Europium Complexes Research Articles

A bimodal time-gated luminescence-magnetic resonance imaging nanoprobe based on a europium(III) complex anchored on BSA-coated MnO2 nanosheets for highly selective detection of H2O2.

A novel nanocomposite, [Eu(BTD)3(DPBT)]-BSA@MnO2, is reported to serve as an effective nanoprobe for bimodal time-gated luminescence (TGL) and magnetic resonance (MR) imaging of H2O2in vitro and in vivo. The nanoprobe was fabricated by immobilizing visible-light-excitable Eu3+ complexes in bovine serum albumin (BSA)-coated lamellar MnO2 nanosheets. The TGL of the Eu3+ complex was effectively quenched by the MnO2 nanosheets. Upon exposure to H2O2, the MnO2 nanosheets underwent reduction to Mn2+, which simultaneously triggered rapid, selective and sensitive "turn-on" responses toward H2O2 in both TGL and MR detection modes. The presence of a protective "corona" formed by BSA enables the nanoprobe to withstand high concentrations of glutathione (GSH), a strong reducing agent of MnO2 nanosheets. This capability allows the nanoprobe to be utilized for detecting H2O2 in living biosamples. The combined utilization of TGL and MR detection modes enables the nanoprobe to image H2O2 across a wide range of resolutions, from the subcellular level to the whole body, without any depth limitations. The results obtained from these modes can be cross-validated, enhancing the accuracy of the detection. The capability of the nanoprobe was validated by TGL imaging of endogenous and exogenous H2O2 in live HeLa cells, as well as bimodal TGL-MR imaging of H2O2 in tumor-bearing mice. The research achievements suggest that the integration of luminescent lanthanide complexes with protein-coated MnO2 nanosheets offers a promising bimodal TGL-MR sensing platform for H2O2in vitro and in vivo.

Deciphering intersystem crossing and energy transfer mechanisms in a nonacoordinated ternary europium(iii) complex: a combined spectroscopic and theoretical study.

A monochromatic red emitting nonacoordinate organoeuropium complex with the formula [Eu(hfaa)3(Ph-TerPyr)] (Eu-1) incorporating hexafluoroacetylacetone (hfaa) primary ligands and a tridentate 4'-phenyl-2,2':6',2''-terpyridine (Ph-TerPyr) ancillary ligand has been synthesized. The complex was characterized by analytical and spectroscopic methods, and its structure was established by single crystal X-ray diffraction (SC-XRD) analysis at low temperature, which explicitly confirms that the coordination sphere is composed of a EuO6N3 core. Under the UV excitation, Eu-1 displayed typical red emission in solution with a long-excited state lifetime (τ obs = 1048.06 ± 9.39 μs) with a good photoluminescence quantum yield (Q L Eu = 41.14%). We have utilized pump-probe ultrafast transient absorption spectroscopy in tandem with the time-dependent density functional theory (TD-DFT) and the Lanthanide Luminescence Software Package (LUMPAC) to explore the intricate photophysical event that occurs in the vicinity of the ligands of Eu-1 sensitized photoluminescence (PL).

Textured anti-reflection and down-conversion composite functional films for high-efficiency solar cells.

Advances in high-efficiency solar cells introduce photon management challenges, including the difficult texturization of flat surfaces and low photon utilization at short wavelengths. While bifacial crystalline silicon solar cells have a front pyramid structure and SiN x layers reduce reflections, managing photons on the flat backside remains a challenge. To enhance light utilization, a soft nanoimprint technique was utilized to create pyramid micro-structured polyurethane films doped with europium (Eu3+) complex. These films, which possess anti-reflection and down-conversion properties, can be applied externally to various high-efficiency solar cells without compromising electrical performance. Research on the backside of bifacial PERC solar cells revealed that the optimal composite functional film increases the integrated current by 5.70%, with a 1.27% gain from down-conversion effects. This specialized film presents a novel approach to interface matching for different types of solar cells.

Synthesis, structure and luminescence of two europium complexes of diphenylimidazophenanthrolines

A dinuclear Eu(iii) complex with long photoluminescence lifetime was synthesized via hydrothermal nitrile hydrolysis and nitro to amino transformation.

