Recent advances in organic pressure-responsive luminescent materials

Pressure is a powerful tool to regulate the molecule aggregation and intermolecular interactions. Organic luminescent materials under high pressure can produce rich phenomena,which have many potential applications.     

近红外稀土荧光在功能材料领域的研究进展

稀土近红外荧光材料具有特征发射峰尖锐、光稳定性好和毒性低等特点。近年来,稀土近红外荧光材料在光纤通讯、激光系统、生物分析传感器及生物成像等方面的应用价值日渐突显,引起了研究者们的极大关注。特别是稀土近红外荧光材料已发展成一种新兴的荧光标记材料,并有希望替代有机染料和量子点应用于生物分析和医学成像。基于稀土近红外发光的荧光探针具有低自荧光背景、宽斯托克斯位移、强抑制光漂白、深层穿透组织和短暂分辨的优势,有潜力成为高灵敏度、高选择性的检测手段。利用稀土离子制备的各种荧光材料,如上转换纳米晶、介孔材料、脂基胶体、离子液体、离子胶体、金属有机框架等,由于荧光敏化机理不同,其近红外荧光性能也各有千秋。然而,稀土近红外荧光的真正挑战仍是提高近红外发光的量子效率。本文结合近红外荧光领域的最新进展,综述了不同的稀土近红外荧光设计思路,介绍了各种近红外稀土荧光功能材料,阐述了稀土离子在近红外荧光功能材料中的优势,并展望了稀土近红外荧光材料的发展前景。     

Some features of luminescent properties of PbS suspensions,stabilized by high‐molecular polyvinylpyrrolidone

The results of the investigations of optical and luminescent properties of PbS suspensions stabilized by high‐molecular polyvinylpyrrolidone are described. Suspensions prepared by liquid colloidal method from sodium sulfide and lead nitrate demonstrate strong luminescence in near infrared spectral range at the excitation by visual light with different wavelengths. It was proposed that Förster resonant energy transfer plays the important role in luminescence properties of closed packed PbS particles. The model, which describes the observed luminescent properties of the suspensions PbS‐stabilized high‐molecular polymer, is proposed. The combination of very wide spectral range of excitation of the luminescence with rather narrow range of light radiation in near infrared spectral range determine wide perspectives of the materials in solar luminescent concentrators and photodetectors. Copyright © 2015 John Wiley & Sons, Ltd.     

Fmoc-protected amino acids as luminescent and circularly polarized luminescence materials based on charge transfer interaction

Fluorenylmethyloxycarbonyl (Fmoc)-protected amino acids are effective building blocks in self-assembled architectures at hierarchical levels, which however show limited luminescent properties and chiroptical activities. Here we introduce a charge-transfer strategy to build two-component luminescent materials with emerged circularly polarized luminescence properties. A library of Fmoc-amino acids was built, which selectively form charge-transfer complexes with the electron-deficient acceptor. Embedding in amorphous polymer matrix or physical grinding could trigger the charge-transfer luminescence with adjusted wavelengths in a general manner. X-ray diffraction results suggest the multiple binding modes between donor and acceptor. And, the solution-processed coassembly could selectively exhibit circularly polarized luminescence with high dissymmetry g-factors. This work illustrates a noncovalent charge-transfer strategy to construct luminescent and chiroptical organic composites based on the easy-accessible and economic chiral N-terminal aromatic amino acids.     

Development of Optical Sensors Based on Luminescent Transition-Metal Complexes

Luminescence-based optical sensors are becoming increasingly important particularly in the area of fibber optic sensors. Most luminescence sensors detect analyses based on the change in luminescent intensity or excited-state lifetime of the sensing material as a function of analyst concentration. Luminescent materials with long excited-state lifetime are essential for the development of inexpensive sensors because it is much simpler and less expensive to measure lifetime in microseconds than in nanoseconds. Luminescent dyes with absorption in the visible region would allow the use of inexpensive light sources such as light emitting diodes (LEDs). Recent studies indicate that luminescent transition metal complexes, especially those with platinum group metals, have desirable spectral characteristics and features including long excited state lifetimes, high luminescence quantum yields and intense visible absorptions. They also tend to be thermally, chemically and photochemically robust. We have been investigating new luminescent sensor materials with the aims to understand the behaviour of luminescent materials in polymer and gel support and to develop new sensor materials with desirable properties.     

