Luminescence Of Eu3 Research Articles

Synthesis of water-soluble europium-containing nanoprobes via polymerization-induced self-assembly and their cellular imaging applications

Lanthanide nanoprobes have attracted extensive attention for applications in cellular imaging and biological sensing. Herein, water-dispersible europium (III)-based (Eu(III)-based) nanoprobes were prepared by reversible addition-fragmentation chain transfer (RAFT) polymerization-induced self-assembly (PISA) of hydrophobic monomers (Eu(III)-containing monomer and methyl methacrylate (MMA)) using hydrophilic macro-chain transfer agent poly(PEGMA)-CTA. The resulted poly(PMEu) nanoprobes showed spherical in shape in good monodispersity with average diameters of around 210 nm. The poly(PMEu) nanoprobles excellent aqueous dispersity, high aqueous stability and good luminescence properties with quantum yields of 37.21% and fluorescence lifetime of 312.4 μs. Moreover, the poly(PMEu) nanoprobes exhibited good cellular biocompatibility with cell viabilities of 88.2% and high fluorescence intensity for in vitro cellular imaging. The present approach provides a facile strategy for fabrication of luminescent Eu(III)-based nanoprobes with great potential applications for biological imaging.

Self-assembly-induced luminescence of Eu3+-complexes and application in bioimaging.

Design and engineering of highly efficient emitting materials with assembly-induced luminescence, such as room-temperature phosphorescence (RTP) and aggregation-induced emission (AIE), have stimulated extensive efforts. Here, we propose a new strategy to obtain size-controlled Eu3+-complex nanoparticles (Eu-NPs) with self-assembly-induced luminescence (SAIL) characteristics without encapsulation or hybridization. Compared with previous RTP or AIE materials, the SAIL phenomena of increased luminescence intensity and lifetime in aqueous solution for the proposed Eu-NPs are due to the combined effect of self-assembly in confining the molecular motion and shielding the water quenching. As proof of concept, we also show that this system can be further applied in bioimaging, temperature measurement and HClO sensing. The SAIL activity of the rare-earth (RE) system proposed here offers a further step forward on the roadmap for the development of RE light conversion systems and their integration in bioimaging and therapy applications.

Studies of Sol-Gel Evolution and Distribution of Eu3+ Ions in Glass-Ceramics Containing LaF3 Nanocrystals Depending on Initial Sols Composition.

In this work, we performed a systematic analysis of the impact of selected chemical reagents used in sol-gel synthesis (i.e., N,N-dimethylformamide) and different catalyst agents (i.e., CH3COOH, HNO3) on the formation and luminescence of Eu3+-doped SiO2–LaF3 nano-glass–ceramics. Due to the characteristic nature of intra-configurational electronic transitions of Eu3+ ions within the 4f6 manifold (5D0 → 7FJ, J = 0–4), they are frequently used as a spectral probe. Thus, the changes in the photoluminescence profile of Eu3+ ions could identify the general tendency of rare earth materials to segregate inside low-phonon energy fluoride nanocrystals, which allows us to assess their application potential in optoelectronics. Fabricated sol-gel materials, from sols to gels and xerogels to nano-glass–ceramics, were examined using several experimental techniques: X-ray diffraction (XRD), transmission electron microscopy (TEM), infrared spectroscopy (IR), and luminescence measurements. It was found that the distribution of Eu3+ ions between the amorphous silicate sol-gel host and LaF3 nanocrystals is strictly dependent on the initial composition of the obtained sols, and the lack of N,N-dimethylformamide significantly promotes the segregation of Eu3+ ions inside LaF3 nanocrystals. As a result, we detected long-lived luminescence from the 5D0 excited state equal to 6.21 ms, which predisposes the obtained glass–ceramic material for use as an optical element in reddish-orange emitting devices.

Ultrasensitive Point-of-Care Test for Tumor Marker in Human Saliva Based on Luminescence-Amplification Strategy of Lanthanide Nanoprobes.

The point‐of‐care detection of tumor markers in saliva with high sensitivity and specificity remains a daunting challenge in biomedical research and clinical applications. Herein, a facile and ultrasensitive detection of tumor marker in saliva based on luminescence‐amplification strategy of lanthanide nanoprobes is proposed. Eu2O3 nanocrystals are employed as bioprobes, which can be easily dissolved in acidic enhancer solution and transform into a large number of highly luminescent Eu3+ micelles. Meanwhile, disposable syringe filter equipped with nitrocellulose membrane is used as bioassay platform, which facilitates the accomplishment of detection process within 10 min. The rational integration of dissolution enhanced luminescent bioassay strategy and miniaturized detection device enables the unique lab‐in‐syringe assay of tumor marker like carcinoembryonic antigen (CEA, an important tumor marker in clinic diagnosis and prognosis of cancer) with a detection limit down to 1.47 pg mL−1 (7.35 × 10−15 m). Upon illumination with a portable UV flashlight, the photoluminescence intensity change above 0.1 ng mL−1 (0.5 × 10−12 m) of CEA can be visually detected by naked eyes, which allows one to qualitatively evaluate the CEA level. Moreover, we confirm the reliability of using the amplified luminescence of Eu2O3 nanoprobes for direct quantitation of CEA in patient saliva samples, thus validates the practicality of the proposed strategy for both clinical diagnosis and home self‐monitoring of tumor marker in human saliva.