A smart microporous block copolymer membrane containing fluorescent europium complexes reports drug release through fluorescence changes

A novel microporous fluorescence membrane of PS-b-PAA doped with Eu3+-complexes and loaded with piperine was developed. It can display the drug content as fluorescence intensity, and can both cure wounds and track drug release.

Plastic scintillation fiber with europium complexes for low-dose X-ray detection and long-distance imaging

This work produces a new type of plastic scintillation fiber with excellent performances to realize X-ray detection and imaging.

Electrofluorochromism based on the valence change of europium complexes in electrochemical devices with Prussian blue as the counter electrode.

The electrofluorochromism of Eu complexes based on the valence change between Eu3+ and Eu2+ is demonstrated in a two-electrode electrochemical device consisting of Prussian blue (PB) as the counter electrode. This study aims to improve the electrofluorochromic (EFC) performance of luminescence switching between Eu3+ and Eu2+ by enhancing the electrochemical reactivity of the EFC device. By introducing a PB film as a counter electrode in a two-electrode device, the redox reaction of Eu3+/2+ is promoted because of charge compensation by the counter PB film. The increase in the reaction charge enables faster changes in the photoluminescence from Eu3+ to Eu2+ and an increase in the blue luminescence intensity from the Eu2+ state. This approach achieves a lowered driving voltage, accelerates the electrochemical redox reaction of the Eu complex, and enhances the reversibility of the valence change of the Eu ion.

Quantum-Chemical Approaches to Creation of Mesogenic Binuclear Europium(III) Complexes with Intensive Luminescence

This article contains data on the application of quantum-chemical methods for simulation of mesogenic binuclear complexes of europium(III) (Eu(III)) with substituted β-diketones and Lewis bases along with the possibility of prediction of their liquid crystalline (LC) properties. The relationships between geometric parameters of the complexes' molecules, the structural features of their coordination polyhedra and the probability of mesophase behavior were considered. According to the calculated parameters of Voronoi-Dirichlet polyhedra, the structural features of the first coordination sphere of Eu(III) complexes were studied and compared with the data for mononuclear complexes. Using the calculated energies of the ligands' excited states, the luminescence efficiency of the complexes was estimated. The results of quantum-chemical simulations provide recommendations for selection of ligand environment for the synthesis of LC binuclear Eu(III) complexes.

Smartphone-integrated paper-based sensing platform for the visualization and quantitative detection of pymetrozine

Pymetrozine (PYM) is an effective pyridine insecticide for controlling aphids, while its residues pose a serious threat to human health. Herein, a europium complex (Eu-DBPA, DBPA represents deprotonated 2,5-dibromoterephthalic acid ligand) probe was prepared for the detection of PYM via fluorescence quenching. The detection process has the advantages of short response time (2 min), wide linear range (0–4 and 4–45 mg/kg) and low detection limit (2.2 μg/kg). Furthermore, a portable detection platform was designed by integrating Eu-DBPA-based paper strip with smartphone and applied for the visual detection of PYM in real cucumber, tomato, cabbage and apple samples, obtaining satisfactory recovery (99.00 %–107.00 %) and low standard deviation (RSD < 3.4 %). In addition, a logic gate device was designed to simplify the detection process. The smartphone-integrated paper-based probe detection platform provides a new strategy for intelligent and online identification of hazards in environmental and biological samples.

Unlocking same-sign CPL: solvent effects on spectral form and racemisation kinetics in nine-coordinate chiral europium(III) complexes.

Understanding the factors that shape the circularly polarised luminescence (CPL) emission profiles of europium(III)-based CPL emitters to have specific sign properties, e. g. monosignate individual CPL transitions, is key to design novel complexes for applications ranging from advanced security inks to bio-probes for live cell imaging. In order to correlate structure and spectral characteristics, a photophysical and kinetic investigation has been conducted on a series of coordinatively saturated nine-coordinate europium(III) systems based on 1,4,7-triazacyclononane. We highlight that lanthanide emission is sensitive to changes in the ligand field by showing the linear dependence of total emission intensity ratios as a function of solvent polarity, for europium(III) complexes displaying an internal charge transfer (ICT) excited state. This sensitivity increases by a factor of 20 when studying changes in CPL spectra, rendering these complexes accurate probes of local polarity. Solvent polarity, solvent-specific effects, and the nature of the chromophores' coordinating donor atoms strongly influence the kinetic stability of europium(III) complexes with respect to enantiomer interconversion. Notably, we show that the choice of donor groups to coordinating to europium(III) and the nature and polarity of the solvent affects the rate of racemisation, leading to systems with very long half-lives at room temperature in non-polar media.

