Synthesis and characterization of deep blue emitters from starburst carbazole/fluorene compounds

A series of well-defined, highly fluorescent starburst compounds with a carbazole core and oligo(2,7-fluorene ethynylene) arms have been synthesized by Sonogashira coupling reaction and fully characterized. These conjugated compounds exhibit good solubility, high thermal stability, and excellent fluorescence quantum yields (up to 0.99). The incorporation of carbazole core interrupted the main-chain conjugation and resulted in blue-shifted absorption and emission. Moreover, deep blue light has been approached from organic light-emitting diodes (OLEDs) adopting these compounds as emitting layer.     

Blue light-emitting and electron-transporting materials based on dialkyl-functionlized anthracene imidazophenanthrolines

Two novel blue light-emitting materials based on bis(tert-butyl)anthracenyl-imidazophenanthrolines (BAIPs) have been synthesized and extensively characterized. Both materials exhibited a non-aggregate feature with high fluorescent quantum efficiency and excellent thermal stability. They can serve both as emissive and electron-transporting materials used in electroluminescence (EL) device for blue emission with high luminescence and external quantum efficiency. This study demonstrates that they are potentially useful for a wide range of applications in EL technology.     

Asymmetric Host Molecule Bearing Pyridine Core for Highly Efficient Blue Thermally Activated Delayed Fluorescence OLEDs

In this study, two host materials, pCzBzbCz and pCzPybCz , are synthesized to achieve a high efficiency and long lifetime of blue thermally activated delayed fluorescence organic light-emitting diodes (TADF-OLEDs). The molecular design strategy involves the introduction of a pyridine group into the core structure of pCzPybCz as an electron-withdrawing unit, and an electron-donating phenyl group into the structure of pCzBzbCz . These host materials demonstrate good thermal stability and high triplet energy (T₁=3.07 eV for pCzBzbCz and 3.06 eV for pCzPybCz ) for the fabrication of blue TADF-OLEDs. In particular, pCzPybCz -based OLED devices demonstrate an external quantum efficiency (EQE) of 22.7 % and an operational lifetime of 24 h (LT₉₀, time to attain 90 % of initial luminance) at an initial luminance of 1000 cd m⁻². This superior lifetime could be explained by the C−N bond dissociation energy (BDE) in the host molecular structure. Furthermore, a mixed-host system using the electron-deficient 2,4-bis(dibenzo[b,d]furan-2-yl)-6-phenyl-1,3,5-triazine (DDBFT) is proposed to inhibit the formation of the anion state of our host materials. In short, the device operational lifetime is further improved by applying DDBFT. The carbazole-based asymmetric host molecule containing a pyridine core realizes a high-efficiency blue TADF-OLED showing a positive effect on the operating lifetime, and can provide useful strategies for designing new host materials.     

Electrochemical fluorescence switching properties of conjugated polymers composed of triphenylamine,fluorene, and cyclic urea moieties

The study of the electrochemical fluorescence switching properties of the conjugated copolymers containing fluorene, triphenylamine, and 1,3‐diphenylimidazolidin‐2‐one moieties is reported. The polymers show high fluorescence quantum yields, excellent thermal stability, and good solubility in polar organic solvents. While the polymer emits blue light under UV irradiation, the fluorescence intensity is quenched upon electrochemical oxidation. The fluorescent behavior can be reversibly switched between nonfluorescent (oxidized) state and strong fluorescence (neutral) state with a high contrast ratio (I_f/I_f0) of 16.3. The role of the electrochemical oxidation of the triphenylamine moieties is to generate the corresponding radical cations that lead to fluorescence quenching in the solid matrix. © 2012 Wiley Periodicals, Inc. J. Polym. Sci. Part A: Polym Chem, 2012     

Optimizing Optoelectronic Properties of Pyrimidine‐Based TADF Emitters by Changing the Substituent for Organic Light‐Emitting Diodes with External Quantum Efficiency Close to 25 % and Slow Efficiency Roll‐Off

A series of green butterfly‐shaped thermally activated delayed fluorescence (TADF) emitters, namely PXZPM , PXZMePM , and PXZPhPM , are developed by integrating an electron‐donor (D) phenoxazine unit and electron‐acceptor (A) 2‐substituted pyrimidine moiety into one molecule via a phenyl‐bridge π linkage to form a D –π–A–π–D configuration. Changing the substituent at pyrimidine unit in these emitters can finely tune their emissive characteristics, thermal properties, and energy gaps between the singlet and triplet states while maintaining frontier molecular orbital levels, and thereby optimizing their optoelectronic properties. Employing these TADF emitters results in a green fluorescent organic light‐emitting diode (OLED) that exhibits a peak forward‐viewing external quantum efficiency (EQE) close to 25 % and a slow efficiency roll‐off characteristic at high luminance.     

