Synthesis and ionophore properties of a series of new tetrapyrazolic macrocycles

The synthesis of several macrocycles containing two bipyrazolic subunits, with different cavity sizes and with donor-group-bearing side arms attached, is reported. Their alkali cation binding ability has been studied from two aspects : extraction and transport through an artificial liquid membrane. Macrocycles described here show a high selectivity towards Li⁺ and Na⁺ cations; furthermore one of them is remarkably well adapted to extract selectively and to transport efficiently the lithium cation in competitive conditions.     

Synthesis, characterization and photoluminescence properties of CaSiO3:Eu3+ red phosphor

CaSiO3:Eu3+ (1-5 mol%) red emitting phosphors have been synthesized by a low-temperature solution combustion method. The phosphors have been well characterized by powder X-ray diffraction (PXRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and optical spectroscopy. PXRD patterns reveal monoclinic CaSiO3 phase can be obtained at 900°C. The SEM micrographs show the crystallites with irregular shape, mostly angular. Upon 254 nm excitation, the phosphor show characteristic fluorescence 5D0→7FJ (J=0, 1, 2, 3, 4) of the Eu3+ ions. The electronic transition located at 614 nm corresponding to 5D0→7F2 of Eu3+ ions, which is stronger than the magnetic dipole transition located at 593 nm corresponding to 5D0→7F1 of Eu3+ ions. Different pathways involved in emission process have been studied. Concentration quenching has been observed for Eu3+ concentration>4 mol%. UV-visible absorption shows an intense band at 240 nm in undoped and 270 nm in Eu3+ doped CaSiO3 which is attributed to oxygen to silicon (O-Si) ligand-to-metal charge-transfer (LMCT) band in the SiO3(2-) group. The optical energy band gap is widened with increase of Eu3+ ion dopant.     

Electronic structure,morphology-controlled synthesis,and luminescence properties of YF3: Eu3+

Journal of Sol-Gel Science and Technology - Studying electronic structure plays a key role in improving the photoluminescence (PL) properties of materials. Therefore, the electronic structure of...     

Synthesis and luminescence properties of novel red-emitting phosphor InNbO4:Eu3+ for white-light emitting diodes

Red-emitting phosphor InNbO₄:Eu³⁺ was synthesized by the solid-state reaction. Its crystal structure, particle size distribution, and luminescence properties were studied. The powder X-ray diffraction pattern shows that pure InNbO₄:Eu³⁺ was obtained. According to the spectra obtained, this phosphor can efficiently be excited with the light at wavelengths of 394 and 466 nm to emit the strong red radiation at 612 nm due to the ⁵ D ₀→⁷ F ₂ transition of Eu³⁺. The best results were obtained at the concentration of the Eu³⁺ dopant equal to 4 mol.%. The chromaticity parameters of InNbO₄:0.04Eu³⁺ are close to standards of the National Television Standard Committee. Thus, InNbO₄:Eu³⁺ is a promising red-emitting phosphor for white-light emitting diodes.     

Synthesis, characterization and luminescence properties of SrLa2(MoO4)4:Eu phosphors

SrLa₂(MoO₄)₄ (SLM) phosphors doped with Eu³⁺ ions were prepared by a sol–gel combustion method using citric acid as a fuel/reductant and nitrates as oxidants. The crystallization processes were tracked by means of X-ray diffraction and thermo-gravimetric analysis and differential scanning calorimetry. The size and shape of the products were characterized using a scanning electron microscope, while the luminescent spectra of these resulting phosphors were recorded using a photoluminescence (PL) spectrophotometer. PL studies reveal that the emission intensity of SLM:Eu phosphors was strongly related to sintering temperature as well as the doping concentration of Eu³⁺ ions. The present phosphor has a strong excitation at 395 and 459 nm, indicating that it could serve as a promising red-emitting candidate for near-UV and GaN-based blue light-emitting diode chips.     