Formation of Complexes of f-Elements with Electron-Withdrawing N-Heterocyclic Diamides: Extraction and Solution Photophysics

To examine the scope of the abnormal aryl strengthening effect (an increase in the extraction of metal ions when an aromatic substituent is introduced into the amide group) on f-metal extraction, a series of tetradentate diamide-type extragents bearing electron-withdrawing pyridine rings in amide moieties of the molecules were tested. The solvent extraction of Am(III)/Eu(III) pairs was investigated under various conditions, the solution chemistry of the lanthanide-extragents systems was studied, and the bonding constants were calculated for complexes of Eu(III) and Tb(III) ions with diamides. The photophysical properties of chemically synthesized ligand/metal (LM) complexes with various LM compositions were additionally studied in depth. The replacement of a phenyl ring by a pyridine one led to a critical reduction in metal affinity, showing the major contribution of electronic nature to the abnormal aryl strengthening effect. However, the pyridine group in the amide side chain provided additional coordination positions for metal ion binding; corresponding complexes with LM2 composition were detected in the system and their stability was calculated. Due to the low stability of the corresponding LM2 complexes, chemical synthesis of the complexes led to the formation of only one metal-containing species with LM composition. The luminescence spectra of europium and terbium complexes of the LM composition were studied. Differences were discovered in the luminescence excitation spectra of europium and terbium complexes with the same ligand. The luminescence quantum yields and luminescence lifetimes of solutions of europium and terbium complexes were determined.

Luminescent Europium(III) Compounds with Quinaldic Acid

Heteroligand luminescent europium(III) complexes with quinaldic acid and neutral ligands were prepared. The compounds obtained were characterized by elemental analysis, X-ray diffraction, thermal gravimetric analysis, and IR spectroscopy. The composition of the complexes was determined. In the course of thermolysis, the nitrogen-containing ligand molecule is eliminated in one step with exo- and endothermic effects. The compounds are thermally stable up to 260°С. The synthesized coordination compounds were introduced into low-density polyethylene to obtain luminescent polymer materials.

Eu3+ and Tb3+ Coordination Compounds with π‐conjugated Ligands: Luminescence and Structural Properties

AbstractNew lanthanide‐based luminescent coordination compounds containing quinoline derivatives and 2‐(4‐hydroxyazobenzene)benzoic acid (HABA) were synthesized. Fourier transform infrared spectroscopy (FTIR), UV‐Vis spectra, Elemental analyses, Energy dispersive X‐ray fluorescence (EDXRF), and mass spectrometry (MALDI) were applied for six complexes′ structural elucidation. In addition, photoluminescence spectroscopy was performed in the solid state. Eu3+ and Tb3+ compounds linked to the π‐conjugated system described energy transfer to the metal through the antenna effect. Emission spectra depicted bands at 616–617 nm, characteristics of red light for Europium complexes, assigned as hypersensitive 5D0→7F2 transition, and depicted bands at 540–542 nm (green light) for Terbium complexes, assigned as 5D4→7F5 transition.

New Pressure Sensitive Paints (PSPs) for mapping pressure distributions on surfaces of building models under turbulent flow conditions in a wind tunnel

