanide complexes with lifetimes in the order of milliseconds. This method is used to determine the intrinsic quantum yields for europium(III)‐containing metallomesogens as well as terbium(III) complexes. The results show that the PA signal is sensitive to both the lifetime and the ratio of the fast‐to‐slow heat component of the samples. It is found that there is an efficient ligand sensitization and a moderate intrinsic quantum yield for the complexes. The intrinsic quantum yield of Eu³⁺ in the metallomesogens exhibits an obvious increase upon the isotropic liquid to smectic A transition. The proposed PA method is quite simple, and can contribute to a clearer understanding of the photophysical processes in luminescent lanthanide complexes.     

Efficient sensitization of europium, ytterbium, and neodymium functionalized tris-dipicolinate lanthanide complexes through tunable charge-transfer excited states

A series of push-pull donor-pi-conjugated dipicolinic acid ligands and related tris-dipicolinate europium and lutetium complexes have been prepared. The ligands present broad absorption and emission transitions in the visible spectral range unambiguously assigned to charge-transfer transitions (CT) by means of time-dependent density functional theory calculations. The photophysical properties (absorption, emission, luminescence quantum yield, and lifetime) of the corresponding europium complexes were thoroughly investigated. Solvatochromism and temperature effects clearly confirm that Eu(III) sensitization directly occurs from the ligand CT state. In addition, modulation of the energy of the CT donating state by changing the nature of the donor fragment allows the optimal energy of the antennae for europium sensitization to be determined, and this optimal energy was found to be close to the (5)D 1 accepting state. Finally, this CT sensitization process has been successfully extended to near-infrared emitters (neodymium and ytterbium).     

Strongly photoluminescent Eu(III) tetrazolate ternary complexes with phosphine oxides as powerful sensitizers

The Eu(III) cation forms electrically neutral photoluminescent complex with 5-(2-pyridyl-1-oxide)tetrazolate (PTO) anion. Although the photoluminescence properties of such tertiary Eu(III) and Tb(III) complexes were not as high (13 and 31% photoluminescence quantum yield, respectively) as reported for other diketonate lanthanide complexes probably because of high number of nitrogen atoms involved in PTO which leads to attachment of water molecules, reducing the luminescence quantum yield with vibrational and rotational quenching. Here, we report the removal of quencher molecules from the coordination sphere of tris–europium tetrazolate oxide complex by replacing them with various phosphine oxides which leads to improved photoluminescence quantum yield for the complexes by acting as auxiliary co-ligands with that of the main antenna 5-(2-pyridyl-1-oxide)tetrazolate. The coordination sphere in these complexes can be complemented by aromatic phosphine oxides to provide highly photoluminescent Eu(III) complexes. The highest quantum yield was 38% in 3 [Eu(PTO)₃·DPEPO](H₂O)₅ containing bis(2-(diphenylphosphino)phenyl) ether oxide (DPEPO) as compared to tris–europium complex with 5-(2-pyridyl-1-oxide)tetrazolate.     

Luminescense properties of new complexes of Eu(III) and Tb(III) with heterotopic ligands

As a result of coordination between ligands L and L' and europium(III) and terbium(III) ions, the new architectures were formed. The formulae of the complexes have been assigned on the basis of the spectroscopic data in solution and microanalyses. The europium complexes show excellent luminescence properties with high quantum yield (1b-Eu(3)L(2)) and effective intramolecular energy transfer from the ligand to the Eu(III) ions.     

Ga‐focused ion beam time‐of‐flight secondary ion mass spectrometer analysis of the grain boundary segregation/precipitation of boron in steel

Ga‐focused ion beam time‐of‐flight secondary ion mass spectrometry (FIB‐TOF‐SIMS) analysis was performed to investigate the grain boundary segregation/precipitation of boron in steel. To overcome the low secondary ion yield from the primary Ga⁺ source and the sensitivity using a high‐resolution Ga‐FIB source, a low energy oxygen ion beam was used prior to the Ga‐FIB‐TOF‐SIMS analysis. As a result, it was found that Ga‐FIB‐TOF‐SIMS is a very powerful tool for mapping boron segregation and/or precipitation in steel with a spatial resolution of ~200 nm. In addition, the results were strongly dependent on the surface composition. Copyright © 2014 John Wiley & Sons, Ltd.     

