Typical Eu3 Research Articles

Fabrication of a novel Eu3+-functionalized Mn-MOF based on the X-type tetracarboxylate ligand for efficient temperature sensing

In this work, by utilizing an X-type tetracarboxylate ligand (1,2,4,5-tetrakis(4-carboxyphenyl)benzene, H4TCPB), a novel Mn-organic framework, namely, [(CH3CH2)2NH2]2[Mn(TCPB)(H2O)2] (SQNU-25, SQNU = Shangqiu Normal University), was prepared under a DEF/HAc solm. Due to the structural advantage of SQNU-25, the Ln3+ ions (Eu3+ and Gd3+) have been successfully introduced into the framework by post-synthetic modification. The result of the energy levels of the H4TCPB ligand and Eu3+ ion shows that the H4TCPB ligand as a chromophore can effectively sensitize Eu3+ ions. Moreover, the Eu@SQNU-25 not only shows a typical Eu3+ ion red emission but also exhibits good temperature sensing in the wide temperature range (80 to 300 K).

Structure-Dopant Concentration Relations in Europium-Doped Yttrium Molybdate and Peak-Sharpening for Luminescence Temperature Sensing.

A set of Eu3+-doped molybdates, Y2-xEuxMo3O12 (x = 0.04; 0.16; 0.2; 0.4; 0.8; 1; 1.6; 2), was synthesized using a solid-state technique and their properties studied as a function of Eu3+ concentration. X-ray diffraction showed that the replacement of Y3+ with larger Eu3+ resulted in a transformation from orthorhombic (low doping concentrations) through tetragonal (high doping concentrations), reaching monoclinic structure for full replacement in Eu2Mo3O12. The intensity of typical Eu3+ red emission slightly increases in the orthorhombic structure then rises significantly with dopant concentration and has the highest value for the tetragonal Y2Mo3O12:80mol% Eu3+. Further, the complete substitution of Y3+ with Eu3+ in the case of monoclinic Eu2Mo3O12 leads to decreased emission intensity. Lifetime follows a similar trend; it is lower in the orthorhombic structure, reaching slightly higher values for the tetragonal structure and showing a strong decrease for monoclinic Eu2Mo3O12. Temperature-sensing properties of the sample with the highest red Eu3+ emission, Y2Mo3O12:80mol% Eu3+, were analyzed by the luminescence intensity ratio method. For the first time, the peak-sharpening algorithm was employed to separate overlapping peaks in luminescence thermometry, in contrast to the peak deconvolution method. The Sr (relative sensitivity) value of 2.8 % K-1 was obtained at room temperature.

Novel Photoluminescence and Optical Thermometry of Solvothermally Derived Tetragonal ZrO2:Ti4+,Eu3+ Nanocrystals

In this paper, we report on the solvothermal preparation and detailed characterization of pristine and intentionally doped zirconium dioxide (ZrO2) nanocrystals (NCs, ~5 nm) with Eu3+ or Ti4+/Eu3+ ions using alkoxide precursors. The results indicated that the ZrO2 NCs were dominantly of a tetragonal phase (t-ZrO2) with a small proportion of monoclinic ZrO2 (m-ZrO2). The high purity of t-ZrO2 NCs could be synthesized with more Eu3+ doping. It was found that the as-obtained ZrO2 NCs contain some naturally present Ti4+ ions originating from precursors, but were being overlooked commonly, and some carbon impurities produced during synthesis. These species showed distinct photoluminescence (PL) properties. At least two types of Eu3+, located at low- and high-symmetry sites (probably sevenfold and eightfold oxygen coordination), respectively, were demonstrated to build into the lattice structure of t-ZrO2 NCs together. The cationic dopants were illustrated to be distributed non-randomly over the sites normally occupied by Zr, while Ti impurities preferentially occupied the sites near the low-symmetry site of Eu3+, yielding efficient energy transfer from the titanate groups to the neighboring Eu3+. Luminescence nanothermometry could measure temperature in a non-contact and remote way and could find great potentials in micro/nano-electronics, integrated photonics, and biomedicine. On the basis of the dual-emitting combination strategy involving the white broadband CT (Ti3+→O−) emissions of the titanate groups and red sharp Eu3+ emissions, t-ZrO2:Eu3+ nanophosphors were demonstrated to be ratiometric self-referencing optical thermometric materials, with a working range of 130–230 K and a maxima of relative sensitivity of ~1.9% K−1 at 230 K.