A new Pressure Sensitive Paint (PSP) has been developed to map pressure distribution on surfaces of building models during aerodynamic tests in wind tunnel. The PSP consists of 2-hydroxyethyl acrylate (HEA) hydrogel matrix and ethyl eosin (EE) as a fluorescent pressure sensor. First, the spectroscopic properties and photostability of the PSP were investigated. The maximum coating thickness was determined to be 3 mm. The PSP system was studied in the Constant-Thickness-Mode (CTM) and Variable-Thickness-Mode (VTM). It was found that fluorescence intensity of the PSP decreased with increasing pressure. Under CTM conditions, the EE-based PSP system behaved like a classic Solvent-Quenched Pressure Sensitive Paint (SQ-PSP). Its sensitivity to changes of pressure was about 35 %/bar, which is comparable to the sensitivity of SQ-PSPs based on europium complexes and sensitivity of Oxygen Quenched Pressure Sensitive Paints (OQ-PSP). However, under VTM conditions, the sensitivity of the PSP studied turned out to be about 50 times higher than that in CTM mode, due to simultaneous solvent quenching of EE sensor and change of the paint thickness upon pressure, while the effect of thickness change on fluorescence intensity was dominating. Next, pressure distribution on the side wall surface of a building model at different angles of inclination to the wind direction was mapped using classic pressure taps (as a reference) and the new PSP system in VTM mode. It has been found that the pressure maps obtained using the new PSP system are consistent with those obtained using pressure taps in the overpressure area, but show some differences in the under-pressure area, which confirms that the new PSP system can be used for aerodynamic tests under certain conditions.

Enhancing c-Si Solar Cell Efficiency in the UV Region: Photophysical Insights into the Use of Eu3+ Complexes for Down-Shifting Layer Applications

[Eu(3DPIQC)3] (where DPIQC = 3-(diphenyl phosphoryl)-1-isoquinolinecarboxylate), a luminescent europium complex with antenna ligands, has been carefully embedded within a polyvinyl butyral (PVB) matrix and the resulting material was used to prepare films used as luminescent down-shifting layers (LDSLs) for crystalline Si-based solar cells. The films were characterized using photoluminescence spectroscopy, atomic force spectroscopy (AFM), UV-Vis spectroscopy, and fluorescence microscopy. The AFM analysis shows films with low surface roughness, while fluorescence microscopy revealed that the Eu complex embedded in PVB assumed a spheroidal configuration, a morphology especially beneficial for optical applications. The so-obtained LDSLs were utilized as energy converters in c-Si solar cells to enhance the utilization of high-energy photons, thereby improving their overall efficiency. The determination of photovoltaic parameters carried out before and after the deposition of the LDSLs on the c-Si cells confirms a positive effect on the efficiency of the cell. The Jsc increases from 121.6 mA/cm2 to 124.9 mA/cm2, and the open circuit voltage (Voc) is found to be unrelated to the complex concentration in the films. The fill factor (FF) remains constant with the Eu concentration. The EQE curves indicate an enhancement in the performance of the photovoltaic cells within the UV region of the spectrum for all coated devices. Electrochemical impedance spectroscopy (EIS) was also carried out in order to analyze the effect of the Eu complex in the charge transfer process of the devices.

A combined experimental-molecular modeling study of crown ether europium complexes: Effects of the coordinated anion on structural and luminescence properties

It is reported the synthesis, characterization by elemental analysis, thermogravimetry; electronic absorption, infrared, excitation, and emission spectroscopies of the [Eu(12C4)(phen)2(X)n]X2 complexes, where 12C4 = 12-crown-4, phen = 1,10-phenanthroline, and X = F−, Cl−, Br−, SCN−, ClO4−, and NO3−. It is verified that the polarizability of the anion X– exerts remarkable effects on the emission process. As a general trend, lower wavenumbers for the 7F0→5L6, 7F0→5D2 and 7F0→5D1 transitions are associated with the anions with higher volumes and, consequently, higher polarizability. The molecular modeling results performed with quantum methods (RHF and DFT) suggest some relationships between the calculated structures, electronic, and luminescence properties with the presence of the LMCT (ligand-to-metal charge transfer) states, which explains the differences in the emission spectra of these complexes due to the coordinated anion.

Molecular Vibrations in Chiral Europium Complexes Revealed by Near-Infrared Raman Optical Activity.

Raman optical activity (ROA) is commonly measured with green light (532nm) excitation. At this wavelength, however, Raman scattering of europium complexes is masked by circularly polarized luminescence (CPL). This can be avoided using near-infrared (near-IR, 785nm) laser excitation, as demonstrated here by Raman and ROA spectra of three chiral europium complexes derived from camphor. Since luminescence is strongly suppressed, many vibrational bands can be detected. They carry a wealth of structural information about the ligand and the metal core, and can be interpreted based on density functional theory (DFT) simulations of the spectra. For example, jointly with ROA experimental data, the simulations make it possible to determine absolute configuration of chiral lanthanide compounds in solution.