New luminescent europium(III) chelates for DNA labeling

The new europium(III) chelate [2,2',2',2'-[[4'-(aminobiphenyl-4-yl)-2,2':6',2'-terpyridine- 6,6'-diyl]bis(methylenenitrilo)]tetrakis(acetato)] europium(III) (ATBTA-Eu3+) and its 4,6-dichloro-1,3,5-triazinyl and succinimidyl derivatives (DTBTA and NHS-ATBTA, respectively) were synthesized and characterized. Both labeling complexes DTBTA-Eu3+ and NHS-ATBTA-Eu3+ are luminescent. Especially DTBTA-Eu3+ is strongly luminescent, with a luminescence quantum yield of 9.1%, molar extinction coefficient of 3.1 x 10(4) cm(-1) M(-1) (335 nm), and luminescence lifetime of 1.02 ms. The excitation and emission maximum wavelengths of DTBTA-Eu3+ are 335 and 616 nm, respectively. The complex is very stable in aqueous buffers, with a conditional formation constant log K(DTBTA-Eu) of 25.0 at pH 8, and can be conjugated to DNA and proteins. The chelates are also highly resistant to thermal decomposition, photodegradation, and ozone oxidation. These properties prove that DTBTA-Eu3+ is suitable as a luminescence label in DNA assays.     

Luminescent properties of europium(III) and terbium(III) complexes with para- and ortho-ethoxybenzoic acids

The luminescent properties of europium(III) and terbium(III) complexes with para- and ortho-ethoxybenzoic acids are studied. The excitation energies of the triplet states of ligands are determined, a hypothesis is made about the efficient luminescence of europium(III) and terbium(III) complexes, the geometry of the coordination polyhedron of a europium complex is established, and the luminescence quantum yields of the complexes in solution are determined.     

Thermally Activated Delayed Fluorescence in a Y3N@C80 Endohedral Fullerene: Time‐Resolved Luminescence and EPR Studies

The endohedral fullerene Y₃N@C₈₀ exhibits luminescence with reasonable quantum yield and extraordinary long lifetime. By variable‐temperature steady‐state and time‐resolved luminescence spectroscopy, it is demonstrated that above 60 K the Y₃N@C₈₀ exhibits thermally activated delayed fluorescence with maximum emission at 120 K and a negligible prompt fluorescence. Below 60 K, a phosphorescence with a lifetime of 192±1 ms is observed. Spin distribution and dynamics in the triplet excited state is investigated with X‐ and W‐band EPR and ENDOR spectroscopies and DFT computations. Finally, electroluminescence of the Y₃N@C₈₀/PFO film is demonstrated opening the possibility for red‐emitting fullerene‐based organic light‐emitting diodes (OLEDs).     

Effect of Aliphatic Chain Length in the Ligand on Photophysical Properties and Thin Films Morphology of the Europium Complexes

Chelating ligands based on polydentate diamides of 2,2'-bipyridyl-6,6'-dicarboxylic acid with a high affinity for lanthanide ions have been synthesized. The effect of the size of lipophilic aliphatic substituents in the ligand on the photophysical characteristics of europium complexes in acetonitrile solutions and in the solid state, as well as on the morphology of thin films obtained by the spin-coating method, was studied. The external and internal luminescence quantum yields have been measured, the luminescence lifetimes at 300 and 77 K were determined, and the sensitization efficiency values for europium complexes were calculated. The phosphorescence of gadolinium(III) complexes was used to determine the energy difference between the triplet level of the ligand and the resonance level of europium.     

Ultrasound‐assisted oxidation of tungsten in oxygen plasma: the early stages of the oxide film growth

The effect of ultrasonic vibrations applied in situ on the formation of W–WO interface during the exposure of a pure tungsten foil to a low‐temperature oxygen plasma is investigated by photoelectron spectroscopy (XPS) and time‐of‐flight secondary ion mass spectrometry (TOF‐SIMS). The tungsten surface was exposed to oxygen plasma at different time intervals and the evolution of the interface formation was studied by angle‐resolved XPS. We show that oxidation without ultrasonic vibrations leads to the formation of a thin oxide film whose growth kinetics is governed by an island growth mechanism. On the other hand, oxide growth in the presence of ultrasonic treatment (UST) appears to follow a layer‐by‐layer growth mode with a distinctly sharper W–WO interface. TOF‐SIMS analysis in this case revealed a reduced amount of water bonded in the film, which suggests an increase in the film's packing density. Copyright © 2006 John Wiley & Sons, Ltd.     