Probing the effect of Y3+/Gd3+ on the optical properties of Gd2-xYxTiO5:Eu3+: Insight into local site-luminescence correlation

Phosphor converted light emitting diodes (pcLEDs) are considered as the most efficient materials to resolve the issue of energy scarcity. In this regard, the design of an efficient red phosphor could be a game changer due to the lack of the same in the current existing phosphor library. Here in this work, we have investigated high color purity, moderate photoluminescence quantum yield (PLQY) and long excited state lifetime red emitting Gd2-xYxTiO5:1.0 %Eu3+ phosphor with varying Y3+/Gd3+ ratio. It was found that higher Y3+ containingGd0.5Y1.50TiO5:1% Eu3+ emerged victorious in terms of luminescence intensity, asymmetry ratio and PLQY ∼ 10 %. Higher PLQY of this particular composition has been attributed to lowest non-radiative channels in them. The same has been further supported by PALS as it suggested lowest defect density in Gd0.5Y1.50TiO5:1% Eu3+ as most of the vacancies have moved out of the lattice to the surface and is responsible for improved optical properties as defect triggered non-radiative pathways reduced significantly. The O2–→ Eu3+ charge transfer energy on the other hand eases in higher gadolinium counterparts owing to more structural distortion of distorted pentagonal bipyramid (DPB) and distorted hexagonal bipyramid (DHB) in them. Based on the number of Stark components of 5D0→7F0 there are two types of Eu3+ with distinct chemical environments. It was inferred that longer lived trivalent europium ions are the one located at a less distorted DPB whereas short lived Eu3+is ascribed to the one occupying a highly distorted DHB. The trend in Judd-Ofelt parameter Ω4 < Ω2 revealed that Eu3+ ions are localized in high asymmetric locations in all the samples under the doping level used in this work. The high branching ratio of 5D0→7F2 transitions for all the samples reflected in very high color purity of more than 99 %. These results suggest that Eu3+doped A2TiO5 luminescent crystals with moderate PLQY, high red color purity and long excited state lifetime could serve as efficient red phosphor and with further improvement can be potential candidate for various applications.

Structural Properties, Photoluminescence, and Judd-Ofelt Parameters of Eu3+- Doped CoNb2O6 Phosphor

Trivalent Eu-activated CoNb2O6 phosphors were fabricated using the molten salt method, which provides enhanced homogeneity and low sintering temperature. The ceramic samples were examined by spectral and structural analyses. In X-ray diffractions, the single phase of orthorhombic columbite type CoNb2O6 structure was obtained for 0.5-10 mol% Eu3+ doping concentrations, while a two theta peak shift towards the smaller angles occurred. SEM examinations show an irregular morphology and sub-micron grain sizes. In photoluminescence (PL) spectra, the phosphors showed typical Eu3+ emissions with the 5F0 → 7FJ (J=0, 1, 2, 3, 4) transitions, and high emission peaks were observed at the 5D0 → 7F2 transition. The photoluminescence of CoNb2O6:Eu3+ decreased over 5 mol% because of the concentration quenching. The energy transfer mechanism and critical distance of the phosphor are the dipole-dipole (d–d) interaction, and 15.70 Å, respectively. The spectral features of the phosphors were assessed by calculating the Judd-Ofelt intensity parameters (Ω2, Ω4) from the PL emission spectrum. The low Ω2 parameter values or/and the Ω4&amp;gt;Ω2 trend for CoNb2O6:Eu3+ phosphors were related to the less covalent or more ionic character of the Eu3+–O2˗ bond and the high local symmetry of the Eu3+ sites, while the high Ω4 parameter values may be ascribed to the decrease in the electron density in the ligands.