Luminescent metal alkynyls - from simple molecules to molecular rods and materials

This review describes the design and synthesis of a number of luminescent transition metal alkynyls by this laboratory. The luminescence properties of the complexes have been studied and their emission origin elucidated. Some of these complexes have been shown to be ideal building blocks for the design and construction of luminescent molecular rods and materials, in which the luminescence properties can be readily tuned by changing the alkynyl ligands. Some of them also exhibited luminescence switching behaviour with the “ON-OFF” luminescence states modulated by redox processes, metal ion-binding or solvent composition.     

Structure and Luminescence Characteristics of Europium Activated Strontium Silicates Sr（Eu ,Bi）SiO3 and Sr（Eu ,Bi）2SiO4

Sr2SiO4 ： Eu^3 , Bi^3 and SrSiO3 ：Eu^3 , Bi^3 samples were synthesized at high temperature and high pressure. The effect of high pressure on the structure and luminescence properties of the samples were stud-ied. As a comparison, the samples were also prepared by the method of sol-gel at high temperature and atmo-spheric pressure. The SrSiO3 ： Eu^3 , Bi^3 prepared at atmosphere has a hexagonal phase structure; in the pressure range of 2. 34—4. 10 GPa, it is transformed into a pseudo-orthorhombic structure (monoclinic), and in the pressure range of 4. 10—4. 15 GPa, the structure change of Sr2SiO4 ： Eu^3 , Bi^3 has not been ob-served, it maintains the monoclinic structure of the samples synthesized at an atmospheric pressure. High pressure makes the luminescence properties of the samples changed obviously. The intensity and the relative quantum luminescent efficiency decrease, the half-width increases obviously and the red shift occurs. The changes of the luminescence properties result from the pressure-induced changes of the crystal structures.     

A Joint Study of Experimental and Computational Chemistry to Probe the Effect of Coordination Modes on the Luminescence of Uranyl-Organic Coordination Polymers

Despite the potential application of uranyl-organic coordination polymers (UOCPs) in detecting metal cations and radiation rays, their luminescence properties have not been sufficiently studied at the molecular level. Herein, we synthesized a series of UOCPs ( UOCP1 – 9 ) with new construction based on bipyridinium salts and diverse auxiliary ligands. The physicochemical properties of the complexes with high purity were systematically characterized, especially the luminescence spectra. A deep theoretical investigation was conducted to illustrate the relation between uranyl coordination and the luminescence spectral property. The results show that the influence of ligand type on the uranyl luminescent spectral properties increases in the order of hydroxide>oxalate>aromatic carboxylate, which can be attributed to the magnitude of orbital interaction between uranyl and ligand. This work helps to profoundly understand uranyl optical properties and electronic structure at the molecular level, providing important hints for recognizing the nature of luminescent spectral features of uranyl-containing materials, as well as the fundamental chemistry of actinide elements.     

Recent advances in the sensitized luminescence of organic europium complexes

In this paper, recent advances in the synthesis, mechanism of sensitized emission, and luminescent properties of organic lanthanide complexes are reviewed. Stress is put on the progress in the development of organic europium complexes and their nanoparticles with excellent visible-light-sensitized and two-photon-sensitized Eu^III luminescence properties. These are of increasing importance because bioanalysis or bioimaging techniques based on such labeled materials will combine the advantages of high sensitivity, high signal-to-noise ratio, deep penetration, and low photodamage to biological samples. In addition, the application of long-wavelength-sensitized luminescence of organic lanthanide complexes and their nanoparticles in bioimaging is discussed.     

Luminescent and photochemical properties of light-transforming polymeric materials

Light-transforming polymeric materials were obtained based on polymethylacrylate and high-pressure polyethylene activated by ytterbium(III) ??-diketonates with various ligands and possessing intensive luminescence in the spectral range of 900?C1100 nm. The study of the photochemical behavior of the polymers by the luminescent spectroscopy and stationary photolysis methods has revealed that the polymer compositions containing heteroligand ytterbium(III) dibenzoylmethanates or thenoyltrifluoroacetonates and triphenylphosphine oxide show high operational properties (an intensive luminescence and photostability).     

