聚集诱导发光及结晶诱导发光增强

阐述了与传统荧光化合物行为相反的"聚集诱导发光"(AIE)及"结晶诱导发光增强"现象,并制备了以AIE化合物为发光层的具有优良器件性能的有机发光二极管.     

聚集诱导的荧光增强体系研究进展

聚集诱导的荧光增强（AIEE）现象是近几年备受关注的一个研究领域，文中纵观了该领域的进展，做了一个较为详尽的综述报道。具有该性质的体系主要包括多苯基取代的烯烃类、吡喃的衍生物以覆二苯基二苯并环戊二烯类等。这种反常的聚集荧光增强现象多数是由于固态或聚集状态下分子内的自由旋转运动受到极大的抑制所引起的。对于具有AIEE性质化合物的结构．性质研究有利于寻找更有效的发光功能材料。     

利用PtOEP掺杂改善Spiro发光器件的发光效率

为了利用有机三线态发光提高有机发光器件的发光效率,用磷光材料掺杂到聚合物主体中作为发光层,制备有机电致发光器件.在测量器件的电流-电压特性、发光亮度-电压特性和电致发光谱的基础上,计算了器件的外量子效率,研究了磷光材料的掺杂浓度对器件发光效率的影响.结果表明,对特定的材料体系,适当控制掺杂浓度,可以同时观察到荧光和磷光光谱,使掺杂器件的外量子效率在纯聚合物发光器件的基础上得到明显提高.     

利用PtOEP掺杂改善Spiro发光器件的发光效率

为了利用有机三线态发光提高有机发光器件的发光效率,用磷光材料掺杂到聚合物主体中作为发光层,制备有机电致发光器件.在测量器件的电流-电压特性、发光亮度-电压特性和电致发光谱的基础上,计算了器件的外量子效率,研究了磷光材料的掺杂浓度对器件发光效率的影响.结果表明,对特定的材料体系,适当控制掺杂浓度,可以同时观察到荧光和磷光光谱,使掺杂器件的外量子效率在纯聚合物发光器件的基础上得到明显提高.     

不同荧光蓝光层厚度的OLED的制备与光电性能

采用蓝色荧光材料1p-TDPVBi结合绿色磷光材料2Ir(ppy)3掺杂到母体材料CBP作为绿光发光层,并且采用3BPhen作为电子传输层和激子阻挡层制备结构为ITO/m-MTDATA(50nm)/NPB(10nm)/p-TDPVBi(dnm)/CBP∶Ir(ppy)38%7nm/BPhen(60nm)/LiF(1nm)/Al的有机发光器件。实验结果表明:通过改变蓝光发光层p-TDPVBi的厚度,得到了高效率的有机发光器件,当p-TDPVBi厚度为5nm时,器件的电流效率和功率效率在4V时达到32.3cd/A和25.3lm/W,亮度在11V时达到31 020cd/m2。研究了p-TDPVBi厚度由3nm变化到9nm,OLED器件的电流密度-电压特性曲线、亮度-电压曲线及电流效率-电压和功率效率-电压等光电性能的变化。     

ZnCdS/Cd_xZn_(1-x)Se_yS_(1-y)量子点量子阱及有机-无机LED北大核心

为了提高无机纳米发光材料的发光效率和有机-无机杂化电致发光器件的性能,使用有机金属前驱体法,制备了具有化学组分梯度的ZnCdS/CdxZn1-xSeyS1-y量子点量子阱材料以及CdxZn1-xSeyS1-y量子点材料。观察到相同反应温度与反应物配比所制得的ZnCdS/CdxZn1-xSeyS1-y光致发光峰相较于CdxZn1-xSeyS1-y出现明显的蓝移,且荧光量子效率有一定的提高,最高可达60.6%。通过在反应过程中调节Se与S的比例,观察到了反应产物的光致发光峰随Se比例的减少而逐渐蓝移。结果表明,与使用纯无机纳米材料作为有源层的器件相比,使用量子点量子阱材料制备的有机-无机杂化LED的电流效率提高了4.3倍。     