Tracking the local environment of Eu3+ in Eu3+-doped calcium phosphate during hydroxyapatite crystallization and its phase transformation to tricalcium phosphate

We present a study on the crystal structure and luminescence of Eu3+-doped calcium phosphate (Eu-CaP) nanoparticles. The sintering treatment on the pristine Eu-CaP leads to its crystallization into hydroxyapatite (HA) and further to biphasic structure that contains both HA and β-tricalcium phosphate (β-TCP). Photoluminescence spectroscopy has been a widely used technique to identify the site occupancy of Eu3+ and its thermal-induced migration behavior in pure phase CaP. However, for sintering process that involves the emergence of a second phase or the doped CaP is not luminescent, PL alone is insufficient to characterize how the dopant ions behave during the formation of a biphasic structure. In this work, we utilize X-ray absorption fine structure (XAFS) as an alternative structure probe, targeting the local structure around Eu3+, and track the change in the interatomic distance and coordination number of Eu with its neighboring O, P, and Ca atoms. A model describing formation process of a biphasic structure from HA with the presence of Eu3+ is proposed.

Coordination Geometrical Effect on Ligand-to-Metal Charge Transfer-Dependent Energy Transfer Processes of Luminescent Eu(III) Complexes

Photophysical properties of europium (Eu(III)) complexes are affected by ligand-to-metal charge transfer (LMCT) states. Two luminescent Eu(III) complexes with three tetramethylheptadionates (tmh) and pyridine (py), [Eu(tmh)3(py)1] (seven-coordinated monocapped-octahedral structure) and [Eu(tmh)3(py)2] (eight-coordinated square antiprismatic structure), were synthesized for geometrical-induced LMCT level control. Distances between Eu(III) and oxygen atoms of tmh ligands were estimated using single-crystal X-ray analyses. The contribution percentages of π-4f mixing in HOMO and LUMO at the optimized structure in the ground state were calculated using DFT (LC-BLYP). The Eu-O distances and their π-4f mixed orbitals affect the energy level of LMCT states in Eu(III) complexes. The LMCT energy level of an eight-coordinated Eu(III) complex was higher than that of a seven-coordinated Eu(III) complex. The energy transfer processes between LMCT and Eu(III) ion were investigated using temperature-dependent and time-resolved emission lifetime measurements of 5D0 → 7FJ transitions of Eu(III) ions. In this study, the LMCT-dependent energy transfer processes of seven- and eight-coordinated Eu(III) complexes are demonstrated for the first time.

Structure, luminescence of Eu2+ and Eu3+ in CaMgSi2O6 and their co-existence for the excitation-wavelength/temperature driven colour evolution.

Luminescent materials with controllable colour evolution features are demanded for the development of multi-level anti-counterfeiting technologies. Here we report the structural and luminescence properties of CaMgSi2O6:Ln (Ln = Eu2+, Eu3+, Eu2+/3+) samples in detail and reveal their excitation-wavelength/temperature driven colour evolution characteristics. By tuning either the excitation-wavelength (276, 304, 343, 394 nm) or temperature (in the 330-505 K range), the designed samples with co-existing Eu2+/Eu3+ ions can achieve diverse and controllable colour evolution from red, to pink, purple and blue. This shows their potential application in anti-counterfeiting with the help of sophisticated pattern design. In addition, the underlying mechanism of the Stokes shift of the Eu2+ emission and valence stability of both Eu2+/Eu3+ ions in CaMgSi2O6 are also studied in depth. These results are valuable for designing colour-controllable luminescent materials based on the co-existence of the Eu2+/Eu3+ ions for anti-counterfeiting applications.

The effect of local structure on the luminescence of Eu2+ in ternary phosphate solid solutions by cationic heterovalent substitution and their application in white LEDs

[Ca9Na3xY1−x(PO4)7 (0 ≤ x ≤ 1/2) ← Ca3(PO4)2 → Ca9+yNa3/2−y/2Y(1−y)/2(PO4)7 (0 ≤ y ≤ 1)] phosphors were achieved by cationic heterovalent substitution strategy.

Point Chirality Regulated Diastereoselective Self-Assembly and Circularly Polarized Luminescence in Eu(III) Triple-Stranded Helicates

Point Chirality Regulated Diastereoselective Self-Assembly and Circularly Polarized Luminescence in Eu(III) Triple-Stranded Helicates

Reduced quenching effect of pyridine ligands in highly luminescent Ln(III) complexes: the role of tertiary amide linkers.

