Design of Lanthanide‐Based OLEDs with Remarkable Circularly Polarized Electroluminescence

Organic light‐emitting diodes (OLEDs) able to directly emit circularly polarized (CP) electroluminescence (CP‐OLEDs) are rapidly gaining much interest, due to their possible applications in displays with antiglare filters and 3D displays. Development of more efficient CP‐OLEDs can open their use also in point‐of‐care and personalized diagnostic tools, since CP light alteration can be related to health state of irradiated tissues. In this work it is shown that the performance of chiral europium complex‐based CP‐OLEDs can be improved both in terms of external quantum efficiency (measured on all the Eu bands) and degree of polarization of emitted photons (as measured by the dissymmetry factor g _EL), by proper active layer formulation and through a fine tuning of the architecture of the device. Polarization performances (g _EL = ?1) are obtained about three times higher than for any other CP‐OLED reported so far. Moreover, for the first time, it is shown that the position of the recombination zone (RZ) plays a major role on the polarization outcomes. In order to rationalize these results the level of light polarization is related to the position of the RZ allied with the reflection on the cathode through a simple mathematical model. The values predicted by this model are in qualitative agreement with the experimental ones.     

Synthesis, spectroscopic characterization, and thermal decomposition kinetics of some lanthanide(Ⅲ) nitrate complexes of 2-(N-o-hydroxyacetophenone) amino-3-carboxyethyl-4,5,6,7-tetrahydrobenzo[b]thiophene

Complexes of La(Ⅲ), Ce(Ⅲ), Pr(Ⅲ), Nd(Ⅲ), Sm(Ⅲ), Eu(Ⅲ), Gd(Ⅲ), Dy(Ⅲ), Yb(Ⅲ), and Lu(Ⅲ) with 2-(N-o- hydroxyacetophenone)amino-3-carboxyethyl-4,5,6,7-tetrahydrobenzo[b]thiophene (HAAT) formed by the condensation of o-hydroxyacetophenone and 2-amino-3-carboxyethyl-4,5,6,7-tetrahydrobenzo[b]thiophene were synthesized and characterized on the basis of elemental analyses, molar conductance measurements, magnetic susceptibility data, UV-Visible, IR, and NMR spectral studies. The spectral data revealed that the ligand acted as a neutral tridentate coordinating to the metal ion through ONO donor sequence. A coordination number nine was proposed for the complexes. Thermal decomposition studies of the ligand and lanthanum(Ⅲ) complex were carried out and kinetic parameters were calculated using Coats-Redfern equation. The decomposition reactions followed random nucleation mechanism with one nucleus on each particle.     

Phase Equilibria of BaO-R2O3-CuO z Systems (R = Y and Lanthanides) under CO2-free Conditions

For applications ranging from phase equilibria to the processing of second-generation high T _c superconductor-coated-conductors, phase diagrams constructed under carbonate-free conditions are needed. Subsolidus phase equilibria of BaO-R₂O₃-CuO _z (R = Ho) have been investigated at (810°C), 21 kPa (875°C) and 0.1 MPa (850 and 930°C) by applying controlled atmosphere methods to minimize the presence of carbonate and CO₂ and H₂O contamination. Under carbonate-free conditions, most of these phase diagrams are different from those reported in the literature. In this paper, we also review and compare the phase diagrams of ten BaO-R₂O₃-CuO _z systems (R = Nd, Sm, Eu, Gd, Dy, Y, Ho, Er, Tm and Yb) that were previously determined in this laboratory under Among these diagrams, a distinct trend of phase formation and tie-line relationships is observed.     

Molecular modeling of the octacoordinated tetracarbonato-Nd(Ⅲ),[Nd(CO3)4]5-,complex and its nonacoordinated fluoro- and aquo-adducts

Theoretical investigation on the structures of the octacoordinated[Nd(CO3)4]5- and the nonacoordinated[Nd(CO3)4·OH2]5- complexes,using the SPARKLE parameters of the lanthanides within MOPAC,revealed that they possessed dodecahedral and square antiprismatic structures respectively with an average Nd-O distance of 0.249 nm.These structures and the Nd-O distances agreed well with those experimentally found in the crystal structures.Replacing the water molecule with a fluoride ion or a mondentatecarbonato ligand resulted in a nonacoordimted distorted square antiprismatic structures where the trans-carbonato groups were twisted.The corresponding decacoordinated structures with two fluoride ions or a bidentatecarbonato group,[Nd(CO3)4·F2]7- and[Nd(CO3)5]7.were also investigated.In both cases considerable twisting of the transcarbonato groups was observed.     

Kinetic and spectral studies of EHPG systems using chemi- and electrochemiluminescence methods