Dual emission of singlet and triplet states boost the sensitivity of pressure-sensing

Pressure-related sensing materials in mechanochromic luminescent materials have received wide attention. However, at present, most piezochromic luminescence (PCL) materials have problems such as aggregation-caused quenching (ACQ) effect due to the presence of powder form, complicated preparation methods and fluorescence quenching effect under high pressure. To solve these problems, we employ three components containing carbon dots (CDs), layered double hydroxides (LDHs) and polyvinyl alcohol (PVA) to construct the CDs-LDHs/PVA film. The LDHs can provide a rigid environment for CDs and improve the luminescent efficiency of CDs. The film shows high sensitivity, stability and reversibility. Moreover, the compressed film can recover to its original state by heating. Therefore, the PCL film with dual emission (fluorescence and phosphorescence) characteristic is constructed, which boosts the sensitivity of pressure-sensing.     

Luminescent Mechanochromic Porous Coordination Polymers

Three 2D luminescent isomeric porous coordination polymers are synthesized and characterized. Their luminescence properties can be modified by grinding and they can act as mechanochromic materials and their properties are probably related to the weak interactions of cuprophilicity and π–π interactions.     

Luminescent nanoscale metal–organic frameworks for chemical sensing

Metal–organic frameworks(MOFs) are a fascinating class of crystalline materials constructed from selfassembly of metal cations/clusters and organic ligands. Both metal and organic components can be used to generate luminescence, and can further interact via antenna effect to increase the quantum yield,providing a versatile platform for chemical sensing based on luminescence emission. Moreover, MOFs can be miniaturized to nanometer scale to form nano-MOF(NMOF) materials, which exhibit many advantages over conventional bulk MOFs in terms of the facile tailorability of compositions, sizes and morphologies, the high dispersity in a wide variety of medium, and the intrinsic biocompatibility. This review will detail the development of NMOF materials as chemical sensors, including the synthetic methodologies for designing NMOF sensory materials, their luminescent properties and potential sensing applications.     

静电纺丝制备荧光导电双功能复合纳米纤维及其表征

采用静电纺丝技术将导电聚苯胺(PANI)和铕/铽稀土配合物掺杂到高分子基质聚乙烯吡咯烷酮(PVP)中,制备出荧光导电复合纳米纤维。用扫描电镜(SEM)、荧光光谱仪(FL)、宽频介电松驰谱仪对荧光导电复合纳米纤维的性能进行分析,结果显示,在270nm紫外光激发下,铕系列与铽系列复合纳米纤维分别发出红光和绿光。同时,复合纳米纤维的电导率可以达到1.18×10~(-6) S/cm,两种复合纳米纤维同时具有优异的荧光性能及良好的导电功能。     

Quantum efficiency of double activated Tb3Al5O12:Ce, Eu

The quantum efficiency and luminescence properties of double activated terbium aluminum garnet samples were investigated in the present study. A mathematical procedure and PL measurement system are developed for express analysis of quantum efficiency of luminescent materials. The energy-level diagram was proposed to explain the luminescence mechanism. Application of TAG:Ce,Eu with improved CIE and CRI in LED device is demonstrated.     

Novel metal-organic ruthenium(II) diimin complexes for use as longwave excitable luminescent oxygen probes

New ruthenium(II) diimine complexes are presented which are useful as luminescent oxygen probes. Because their luminescence excitation maxima are between 535 and 570 nm, they can be photo-excited by green LEDs which are much brighter than the blue LEDs used so far for existing Ru diimines. The spectral and photophysical properties as well as the solubility properties of the new probes are investigated and discussed in terms of quenching, photostability, and lifetimes. The probes were incorporated into organic polymers by three different methods, to obtain oxygen-sensitive materials for use in optical oxygen sensing. The membranes were characterized with respect to oxygen sensitivity, luminescence intensity, response times, and stability. Notwithstanding the poor luminescence of the new ruthenium(II) probes, their stability, LED compatibility and efficient quenching by oxygen makes them an interesting alternative to existing luminescent oxygen probes.     