具有聚集诱导发光功能的圆偏振发光液晶材料

圆偏振光是光矢量端点轨迹为圆的光，它在传播时光矢量的大小不变而振动方向随相位而改变。通常，非偏振光首先通过偏振片转化为线偏振光，再通过λ/4波片分解为左旋或右旋圆偏振光。这一物理过程所获得的圆偏振光能量损耗一般超过50%。而通过构筑聚集诱导发光手性液晶分子直接获得圆偏振光，可以获得高的荧光量子效率和大的不对称因子，有效降低了能量损耗。因此，聚集诱导发光手性液晶受到了研究人员的广泛关注。本文基于聚集诱导发光基团修饰手性液晶分子的设计与合成，以及手性聚集诱导发光分子体系掺杂向列相液晶这两类方法，综述了本领域的研究进展，讨论了聚集诱导发光液晶分子结构设计和聚集态的形成对圆偏振发光和聚集诱导发光性能的影响，展望了这种新型光学材料所面临的机遇和挑战。     

有机层界面电荷聚集及其对OLED性能的影响

采用金属Al、合金Mg:Ag以及复合层LiF-Al作为阴极材料,利用真空加热蒸镀法制备了异质结有机发光器件(OLED),研究了阴极材料与器件有机层界面电荷聚集之间的关系.结果表明,界面电荷聚集与阴极材料密切相关,LiF-Al复合层阴极器件的界面聚集电荷最少,而Al金属阴极器件的界面聚集电荷最多.同时,通过测试器件的光电性能,进一步研究了阴极材料对OLED发光特性的影响.实验结果显示,LiF-Al复合层阴极器件具有最大的发光亮度和效率、最小的启亮电压和驱动电压.     

高色纯度有机发光器件研究进展

为了使有机发光显示技术满足国际电信联盟为超高清电视所制定的色域标准（BT 2020），高色纯度有机发光器件（OLED）的研究与开发具有重要意义。本文分别从窄带发光OLED材料和微腔OLED器件两方面介绍高色纯度有机发光器件的重要研究进展。首先，分析了分子的振动耦合对有机发光材料色纯度的影响，并针对荧光、磷光和热激活延迟荧光（TADF）3种材料，分别讨论了目前改善有机发光色纯度的方法，总结了最新的材料设计策略与研究结果。然后，介绍了微腔效应的原理，分析其对有机发光器件光谱的修饰与窄化作用，并介绍了利用微腔效应实现高色纯度发光的器件结构设计与优化方案。最后，讨论了高色纯度OLED器件在显示领域的未来前景与挑战。     

Cu掺杂ZnO薄膜光学性质的研究

为了制备结晶质量好的Cu掺杂ZnO薄膜,研究其结构和光学性质,采用脉冲激光沉积方法,在Si衬底上选择不同的衬底温度来制备薄膜。实验成功制得了结晶质量较好的Cu掺杂ZnO薄膜。利用X射线衍射仪、扫描电子显微镜和荧光分光光度计对样品进行了测量和分析。所制备的样品均表现出高度的c轴择优取向,衬底温度为300℃时,薄膜表面形貌均匀致密;在样品的光致发光谱中,发现样品除了在380nm附近出现紫外发光峰外,在460nm附近出现了蓝光发光峰,真正意义上实现了ZnO薄膜的蓝光发射。结果表明,衬底温度对其晶体质量有较大影响。     

Enhancement of Aggregation‐Induced Emission in Dye‐Encapsulating Polymeric Micelles for Bioimaging