一种蓝光发射星型有机分子的合成及光电性质

采用分子设计的思想,通过多步反应合成了一种新型的以N原子为中心的蓝光发射星型有机小分子。用1H NMR,MS和元素分析进行了表征,研究了化合物的热稳定性和真空镀膜膜层的光致发光性质,用循环伏安法测定了其电化学性能。结果表明,这种合成的有机化合物光致发光性能优良(量子效率达到87%),热稳定性好,可作为制作有机电致发光器件的候选材料。     

Synthesis and characterization of a strong-fluorescent Eu-containing hydrotalcite-like compound

A novel strong-fluorescent Eu-containing hydrotalcite-like compound (Eu-HTlc) was synthesized using the coprecipitation method, in which aluminum(III) was partially substituted by Europium (III) in the hydrotalcite-like layers, and thenoyltrifluoroacetone, 1,10-phenanthroline were dispersed into the anions in the interlayer region. The sample was characterized by XRD, XPS, FT-IR, ICP, TG-DSC, TEM and fluorescence spectra, and its composition and structure were determined. The results indicated that the sample exhibited a characteristic red light (614 nm). The fluorescent lifetime and fluorescence quantum yield of Eu-HTlc were measured to be respectively 893 μs and 66.44%, higher than those of Eu(III)-thenoyltrifluoroacetone-1,10-phenanthroline complex [Eu(TTA)₃phen]. The result of TG-DSC measurement showed the enhanced thermal stability of Eu-HTlc compared with that of MgAl-LDHs and Eu(TTA)₃phen. With excellent photoluminescent property and thermal stability, low contents of rare earth ions and ligands, the Eu-HTlc may become one of the novel fluorescent materials with potential applications.     

A unique class of near-infrared functional fluorescent dyes with carboxylic-acid-modulated fluorescence ON/OFF switching: rational design, synthesis, optical properties, theoretical calculations, and applications for fluorescence imaging in living animals

Fluorescence imaging is one of the most powerful techniques for monitoring biomolecules in living systems. Fluorescent sensors with absorption and emission in the near-infrared (NIR) region are favorable for biological imaging applications in living animals, as NIR light leads to minimum photodamage, deep tissue penetration, and minimum background autofluorescence interference. Herein, we have introduced a new strategy to design NIR functional dyes with the carboxylic-acid-controlled fluorescence on-off switching mechanism by the spirocyclization. Based on the design strategy, we have developed a series of Changsha (CS1-6) NIR fluorophores, a unique new class of NIR functional fluorescent dyes, bearing excellent photophysical properties including large absorption extinction coefficients, high fluorescence quantum yields, high brightness, good photostability, and sufficient chemical stability. Significantly, the new CS1-6 NIR dyes are superior to the traditional rhodamine dyes with both absorption and emission in the NIR region while retaining the rhodamine-like fluorescence ON-OFF switching mechanism. In addition, we have performed quantum chemical calculations with the B3LYP exchange functional employing 6-31G* basis sets to shed light on the structure-optical properties of the new CS1-6 NIR dyes. Furthermore, using CS2 as a platform, we further constructed the novel NIR fluorescent TURN-ON sensor 7, which is capable of imaging endogenously produced HClO in the living animals, demonstrating the value of our new CS NIR functional fluorescent dyes. We expect that the design strategy may be extended for development of a wide variety of NIR functional dyes with a suitable fluorescence-controlled mechanism for many useful applications in biological studies.     

光致发光聚酰亚胺研究进展

聚酰亚胺是一类重要的高性能高分子材料,具有优异的热性能、机械性能、电学性能和尺寸稳定性等,同时具有良好的结构可设计性,已逐渐成为有机光电领域的研究热点.然而,传统聚酰亚胺材料一般不发光,文献中有关发光聚酰亚胺的研究并不多.同时,所报道的荧光量子产率普遍较低,极大地限制了其作为发光功能层在有机光电器件领域的应用.为了更好地了解聚酰亚胺发光的规律,拓展高性能聚酰亚胺材料在有机发光器件中的应用领域,本文介绍了聚酰亚胺光致发光的机理,综述了国内外有关光致发光聚酰亚胺的研究进展,总结了提高聚酰亚胺荧光量子产率的方法,并对未来高性能高效发光聚酰亚胺材料的研究方向做了展望.     

Fabrication of Multiresponsive Bioactive Nanocapsules through Orthogonal Self‐Assembly

Multifunctional self‐assembled systems present platforms for fundamental research and practical applications as they provide tunability of structure, functionality, and stimuli responsiveness. Pragmatic structures for biological applications have multiple design requirements, including control of size, stability, and environmental response. Here we present the fabrication of multifunctional nanoparticle‐stabilized capsules (NPSCs) by using a set of orthogonal supramolecular interactions. In these capsules, fluorescent proteins are attached to quantum dots through polyhistidine coordination. These anionic assemblies interact laterally with cationic gold nanoparticles that are anchored to the fatty acid core through guanidinium–carboxylate interactions. The lipophilic core then provides a reservoir for hydrophobic endosome‐disrupting agents, thereby generating a system featuring stimuli‐responsive release of a payload into the cytosol with fluorescence monitoring.     