Development of europium(III) complex fluorescent probe for hydrogen sulfide detection and its application in water samples.

Hydrogen sulfide (H2 S) is a crucial endogenous signaling component in organisms that is involved in redox homeostasis and numerous biological processes. Modern medical research has confirmed that hydrogen sulfide plays an important role in the pathogenesis of many diseases. Herein, a fluorescent probe Eu(ttbd)3 abt based on europium(III) complex was designed and synthesized for the detection of H2 S. Eu(ttbd)3 abt exhibited significant quenching for H2 S at long emission wavelength (625 nm), with rapid detection ability (less than 2min), high sensitivity [limit of detection (LOD) = 0.41 μM], and massive Stokes shift (300 nm). Additionally, this probe showed superior selectivity for H2 S despite the presence of other possible interference species such as biothiols. Furthermore, the probe Eu(ttbd)3 abt was successfully applied to detect H2 S in water samples.

Flour moisture detection with an europium-based luminescent probe

In this work, we describe the application of the self-assembled europium complex 1:Eu(III) (where 1: diethyl 8-methoxy-2-oxo-1,2,4,5-tetrahydro-cyclopenta[de]quinolin-3-yl)phosphonate) for the analysis of water content of wheat flour. The methodology herein described represents a robust and accurate way for the detection of small amounts of water in food, providing comparing results with well-established methods such as thermogravimetry and Karl-Fischer titration. Interestingly, as an advantage over other methods, our luminescence-based approach can be implemented in lab-on-a-chip microfluidic devices for real-time and on-line detection of water content of food samples. Additionally, the remarkably long luminescence lifetime of Eu(III) allows the use of state-of-the-art imaging strategies based on PLIM microscopy for the direct visualization of unique water content maps of wheat flour particles.

A Novel ppb-Level Sensitive and Highly Selective Europium-Based Diketone Luminescent Sensor for the Quantitative Detection of Aluminum Ions in Water Samples

A novel Eu(tta)3([4,4′-(t-bu)2-2,2′-bpy)] complex (tta-thenoyltrifluoroacetone), a ratiometric luminescent-based optical sensor for the quantitative determination of aluminum ion, is synthesized and characterized using XRD and 1H NMR. The XRD data reveal the slightly distorted octahedral structure. The complex displays a bright red emission at 613 nm in methanol which is characteristic of europium (III) complexes. Upon the addition of Al3+ ions, the red emission disappears, and a new blue emission at 398 nm emerges, manifesting the ratiometric nature of the complex. The turn-off of the red emission and turn-on of the blue emission are attributed to Eu-Al trans-metalation, as supported by Raman data that show the emergence of Al-O vibrations at 418, 495, and 608 cm−1 concomitant with the disappearance of Eu-O and Eu-N bond vibrations. Most aluminum sensors are known to suffer from interferences from other metals including Cu2+, Co2+, and Cd2+. However, the sensor reported here is tested for 11 common cations and shows no interference on sensitivity. To the best of our knowledge, this is the first known Eu-based luminescence sensor that successfully exhibited the ability to detect aluminum ions in ppb levels in aqueous environments. The calculated Al3+ binding constant is 2.496 × 103 ± 172. The complex shows a linear relationship in the range of 0–47.6 ppb (1.76 × 10−6 M) Al3+ and the limit of detection (LOD) is 4.79 ppb (1.77 × 10−7 M) in MeOH. ICP-OES is used for validation of the sensor complex in water and then it was used for quantitative detection of Al3+ ions in water as a real-life application. The complex can accurately detect Al3+ ions in the range of 4.97–24.9 ppb (1.84 × 10−7 M–9.2 × 10−7 M) with an LOD of 8.11 ppb (2.99 × 10−7 M). Considering that the aluminum ion serves no recognized function within the human body, its accumulation can lead to severe neurological disorders, including Parkinson’s and Alzheimer’s diseases. With the LOD value significantly lower than the WHO-recommended maximum permissible level of 200 ppb for aluminum in drinking water, even without high-power laser-aided signal enhancement, the sensor shows promise for detecting trace amounts of aluminum contamination in water. Therefore, it can significantly aid in the monitoring of even the smallest aluminum ion contamination in drinking water, industrial effluents, and natural water bodies.