Luminescent Eu(III) and Tb(III) complexes were synthesised from octadentate ligands carrying various carbostyril sensitizing antennae and two bidentate picolinate donors. Antennae were connected to the metal binding site via tertiary amide linkers. Antennae and donors were assembled on a 1,4,7-triazacyclononane (tacn) platform. Solution- and solid-state structures were comparable to those of previously reported complexes with tacn architectures, with nine-coordinate distorted tricapped trigonal prismatic Ln(III) centres, and distinct from those based on 1,4,7,10-tetraazacyclododecane (cyclen) macrocycles. In contrast, the photophysical properties of these tertiary amide tacn-based complexes were more comparable to those of previously reported systems with cyclen ligands, showing efficient Eu(III) and Tb(III) luminescence. This represents an improvement over secondary amide-linked analogues, and is due to a greatly increased sensitization efficiency in the tertiary amide-linked complexes. Tertiary amide-linked Eu(III) and Tb(III) emitters were more photostable than their secondary amide-linked analogues due to the suppression of photoinduced electron transfer and back energy transfer.

Europium(iii)-containing nanohydrogels for cellular imaging and drug delivery applications

By employing the excellent luminescence of Eu(iii) complexes and the versatility of nanohydrogels, Eu(iii)-containing nanohydrogels were prepared as a potential theranostic nanoplatform for cancer therapy.

A red luminescent Eu3+ doped conjugated microporous polymer for highly sensitive and selective detection of aluminum ions

A Eu3+ doped-CMP composite can be used as a chemosensor for highly sensitive and selective detection of Al3+.

Smart luminescent molecular europium complexes and their versatile applications

A series of smart luminescent Eu(iii) complexes (C1 = Eu(DBM)3ligand 1, C2 = Eu(DBM)3ligand 2, C3 = Eu(DBM)3ligand 3, C4 = Eu(DBM)3 ligand 4, C5 = Eu(DBM)3ligand 5) were synthesized by using C1-functionalized phenanthro-imidazole derivatives as the neutral ligands and dibenzoylmethanate (DBM) as the anionic ligand.

Charge-transfer excited states of π- and 4f-orbitals for development of luminescent Eu(III) complexes.

Transition metal complexes provide photofunctional properties through the charge transfer excited states of their metal ion and organic ligand components. Recently, there are increasing reports on the charge transfer excited states of the ligand (π)- and 4f-orbitals of lanthanide complexes, where the latter are shielded by filled 5s2 and 5p6 orbitals. This area of research is relatively unestablished; thus, the study of photo-excited organic-lanthanide charge transfer would lead to the construction of next-generation photofunctional metal complexes. In this review, we summarize the latest research progress in photofunctional materials using the charge transfer excited states of lanthanide complexes, and discuss the photophysical/theoretical analyses of these charge transfer excited states.

Time-resolved circularly polarized luminescence of Eu3+ -based systems.

Chiral Eu3+ -based systems are frequently studied via circularly polarized luminescence spectroscopy. The emission lifetimes of each circular polarization, however, are virtually always ignored, because in a homogeneous sample of emitters, there should be no difference between the two. However, we show that in less robust Eu3+ complex structures, as in the chiral complex Eu (facam)3 , a difference in the lifetimes of the two circularly polarized emission components arises due to heterogeneity of the complexes. In this case, each species within the sample could have different degrees of circularly polarized luminescence and decay rates at certain emission lines. The superposition of the emission components of the various chiral species leads to an overall difference in decay rate between the two circular polarizations. Such a difference is also shown for Eu3+ -doped chiral TbPO4 ·D2 O nanocrystals. We believe that this kind of measurement could be a unique tool for determining the homogeneity of a lanthanide-based chiral system, where other methods might fail in this task.

Bifunctional luminescent Eu metal–organic framework for sensing nitroaromatic pollutants and Fe3+ ion with high sensitivity and selectivity

In recent years, heavy metal ions and nitroaromatic explosives in environmental pollutants have been a serious threat to human health due to their high toxicity, carcinogenicity, and nondegradability. The detection of metal ions and nitroaromatics has become an urgent problem. In this paper, a new water stable luminescent Eu‐based metal–organic framework ([Eu(L)(DMF)2]n) was prepared by the reaction of rigid ligand H3L (3,5‐bis‐(3‐carboxyphenoxy)benzoic acid) and Eu (NO3)3·6H2O under solvothermal conditions. Luminescent detection of the nitroaromatic compounds and metal ions showed that the complex had high sensitivity to Fe3+, o‐nitrophenol, p‐nitrophenol, and m‐nitrophenol.