Luminescence properties and energy-transfer behavior of Y2-x-yBixEuyMgTiO6 phosphors

In recent years, double perovskite has become a research hotspot of luminescent matrix materials due to its flexible structure, easy doping and good thermal stability. By using a high temperature solid-state technique, Bi3+ and Eu3+ co-doped Y2-x-yBixEuyMgTiO6 (0 ≤ x ≤ 0.1, 0 ≤ y ≤ 0.5) phosphors were made. X-ray diffraction (XRD) analysis shows that the crystal structure of all samples is monoclinic system, P21/n; Bi3+ and Eu3+ can be doped into the position of Y3+ in the substitution system of Y2MgTiO6. Both photoluminescence spectroscopy (PL) and X-ray excitation luminescence spectroscopy (XEL) were used to investigate the link between Bi3+ and Eu3+ doping concentrations and luminescence intensity. PL shows that: When 375 nm is used as the excitation wavelength, by varying the doping concentration of Eu3+ in the Y1.995-yBi0.005EuyMgTiO6 phosphor, it is possible to create the color-tunable emission from blue to red; The introduction of an appropriate amount of Bi3+ will increase the typical Eu3+ emission; The way that the system's Bi3+ and Eu3+ exchange energy can be observed by combining the fluorescence decay curve and photoluminescence. Fitting by concentration quenching model shows that the resonant dipole-dipole transition is the mechanism of energy transfer between Bi3+→Eu3+; X-rays may successfully stimulate the phosphor, and the spectral distribution of XEL and PL is basically the same; The introduction of an appropriate amount of Bi3+ is also beneficial to improving the sensitivity of XEL; Changes in temperature affect the sample's emission intensity; In addition, the samples remain stable for an extended period while being continuously exposed to X-rays at various environmental temperatures. The a forementioned findings suggest that the phosphor has potential use value in the lighting industry, X-ray imaging and temperature sensor.

Red emission enhancement in YVO4:Eu3+ nanoparticle by changing the complexing agent in modified sol-gel route

The complexing agent modification can realize systematically the red emission enhancement of YVO4:Eu3+ nanoparticle. Using sucrose, glucose, and arabic gum as complexing agents, Eu3+-doped YVO4 nanoparticles were synthesized by a modified sol-gel route. The crystallographic structure, morphology, and composition of samples were investigated through X-ray diffraction (XRD) and transmission electron microscopy (TEM). It is found that changing the complexing agent can be used to improve the Eu3+ emission. Structural characterizations reveal that the YVO4:Eu3+ nanoparticle can be successfully prepared using the sucrose, glucose, and arabic gum complexing agent and that particle size is strongly influenced by them. As the complexing agent change, the size of the sample particles changes. Photoluminescence (PL) emission exhibit typical Eu3+ emission lines with the 5D0→7F2 transition dominating and varying with the complexing agents.

Customized structural and mechanical characteristics of Eu3+ imbued boro-telluro-dolomite glasses: effect of Dy3+ co-doping

Inorganic oxide glasses with high mechanical strength and durability became demanding. Thus, a new type of Eu3+/Dy3+ co-doped boro-telluro-dolomite glass system with customized structures and mechanical properties were prepared by the melt-quenching method and characterized. The densities, FTIR and Raman spectra of the glasses revealed a significant modification in the network structure with the increase of Dy3+ contents. The values of microhardness and elastic moduli of the glasses were increased with the increase of co-doping contents. In addition, a correlation between the glass hardness and applied load was established. The proposed glasses were shown to withstand about 300 g applied force without any distortion, confirming their usefulness to design mechanically stable screen shield and high strength surfaces.