Three amphiphilic block copolymers are employed to form polymeric micelles and function as nanocarriers to disperse hydrophobic aggregation‐induced emission (AIE) dyes, 1,1,2,3,4,5‐hexaphenylsilole (HPS) and/or bis(4‐(N‐(1‐naphthyl) phenylamino)‐phenyl)fumaronitrile (NPAFN), into aqueous solution for biological studies. Compared to their virtually non‐emissive properties in organic solutions, the fluorescence intensity of these AIE dyes has increased significantly due to the spatial confinement that restricts intramolecular rotation of these dyes and their better compatibility in the hydrophobic core of polymeric micelles. The effect of the chemical structure of micelle cores on the photophysical properties of AIE dyes are investigated, and the fluorescence resonance energy transfer (FRET) from the green‐emitting donor (HPS) to the red‐emitting acceptor (NPAFN) is explored by co‐encapsulating this FRET pair in the same micelle core. The highest fluorescence quantum yield (～62%) could be achieved by encapsulating HPS aggregates in the micelles. Efficient energy transfer (>99%) and high amplification of emission (as high as 8 times) from the NPAFN acceptor could also be achieved by spatially confining the HPS/NPAFN FRET pair in the hydrophobic core of polymeric micelles. These micelles could be successfully internalized into the RAW 264.7 cells to demonstrate high‐quality fluorescent images and cell viability due to improved quantum yield and reduced cytotoxicity.     

Tailoring the Molecular Properties with Isomerism Effect of AIEgens

It is challenging to achieve precise control on the properties of organic π‐functional materials to widen their practical applications. On the other hand, the study of aggregation‐induced emission luminogens (AIEgens) helps achieve such goals because of inherent relationships between their luminescence behaviors and conformational variations that allow for the visual monitoring of the changes in the material properties. Inspired by this, in this work, three AIE isomers are fabricated in structures consisting of tetraphenylpyrazine and triphenylethene units with para‐, meta‐, and ortho‐position linkages, respectively. The isomerism effect brings about significantly decreased luminescence efficiency, subtly blueshifted emission, basically reduced AIE effect but boosted porosity in the aggregate state as the conformation of AIEgens evolves from an extended to a folded one. Based on the distinct properties, their respective use in blue organic light‐emitting diodes, nanofluorescent probes, and molecule‐capturing porous crystals are investigated. This work not only achieves precise property control by using the isomerism effect of AIEgens but also provides useful information on the future design of π‐conjugated materials with advanced functionalities.     

Highly Efficient Circularly Polarized Electroluminescence from Aggregation‐Induced Emission Luminogens with Amplified Chirality and Delayed Fluorescence

Development of highly efficient circularly polarized organic light‐emitting diodes (CPOLEDs) has gained increasing interest as they show improved luminous efficiency and high contract 3D images in OLED displays. In this work, a series of binaphthalene‐containing luminogenic enantiomers with aggregation‐induced emission (AIE) and delayed fluorescence properties is designed and synthesized. These molecules can emit from green to red light depending on the solvent polarity due to the twisted intramolecular charge transfer effect. However, their solid powders show bright light emissions, demonstrating a phenomenon of AIE. All the molecules exhibit Cotton effects and circularly polarized luminescence in toluene solution and films. Multilayer CPOLEDs using the doped and neat films of the molecules as emitting layers are fabricated, which exhibit high external quantum efficiency of up to 9.3% and 3.5% and electroluminescence dissymmetry factor (g_EL) of up to +0.026/?0.021 and +0.06/?0.06, respectively. Compared with doped CPOLEDs, the nondoped ones show higher g_EL and much smaller current efficiency roll‐off due to the stronger AIE effect. By altering the donor unit, the electroluminescence maximum of the doped film can vary from 493 to 571 nm. As far as it is known, this is the first example of efficient CPOLEDs based on small chiral organic molecules.     

Creation of Bifunctional Materials: Improve Electron‐Transporting Ability of Light Emitters Based on AIE‐Active 2,3,4,5‐Tetraphenylsiloles

2,3,4,5‐Tetraphenylsiloles are excellent solid‐state light emitters featured aggregation‐induced emission (AIE) characteristics, but those that can efficiently function as both light‐emitting and electron‐transporting layers in one organic light‐emitting diode (OLED) are much rare. To address this issue, herein, three tailored n‐type light emitters comprised of 2,3,4,5‐tetraphenylsilole and dimesitylboryl functional groups are designed and synthesized. The new siloles are fully characterized by standard spectroscopic and crystallographic methods with satisfactory results. Their thermal stabilities, electronic structures, photophysical properties, electrochemical behaviors and applications in OLEDs are investigated. These new siloles exhibit AIE characteristics with high emission efficiencies in solid films, and possess lower LUMO energy levels than their parents, 2,3,4,5‐tetraphenylsiloles. The double‐layer OLEDs [ITO/NPB (60 nm)/silole (60 nm)/LiF (1 nm)/Al (100 nm)] fabricated by adopting the new siloles as both light emitter and electron transporter afford excellent performances, with high electroluminescence efficiencies up to 13.9 cd A^–1, 4.35% and 11.6 lm W^–1, which are increased greatly relative to those attained from the triple‐layer devices with an additional electron‐transporting layer. These results demonstrate effective access to n‐type solid‐state emissive materials with practical utility.     

