Dioxouranium complexes with ‘Jaeger-type’ ligands

Azomethine ligands with electron-withdrawing groups such as bis{N,N^′-(2-ethoxycarbonyl-3-oxo-but-1-en(1)yl)-1,2-diaminobenzene (H₂L¹) or N-(2-ethoxycarbonyl-3-oxo-but-1-en(1)yl)-2-aminophenol (H₂L²) react with uranyl nitrate under deprotonation and formation of chelate complexes. The composition of the products can be controlled by the reaction conditions and the denticity of the ligands. Structure determinations have been performed on [NEt₃H][UO₂(L¹)(OMe)], [UO₂(L¹)(DMSO)] and [NEt₃H]₂[{UO₂(L²)}₃(μ₃-O)].     

KNN–Eu transparent ferroelectrics: Local structure and luminescent property

Differ from the rapid development of piezoelectricity in potassium sodium niobate (KNN) ceramics, the progress of photoluminescence in transparent KNN ferroelectric ceramics remains stagnant. Herein, europium (Eu)-doped KNN ceramics have been prepared to investigate its local structure and optical–electrical multi-functionality. Both enhanced piezoelectricity in ceramics with a bimodal distribution of grain size and improved luminescent property in ceramics with refined grain size can be achieved by adjusting the content of Eu. The addition of Eu can destroy long-range ferroelectric orders, leading to the formation of pseudo-cubic phase and polar nanoregions (PNRs). The highly activated PNRs promoted electric field-induced domain switching and nearly reversible piezo/ferroelectric properties. First-principles calculations show that Eu substitution will lead to local inhomogeneous chemical bond environment, affecting the local electric/elastic fields and crystal fields, and then benefiting to the luminescence behavior, including both the intensity and lifetime. We believe that this work can benefit to the development of KNN transparent luminescent ceramics and the light-emitting devices.     

LiSr3SiO4Cl3—A novel host lattice for Eu2+-activated luminescent materials

Eu²⁺-activated LiSr₃SiO₄Cl₃ phosphors were successfully designed, and prepared at low calcination temperature (650 °C). The crystal structure, morphology, and photoluminescence properties have been investigated in detail. The LiSr₃SiO₄Cl₃ crystallizes in orthorhombic LiEu₃SiO₄Cl₃-type structure. Under 316 nm excitation, the phosphor exhibits an asymmetric emission band peaking at 495 nm, which is probably attributed to the 4f–5d transitions of Eu²⁺ in various crystallographic sites. Their luminescence properties are investigated as a function of activator concentration (Eu²⁺). The quenching concentration of Eu²⁺ in LiEu₃SiO₄Cl₃ is about 0.01 due to dipole–dipole interaction. The investigation indicates that Eu²⁺-activated LiEu₃SiO₄Cl₃ phosphor can be used as a green emitting phosphor for white LEDs.     

Citrate-based sol–gel synthesis and luminescent properties of Y6WO12:Eu3+, Dy3+ phosphors for solid-state lighting applications

The rare-earth ions (Eu³⁺, Dy³⁺) doped Y₆WO₁₂ phosphors were prepared by a citrate-based sol–gel method. The morphologies and structural properties of the as-prepared and doped samples were analyzed by scanning electron microscope images and X-ray diffraction patterns. The luminescent properties were studied by examining the excitation and emission spectra of the samples. The Eu³⁺ and Dy³⁺ ions doped samples exhibited their characteristic emission bands in the visible region under ultraviolet light excitation. The temperature-dependent photoluminescence (PL) properties of the samples were also investigated. The PL spectra of the synthesized samples by the sol–gel method were compared with those of the bulk sample prepared by a solid-state reaction. Similarly, the Commission International de I’Eclairage chromaticity coordinates and the decay times of Y₆WO₁₂:Eu³⁺ (3 mol%) and Y₆WO₁₂:Dy³⁺ (2 mol%) phosphors were studied.     

In-air self-reduction synthesis and photoluminescent properties of Eu2+–Eu3+ activated CaAl2SixO2x+4 phosphors

In this paper, CaAl₂Si_xO_2x+4:Eu²⁺/Eu³⁺ (2%, molar ratio) phosphors with different SiO₂ concentrations (x=0, 0.025, 0.05, 0.1, 0.25, 0.5, 1, 1.5, and 2) were prepared by a high-temperature solid-state reaction under air condition with the absence of the reduction atmosphere. The crystalline phase, photoluminescent properties and luminescent lifetimes of the prepared samples were systematically studied. The results indicated that Eu²⁺ was reduced and obtained in air through self-reduction. The doping of SiO₂ in calcium aluminates strongly affects the crystalline phase, excitation and emission spectra, CIE (Commission Intemationale de I'Eclairage 1931 chromaticity) (x, y) position and lifetimes of europium. It is interesting and important that different luminescent colors can be obtained and modulated by changing the content of SiO₂.     

