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.

Syntheses,Crystal Structures and Luminescent Properties of Two Lanthanide Coordination Polymers Based on Bifunctional Ligand

Two lanthanide coordination polymers, [Eu（HL）（L）（H2O）2]n（1） and [Tb（H0.5L）2]n（2）, based on bifunctional 5-（1H-imidazol-1-yl） isophthalic acid（H2L）, are hydrothermally synthesized and characterized by both single-crystal and powder X-ray diffraction analyses, and FT-IR. In compound 1, the basic inorganic building unit of the coordination network is the dinuclear [Eu2（COO）6] cluster. Each [Eu2（COO）6] cluster connects four HL^- ligands and each HLligand links two [Eu2（COO）6] clusters, resulting in a 2D coordination layer. The adjacent 2 D layers are further connected via neighboring inter-layer hydrogen bonds to give a 3D supramolecular structure. In compound 2, the Tb^3＋ is coordinated to six oxygen atoms. Each Tb^3＋ ion connects six ligands and each ligand links three Tb^3＋ ions, leading to a 3D coordination polymeric network which exhibits remarkably high thermal stability up to 500℃. Furthermore, due to the successful incorporation of Tb^3＋, compound 2 displays characteristic luminescent emission in the solid state at room temperature. The combination of high thermal stability and fluorescent property of compound 2 would make it as a promising light-emitting material.

Tunable white-light emission of lanthanide(Ⅲ) hybrid material based on hectorite

In this work, we present novel trivalent lanthanide ions（Ln^3＋）-based luminescent hybrid materials, in which the organic ligands are covalently grafted on the hectorite templates and the Ln^3＋ ions can be well immobilized by the ligands through coordination bond. The hybrid materials exhibit tunable emission colors by varying the molar ratio of Eu^3＋ to Tb^3＋, and the one with Eu^3＋：Tb^3＋=1：1 exhibits excellent coordinate of（0.327, 0.328） located in the ＂white region＂ of the CIE 1931 chromaticity diagram（under300 nm UV illumination）. These properties make the hybrid composites suitable for fabricating optoelectronic devices such as full-color displays and white LED.

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.

Using europium(Ⅲ) complex of 1,4,7,10-tetraazacyclododecane-1,4,7-triacedic acid Eu.DO3A as a luminescent sensor for bicarbonate

Sensing of analyte s in biological fluids and biotechnological production media remains a challenge.He re,the luminescent response of the europium(Ⅲ)complex of 1,4,7,10-tetraazacyclododecane-1,4,7-triacetic acid(DO3A)to bicarbonate was investigated in detail.The response of Eu.DO3A to changes in bicarbonate concentration was studied in different buffers,and the influence of ionic strength,pH,and specific ions was determined.The response is found to depend on pH and ionic strength,but it is not possible to separate contributions from the sensing event from those in the bicarbonate activity.Prior to demonstrating the ability to determine the bicarbonate concentration in bioproduction media and serum,the influence of competing carboxy anions was evaluated.It is established that while competing anions bind stronger to the responsive complex,at the relevant concentration their contribution to the recorded signal is negligible.We are thus able to conclude that Eu.DO3A is a good platform for building a bicarbonate sensor.

Synthesis and luminescent properties of a silylated-terpyridine derivative and its metalated complexes in solutions and self-assembled monolayers

A silylated-terpyridine（Si TPy） derivative was newly synthesized and reacted with various transition metal ions in the solutions and self-assembled monolayers（SAMs）.Composition and morphology of the SAMs were characterized by using absorption spectra,X-ray photoelectron spectra and atomic force microscope.The silylated-TPy compound gave off a luminescent emission at about 456 nm,which slightly shifted to 452 nm in the Zn^2＋-Si TPy and Fe^2＋-Si TPy metalated complexes.The absorbed energy can be further transferred to lanthanide ions（Tb^3＋and Eu^3＋） to give off the typical emissions of the lanthanide complexes together with an emission of the silylated-TPy at about 363 nm.