Recent progress in luminescent materials based on lanthanide complexes intercalated synthetic clays

Interest in lanthanide complexes in the synthetic clays remains growing considerably during the last decades because of the attractive features of the individuals. Synthetic clays like Laponite^® and Aminoclay show great potentials in building up the luminescent hybrid materials due to their obvious advantages such as high purity, high dispersibility (or solubility) in water to yield translucent gels and clear aqueous solution. Additionally, their strong adsorption capacity for non-polar molecules or complexes is favorable to the formation of water-soluble and aqueous processable luminescent materials. This feature article summarizes the latest developments in the design and preparation of highly luminescent organic-inorganic hybrid materials with excellent aqueous process ability based on lanthanide complexes intercalated synthetic clays.     

Highly luminescent europium and terbium complexes based on succinimide and N-hydroxysuccinimide

The preparation of two highly luminescent europium(III) and terbium(III) complexes with succinimide(SI) and N-hydroxysuccinimide(NHSI) were reported,which were further investigated through elemental chemical analysis,thermal analysis,FT-IR,powder X-ray diffraction,SEM and fluorescence spectroscopy.Data collected through these analysis revealed the formation of the Eu(III) and Tb(III) complexes with the above mentioned ligands at a metal to ligand(M:L) molar ratio of 1:3.Interesting conclusions regarding the efficient sensitization through the coordination site of the lanthanide luminescent centers were retained from the photoluminescent spectra investigation.Strong luminescence emission was observed in case of Eu(III)-SI and Tb(III)-NHSI complexes while the corresponding Eu(III)-NHSI and Tb(III)-SI complexes exhibited no photo luminescent properties.Newly obtained luminescent lanthanide complexes may be of particular interest for various applications in optoelectronics.     

稀土掺杂Sr2MgSi2O7长余辉发光材料的研究进展

硅酸镁锶(Sr2MgSi2O7)作为目前常用的一种长余辉发光材料基质,性能稳定,耐酸碱性能良好。本文介绍了长余辉发光材料的发光原理,综述了近年来Sr2MgSi2O7长余辉发光材料的主要制备方法以及稀土掺杂Sr2MgSi2O7材料的研究进展,并对该材料的发展做出了展望。制备Sr2MgSi2O7长余辉发光材料的方法主要包括高温固相法,溶胶-凝胶法,化学沉淀法和燃烧合成法,其中最常用的为高温固相法。通过掺杂稀土离子可以形成具有不同发光特性的长余辉发光材料。稀土掺杂Sr2MgSi2O7材料作为一种储能、节能的长余辉发光材料,展现出了广阔的发展和应用前景。     

New Opportunities for Lanthanide Luminescence

Trivalent lanthanide ions display fascinating optical properties. The discovery of the corresponding elements and their first industrial uses were intimately linked to their optical properties. This relationship has been kept alive until today when many high-technology applications of lanthanide-containing materials such as energy-saving lighting devices, displays, optical fibers and amplifiers, lasers, responsive luminescent stains for biomedical analyses and in cellulo sensing and imaging, heavily rely on the brilliant and pure-color emission of lanthanide ions. In this review we first outlined the basics of lanthanide luminescence with emphasis on f-f transitions, the sensitization mechanisms, and the assessment of the luminescence efficiency of lanthanide-containing emissive molecular edifices. Emphasis was then put on two fast developing aspects of lanthanide luminescence: materials for telecommunications and light emitting diodes, and biomedical imaging and sensing. Recent advances in NIR-emitting materials for plastic amplifiers and waveguides were described, together with the main solutions brought by researchers to minimize non-radiative deactivation of excited states. The demonstration in 1999 that erbium tris(8-hydroxyquinolinate) displayed a bright green emission suitable for organic light emitting diodes (OLEDs) was followed by realizing that in OLEDs, 25% of the excitation energy leads to singlet states and 75% to triplet states. Since lanthanide ions are good triplet quenchers, they now also play a key role in the development of these lighting devices. Luminescence analyses of biological molecules are among the most sensitive analytical techniques known. The long lifetime of the lanthanide excited states allows time-resolved spectroscopy to be used, suppressing the sample autofluorescence and reaching very low detection limits. Not only visible lanthanide sensors are now ubiquitously provided in medical diagnosis and in cell imaging, but the feasibility of using NIR emission of ions such as YbⅢ is now being tested because of deeper penetration in biological tissues.     