Thermal study in Eu3+-doped boehmite nanofibers and luminescence properties of the corresponding Eu3+:Al2O3

Eu³⁺-doped boehmite nanofiber materials with different Eu³⁺ concentrations were synthesized without any surfactant, and followed by a series of characterizations. It was found that the boehmite nanofibers became coarser with the increase of Eu³⁺ concentration, which resulted in a gradual decrease of their specific surface areas. Moreover, the thermal stability of the boehmite nanofibers was studied by thermogravimetry–differential scanning calorimetry. All materials showed the phase transition from γ-Al₂O₃ to other forms. Yet the transition temperature was increased with the increase of Eu³⁺ concentration. The Eu³⁺-doped boehmite nanofibers with the maximum Eu³⁺ concentrations showed the best thermal stability. Photoluminescence spectra showed that the 2 mol% of doping concentration of Eu³⁺ ions in Eu³⁺:Al₂O₃ nanofiber was optimum.     

链状Eu(BO_2)_3的合成与发光性能研究

采用固相反应合成出链状结构的稀土硼酸盐Eu(BO2)3发光材料。分别利用XRD、TEM、SAED、EDS和PL等测试技术对产物进行了研究,结果表明:链状结构的Eu(BO2)3属于单斜晶系,空间群为I2/a,直径约10～15nm,长度达几个微米,探讨了链状Eu(BO2)3的生长机理。在395nm紫外光激发下,Eu(BO2)3能发出Eu3+的特征红色荧光,发射主峰位于591nm,归属于5D0→7F1磁偶极跃迁。     

Sensitization of Eu(III) luminescence by donor-phenylethynyl-functionalized DTPA and DO3A macrocycles

The synthesis and complexation to Eu(III) of two macrocyclic ligands functionalized donor-phenylethynyl-moieties as sensitizer is presented. The two ligands based on DTPA bis-amide ([Eu(L¹)]) and DO3A ([Na][Eu(L²)]) have been chosen because of their increased stability in water for potential applications as luminescent bioprobes for one- or two-photon excited scanning microscopy. The DTPA and DO3A ligands possess oxygen or sulfur donor atoms, respectively, connected to a triethyleneglycol (PEG) chain to ensure the water solubility. The optical properties were studied and reveal that ([Eu(L¹)]) present a lower brightness than the ([Na][Eu(L²)]) counterpart because of its inner sphere water molecule coordination that quenches the emission. On the other hand, [Na][Eu(L²)] exhibits excellent spectroscopic properties with high quantum yield ? = 0.284, and brightness B = 10,220 M^?1cm^?1(defined as ?.?). Unfortunately, the two-photon cross-section of this last complex was measured to be only 4 GM limiting its potential applications to linear microscopy.     

Photofunctional Eu3+/Tb3+ hybrids through sulfoxide linkages: coordination bonds construction, characterization and luminescence

New kinds of organic-inorganic hybrid materials consisting of rare earth (Eu(3+), Tb(3+)) complexes covalently bonded to a silica-based network have been obtained by a sol-gel approach. Three novel versatile molecular building blocks containing sulfoxide organic units have been synthesized by methylene modification reaction, which are used as the ligands of rare earth ions and also as siloxane network precursors. The obtained hybrids are characterized by chemical analysis and spectroscopic methods such as FTIR and UV; XRD and SEM. Photoluminescence measurements on the prepared hybrids were performed showing the intra-4f(n) emission in the visible (Eu(3+), Tb(3+)) region and in all the cases being sensitized by the sulfoxide ligands. The emission quantum efficiency and the Judd-Ofelt intensity parameters of Eu(3+) hybrid materials were also investigated in detail.     