ENGINEERING OF THE LUMINESCENT PROPERTIES OF GLASS-CERAMIC NANOCOMPOSITES

The “mixture”- like composite materials consist of a matrix and a filler. An interaction between these components, i.e., the matrix and filler particles, can result in formation of the transition layers (interphases). A chemical composition, spatial and energetic structures of these interphase layers differ from those peculiar for initial components. Accordingly, the properties of such transitional layers could be significantly different from those ones for a matrix or a filler. The role of interphase layers increases when particles became nanosized and with their concentration increasing. An influence of the interphase layers on the properties of composite increases at such conditions and even could be determining. The considerations described above are a basement of the proposed method of control (engineering) of the composite materials properties. This paper reports the results of the study of the interphase layers manifestations in luminescence properties of the “glass-ceramics” type of composites, those consist of mK2O-kP2O5-nB2O3:xPb-yEu oxide glass matrix and Eu3+- doped luminescent oxide polycrystalline KCa(BO3)3compound, as a filler. A possibility of tailoring the emission wavelength of the glass-ceramics has been discussed as well. A morphology, structure and optical properties of the prepared glass-ceramics have been studied by means of scanning electron microscopy (SEM), X-ray diffraction (XRD) and photoluminescence (PL) spectroscopy, respectively. The SEM images are typical for vitreous materials when some micro/nanocrystallites of KCa(BO3)3 oxide incorporated into matrix can be seen in case of glass-ceramics. XRD patterns reveal wide bands those are peculiar to vitreous materials, while the patterns of glass-ceramics additionally contain the narrow bands related with crystalline filler. Wide-band spectra of own luminescence have been observed under photo-excitation of glassy samples. In contrast, weakening of this PL emission and a domination of a linear emission related with f-f transitions in Eu3+ ions, takes place in the case of glass-ceramics. A detailed analysis of the linear PL has been shown the presence of three types of Eu3+ ions in glass-ceramics: there are ions located in the oxide particles, glass and interphase layer. Spectral characteristics of the PL related with each of these types of ions are significantly different, that provide a possibility to control PL emission spectra by changing contribution of interphase layer to overall spectra of the glass ceramics studied.

Spectroscopic, optical properties and ab-initio calculation of thermally stable Na2Ca1-xP2O7:xEu3+ phosphors for wLEDs

A series of Na2Ca1-xP2O7:xEu3+ phosphors (x = 0.01–0.1) were synthesized via solid-state reaction route. The phase purity and crystal structure were confirmed via XRD and Rietveld refinement analysis. Density functional theory (DFT) calculations and experimental analysis were utilized simultaneously to study the electronic and optical properties. The phosphors emit the typical Eu3+ ions emissions associated with the f-f transitions when excited at 394 nm. Energy transfer with the nearest neighbor or next nearest neighbor dopants caused the concentration quenching in present phosphors. To confirm the Eu3+ ion's local symmetry characteristics, the optical transition parameters were calculated using the Judd-Ofelt theory. Furthermore, the thermal stability was explored in depth. The temperature-dependent photoluminescence (PL) emission spectra of the developed phosphors showed excellent thermal stability (90.63%) at 423 K and the calculated activation energy was 0.26 eV. Moreover, the Na2Ca1-xP2O7:xEu3+ phosphors were mixed with commercial green-blue emitting and coated over a NUV chip to fabricate the wLED. The findings indicate that Eu3+ activated Na2CaP2O7 phosphors are potential wLED materials.

Efficient photoluminescence from 1-(2-Naphthoyl)-3,3,3-trifluroacetonate complex of Eu3+ with bidentate neutral donors

Two new europium complexes, Eu(NTA)3(bath) and Eu(NTA)3(DPEPO), were synthesized and characterized by elemental analysis, Fourier transform infrared, mass spectrometry, thermogravimetric analysis and photoluminescence spectroscopy. The room-temperature photoluminescence spectra of the Eu3+ complexes are composed of the typical Eu3+ red emission, assigned to transitions between the first excited state (5Δ0) and the multiplet (7F0-4). The results demonstrate that the substitution of water molecules by bidentate oxygen or nitrogen ligands in Eu(NTA)3(H2O)2 richly enhances the overall quantum yield (Φoverall = 12% vs. 87%) and life time values (τobs = 339 vs. 521 μs).

PL, TL and Persistent Luminescence Characterization of Undoped and Eu Doped Nanostructured Hydroxyapatite