Progress on Study of Luminescence of Rare Earth Organic Chelates

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Lanthanide complexes-functionalized ordered mesoporous TiO2: Multicolor emission (visible and near-infrared luminescence) based on visible-light sensitization

Recently, much attention has been paid to the lanthanide luminescent materials based on the visible-light sensitization for their potential applications in the fields of bio-imaging and optical devices. In this work, the lanthanide complexes have been covalently bonded to the ordered mesoporous titania (OMT) matrix, and the resulting titania-based hybrid ordered mesoporous materials (named as LnDB-OMT, Ln = Eu, Sm, Yb, Nd) were characterized by using Fourier-transform infrared (FT-IR) spectroscopy, small-angle X-ray powder diffraction (SAXD), N₂ adsorption–desorption isotherms, transmission electron microscopy (TEM), fluorescence spectroscopy, and thermogravimetric analysis. Generally, exciting with visible light is advantageous over UV excitation. Of importance here is that, under excitation with visible light, the LnDB-OMT all show characteristic visible (Eu³⁺, Sm³⁺) as well as near-infrared (Sm³⁺, Yb³⁺, Nd³⁺) luminescence of the corresponding Ln³⁺ ions (multicolor emission covered from 500 to 1400 nm spectral region), which is attributed to the energy transfer from the ligands to the Ln³⁺ ions via an antenna effect.     

Hierarchical porous cellulose/lanthanide hybrid materials as luminescent sensor

Photoluminescent hybrid materials containing carboxymethyl cellulose and lanthanide ions (Eu³⁺, Tb³⁺) were prepared by a facile method under ambient conditions. Lanthanide ions were covalently grafted to the cellulose framework through coordination with the carboxylic groups of the cellulose. Hybrid materials were fabricated as hydrogel and aerogel. As shown by SEM and pore parameters, aerogel materials which were obtained by supercritical CO₂ drying show hierarchical porous structure. The photoluminescence spectrum of the hybrid materials shows the characteristic red emission of Eu³⁺ ion and green emission of Tb³⁺. Further luminescent investigations reveal that these hybrid materials can detect Fe³⁺ with relative selectivity and high sensitivity, which suggests that the hybrid materials could be a promising luminescent probe for selectively sensing Fe³⁺ ion.     

Luminescence properties of rare earth complexes bonded to novel mesoporous spherical hybrid materials

YVO₄:Eu³⁺phosphors have been widely used in optoelectronic integration fields of its chemical and thermal stability.However,the excitation spectrum band of VO₄^3- is too narrow for high-efficiency luminescence,restricting its further development.Herein,flower-like and linear-like YVO₄:Eu³⁺ hollow mesoporous spheres were synthesized and connected with Eu organic ligand,to obtain a new hybrid luminescent material.The characterization...     

Optical analysis and separation of trivalent lanthanides in deep eutectic solvents

Deep eutectic solvents(DESs) were used for luminescence measurements in quantitative analysis of trivalent lanthanide ions and as solvents for light rare earth elements(LREE) in solid-liquid separation.The spectroscopic characteristics of lanthanide chlorides LnCl_3(Ln=Eu,Tb),respectively their aquo complexes,are described in a comprehensive study that demonstrates the significant enhancement of the phosphorescence emission intensity in DESs as polar and weakly coordinating solvent.Several DESs stabilize the lanthanide ion luminescence against changes in temperature and moisture,which is advantageous compared with the use of ionic liquids.Small amounts of water lead in certain eutectic systems even to a further increase in phosphorescence emission intensity.By investigating the solubility of lanthanide sesquioxides Ln_2 O_3(Ln=La,Nd,Sm,Eu,Gd,Tb,Dy) in DESs,selectivities are identified that may be of use for the separation of LREE.     

Aminoclay decorated with lanthanide complexes and carbon dots:Tunable emission and information encryption

Herein we present emission color-tunable and multi-functional lanthanide(III) luminescent hybrid materials(Ln(DPA)@AC-CDs) by mixing aminoclay(AC), 2,6-pyridinedicarboxylic acid(DPA), Ln~(3+)(Ln = Eu,Tb or Eu and Tb in different molar ratios), and carbon dots(N,S-CDs) in water, showing high quantum yields up to 58.8%. The emission colors can be finely tuned by altering the excitation wavelength and the amounts of the components, and white light emission(CIE-(0.27, 0.25)) can be achieved for sample Eu_1Tb_2(DPA)@AC-CDs under 325 nm light irradiation. In addition, under 365 nm UV light excitation, the Eu(DPA)@AC-CDs powder exhibits red luminescence due to the sensitization effect of N,S-CDs on Eu~(3+),which turns to bright blue when the powder is dispersed in water attributed to the high dispersion of the aggregated N,S-CDs particles. These luminescent properties afford Ln(DPA)@AC-CDs potential candidates for designing optoelectronic devices like WLEDs or in information encryption applications.     