纳米Y2O3:Eu3+超声辐射沉淀制备及其性能研究

采用超声辐射沉淀法以草酸为沉淀剂制备出纳米Y2O3:Eu^3 粉体。利用XRD、TG-DTA、TEM等手段对其进行了表征．并对其光谱特性进行了研究。结果表明：将超声辐射引入普通沉淀法中,可显著提高粉体性能,所得纳米Y2O3:Eu^3 为球形,粒度分布均匀,粒径约为38～45nm,与微米晶相比,该纳米晶的发射光谱发生蓝移,激发光谱发生红移。     

Thermal annealing of LaF3:Eu3+ nanocrystals synthesized by a solvothermal method and their luminescence properties

In this work, we used a low temperature solvothermal method to synthesize Eu³⁺-doped LaF₃ (LaF₃:Eu³⁺) nanocrystals. The effect of thermal annealing on their phase structures and luminescence properties was studied. Transformation from LaF₃ to LaOF was observed after the annealing, and the initial transformation process was studied using a rapid thermal annealing technique. It was found that a sufficiently high annealing temperature is required for the transformation of LaF₃ to LaOF. LaOF phase started to be formed after annealing at 500 °C for as short as 5 min, and higher annealing temperatures and longer annealing time led to a larger amount of LaOF formed. With the increase of the formation of LaOF, the luminescence was greatly enhanced. Strong O^2? → Eu³⁺ charge transfer band was present in these samples annealed at 500 °C and higher temperatures, and greatly enhanced ⁷F₀ → ⁵D₂ transition of Eu³⁺ was also observed.     

Synthesis and chiroptical properties of two new planar-chiral macrocycles

Could simple intraannular-arm macrocyclic systems exist in enantiopure stable forms? The effective synthesis of two representative compounds of such a class, their resolution into enantiomers, and experiments justifying their stability toward racemization are presented.     

Energy transfer and tunable luminescence properties of Eu3+ in TbBO3 microspheres via a facile hydrothermal process

Tb (1- x) BO 3: xEu (3+) ( x = 0-1) microsphere phosphors have been successfully prepared by a simple hydrothermal process directly without further sintering treatment. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED), photoluminescence (PL), low-voltage cathodoluminescence (CL), and time-resolved emission spectra as well as lifetimes were used to characterize the samples. The as-obtained phosphor samples present sphere-like agglomerates composed of nanosheets with highly crystallinity in spite of the moderate reaction temperature of 200 degrees C. Under ultraviolet excitation into the 4f (8) --> 4f (7)5d transition of Tb (3+) at 245 nm (or 284 nm) and low-voltage electron beams' excitation, TbBO 3 samples show the characteristic emission of Tb (3+) corresponding to (5)D 4 --> (7)F 6, 5, 4, 3 transitions; whereas TbBO 3:Eu (3+) samples mainly exhibit the characteristic emission of Eu (3+) corresponding to (5)D 0 --> (7)F 0, 1, 2, 3, 4 transitions due to an efficient energy transfer occurs from Tb (3+) to Eu (3+). The increase of Eu (3+) concentration leads to the increase of the energy-transfer efficiency from Tb (3+) to Eu (3+) but also enhances the probability of the interaction between neighboring Eu (3+), which results in the concentration quenching. The PL color of TbBO 3: xEu (3+) phosphors can be easily tuned from green, yellow, orange, to red-orange by changing the doping concentration ( x) of Eu (3+), making the materials have potential applications in fluorescent lamps for advertizing signs and other color display fields.     

Novel dumbbell-like LaVO4:Eu3+ nanocrystals and effect of Ba2+ codoping on luminescence properties of LaVO4:Eu3+ nanocrystals

Journal of Sol-Gel Science and Technology - LaVO4:Eu3+ nanocrystals with different morphologies were synthesized via a simple hydrothermal method in a wide pH range. The as-synthesized samples were...     

Review of the preparation,characterization, and luminescence properties of Pr3+-doped CaTiO3 phosphors

Research on Chemical Intermediates - In this paper we review the luminescence properties of Pr3+-doped CaTiO3 phosphors, the different methods of sample preparation, and characterization of the...     