Time‐of‐flight secondary ion mass spectroscopic characterization of the nitrogen profile of shallow gate oxynitride thermally grown on a silicon substrate

Silicon oxynitride has been used as a shallow gate oxide material for microelectronics and its thickness has been reduced over the years to only a few tens of angstroms due to device size scaling. The nitride distribution and density characteristic in the gate oxide thus becomes imperative for the devices. The shallow depth profiling capability using time‐of‐flight secondary ion mass spectrometry (TOF‐SIMS) has huge potential for the nitrogen characterization of the shallow gate oxide film. In this article, both positive and negative spectra of TOF‐SIMS on silicon oxynitride have been extensively studied and it was found that the silicon nitride clusters Si_xN^? (x = 1–4) are able to represent the nitrogen profiles because their ion yields are high enough, especially for the low‐level nitride doping in the oxide, which is formed by the annealing of nitric oxide on SiO₂/Si. The gate oxide thickness measured by the TOF‐SIMS profiling method using ¹⁸O or CsO profile calibration was found to correlate very well with transmission electron microscope measurement. The nitrogen concentration in the gate oxide measured using the TOF‐SIMS method was consistent with the results obtained using the dynamic SIMS method, which is currently applied to relatively thicker oxynitride films. Copyright © 2012 John Wiley & Sons, Ltd.     

Synthesis and photoluminescence properties of novel europium complexes of 2'-hydroxyacetophenone and 4,6-diacetylresorcinol

Novel europium (III) complexes of the formulae Eu(OHAP)(3).2H2O, Eu(OHAP)(3)Phen, Eu2(DAR)(3).4H2O and Eu2(DAR)(3)Phen2 (HOHAP=2'-hydroxyacetophenone, H2DAR=4,6-diacetylresorcinol, Phen=1,10-phenanthroline) have been designed and synthesized in this paper. These complexes were characterized by elemental analysis, FT-IR, and UV-vis. Based on these observations, the ligands are coordinated to Eu(III) via the acetyl and phenolic oxygens, and H2DAR is concluded to be bis-bidentate donor. Photoluminescence studies showed that the several complexes emitted red luminescence. Thermo-gravimetric analysis showed that the complexes possess good thermal stability. Also, it was found that Phen as a synergic ligand, coordinated to Eu(III) in a composite system like 2'-hydroxyacetophenone and 4,6-diacetylresorcinol, could enhance the complexes luminescence intensity, quantum yield and lifetime.     

Photochemical behavior of luminescent compositions based on antimony(III) and europium(III) complexes in high-pressure polyethylene

Luminescent and photochemical properties of polymer compositions based on the Eu(NO₃)₃(Phen)₂ complex and complexes of antimony(III) halides with diphenylguanidine are investigated. It is found that high-pressure polyethylene (HPPE) containing europium(III) and antimony(III) complexes in combination exhibits efficient transfer of electronic excitation energy from antimony(III) levels to europium(III) levels and photosensitization of europium(III) luminescence. It is shown that the europium(III) and antimony(III) complexes increase the stability of HPPE to UV radiation.     

Synthesis and photoproperties of Eu(III)‐bearing star polymers as luminescent materials

Water‐soluble luminescent material was developed by introducing europium (Eu(III)) ions into the core of a star polymer. Living radical polymerization was used to obtain the star polymer. The strategy to introduce Eu(III) ions into the star polymer was studied using poly(methyl methacrylate) as an arm. The best Eu(III) ion introduction was obtained by simultaneous introduction, resulting in about 30 µmol/g‐polymer, which needed only one step for synthesis. The utilization of a hydrophilic polymer such as poly(ethylene oxide) (PEO) as an arm produced a water‐soluble star polymer. The Eu(III)‐bearing PEO star polymer obtained in this study was water soluble and showed fluorescence. In addition, it was stable in water after 1 month. The Eu(III)‐bearing star polymer exhibited luminescent properties under UV light irradiation with relatively high quantum yields of 60% in organic solution and 19% in aqueous solution. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 2527–2535