Raman spectra of RE2O3 （RE=Eu,Gd, Dy,Ho, Er,Tm, Yb,Lu, Sc and Y）：laser-excited luminescence and trace impurity analysis

Raman spectra of a series of cubic rare earth sesquioxides RE2O3 （RE=Eu, Gd, Dy, Ho, Er, Tm, Yb, Lu, Sc and Y） were investigated by Raman spectroscopy with both 532 and 785 nm laser lines. Abundant additional bands due to laser-excited lumines-cence were observed. For Eu2O3, Dy2O3, Ho2O3, Er2O3, Tm2O3 and Yb2O3, the luminescence mainly came from the intrinsic trivalent lanthanide ions, while for Gd2O3, Lu2O3, Sc2O3 and Y2O3, their luminescence were attributed to the trace impurities of other lumines-cent lanthanide ions such as Eu3＋, Nd3＋and Er3＋. This investigation confirmed Raman spectroscopy as a useful tool for detecting trace luminescent lanthanide impurities.     

Synthesis,characterization, biological activities and luminescent properties of lanthanide complexes with [2-thiophenecarboxylic acid, 2-(2-pyridinylmethylene)hydrazide] Schiff bases ligand

A Schiff base L [2-thiophenecarboxylic acid, 2-(2-pyridinylmethylene)hydrazide] with its lanthanide metal complexes was synthesized. These complexes were characterized by elemental analysis, molar conductivity measurements, spectral analysis(NMR, FT-IR, and UV-Vis), luminescence and thermal gravimetric analysis. The Schiff base ligand was a tridentate chelate and coordinates to the central lanthanide ion with 1:2 metal:ligand ratio. The conductivity data showed a 1:1 electrolytic nature with a general formula [LnL_2(NO_3)_2]NO_3. The luminescence emission properties for Sm, Tb, and Eu complexes were observed and showed that the ligand L could absorb and transfer energy to Sm(III), Tb(III) and Eu(III) ions. The complexes possessed a good antibacterial activity against different bacterial strains. In addition, the scavenging activity of the Ln(III) complexes on DPPH was concentration dependant and the complexes were significantly more efficient in quenching DPPH than the free Schiff base ligand.     

Study on Material Composition and REE－host Forms of Ion－type RE Deposits in South China

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Sub-10 nm lanthanide-doped SrFCl nanoprobes:Controlled synthesis,optical properties and bioimaging

Alkaline-earth dihalide nanocrystals(NCs) such as SrFCl, owing to their high chemical stability and low phonon energy, are excellent host materials for lanthanide(Ln~(3+)) doping to achieve desirable optical properties for various bioapplications, Herein, we report a novel strategy for the synthesis of sub-10 nm Ln~(3+)-doped SrFCl NCs with efficient upconverting and downshifting luminescence through a facile onestep hot-injection method. Utilizing the temperature-dependent upconverting luminescence(UCL) from the thermally coupled ~2H_(11/2) and ~4S_(3/2) levels of Er~(3+), we showed the potential of SrFCl:Yb,Er NCs as sensitive UCL nanoprobes for non-contact thermal sensing with a maximum detection sensitivity of 0.0066 K~(-1), which is among the highest values for thermal sensing based on Er~(3+)-activated UCL nanoprobes. Furthermore, by employing the intense downshifting luminescence from Tb~(3+) and Eu~(3+), we demonstrated the successful use of biotinylated SrFCl:Ce,Tb and SrFCl:Eu~(3+) nanoprobes for biotin receptor-targeted cancer cell imaging, thus revealing the great promise of SrFCl:Ln~(3+) nanoprobes for versatile bioapplications.     

Corticosteroid sparing effect of low dose methotrexate treatment in adult Still''s disease

The techniques of molecular imprinting and sensitized lanthanide luminescence have been combined to create the basis for a sensor that can selectively measure the hydrolysis product of the nerve agent Soman in water. The sensor functions by selectively and reversibly binding the phosphonate hydrolysis product of this agent to a functionality-imprinted copolymer possessing a coordinatively bound luminescent lanthanide ion, Eu3+. Instrumental support for this device is designed to monitor the appearance of a narrow luminescence band in the 610-nm region of the Eu3+ spectrum that results when the analyte is coordinated to the copolymer. The ligand field shifted luminescence was excited using 1 mW of the 465.8-nm line of an argon ion laser and monitored via an optical fiber using a miniature spectrometer. For this configuration, the limit of detection for the hydrolysis product is 7 parts per trillion (ppt) in solution with a linear range from 10 ppt to 10 ppm. Chemical and spectroscopic selectivities have been combined to reduce the likelihood of false positive analyses. Chemically analogous organophosphorus pesticides tested against the sensor have been shown to not interfere with determination.     

