Photoluminescence lifetime stability studies of ß-diketonate europium complexes based phenanthroline derivatives in poly(methyl methacrylate) films.

In this work, five phenanthroline derivatives substituted with different methyl groups have been selected to synthesize ß-diketonate-based europium complexes to check the influence of the substitutions on the degradation effect of those complexes in poly(methyl methacrylate) (PMMA) films. The photophysical properties of Eu(III) complexes, including absorbance, excitation, and emission have been carefully investigated in solution, solid-state, and doped in PMMA film. In all these states, the complexes exhibit an impressive red emission at 614 nm with a high photoluminescence quantum yield of up to 85 %. The films have been exposed under outdoor, indoor, and dark storage stability lifetime conditions for 1200 hours. The photoluminescence measurements recorded every 400, 800, and 1200 hours demonstrated that the film containing europium complex with phenanthroline ligand substituted by a high number of methyl groups (Eu(TTA)3L5) showed good photoluminescent stability in indoor and dark conditions, and exhibited better resistance to degradation in outdoor conditions compared to other complexes. This study has proved that phenanthroline ligands could be tuned chemically leading to better stability of those types of complexes in films which can be end-used for future stable optoelectronic devices such as luminescent solar concentrators.

Highly Luminescent Europium(III) Complexes in Solution and PMMA-Doped Films for Bright Red Electroluminescent Devices.

This paper reports the synthesis, structure, photophysical, and optoelectronic properties of five eight-coordinate Europium(III) ternary complexes, namely, [Eu(hth)3(L)2], bearing 4,4,5,5,6,6,6-heptafluoro-1-(2-thienyl)-1,3-hexanedione (hth) as a sensitizer and L = H2O (1), dpso (diphenyl sulphoxide, 2), dpsoCH3 (4,4'-dimethyl diphenyl sulfoxide, 3), dpsoCl (bis(4-chlorophenyl)sulphoxide, 4), and tppo (triphenylphosphine oxide, 5) as co-ligands. The NMR and the crystal structure analysis confirmed the eight-coordinate structures of the complexes in solution and in a solid state. Upon UV-excitation on the absorption band of the ß-diketonate ligand hth, all complexes showed the characteristic bright red luminescence of the Europium ion. The tppo derivative (5) displayed the highest quantum yield (up to 66%). As a result, an organic light-emitting device, OLED, was fabricated with a multi-layered structure-ITO/MoO3/mCP/SF3PO:[complex 5] (10%)/TPBi:[complex 5] (10%)/TmPyPB/LiF/Al-using complex 5 as the emitting component.

Polymeric Nanoparticles with Embedded Eu(III) Complexes as Molecular Probes for Temperature Sensing.

Three novel luminescent Eu(III) complexes, Eu1-Eu3, have been synthesized and characterized with CHN analysis, mass-spectrometry and 1H NMR spectroscopy. The complexes display strong emission in dichloromethane solution upon excitation at 405 and 800 nm with a quantum yield from 18.3 to 31.6%, excited-state lifetimes in the range of 243-1016 ms at 20 °C, and lifetime temperature sensitivity of 0.9%/K (Eu1), 1.9%/K (Eu2), and 1.7%/K (Eu3). The chromophores were embedded into biocompatible latex nanoparticles (NPs_Eu1-NPs_Eu3) that prevented emission quenching and kept the photophysical characteristics of emitters unchanged with the highest temperature sensitivity of 1.3%/K (NPs_Eu2). For this probe cytotoxicity, internalization dynamics and localization in CHO-K1 cells were studied together with lifetime vs. temperature calibration in aqueous solution, phosphate buffer, and in a mixture of growth media and fetal bovine serum. The obtained data were then averaged to give the calibration curve, which was further used for temperature estimation in biological samples. The probe was stable in physiological media and displayed good reproducibility in cycling experiments between 20 and 40 °C. PLIM experiments with thermostated CHO-K1 cells incubated with NPs_Eu2 indicated that the probe could be used for temperature estimation in cells including the assessment of temperature variations upon chemical shock (sample treatment with mitochondrial uncoupling reagent).