The systems containing EHPG, EHPG-OCH3 and EHPG-NH-Ac and Tb(Ⅲ) ions were used to study chemiluminescence (CL) and electrochemiluminescence (ECL) processes. In the CL studies the Fenton system (Fe(Ⅱ)/(Ⅲ)-H2O2) was used as a source of reactive oxygen species (ROS). Kinetic CL curves and CL spectral distributions were recorded. On the basis of the results obtained, it was demonstrated that Tb(Ⅲ) acted as a sensitizer. Similarly obtained CL decays in the systems of Fe(Ⅱ)/(Ⅲ)-EHPG (or its derivatives)-H2O2 and Fe(Ⅱ)/(Ⅲ)-EHPG (or its derivatives)-Tb(Ⅲ)-H2O2, independently on the Tb(Ⅲ) concentration, showed that the lanthanide ions did not influence the kinetics of the oxidation of EHPG (or its derivatives) in the Fenton systems. The CL intensity increased with the increasing concentration of Tb(Ⅲ) ions, which were the main emitters in the reaction systems. Spectrophotometric and luminescent studies of the systems before and after the additions of hydrogen peroxide proved that the excitation of the lanthanide ion was a result of energy transfer from the excited products of the oxidation of EHPG or its derivatives to the uncomplexed Tb(Ⅲ) ions. ECL was generated on the surface of a nonstructural modified aluminum electrode with the use of K2S2O8, H2O2 or KN3 as coreactants in aqueous solution. In these studies we employed Al electrodes covered with a 2-4 nm layer of Al2O3 doted with Tb(Ⅲ) or Dy(Ⅲ) ions. The electrodes were polarized using cathodic and anodic pulses of various amplitude and frequency. The relative ECL efficiencies were determined as a function of electric pulse parameters, electrolyte compositions and the thickness of barrier or porous layer of the Al2O3 electrode.     

单个纳米颗粒的上转换光谱现象研究

稀土离子掺杂上转换纳米颗粒具有独特的光谱学特征, 在太阳能利用、三维显示和生物医学等众多领域有着广泛的应用价值。然而, 传统基于统计平均效应的上转换纳米颗粒群体性光谱学研究忽视了众多来自单个颗粒的非均一性信息。单颗粒光谱检测成为一种突破上述瓶颈, 获取源自纳米颗粒非均一性本征结构的独特光谱现象, 并实现单个纳米颗粒器件化的有效技术手段。对于单个纳米颗粒电子行为的研究能够揭示来自微结构本身的信息, 甚至能够在没有介质干扰下清晰洞见材料本征结构和外部作用的相互影响, 从而为制备高质量的纳米颗粒提供指导意义。同时, 单颗粒光谱检测也具有在微纳米尺度探索晶体结构各向异性光学特性及一些尚未预见的新型光学现象的强大能力。本文介绍了单个纳米颗粒上转换发光表征的重要性以及常见的几种检测方法。论述了单颗粒上转换发光的一些最新研究成果, 并对未来发展方向进行了展望。     

Synthesis and Photoluminescence Properties of Eu3+‐Doped Silica@Coordination Polymer Core–Shell Structures and Their Calcinated Silica@Gd2O3:Eu and Hollow Gd2O3:Eu Microsphere Products

The conjugation of Eu³⁺‐doped coordination polymers constructed from Gd³⁺ and isophthalic acid (H₂IPA) with silica particles is investigated for the production of luminescent microspheres. A series of doping ratio‐controlled silica@coordination polymer core–shell spheres is easily synthesized by altering the amounts of metal nodes used in the reactions, where the ratios of Gd³⁺ and Eu³⁺ are 10:0 ( 1a ), 9:1 ( 1b ), 8:2 ( 1c ), 7:3 ( 1d ), 5:5 ( 1e ), and 0:10 ( 1f ). The formation of monodisperse uniform core–shell structures is achieved throughout the entirety of a series. Investigations of the photoluminescence property of the resulting series of silica@coordination polymer core–shell spheres reveal that 20% Eu³⁺‐doped product ( 1c ) has the strongest emission intensity. The subsequent calcination process on the silica@coordination polymer core–shell structures ( 1a ‐ f ) results in the formation of a series of doping ratio‐controlled silica@Gd₂O₃:Eu core–shell microspheres ( 2a ‐ f ) with uniform shell thickness. During the calcination step, the coordination polymers within silica@coordination polymer core–shells are transformed into metal oxides, resulting in silica@Gd₂O₃:Eu core–shell structures. The final etching process on the silica@Gd₂O₃:Eu core–shell microspheres ( 2a ‐ f ) produces a series of hollow Gd₂O₃:Eu microspheres ( 3a ‐ f ) as a result of the elimination of silica cores. The luminescence intensities of silica@Gd₂O₃:Eu core–shell ( 2a ‐ f ) and hollow Gd₂O₃:Eu microspheres ( 3a ‐ f ) also vary depending upon the doping ratio of Eu³⁺ ions.     

Poly[(2-Hydroxy-4-Methoxy Benzophenone) Butylene] Resin and its Polychelates with Lanthanides(III): Synthesis and Characterization

ABSTRACT

The resin (polymeric ligand) was prepared from 2-hydroxy-4-methoxy benzophenone with 1,4-butane diol in the presence of polyphosphoric acid as a catalyst at 160°C for 9 h. The poly[(2-hydroxy-4-methoxy benzophenone) butylene] L = H(HMBP-BD) form 1:2, ML₂, complexes with M = La(III), Pr(III), Nd(III), Sm(III), Gd(III), Tb(III), and Dy(III). The polymeric ligand and its polychelates were characterized by elemental analyses, electronic spectra, and magnetic susceptibilities, IR-spectroscopy, NMR, and thermogravimetric analyses. The number average molecular weight (M¯n) of the resin was determined by Vapour Pressure Osmometry (VPO). All the polychelates are paramagnetic in nature. The resins and their polychelates were screened for their antimicrobial activity against E. coli, B. substilis, S. aureus (bacteria), and S. cerevisiae (yeast). It was found that the polychelates show good antimicrobial activity compared to the free polymeric ligand.