Hydroxyapatite (HAp, Ca10(PO4)6(OH)2) possesses the closest mineralized structure to natural bone tissue and has been widely using in as bone substitutes and for various biomedical applications. Undoped and doped with rare earth elements HAps are the basis of promising biomedical imaging, bone tissue engineering, gene and drug delivery applications. In the present work, we present the results of investigation of the photoluminescence (PL), thermoluminescence (TL) and persistent luminescence (PersL) of synthetic nanostructured HAp (n-HAp). Undoped and Eudoped (0.0, 0.1, 0.5, 1.0, 2.0 mol %) n-HAp powders were synthesized by solution-precipitation method and characterized by SEM-EDS, FTIR and Raman techniques. The 3D excitation-emission spectrum of undoped n-HAp exhibits a broad band with excitation/emission maximum at 376/454 nm, respectively. The maximum position slightly shifts to shorter excitation and emission wavelengths with increases of the Eu concentration that could be due to a possible overlapping between the Eu emission band and intrinsic emission of undoped n-HAp. It was found that (similarly to behavior of PL in Si nanocrystals, Xin et al., RSC Adv., 2019, 9, 8310) the emission peak is red-shifted as the excitation wavelength red-shifts. The typical Eu3+ emission bands were observed for high Eu doping concentrations. TL glow curves of n-HAp samples exposed to beta radiation from Sr-Y source display a broad TL peak with maxima in-between 145 and 165 oC depending on the Eu concentration. The highest TL intensity is observed for undoped n-HAp, showing quenching effect of Eu on TL emission. This TL quenching effect contrasted with the PersL decay emission measured immediately after irradiation exposure, which was highest for 0.1 mol % Eu. The intrinsic defects in n-HAp host is related to the PL, TL and PersL emissions; however, the nature of the radiative and non-radiative recombination mechanisms requires further investigation. The PL, TL and PersL of undoped HAp may have prospective application in the fields of radiation detection, ionizing radiation dosimetry and biomedical imaging. Keywords: Hydroxylapatite, thermoluminescence, persistent luminescence.

Effect of Reducing and Oxidizing Atmosphere on Photoluminescence of Undoped, Eu Doped and Dy Doped Nanostructured CaAl2O4

Monocalcium aluminate (CaAl2O4) doped with Eu2+ is a phosphor that produces phosphorescence in the blue light (440 nm). It has attracting a great deal of attention because of its wide applications in energy-efficient illumination systems and information displays. CaAl2O4 codoped with Eu2+ and Dy3+ exhibits a very strong and long lasting persistence luminescence that could have many applications in the fields of emergency lighting signs, night-vision signage, in vivo bioimaging, dosimetry and optical data storage.In this work, we present the effect of the thermal treatment in the reducing (nitrogen) and oxidizing (air) atmosphere on the photoluminescence (PL) properties of nanostructured undoped CaAl2O4, CaAl2O4:Eu and CaAl2O4:Dy synthesized by the combustion method. The synthesized powders were characterized by XRD, SEM-EDS, FTIR and Raman techniques. The XRD analysis revealed that the powder mainly consists of krotite (CaAl2O4) together with a small amount of grossite (CaAl4O7) and mayenite (C12Al14O33).The 3D excitation-emission spectra of undoped and untreated CaAl2O4 exhibits a broad band with excitation/emission maximum at 338/412 nm, respectively. The thermal treatment slightly shift the position of the maximum for both the reducing and oxidizing atmosphere. It is interesting to note that the emission peak is red-shifted as the excitation wavelength red-shifts in the untreated sample while the emission peak positions are independent of the excitation wavelength in both reduced and oxidized samples. It is interesting to note that the emission peak shifts to red as the excitation wavelength shifts to red in the untreated sample, while the emission peak positions are independent of the excitation wavelength in reducing or oxidizing samples.The Eu doped sample treated in the oxidizing atmosphere exhibit the typical Eu3+ emission sharp bands while the reduced Eu doped sample reveals only broad Eu2+ emission band that partially overlaps with the band observed in undoped samples. The Dy doped samples exhibit the typical Dy3+ emission sharp bands regardless of their reducing or oxidizing thermal treatment.

Recent development of Eu3+-doped phosphor for white LED application: A review

The phosphor converted w-LEDs gaincrucial attention in solid state lighting (SSL) for generation of illumination owing to their numerous meritorious advantages such as superior life time, excellent efficiency, compactness, reliability and power saving consumption as well as environmental friendly. The quality of w-LEDs in lighting and display is influence by host phosphorand the choice of activator. So greatlyattemptwere dedicated to developed inventiveuni-nucleiluminescent phosphor materials compose of chromatic stability, optimum CRI and low correlated color temperature. This review elaborate theintroduction ofEu3+rare earth activated red emitting phosphor assigned to 5D0→7FJ (J= 1,2,3,4) energy levelsand its fundamental merit for w-LEDs. This article represent the analyseofcombination of different types of Eu3+ activated luminescent materials by traditional and novel methods and its impact on photoluminescence for SSL.