Luminescent 1,10-Phenanthroline ß-Diketonate Europium Complexes with Large Second-Order Nonlinear Optical Properties.

Substitution of the diglyme ligand of [Eu(hfa)3(diglyme)] (where hfa is hexafluoroacetylacetonate) with a simple 1,10-phenanthroline leads to a six-fold increase of the product µßEFISH, as measured by the Electric-Field-Induced Second Harmonic generation (EFISH) technique. Similarly, [Eu(tta)3(1,10-phenanthroline)] (where Htta is 2-thenoyltrifluoroacetone) is characterized by a large second-order NLO response. Both 1,10-phenanthroline europium complexes have great potential as multifunctional materials for photonics.

Luminescent Features of Ternary Europium Complexes: Photophysical and Optoelectronic Evaluation.

Trivalent europium complexes exhibit good luminescent characteristics. A series of octacoordinated ternary europium complexes with fluorinated diketone and heteroaromatic auxiliary unit were synthesized. The synthesized europium complexes were characterized by elemental, thermal, electrochemical and spectroscopic analyses. Band gap values lie in range of semiconductors which confirm the conducting behavior of prepared complexes. Photoluminescence spectra were recorded in solid state and DMSO solvent. Emission spectral profiles have displayed most intense peak at ~ 612 nm corresponding to hypersensitive 5D0 → 7F2 transition. Colorimetric parameters suggest red luminous nature of europium complexes. The luminescent heteroleptic europium complexes might be utilized as emissive materials for fabricating display.

Hybrid EuIII Coordination Luminophore Standing on Two Legs on Silica Nanoparticles for Enhanced Luminescence.

In this study, we have demonstrated a two-legged, upright molecular design method for monochromatic and bright red luminescent LnIII -silica nanomaterials. A novel EuIII -silica hybrid nanoparticle was developed by using a doubly binding TPPO-Si(OEt)3 (TPPO: triphenyl phosphine oxide) linker. The TPPO-Si(OEt)3 was confirmed by 1 H, 31 P, 29 Si NMR spectroscopy and single-crystal X-ray analysis. Luminescent Eu(hfa)3 and Eu(tfc)3 moieties (hfa: hexafluoroacetylacetonate, tfc: 3-(trifluoromethylhydroxymethylene)camphorate) were fixed onto TPPO-Si(OEt)3 -modified silica nanoparticles, producing Eu(hfa)3 (TPPO-Si)2 -SiO2 and Eu(tfc)3 (TPPO-Si)2 -SiO2 , respectively. Eu(hfa)3 (TPPO-Si)2 -SiO2 exhibited the higher intrinsic luminescence quantum yield (93 %) and longer emission lifetime (0.98 ms), which is much larger than those of previously reported EuIII -based hybrid materials. Eu(tfc)3 (TPPO-Si)2 -SiO2 showed an extra-large intrinsic emission quantum yield (54 %), although the emission quantum yield for the precursor Eu(tfc)3 (TPPO-Si(OEt)3 )2 was found to be 39 %. These results confirmed that the TPPO-Si(OEt)3 linker is a promising candidate for development of EuIII -based luminescent materials.

Temperature sensitive properties and preparation of europium complexes with double ligands.