Luminescent and photochemical properties of the lanthanide-containing polymer materials

The light-transforming polymer materials have been obtained based on the mixed europium cinnamates, cinnamic acid, and high density polyethylene. The materials exhibit an intensive luminescence in the range of 400–700 nm. The photostability of the materials has been higher than that of polymer materials activated solely with europium compounds. The photolysis of the luminescent polymers has been studied. For the obtained polymer compositions the build-up of europium ion and cinnamic acid luminescence has been observed.     

Luminescence of lanthanide complexes: From fundamental to prospective approaches related to water- and molecular-stimuli

Luminescent lanthanide (Ln) complexes are attracted much attention because of their stable emission colors induced by the photo-antenna effect through the photo-excited energy transfer from aromatic ligands to Ln ions. Here, we will introduce some systems of luminescent Ln complexes with metastable states with the phase transition induced by water and other small molecules, the relative arrangement of hydrogel formation and Ln luminescence enhancement, and the diversity of the thin air-water interface. The energy donor levels in each system should be designed to sensitize Ln-luminescence with the consideration of media, interaction and assembling. Luminescence quenching of Ln complexes in water is a point that should be considered for the development of materials and for the purpose of bio-related materials. Then, the principle of the change in luminescence intensity by the effect of water molecules is described, and the estimation of a hydrated structure of the complex is estimated using the luminescence lifetimes in H₂O and D₂O. The molecular arrangement of these crystals changes under the vapor-stimuli, and the coloration and luminescence may be enhanced. Some interesting cases of luminescent Ln complexes with the crystal-to-crystal phase transitions will be introduced with the vapor adsorption. Hydrogels are mostly water by volume; a system in which Ln luminescence is maintained implies that Ln ions are placed in hydrophobic positions in self-assemblies with strong luminescence. The formation of thin films at the molecular level and their Ln luminescence properties are introduced. For example, when a monolayer of a surface-active Ln complex is formed at the air-water interface, the repeated accumulation of the flexible film forms a metastable structure with a regular structure different from that of a crystal, and no water is incorporated into the film. These can not only derive circularly or linearly polarized light, but also take in other molecules and change the emission. Finally, we will suggest the prospects for the development of Ln complexes.     

树枝状有机电致发光材料*

高度有序、三维结构的树枝状大分子(Dendrimers)作为功能有机材料越来越引起人们的兴趣。与传统的小分子和高分子发光材料相比,树枝状化合物在发光材料方面的应用具有无可比拟的优势。树枝状发光材料的发光特性可以方便地由中心核的调换不同的荧光染料来实现,另外大量的表面功能团和不同的代数可供选择来得到一些有趣的性质,如载流子传输功能、区域隔离效应、溶解性和天线效应等。该类型的发光材料已被认为是第三类电致发光材料。本文简要介绍近期树枝状分子在有机电致发光材料领域中的研究进展,评述树枝状分子在该研究领域所特有的优势,重点介绍了树枝状化合物的设计及其对应的性质,并进一步展望树枝状分子未来在有机电致发光领域的研究前景。     

Efficient Formation of Luminescent Lanthanide(III) Complexes by Solid‐Phase Synthesis and On‐Resin Screening

Time‐resolved luminescence measurements of luminescent lanthanide complexes have advantages in biological assays and high‐throughput screening, owing to their high sensitivity. In spite of the recent advances in their energy‐transfer mechanism and molecular‐orbital‐based computational molecular design, it is still difficult to estimate the quantum yields of new luminescent lanthanide complexes. Herein, solid‐phase libraries of luminescent lanthanide complexes were prepared through amide‐condensation and Pd‐catalyzed coupling reactions and their luminescent properties were screened with a microplate reader. Good correlation was observed between the time‐resolved luminescence intensities of the solid‐phase libraries and those of the corresponding complexes that were synthesized by using liquid‐phase chemistry. This method enabled the rapid and efficient development of new sensitizers for Sm^III, Eu^III, and Tb^III luminescence. Thus, solid‐phase combinatorial synthesis combined with on‐resin screening led to the discovery of a wide variety of luminescent sensitizers.