Hydrothermal preparation and luminescence of LaF3:Eu3+ nanoparticles

LaF3:Eu3+ nanoparticles were prepared by a simple hydrothermal process at low temperature and characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and fluorescence spectrum. Well-dispersed nanoparticles with an average size of 30 nm and a hexagonal shape were obtained. The influences of reaction temperature and time on the preparation and luminescence of LaF3:Eu3+ nanoparticles were investigated. Luminescent quenching occurred at a much higher concentration ( approximately 25mol%) and stronger luminescent intensity than in bulk LaF3:Eu3+. Fluorescence intensity of the LaF3:Eu3+ nanoparticles varied remarkably with calcination temperatures. It was found that samples without any further calcinations can emit quite strong fluorescence.     

Synthesis, characterization, and properties of subporphyrazines: a new class of nonplanar, aromatic macrocycles with absorption in the green region

Novel subphthalocyanine analogues that display strong absorption in the green region have been synthesized by using a boron template cyclotrimerization of maleonitrile derivatives. The spectroscopic properties of these macrocycles indicate that, like subphthalocyanines, they have 14 pi electrons and are aromatic compounds with a conical shape. The removal of the three fused benzene rings from the subphthalocyanine skeleton produces a 75-80 nm blue shift of the Q-band and a slight lowering of the absorption coefficients for this band. In addition, the reduction of the pi system from 18 to 14 electrons that accompanies progression from porphyrazines to subporphyrazines causes a hypsochromic shift of the Q-band of around 100 nm. Subporphyrazines that are peripherally functionalized with six thioether chains, and in which the sulfur atoms are attached directly to the pyrrole moieties, exhibit optical features that may be explained in terms of the extension of pi conjugation over the six thiolene groups, as well as strong pi donation from the sulfur lone pairs to the macrocycle. These two effects are quantitatively and qualitatively very similar to those observed for porphyrazines that possess the same type of substitution. In addition, the mesomorphic behavior at low temperatures of a macrocycle that is substituted with six thiododecyl chains was demonstrated by using differential scanning calorimetry and optical polarising microscopy.     

Preparation of nano-sized YAG:Eu3+ particles by a microwave-assisted polyol process and their luminescence properties

Phases of yttrium-aluminum binary oxide have been selectively prepared by selecting a polyol solvent in a microwave-assisted polyol process. Using 1,4-butanediol as a polyol solvent, nano-sized particles of a pure phase of YAG have been prepared. Furthermore, Eu³⁺-doped YAG has been synthesized by applying this method. We have demonstrated that 8 at% Eu³⁺-doped YAG (replacement of Y³⁺) gave the strongest emission when the content of Eu³⁺ was varied.     

Boron macrocycles having a calix-like shape. Synthesis, characterization, X-ray analysis, and inclusion properties

The syntheses, structure, and inclusion properties of trinuclear boron compounds having a calix-like shape are described. The compounds have been obtained via self-assembly reactions between salicylaldehyde derivatives and 3-aminophenylboronic acid, whereby the formation of three N --> B coordination bonds favored the oligomerization. The products have high melting points (>370 degrees C), are stable to moisture, and have good solubility in organic solvents; the latter property is useful for host-guest recognition experiments. The structural analysis by X-ray diffraction revealed that diverse conformations are possible because of the presence of two different units of aromatic rims. A cone-cone (double-cone) conformation is observed for three of these compounds, while the remaining one has a cone-partial cone conformation. An analysis of the molecular packing showed that the molecules are stacked in columns in two different orientations in relation to the organization of the macrocycles when referred to the N-B bonds. The inclusion properties toward primary amines and ammonium chlorides were analyzed by titration experiments and monitored by UV spectroscopy, whereby association constants on the order of 10(2)-10(3) M(-1) were determined.     

The critical concentration for quenching of the Eu3+ luminescence in some Gd3+ : Eu3+ systems

The critical concentration for quenching of the Eu³⁺ luminescence is calculated theoretically for several Gd³⁺ : Eu³⁺ systems. A comparison is made with the experimental values. The results are discussed in terms of energy migration.