Temperature sensitive paints (TSPs) are a class of rising materials for non-contact temperature measurement technology. Efficient complexes with remarkable luminescent properties play the core role in TSPs. Rare earth organic complexes are often used as probe molecules for TSPs because of their long fluorescence lifetime, narrow fluorescence emission peaks, high fluorescence intensity, and large Stokes shift. Herein, two europium-based complexes, Eu(PCCA)3 phen and Eu (PMCA)3 phen, were synthesized under hydrothermal conditions, using europium(III) oxide (Eu2 O3 ), p-chlorocinnamic acid (PCCA), p-methoxy cinnamic acid (PMCA) and 1,10-phenanthroline (phen) as raw materials. Two temperature sensitive paints (Eu(PCCA)3 phen/PMMA and Eu(PMCA)3 phen/PMMA) were obtained by the polymerization of methyl methacrylate (MMA) with different europium complexes. The structure, morphology, luminescent properties of the europium complexes and temperature quenching properties of the TSPs were characterized by infrared (IR) spectroscopy, scanning electron microscopy (SEM), and fluorescence spectroscopy. The fluorescence results show that both of the two TSPs have good temperature quenching performance in the range 20-100°C with high sensitivity 50-60°C and 80-90°C, respectively. Furthermore, the highest sensitivity of Eu(PCCA)3 phen/PMMA is greater than that of Eu(PMCA)3 phen/PMMA. This work can provide a universal way for preparing efficient TSPs in practical applications.

Unexpected luminescent and photochemical properties of europium(III) cinnamates - Theoretical and experimental study.

The luminescent and photochemical properties of europium(III) cinnamates [Eu(Cin)3]n (I) and Eu(Cin)3·(phen) (II) were investigated in theoretical and experimental aspects. The high photostability of the complex I was explained. The complex II displays weak luminescence and low photostability in spite of the presence of a powerful antenna ligand 1,10-phenantroline in its coordination sphere. The unexpected luminescent and photochemical properties of europium(III) cinnamates were interpreted by the quantum chemistry methods. It was revealed that inclusion of phen molecule into Eu(Cin)3 complex results in lengthening of Eu-Cin distances that promotes weakening of antenna effect. In the process of photoexcitation of this complex noticeable lengthening of Eu-Cin-2 bond takes place and Cin-3 ligand is detached from the molecule that is the cause of low photostability and weak luminescence of II.

Magnetofluorescent Nanocomposite Comprised of Carboxymethyl Dextran Coated Superparamagnetic Iron Oxide Nanoparticles and ß-Diketon Coordinated Europium Complexes.

Red emitting europium (III) complexes Eu(TFAAN)3(P(Oct)3)3 (TFAAN = 2-(4,4,4-Trifluoroacetoacetyl)naphthalene, P(Oct)3 = trioctylphosphine) chelated on carboxymethyl dextran coated superparamagnetic iron oxide nanoparticles (CMD-SPIONs) was synthesized and the step wise synthetic process was reported. All the excitation spectra of distinctive photoluminesces were originated from f-f transition of EuIII with a strong red emission. The emission peaks are due to the hypersensitive transition 5D0→7F2 at 621 nm and 5D0→7F1 at 597 nm, 5D0→7F0 at 584 nm. No significant change in PL properties due to addition of CMD-SPIONs was observed. The cytotoxic effects of different concentrations and incubation times of Eu(TFAAN)3(P(Oct)3)3 chelated CMD-SPIONs were evaluated in HEK293T and HepG2 cells using the WST assay. The results imply that Eu(TFAAN)3(P(Oct)3)3 chelated CMD-SPIONs are not affecting the cell viability without altering the apoptosis and necrosis in the range of 10 to 240 µg/mL concentrations.

Polystyrene latex particles containing europium complexes prepared by miniemulsion polymerization using bovine serum albumin as a surfactant for biochemical diagnosis.