Bacterium‐Templated Polymer for Self‐Selective Ablation of Multidrug‐Resistant Bacteria

The recognition and inactivation of specific pathogenic bacteria remain an enormous scientific challenge and an important therapeutic goal. Therefore, materials that can selectively target and kill specific pathogenic bacteria, without harming beneficial strains are highly desirable. Here, a material platform is reported that exploits bacteria as a template to synthesize polymers with aggregation‐induced emission (AIE) characteristic by copper‐catalyzed atom transfer radical polymerization for self‐selective killing of the bacteria that templates them with no antimicrobial resistance. The bacteria‐templated polymers show very weak fluorescence in aqueous media, however, the fluorescence is turned on upon recognition of the bacteria used as the template to synthesize the polymer even at a low concentration of 600 ng mL^?1. Moreover, the incorporated AIE fluorogens (AIEgens) can act as an efficient photosensitizer for reactive oxygen species (ROS) generation after bacteria surface binding, which endows the templated polymers with the capability for selective bacterial killing. The bacterium‐templated synthesis is generally applicable to a wide range of bacteria, including clinically isolated multidrug‐resistant bacterial strains. It is envisioned that the bacterium‐templated method provides a new strategy for bacteria‐specific diagnostic and therapeutic applications.     

Fluorescent Protein Nanovessels: A New Platform to Generate Bio–Abiotic Hybrid Materials for Bioimaging

In this report, a new platform to generate fluorescent protein nanovessels is described. Based on systemic analyses and reconstitution experiments, a combination of protein scaffold and organic dye is identified. Briefly, certain proteins such as bovine serum albumin (BSA) can rapidly form cube‐like scaffold upon heating. This protein scaffolds intrinsically interact with nonfluorescent dyes such as bromophenol blue (BPB), forming BSA‐BPB nanocubes (BBNCs). Moreover, it turns out that the commercially available dye BPB contains aggregation‐induced emission (AIE) properties, allowing the BBNCs emissive upon irradiation. The fluorescent protein nanovessels are highly biocompatible and can be readily internalized by different type of cells. The fluorescent signal of the materials is well‐penetrable from mouse tissues and can be detected at near‐infrared region, making it a useful tool for various biological imaging studies. This platform for making fluorescent protein nanovessels is green, rapid, and cost‐effective and can be extended to other protein scaffolds and possibly other dye/AIE molecules.     

Mechanistic Study on High Efficiency Deep Blue AIE‐Based Organic Light‐Emitting Diodes by Magneto‐Electroluminescence

Aggregation‐induced emission (AIE) materials are highly attractive because of their excellent properties of high efficiency emission in nondoped organic light‐emitting diodes (OLEDs). Therefore, a deep understanding of the working mechanisms, further improving the electroluminescence (EL) efficiency of the resulting AIE‐based OLEDs, is necessary. Herein, the conversion process from higher energy triplet state (T₂) to the lowest singlet state (SS₁) is found in OLEDs based on a blue AIE material, 4′‐(4‐(diphenylamino)phenyl)‐5′‐phenyl‐[1,1′:2′,1′′‐terphenyl]‐4‐carbonitrile (TPB‐AC), obviously relating to the device efficiency, by magneto‐EL (MEL) measurements. A special line shape with rise at low field and reduction at high field is observed. The phenomenon is further clarified by theoretical calculations, temperature‐dependent MELs, and transient photoluminescence emission properties. On the basis of the T₂‐S₁ conversion process, the EL performances of the blue OLEDs based on TPB‐AC are further enhanced by introducing a phosphorescence doping emitter in the emitting layer, which effectively regulates the excitons on TPB‐AC molecules. The maximum external quantum efficiency (EQE) reaches 7.93% and the EQE keeps 7.57% at the luminance of 1000 cd m^?2. This work establishes a physical insight for designing high‐performance AIE materials and devices in the future.     