Engineering defect clusters in distorted NaMgF3 perovskite and their important roles in tuning the emission characteristics of Eu3+ dopant ion.

An attempt has been made to explore various new defect clusters in distorted NaMgF3 perovskite and their important role in tuning optical properties. We have tried to tailor the defect clusters and to understand the impact on the luminescence of the lanthanide, for example the Eu3+ ion. Defect engineering has been carried out by doping aliovalent dopant ions to create a charge imbalance in the matrix, which in turn led to the creation of various mono-, di- and new cluster vacancies. Such vacancies have been characterized by Electron Para-magnetic Resonance (EPR), Positron Annihilation Lifetime Spectroscopy (PALS) and Photoluminescence (PL) studies. The PALS data of both undoped and Eu3+ doped compounds confirmed that in addition to Mg mono vacancies, cluster vacancies with different configurations comprising Mg, Na and F atom vacancies also exist in the matrix. The PL study revealed that depending on the surrounding defect structure, three different types of Eu3+ components can be created. The position of the Eu3+ ion with respect to these cluster vacancies determines the respective emission profiles and the decay kinetics. It has been found that when Li+ ions are co-doped with Eu3+, there is a sudden change in the decay kinetics and the emission profiles. The PALS study revealed that Li+ co-doping modified the configuration of the vacancy clusters, which in turn changes the emission characteristics. The EPR study confirmed the presence of different types of F-centers (F, F2, etc.) which are responsible for the host emission. Overall, this new study will be very helpful for a detailed understanding of the defect structures, in particular the cluster vacancies in distorted NaMgF3 perovskite, which have a direct or indirect impact on many physical properties.

Elastic changes in luminescence intensity of vitrified film of europium(III) β-diketonate complex

We have observed an elastic change in luminescent properties of a 20 µm thick vitrified film (prepared from an amorphous powder of an anisometric europium(III) β-diketonate complex through a melt-processing technique and sandwiched between two quartz plates) caused by the prolonged UV irradiation. The film under UV light irradiation exhibits a typical Eu3+ ion emission peaked at 611 nm. The irradiation of the film by a 337 nm pulsed nitrogen laser with 0.2 mW average output power for 80 min leads to 1.5-fold decrease in the luminescence intensity at 611 nm. Despite the fact that in the case of traditional film-type materials based on lanthanide(III) β-diketonate complexes such effect is attributed to irreversible ligand photofragmentation, we have observed no photodecomposition of the anisometric complexes in the vitrified film. Moreover, we detected full reversibility of the luminescence intensity by keeping the film in the dark for 21 h. It is worth noting that this feature can be used for the design of new reusable luminescent dosimeters for UV light.

The influence of the complexing agent on the luminescence of multicolor-emitting Y2O3:Eu3+,Er3+,Yb3+ phosphors obtained by the Pechini's method

In this study, it is reported the enhancement of the downshifting and the upconversion emission of Y2O3:Eu3+,Er3+,Yb3+ phosphor drove by sorbitol instead of the classic ethylene glycol used as polymerizing agent in the Pechini's synthesis. The RE3+ doping concentration was also varied to optimize the red or the green Er3+ emission or the Eu3+ red emission. Phosphors were obtained as high-crystalline and micro-sized particles, yet the doping concentration and the polymerizing agent influence the crystallite size and the lattice strain of the Y2O3 matrix that features optical band gap near to 5.6 eV. Under excitation at 378 nm, the downshifting emissions of Eu3+ and Er3+ are noticed, but under excitation at 463 nm, only the typical Eu3+ emission in the red spectral region is viewed. Contrarily, by exciting the phosphors at 980 nm within the IV spectral region, both green and red emissions of Er3+ plus the red emission of Eu3+ are seen through upconversion emission, and in this case, the pair Er3+/Yb3+ acts as sensitizers to the Eu3+ luminescence. Moreover, the use of sorbitol instead of ethylene glycol in the Pechini's synthesis enhances both downshifting and upconversion luminescence of phosphors due to a lowering of the Eu3+ local microssymmetry played by sorbitol, accordingly to the analyses of Judd-Ofelt intensity parameters of the phosphors. Finally, by varying the doping concentration, the polymerizing agent, and the excitation wavelength, the phosphor emission color may be tuned from the green towards the red spectral region.