Luminescent particles have been attracting significant attention because they can be used in biochemical applications, such as detecting and imaging biomolecules. In this study, luminescent polystyrene latex particles were prepared through miniemulsion polymerization of styrene with dissolved europium complexes in the presence of bovine serum albumin (BSA) and poly(ethylene glycol) monomethoxy methacrylate as surfactants. The solubility of the europium complex in styrene has a strong effect on the yield of the particle. Europium tris(2-thenoyl trifluoroacetonate) di(tri-n-octyl phosphine oxide), which has a high solubility in styrene, was sufficiently incorporated into the polystyrene particles compared to europium tris(2-thenoyl trifluoroacetonate), which has a low solubility in styrene. The luminescence property of the europium complex could remain intact even after its incorporation through the miniemulsion polymerization. In the aqueous dispersion, the resulting particles could emit strong luminescence, which is a characteristic of the europium complex. The antibody fragments were covalently attached to BSA-covered particles after a reaction with a bifunctional linker, N-(6-maleimidocaproyloxy)succinimide. The time-resolved fluoroimmunoassay technique showed that 3.3pg/mL of human α-fetoproteins (AFP) can be detected by using the resulting luminescent particles. An immunochromatographic assay using the resulting particles was also performed as a convenient method to qualitatively detect biomolecules. The detection limit of AFP measured by the immunochromatographic assay was determined to be 2000pg/mL. These results revealed that the luminescent particles obtained in this study can be utilized for the highly sensitive detection of biomolecules and in vitro biochemical diagnosis.

Tetranuclear Heterometallic {Zn2Eu2} Complexes With 1-Naphthoate Anions: Synthesis, Structure and Photoluminescence Properties.

A series of new tetranuclear heterometallic Zn(II) -Eu(III) complexes have been synthesized, that is, (bpy)2 Zn2Eu2 (naph)10 (1), (bpy)2 Zn2Eu2 (naph)8 (NO3)2 (2), and (phen)2 Zn2Eu2 (naph)8 (NO3)2 (3), and other ones, where naph(-) is the 1-naphthoate anion, bpy=2,2'-bipyridyl, and phen=1,10-phenanthroline. The solid-phase complexes consist of large supramolecular ensembles due to stacking interactions between the aromatic ligands. Photoluminescence (PL) measurements were carried out to study PL spectra, lifetimes and quantum yields (QY) of the synthesized complexes at different temperatures. The external QY for the solid phases of complexes under UV excitation was found to exceed 20 %. It has been shown that partial replacement of naphthoate ligands in the coordination environment of Eu(3+) by NO3(-) anions influences the PL properties. To investigate the behavior of these complexes in solvent, we dissolved complex 3 in MeCN, put it on a transparent glass as a substrate, and studied the PL properties at room temperature.

Fluorescence enhancement of europium (III) perchlorate by 1,10-phenanthroline on the 1-(naphthalen-2-yl)-2-(phenylsulthio)ethanone complex and luminescence mechanism.

A novel ligand, 1-(naphthalen-2-yl)-2-(phenylsulthio)ethanone was synthesized using a new method and its two europium (Eu) (III) complexes were synthesized. The compounds were characterized by elemental analysis, coordination titration analysis, molar conductivity, infrared, thermo gravimetric analyzer-differential scanning calorimetry (TGA-DSC), (1)H NMR and UV spectra. The composition was suggested as EuL5 · (ClO4)3 · 2H2O and EuL4 · phen(ClO4)3 · 2H2O (L = C(10)H(7)COCH(2)SOC(6)H(5)). The fluorescence spectra showed that the Eu(III) displayed strong characteristic metal-centered fluorescence in the solid state. The ternary rare earth complex showed stronger fluorescence intensity than the binary rare earth complex in such material. The strongest characteristic fluorescence emission intensity of the ternary system was 1.49 times as strong as that of the binary system. The phosphorescence spectra were also discussed.

Transition polarizability model of induced resonance Raman optical activity.

Induced resonance Raman optical activity (IRROA) proved to be a very sensitive method to detect molecular chirality. It is exhibited, for example, by complexes of lanthanides with chiral alcohols or ketones. So far, the phenomenon has not been understood at a quantitative level. To elucidate its mechanisms and to correctly relate the spectra to the structure, a transition polarizability model (TPM) is developed and applied to a camphor-europium complex. The model well reproduces the high ROA/Raman intensity ratio of the IRROA observed experimentally. The results additionally indicate a fundamental role of the nonchiral fod ligand in the Eu(fod)3 compound for the chirality enhancement. The TPM model thus serves as a guidance for both experimental and theoretical studies to come.