Uranyl complex with phenolate–sulphonate and diphenyldiazenecarbohydrazonate ligands

Reaction of uranyl nitrate hexahydrate with 3-(2-(2,4-dioxopentan-3-ylidene)hydrazinyl)-2-hydroxybenzenesulfonic acid (H₃L) and bis((E)-phenyldiazenyl)methanone (bpm) yields mononuclear zwitterionic uranyl complex, [UO₂(HL)(bpm)(H₂O)₂]∙3H₂O (1), which was characterized by IR, ESI-MS spectroscopies, and elemental and X-ray single-crystal analyses. In 1, the uranium center is in distorted pentagonal bipyramidal geometry with HL^2 − and bpm ligands coordinated in equatorial plane. The coordination to uranyl and intramolecular hydrogen bonding assist the tautomerization of bpm and formation of zwitterion.     

Physicochemical properties of amide–AlCl_3 based ionic liquid analogues and their mixtures with copper salt

The physicochemical properties of three different amide–AlCl_3 based ionic liquid(IL) analogues and their mixtures with copper salt, such as conductivity, viscosity, density and isobutane solubility were determined over a wide range of temperatures.The effects of amide structure, amide/AlCl_3 molar ratio and CuCl modification on these physicochemical properties were investigated.Results showed that the conductivity of amide–AlCl_3 based IL analogues was much lower than that of traditional Et_3NHCl–AlCl_3 IL with same ligand/AlCl_3 molar ratio due to incomplete splitting of AlCl_3, whereas the density and viscosity of amide–AlCl_3 based IL analogues were slightly higher.The viscosity of amide–AlCl_3 based IL analogues was closely related to the amide structure,and followed the order of DMA–AlCl_3AA–AlCl_3NMA–AlCl_3 with same amide/AlCl_3 molar ratio.Meanwhile,the density of amide–AlCl_3 based IL analogues ranked in the following order: AA–AlCl_3NMA–AlCl_3DMA–AlCl_3.Increasing the amide/AlCl_3 molar ratio decreased the conductivity and density, while increased the viscosity.The solubility experiment indicated that the isobutane solubility in NMA–AlCl_3 was highest than that in two other IL analogues.Under the modification of CuCl, the conductivity, viscosity and density of these IL analogues increased, whereas the isobutane solubility decreased.These results provide the foundation for the development of a suitable IL analogue catalyst for isobutane alkylation.     

Magnetic,luminescent and core–shell structured Fe3O4@YF3:Ce3+,Tb3+ bifunctional nanocomposites

Bifunctional magnetic–luminescent nanocomposites with Fe₃O₄ nanoparticles as the cores and YF₃:Ce³⁺,Tb³⁺ as the shells were synthesized by a facile direct precipitation method. Transmission electron microscopy (TEM) images revealed that the obtained bifunctional nanocomposites had a core–shell structure, in a spherical shape with a size ranging from 160 to 220 nm, and the shell thickness of about 25 nm. The X-ray diffraction (XRD) patterns showed that a cubic spinel structure of Fe₃O₄ core and an orthogonal phase of YF₃ shell were obtained. Photoluminescence (PL) spectra confirmed that the nanocomposites displayed a strong green light emission. Magnetic measurements indicated that the obtained bifunctional nanocomposites exhibited a stronger magnetic behavior at room temperature. Therefore, the bifunctional nanocomposites are expected to develop many potential applications in biomedical fields.     

Monomeric complexes of Re(CO)3+ ion with tridentate N∩N∩O−ligands — Schiff base derivatives of salicylic aldehyde

Simple synthetic procedures, reactions of Re(CO)₅Cl with potentially tridentate N∩N∩OH ligands (Schiff bases prepared from aliphatic or aromatic amines and salicylic aldehyde) lead to formation of monomeric complexes of fac-Re(CO)₃⁺ ion. Three obtained complexes have been characterized by means of elemental analyses and IR, UV–vis, and EI-MS techniques. Molecular structures of the synthesized species were investigated using X-ray diffraction measurements. Depending on the nature of N∩N∩OH ligand the investigated Schiff bases form with fac-Re(CO)₃⁺ ion bidentate or tridentate chelates with N∩N, N∩O⁻ or N∩N∩O⁻ coordination types.     