Europium metal-organic framework containing helical metal-carboxylate chains for fluorescence sensing of nitrobenzene and nitrofunans antibiotics

Food safety and environmental pollution have become prevalent concerns around the world. The development of a facile detection method towards nitroaromatic pollutants and antibiotics in the environment is exceedingly desirable for protecting human health and controlling the risks of sanitation pollution. Herein, a new europium metal-organic framework (Eu-MOF), which is built from helical rod-shaped europium carboxylate chains, has been synthesized and broadly explored. The compound exhibits intense red luminescence output of typical Eu3+ ions both in solid and in the alcohol solutions. Notably, it shows rapid and efficient fluorescence quenching effects towards the nitrobenzene (NB) and nitrofurans antibiotics (NFAs). As a dual-functional chemosensor, the Eu-MOF has a broad application prospect for its sensitive identification and visual detection in the future. The mechanism of the quenching effect was investigated in detail, and the density functional theory also proved the result.

Luminescent properties of biohybrid (kaolinite-proline) materials synthesized by a new boric acid catalyzed route and complexed to Eu3+

The properties of Eu3+-biohybrid (kaolinite-proline) materials were investigated by powder X-ray diffraction, vibrational spectroscopy, scanning electron microscopy, nitrogen adsorption and photoluminescence to understand how Eu3+ interacts with the biohybrid matrices. Biohybrids were obtained through the conventional route and by two new catalytic routes for functionalization of clay minerals, and were then complexed to Eu3+ ions at a constant proline:Eu3+ molar ratio of 3:1, while the water molecules originally existing in the first coordination sphere of Eu3+ ions in the kaolinite-grafted complexes were replaced by 2-thenoyltrifluoroacetone (tta). The typical Eu3+ emission spectra for solids containing tta revealed the characteristic Eu3+ transitions from fundamental 5D0 state to excited 7FJ (J = 0, 1, 2, 3 and 4) states. The lifetime measurements also confirmed that water molecules were exchanged, increasing emission efficiency. The time-resolved spectra allowed to remove the matrix and ligand emissions and thus to evaluate their influence on the emission of the lanthanide ion. After incorporation of Eu3+, the thermal stability of the solids improved. The intercalated europium complexes did not show the same ligand/Eu3+ molar ratio as the free complexes, due to the restricted mobility of the ligands grafted within the interlayer spaces of kaolinite. On the contrary, these complexes showed high internal quantum yields, low luminescence suppression (after tta coordination), preserved the kaolinite layered structure. They also showed a low water molecules coordination number, which made them very attractive for luminescent applications, in addition to bringing high added value, due to a low cost, non-toxicity, non-polluting and high efficiency.

High-pressure luminescence of monoclinic and triclinic GdBO3: Eu3+

The monoclinic (α) and triclinic (β) GdBO3 submicron-sized crystals doped with Eu3+ ions were synthesized using different approaches (sol-gel Pechini and hydrothermal method). The luminescence properties of these two types of GdBO3 are different due to the different symmetry of the local coordination environment of Eu3+ ions, embedded in the investigated materials. Crystal structures of GdBO3: Eu3+ were investigated using X-ray diffractometry under high-pressure conditions. High-pressure luminescent properties of the monoclinic and triclinic phases were investigated up to about 8 GPa, and they differ for two types of Eu3+-doped GdBO3 crystals. Changes in emission spectra, such as broadening and splitting of bands in the compression cycle are shown for both matrices with Eu3+ ions. The band centroid shifts and Stark sub-level were calculated and correlated with the increase in pressure value. The maximum shifts were 0.25 nm/GPa for the Stark sub-level of the 5D0→7F2 transition in the monoclinic GdBO3: Eu3+, and 0.35 nm/GPa for the Stark sub-level of the 5D0→7F1 transition in the triclinic GdBO3: Eu3+.