Highly fluorescence Ta4C3 MXene quantum dots as fluorescent nanoprobe for heavy ion detection and stress monitoring of fluorescent hydrogels

Compared with other transition metal Mxene derived quantum dots（MQD_S）,Ta-based Mxene quantum dots have good functionality,but Ta-based Mxene quantum dots and their applications have not been studied so far.In this paper,we report for the first time the synthesis of high fluorescence quantum yield（QY） N-doped Ta₄ C₃ quantum dots（N-MQDs） using Ta₄ C₃ quantum dots in acid reflux damaged Ta₄ C₃ nanosheets as precursors and ...     

A universal nucleoside with strong two-band switchable fluorescence and sensitivity to the environment for investigating DNA interactions

With the aim of developing a new tool to investigate DNA interactions, a nucleoside analogue incorporating a 3-hydroxychromone (3HC) fluorophore as a nucleobase mimic was synthesized and incorporated into oligonucleotide chains. In comparison with existing fluorescent nucleoside analogues, this dye features exceptional environmental sensitivity switching between two well-resolved fluorescence bands. In labeled DNA, this nucleoside analogue does not alter the duplex conformation and exhibits a high fluorescence quantum yield. This probe is up to 50-fold brighter than 2-aminopurine, the fluorescent nucleoside standard. Moreover, the dual emission is highly sensitive to the polarity of the environment; thus, a strong shielding effect of the flanking bases from water was observed. With this nucleoside, the effect of a viral chaperone protein on DNA base stacking was site-selectively monitored.     

A fluorogenic ‘click’ reaction of azidoanthracene derivatives

Fluorogenic reactions have broad applications in biolabeling, combinatorial synthesis of fluorescent dyes, and materials development. It was recently reported that the highly selective and efficient Cu(I)-catalyzed azide-alkyne cycloaddition (CuAAC) reaction can be employed in designing new types of fluorogenic reactions. In this study, we report a fluorogenic reaction using anthracene azides as starting materials. The fluorescence of the anthryl core can be greatly inhibited upon introducing electron-donating azido groups in the proximity. Such weakly fluorescent anthracene azides demonstrate high reactivity with a variety of alkynes under the CuAAC conditions producing a strongly fluorescent triazole product with high quantum yields. This reaction can be used in the synthesis and screening of fluorescent dyes combinatorially. Compared with most existing methods, the fluorogenic CuAAC reaction is a much milder and simpler technique to prepare large libraries of fluorescent dyes without further purification. In order to demonstrate the efficiency of using anthracene azides for biolabeling applications, both small molecules and biomolecules including the multialkyne-derivatized cowpea mosaic virus and tobacco mosaic virus had been studied.     

Reversible Photoswitching of RNA Hybridization at Room Temperature with an Azobenzene C‐Nucleoside

Photoregulation of RNA remains a challenging task as the introduction of a photoswitch entails changes in the shape and the stability of the duplex that strongly depend on the chosen linker strategy. Herein, the influence of a novel nucleosidic linker moiety on the photoregulation efficiency of azobenzene is investigated. To this purpose, two azobenzene C‐nucleosides were stereoselectively synthesized, characterized, and incorporated into RNA oligonucleotides. Spectroscopic characterization revealed a reversible and fast switching process, even at 20 °C, and a high thermal stability of the respective cis isomers. The photoregulation efficiency of RNA duplexes upon trans‐to‐cis isomerization was investigated by using melting point studies and compared with the known D ‐threoninol‐based azobenzene system, revealing a photoswitching amplitude of the new residues exceeding 90 % even at room temperature. Structural changes in the duplexes upon photoisomerization were investigated by using MM/MD calculations. The excellent photoswitching performance at room temperature and the high thermal stability make these new azobenzene residues promising candidates for in‐vivo and nanoarchitecture photoregulation applications of RNA.     

A Fluorescent Polymeric Quantum Dot/Aptamer Superstructure and Its Application for Imaging of Cancer Cells

In this work, a novel polymeric quantum dot/aptamer superstructure with a highly intense fluorescence was fabricated by a molecular engineering strategy and successfully applied to fluorescence imaging of cancer cells. The polymeric superstructure, which is composed of both multiple cell‐based aptamers and a high ratio of quantum dot (QD)‐labeled DNA, exploits the target recognition capability of the aptamer, an enhanced cell internalization through multivalent effects, and cellular disruption by the polymeric conjugate. Importantly, the polymeric superstructure exhibits an increasingly enhanced fluorescence with recording time and is thus suitable for long‐term fluorescent cellular imaging. The unique and excellent fluorescence property of the QD superstructure paves the way for developing polymeric QD superstructures that hold promise for applications such as in vivo imaging.     