Photoluminescence properties of dinuclear lanthanide complexes in visible and near-infrared region

Several dinuclear lanthanide complexes of Ln2(HTH)6TPPHZ (Ln=Eu, Sm, Er, Nd, Yb, Ho; TPPHZ=Tetrapyrido (3,2-a:2',3'-c:3',2"-h:2"',3'"-j) phenazine; HTH=4,5,5,6,6,6-heptafluroro-1-(2-thienyl)hexane-1,3-dione were synthesized and their photoluminescence properties were investigated. After ligand-mediated excitation, all the complexes showed the characteristic luminescence of the corresponding Ln(III) ions in the visible and NIR regions attributed to energy transfer from the ligands to the metal center. For Eu...     

Characteristics of Trivalent Lanthanides in Coordination Chemistry

Some basic characteristics of lanthanide-oxygen bonds in various trivalent lanthanide metal-organic complexes are quantitatively studied by the bond valence model. Some important relationships among the electronegativity, bond valence parameter, bond length and lanthanide coordination number in these complexes are generally found , which show that for each trivalent lanthanide cation all calculated parameters may well be correlated with its coordination number in their coordination complexes. Specifically ,32 new data for the bond valence parameter are first calculated in this work. An approximate linear relationship between the Ln - O bond valence parameter and the coordination number of Ln^3 is obtained. The Ln - O bond length increases with the increase in the lanthanide coordination number. The difference of electronegative values decreases with the increase in the lanthanide coordination number.     

铝酸盐系长余辉材料的研究进展

铝酸盐系长余辉材料是一种比较成熟的发光材料,具有价格低廉、易于推广等优点,能广泛地应用到各个领域.文中介绍了铝酸盐系长余辉发光材料制备方法的改进、发光机理、光学计算和第一性原理计算,并详细阐述了铝酸盐系长余辉发光材料被应用于光催化、电池、生物医学材料等领域状况,最后对铝酸盐系长余辉材料的应用前景进行了展望.     

Broadband Cr~(3+)-sensitized upconversion luminescence of LiScSi_2O_6:Cr~(3+)/Er~(3+)

Broadband sensitization is an effective strategy to enhance the upconversion luminescence(UCL) of lanthanide ions.Herein,novel UC materials LiScSi_2 O_6:Cr~(3+)/Er~(3+)(LSS:Cr~(3+)/Er~(3+)) were synthesized by high-temperature solid state reaction and their luminescent properties were investigated.LSS:Cr~(3+)/Er~(3+)has the broadband absorption in the spectral range of 600-800 nm,and meanwhile shows green UC emissions of Er~(3+)upon pumping Cr~(3+) by the 690 nm laser.The UCL of LSS:Cr~(3+)/Er~(3+)belongs to the twophoton process and is attributed to the energy transfer upconversion mechanism.The effects of the Cr~(3+)and Er~(3+)concentration as well as the Yb~(3+)introduction were also studied.LSS:Cr~(3+)/Yb~(3+)/Er~(3+) exhibits the interesting dual-mode UCL,capable of generating the UCL of Cr~(3+) upon pumping Yb~(3+)ions and the UCL of upon pumping Cr~(3+) ions.This research might promote the development of novel broadband Cr~(3+)-sensitized UC materials.     

Solid-state synthesis of LnOCl/Ln2O3 (Ln = Eu,Nd) by using chitosan and PS-co-P4VP as polymeric supports

A series of lanthanide materials of type LnOCl or Ln_2 O_3(Ln = Eu, Nd) were successfully prepared via a convenient and straightforward two-step procedure. Firstly, and by using chitosan and PS-co-P4 VP as polymeric supports, macromolecular complexes of type chitosan ·LnCl_3 and PS-co-P4 VP·LnCl3 were prepared. These macro molecular complexes were treated in solid state at 800 ℃ under air, leading to the corresponding LnOCl or Ln_2 O_3 materials(Ln = Eu, Nd) with moderate to good yields. The nature of the asprepared lanthanide materials(LnOCl and/or Ln_2 O_3) is strongly influenced by the polymeric template(i.e.,chitosan or PS-co-P4 VP), the lanthanide salt precursor, and the polymer/lanthanide molar ratio. Thus, when chitosan · EuCl_3 and PS-co-P4 VP·EuCl_3 are used as macromolecular precursors, a mixture of crystalline phases of both EuOCl and Eu_2 O_3 are obtained. However, when chitosan· NdCl_3 and PS-co-P4 VP· NdCl_3 are used, a sole pure crystalline phase of NdOCl is obtained. The nano structured lanthanide materials were characterized by means of XRD(X-ray diffraction of powder), SEM, EDS, TEM, and HRTEM. The luminescent spectra of the asprepared EuOCI/Eu_2 O_3 mixture materials show an emission pattern whose intensity is strongly influenced by the nature of the polymeric precursor, as well as on the metal/polymer molar ratios.