A luminescent [Ag3S3]n-tube based metal–organic framework

Solvothermal treatment of silver nitrate, pyridine-4-thione (4-pdtH) and NH₄SCN at 140 °C for 3 days produced a three-dimensional metal–organic framework [Ag₃(4-pdt)(SCN)₂] (1) in which [Ag₃S₃]_n tubes act as secondary building units and pyridine rings and CN groups act as linkers. At ambient temperature, 1 shows a blue emission band assigned as from a ligand-centred n → π¹ or π → π¹ process.     

Study of Eu3+–Gd3+ co-doped Ba–Bi–B glasses for red-laser applications: Physical,structural, photoluminescence and time-resolved spectral characteristics

A series of Eu³⁺ and Eu³⁺/Gd³⁺ co-doped barium-bismuth-borate (Ba–Bi–B) glasses were prepared by melt-quench technique. And deliberated the physical, structural, and spectroscopic properties of all glasses and explored the energy transfer process from Gd³⁺ to Eu³⁺ ions. The density of glasses increased with increasing of Gd³⁺ concentration in co-doped glasses. Characteristics of steady-state and time-resolved photoluminescence (PL) of Eu-doped and Eu³⁺-Gd³⁺ co-doped glasses under different excitation wavelengths suggested the prospects of the investigated glass system for display device applications. PL spectrum displays a strong red emission peak centered at 612 nm due to the Eu³⁺: ⁵D₀→ ⁷F₂ transition. Less intense emissions centered at 577 nm (⁷F₀), 590 nm (⁷F₁), 651 nm (⁷F₃) and 700 nm (⁷F₄) are also observed from the radiative transitions of the excited state ⁵D₀ of Eu³⁺ions. The values of radiative parameters such as transition probability, branching ratios, and stimulated emission cross-sections were obtained from Judd–Ofelt theory analysis and indicated the aptness of the Ba–Bi–B glasses for optical devices. A 5-fold enhancement in the PL intensity was observed in 1.0 mol% Eu³⁺ and 3.0 mol% Gd³⁺ co-doped glass under λ_Exci. = 394 nm excitation. The calculated commission Internationale de l'eclairage color coordinates and correlated color temperature values show that the Ba–Bi–B glasses are useful for red-laser and display device applications.     

Eu3+和Lu3+对氟化镓基玻璃形成能力的影响

以20GaFs-15InFs-20CdF2-15ZnF2-20PbF2-10SnF2(GICZPS)玻璃为基玻璃,引入不同含量的EuFs,LuF3替代玻璃中等摩尔含量的PbF2.用差示扫描量热法、X射线粉末衍射和发射光谱研究了掺EuF3,LuFs对GICZPS玻璃形成能力的影响.结果表明:在GICZPS玻璃中按摩尔计分别掺人1.0%EuFs和2.0%LuFs时,可以获得相应最佳的抗析晶能力.同时发现在掺有不同量EuF3的GICZPS玻璃中,形成了大小不一的10～100 nm量级的晶粒,这些晶粒有利于提高玻璃的光谱性能.     

Radiation response properties of Eu3+-doped K2O–Ta2O5–Ga2O3 glasses

Eu₂O₃-doped 40K₂O–20Ta₂O₅–40Ga₂O₃ gallate glasses were synthesized, and their radiation response characteristics were studied systematically. According to their photoluminescence spectra, they showed intense emissions with sharp peaks centered at around 580, 594, 613, 656, and 706 nm when irradiated by 380 nm light. The sharp peaks originate from the 4f-4f transitions of Eu³⁺. Moreover, these sharp peaks were also detected when excited by X-ray, and the 1.0% Eu₂O₃-doped gallate glasses showed the largest luminescence intensity under UV light and X-ray. Furthermore, the afterglow levels of the Eu₂O₃-doped 40K₂O–20Ta₂O₅–40Ga₂O₃ gallate glasses were determined to be approximately 300 ppm. These levels are close to the levels of TI-doped CsI single crystals.     