Bright and Photostable Organic Fluorescent Dots with Aggregation‐Induced Emission Characteristics for Noninvasive Long‐Term Cell Imaging

Efficient long‐term cell tracing in a noninvasive and real‐time manner is of great importance to understand genesis, development, invasion, and metastasis of cancerous cells. Cell penetrating organic dots with aggregation‐ induced emission (AIE) characteristics are successfully developed as long‐term cell trackers. The AIE dots enjoy the advantages of high emission efficiency, large Stokes shift, good biocompatibility, and high photostability, which ensure their good performance in long‐term non‐invasive in vitro cell tracing. Moreover, it is the first report that AIE dots exhibit certain permeability to cellular nucleus, making them attractive potential candidates for nucleus imaging. The AIE dots display superior performance compared to their counterparts of inorganic quantum dots, opening a new avenue in the development of fluorescent probes for monitoring biological processes.     

Plasmon‐Enhanced Fluorescent Sensor based on Aggregation‐Induced Emission for the Study of Protein Conformational Transformation

The alteration in protein conformation not only affects the performance of its biological functions, but also leads to a variety of protein‐mediated diseases. Developing a sensitive strategy for protein detection and monitoring its conformation changes is of great significance for the diagnosis and treatment of protein conformation diseases. Herein, a plasmon‐enhanced fluorescence (PEF) sensor is developed, based on an aggregation‐induced emission (AIE) molecule to monitor conformational changes in protein, using prion protein as a model. Three anthracene derivatives with AIE characteristics are synthesized and a water‐miscible sulfonate salt of 9,10‐bis(2‐(6‐sulfonaphthalen‐2‐yl)vinyl)anthracene (BSNVA) is selected to construct the PEF–AIE sensor. The sensor is nearly non‐emissive when it is mixed with cellular prion protein while emits fluorescence when mixed with disease‐associated prion protein (PrP^Sc). The kinetic process of conformational conversion can be monitored through the fluorescence changes of the PEF–AIE sensor. By right of the amplified fluorescence signal, this PEF–AIE sensor can achieve a detection limit 10 pM lower than the traditional AIE probe and exhibit a good performance in human serum sample. Furthermore, molecular docking simulations suggest that BSNVA tends to dock in the β‐sheet structure of PrP by hydrophobic interaction between BSNVA and the exposed hydrophobic residues.     

Molecular Engineering to Boost AIE‐Active Free Radical Photogenerators and Enable High‐Performance Photodynamic Therapy under Hypoxia

The severe hypoxia in solid tumors and the vicious aggregation‐caused fluorescence quenching (ACQ) of conventional photosensitizers (PSs) have limited the application of fluorescence imaging‐guided photodynamic therapy (PDT), although this therapy has obvious advantages in terms of its precise spatial–temporal control and noninvasive character. PSs featuring type I reactive oxygen species (ROS) based on free radicals and novel aggregation‐induced emission (AIE) characteristics (AIE‐PSs) could offer valuable opportunities to resolve the above problems, but molecular engineering methods are rare in previous reports. Herein, a strategy is proposed for generating stronger intramolecular charge transfer in electron‐rich anion‐π⁺ AIE‐active luminogens (AIEgens) to help suppress nonradiative internal conversion and to promote radiative and intersystem crossing to boost free radical generation. Systematic and detailed experimental and theoretical calculations prove the proposal herein: the electron‐donating abilities are enhanced in collaborative donors, and the AIE‐PSs exhibit higher performance in near‐infrared fluorescence imaging‐guided cancer PDT in vitro/vivo. This work serves as an important reference for the design of AIE‐active free radical generators to overcome the ACQ and tumor hypoxia challenges in PDT.