Optical and photophysical properties of light-harvesting phenylacetylene monodendrons based on unsymmetrical branching

The optical and photophysical properties of phenylacetylene dendritic macromolecules based on unsymmetrical branching are investigated using steady-state and time-dependent spectroscopy. Monodendrons, up to the fourth generation, are characterized with and without a fluorescent perylene trap at the core. The higher generation monodendrons without the perylene trap exhibit high molar extinction coefficients (>10(5) M(-1) cm(-1)) and high fluorescence quantum yields (65-81%). When a perylene trap is placed at the core, then the monodendrons typically exhibit high energy transfer quantum yields (approximately 90%), as well as subpicosecond time scale excited-state dynamics, as evidenced by ultrafast pump-probe measurements. The photophysical properties of the unsymmetrical monodendrons are compared to those of phenylacetylene monodendrons with symmetrical branching, which have been described recently. The high fluorescence quantum yields and large energy transfer quantum efficiencies exhibited by the unsymmetrical monodendrons suggest they have potential for applications in molecular-based photonics devices.     

Preparation and characterization of monodisperse CdS quantum dot‐polymer microspheres

A novel and effective method for the preparation of monodisperse CdS quantum dot‐polymer microspheres was proposed. The monodisperse hollow polymer microspheres were firstly swelled in chloroform. Then, the reaction precursor composed of CdO and sulfur, was impregnated into the hollow polymer microspheres. Subsequently, the CdS quantum dots were synthesized directly within the polymer microspheres by thermal decomposition. The morphology, structure, and fluorescence properties of CdS quantum dot‐polymer microspheres were studied by scanning electron microscope, transmission electron microscope, fluorescence microscope, and flow cytometry. The results indicate that the fluorescent CdS quantum dots are successfully synthesized in the monodisperse hollow polymer microspeheres, which provide very strong fluorescence intensity, and offer excellent photostability due to the compact structure of the polymer matrix. These CdS quantum dot‐polymer microspheres have potential applications in biotechnology and biomedicine. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 751–755, 2010     

碲化镉量子点作为探针研究核黄素与鲑鱼精DNA的相互作用

在水相中合成了巯基丙酸包覆的CdTe量子点（CdTe QDs）,以CdTe QDs作为探针,在pH 7.25 Britton-Robinson（B-R）缓冲溶液中,应用荧光光谱法、紫外吸收光谱法,对核黄素（RF）与鲑鱼精DNA作用方式进行了研究.RF与DNA作用时,使荧光强度降低,紫外吸收明显减色,通过盐效应实验和DN...     

Fluorescence Intensity Enhancement of Green Carbon Dots: Synthesis,Characterization and Cell Imaging

The hydrothermal treatment of green carbon dots (CDs) is an appropriate fluorescent probe synthesis method. CDs are exploited as biological staining agents, especially for cellular detection and imaging. The nitrogen-doped green carbon dots (N-CDs) formation can improve the fluorescence intensity property in a one-step process. Here, we report two N-CDs from lemon and tomato extraction in the presence of hydroxylamine. Lemon and tomato N-CDs showed the blue fluorescence under ultraviolet radiation of about 360 nm. The characterization of CDs and N-CDs showed the presence of N-H and C–N bonds which enhanced the fluorescence efficiency. The mean size of lemon and tomato N-CDs were about 2 and 3 nm with an increased quantum yield (QY) of 5% and 3.38%, respectively. The CDs and N-CDs cytotoxicity assay exhibited high cell viability approximately 85% and 73%, respectively. N-CDs show superior fluorescent intensity in different solvents and significant stability under long-time UV irradiation, different PH and high ionic strength. Our results indicated that the use of N-CDs in cell imaging can lead to fluorescence intensity enhancement as well as proper biocompatibility. Therefore, the safe and high fluorescence intensity of green N-CDs can be utilized for fluorescent probes in biolabeling and bioimaging applications.     

Synthesis and characterization of photoswitchable fluorescent SiO2 nanoparticles

Switchable fluorescent silica nanoparticles have been prepared by covalently incorporating a fluorophore and a photochromic compound inside the particle core. The fluorescence can be switched reversibly between an on‐ and off‐state via energy transfer. The particles were synthesized using different amounts of the photoswitchable compound (spiropyran) and the fluorophore (rhodamine B) in a size distribution between 98 and 140 nm and were characterized in terms of size, switching properties, and fluorescence efficiency by TEM, and UV\Vis and fluorescence spectroscopy.