InBO3:Eu3+荧光粉的制备及光谱特性

合成了InBO3:Eu3 红色荧光粉 ,测定了其发光光谱 ,讨论了其发光亮度与稀土离子Eu3 浓度的关系     

Eu3+对槲皮素与BSA相互作用的影响

运用荧光光谱、紫外吸收光谱、红外光谱等研究了槲皮素(Quercetin,Que)与BSA的结合作用,并从Eu3+与Que的竞争作用、热力学参数的变化、配位化合物的生成三个方面分析了Que与BSA结合作用的影响因素.结果表明,Que对BSA的荧光光谱具有猝灭作用,其猝灭机制为静态猝灭,BSA发射峰显著蓝移;Eu3+的存在...     

Fabrication and properties of pressure-sintered reaction-bonded Si3N4 ceramics with addition of Eu2O3–MgO–Y2O3

Dense pressure-sintered reaction-bonded Si₃N₄ (PSRBSN) ceramics were obtained by a hot-press sintering method. Precursor Si powders were prepared with Eu₂O₃–MgO–Y₂O₃ sintering additive. The addition of Eu₂O₃–MgO–Y₂O₃ was shown to promote full nitridation of the Si powder. The nitrided Si₃N₄ particles had an equiaxial morphology, without whisker formation, after the Si powders doped with Eu₂O₃–MgO–Y₂O₃ were nitrided at 1400 °C for 2 h. After hot pressing, the relative density, Vickers hardness, flexural strength, and fracture toughness of the PSRBSN ceramics, with 5 wt% Eu₂O₃ doping, were 98.3 ± 0.2%, 17.8 ± 0.8 GPa, 697.0 ± 67.0 MPa, and 7.3 ± 0.3 MPa m^1/2, respectively. The thermal conductivity was 73.6 ± 0.2 W m^?1 K^?1, significantly higher than the counterpart without Eu₂O₃ doping, or with ZrO₂ doping by conventional methods.     

Eu3+和Gd3+共掺杂TiO2粉体的制备及催化活性

采用溶胶-凝胶法制备纯TiO2和Gd3+/Eu3+共掺杂TiO2复合粉体,采用X射线衍射、漫反射光谱和扫描电镜等技术对样品进行表征,以亚甲基蓝(methyleneblue,MB)的光催化降解为目标反应评价其光催化活性,探讨Gd3+/Eu3+共掺杂对TiO2粉体光催化的影响机制。结果表明:Gd3+/Eu3+共掺杂可以显著提高TiO2粉体光催化活性。Gd3+/Eu3+共掺杂在TiO2粉体中产生协同作用,可以抑制TiO2由锐钛矿向金红石相转变,使TiO2的粒径减小。Gd3+/Eu3+共掺杂增大了TiO2粉体的晶格畸变,使TiO2粉体吸收带边蓝移。当Gd3+和Eu3+的质量掺量分别为0.05%和0.4%时,TiO2粉体光催化活性最高,降解率达到95.31%。     

Long wavelength Eu2+ emission in Eu-doped Y–Si–Al–O–N glasses

A number of (Eu,Y)–Si–Al–O–N glasses have been prepared and their optical properties examined. Eu was found to be present in the divalent instead of in the trivalent state due to a reaction between the Eu³⁺ and the chemically incorporated N^3- during the preparation of the glasses. The luminescence characteristics were found to be negligibly influenced by the O/N and Si/Al ratio, but appear to be strongly dependent on the concentration and type of modifying cations (Eu,Y). As a function of the cationic composition the emission shifts from wavelengths below 500 nm to wavelengths as long as 640 nm, which is very unusual for Eu²⁺ containing compounds. This shift to longer wavelengths is ascribed to a combination of energy transfer between the different sites and change of the Eu²⁺ site distribution.     

Electrocatalytic reduction of CO2 using rhenium complexes with dipyrido[3,2-a:2′,3′-c]phenazine ligands

A series of rhenium(I) complexes (1–4) with substituted dipyrido[3,2-a:2′,3′-c]phenazine (dppz) ligands were synthesized and analyzed as electrocatalysts for CO₂ reduction. Cyclic voltammetry study shows that complexes 1–4 exhibit dppz ligand-based and metal center-based quasi-reversible reductions under N₂. Under a CO₂ atmosphere, complexes 1–4 exhibit electrocatalytic response consistent with CO₂ → CO reduction with the presence of the gaseous phase product CO confirmed by gas chromatography (GC). Re(2,2′-bpy)(CO)₃Br (Lehn catalyst), a benchmark for electrocatalytic reduction of CO₂ to CO, was also prepared and tested for electrocatalytic properties for comparison. The results suggest that chemical modification on the dppz ligand leads to interesting electrocatalytic properties and the large conjugation of the dppz ligand can help store multiple electrons and lower the energy barrier for CO₂ reduction.