A supramolecular strategy for ratiometric luminescence sensing of nitroaromatic explosives in water

In the present work we have demonstrated a supramolecular approach for ratiometric luminescence sensing of nitroaromatic explosive compounds (NAEs) by employing a red luminescent Eu(III) complex and a green luminescent Pt(II) complex with in a Triton X-100 surfactant based micellar host in water. The Eu-complex gets entrapped inside micellar core whereas the Pt-C2 remains grafted on the surface of the spherical micelles due to their structural amendments and thus facilitates preferential interaction of Pt-C2 with NAE molecules mainly through p-p interaction. The presence of explosive traces quenches the green emission (508-545 nm) of Pt-complex whereas the red emission (614 nm) of Eu-complex remains unaffected. The strategy demonstrates first report of two independent luminophore based ratiometric sensing in water using a micellar host.

Microstructural development and in vitro bioactivity of luminescent Eu doped monticellite based ceramics as multifunctional bone graft substitutes

ABSTRACT In the present study, the effects of Eu content and sintering temperature on microstructural development and in vitro bioactive characteristic of Eu-doped monticellite-based ceramics prepared using boron derivative waste were investigated. Spherical closed porosities with a diameter below 20 μm were observed on cross-section of all ceramics. The increment of Eu content from 1% to 10% resulted in narrower size distribution of closed porosities. The increasing of sintering temperature from 900°C to 1000°C allowed amorphisation of crystalline phases and the replacement of them into porosities. In vitro bone-like apatite formation ability altered by surface feature and sintering temperature, regardless of Eu content. The ceramics sintered at 1000°C for 2 h have desired bioactive response allowing formation of dense bone-like apatite layer on the surface. Therefore, 10% Eu-doped monticellite-based ceramics achieved in an eco-friendly route have potential to be used as multifunctional bone graft substitutes for biolabeling applications.

SPECTROSCOPIC PROPERTIES OF SOLIDIFIED MELTS OF THE EuF3-CeF3-NaCl-KCl SYSTEM

The nature of the interaction in the EuF3-CeF3 system in the process of high-temperature (1050 °C) oxidation - reduction reaction was established by the methods of IR transmission spectroscopy, diffuse reflection spectroscopy and fluorescence spectroscopy. Here is a significant bathochromic shift to 480-485 nm band of blue luminescence of Eu(II) - containing phases, due to the 5d–4f electronic transitions, as well as the manifestation of orange-red luminescence of Eu(III) - containing phases due to 4f–4f electronic transitions in the range of 590–690 nm. There is a bathochromic shift of the IR bandwidth in the spectrum of the solidified salt melt as a result of dissolution of the fluoride system. Diffuse reflection spectra reveal changes in the composition of the phases that dissolve in the salt melt due to exchange reactions. The wide absorption band in the UV range gives way to a negative absorption band consisting of two peaks due to luminescence. The almost complete disappearance of the band of 4f–4f transitions in Eu(III) in the near-IR range of the spectrum is evidence of its entire reduction in the chloride melt to Eu(II). The character of the luminescence spectra of solidified salt melts also changes in comparison with the initial sample of the EuF3-CeF3 system, namely, the luminescence band of Ce3+ ions disappears, and the luminescence band of Eu2+ ions at 430–440 nm becomes narrow and highly intensive. The luminescence band of Eu3+ ions in the orange-red region of the spectrum disappears completely. Thus, Eu2+ ions become dominant in the formation of the spectral picture of the solidified salt melt, which is evidence of the completion of the redox process in the system.

Cation substitution and luminescence properties of Eu2+/Ga3+-codoped Na2ZrSi2O7

Eu2+/Ga3+ co-doped Na2ZrSi2O7 phosphors were prepared via a facile solid-state reaction route. The structural characteristics, photoluminescence spectra, and application performances of Na2-x Eu x Zr1-x Ga x Si2O7 (x= 0, 0.02, 0.04, 0.06, 0.08, 0.10) were investigated. The main motivation of Ga3+ co-doping on Zr4+ is to eliminate the charge imbalance created by the aliovalent substitution of Eu2+ on Na+ sites in the lattices. The results indicated that the Eu2+/Ga3+ co-doped Na2ZrSi2O7 kept a good esseneite-like structure with a triclinic space group of P-1. The phosphor presents a narrow cyan-emitting band centered at 485 nm under near-UV light excitation. The luminescence efficiency of Eu2+ activator was significantly improved through the co-doping of Ga3+ for Zr4+ ions in Na2ZrSi2O7. The maximum luminescence absolute quantum efficiency of 43% was observed in Na2-x Eu x Zr1-x Ga x Si2O7 (x = 0.1) under the excitation of the near-UV light. The phosphor has good thermal stability with an activation energy of 0.31 eV. To realize charge compensation via cation co-substitution could be a practical strategy to improve luminescence in Eu2+-activated phosphors on aliovalent sites.