The synthesis of novel AIE emitters with the triphenylethene-carbazole skeleton and para-/meta-substituted arylboron groups and their application in efficient non-doped OLEDs

Four novel aggregation-induced emission (AIE)-active luminogens (p-DPDECZ, p-DBPDECZ, m-DPDECZ and m-DBPDECZ) with triphenylethene-carbazole skeleton and para-/meta-substituted arylboron groups have been synthesized. Their structures are fully characterized using elemental analysis, mass spectrometry and proton nuclear magnetic resonance spectroscopy. The thermal stabilities, photophysical properties, electronic structures, and electrochemical properties of these molecules are investigated systematically using thermal analysis, UV-vis absorption spectroscopy, fluorescence spectroscopy, theoretical calculation and electrochemical methods. The effects of donor–acceptor interaction and conjugation degree on the photoluminescent and electroluminescent properties of these compounds are investigated. The results show that these donor–AIE–acceptor type compounds exhibit good thermal stability and electrochemical stability as well as AIE properties. Non-doped fluorescent OLEDs fabricated by using para-linked p-DPDECZ as an emitting layer emits a green light with a turn-on voltage of 4.8 V, a maximum brightness of 30210 cd m-2 and a maximum current efficiency of 9.96 cd A-1. While the OLED prepared with meta-linked m-DBPDECZ exhibits efficient blue light emission with a maximum current efficiency of 4.49 cd A-1 and a maximum luminance of 16410 cd m-2. The electroluminescence properties of these compounds demonstrate their potential application in OLEDs

AIE-Active Photosensitizers: Manipulation of Reactive Oxygen Species Generation and Applications in Photodynamic Therapy

Photodynamic therapy (PDT) is a non-invasive approach for tumor elimination that is attracting more and more attention due to the advantages of minimal side effects and high precision. In typical PDT, reactive oxygen species (ROS) generated from photosensitizers play the pivotal role, determining the efficiency of PDT. However, applications of traditional PDT were usually limited by the aggregation-caused quenching (ACQ) effect of the photosensitizers employed. Fortunately, photosensitizers with aggregation-induced emission (AIE-active photosensitizers) have been developed with biocompatibility, effective ROS generation, and superior absorption, bringing about great interest for applications in oncotherapy. In this review, we review the development of AIE-active photosensitizers and describe molecule and aggregation strategies for manipulating photosensitization. For the molecule strategy, we describe the approaches utilized for tuning ROS generation by attaching heavy atoms, constructing a donor-acceptor effect, introducing ionization, and modifying with activatable moieties. The aggregation strategy to boost ROS generation is reviewed for the first time, including consideration of the aggregation of photosensitizers, polymerization, and aggregation microenvironment manipulation. Moreover, based on AIE-active photosensitizers, the cutting-edge applications of PDT with NIR irradiated therapy, activatable therapy, hypoxic therapy, and synergistic treatment are also outlined

Interfacial Assembly and Jamming of Soft Nanoparticle Surfactants into Colloidosomes and Structured Liquids

Nanoparticle surfactant (NPS) offers a powerful strategy to generate all-liquid constructs that integrate the inherent properties of the NPs into 3D architectures. Here, using the co-assembly of fluorescent polymeric nanoparticles and amine-functionalized polyhedral oligomeric silsesquioxane, the assembly and jamming behavior of a new type of NPS at the oil-water interface is uncovered. Unlike "solid" inorganic nanoparticles, "soft" polymeric nanoparticles can reorganize when jammed, leading to a relaxation and deformation of the interfacial assemblies, for example, the 3D printed sugar-coated haw stick-like liquid tubules. With NPS serving as emulsifiers, stable Pickering emulsions are prepared that can be converted into robust colloidosomes with pH responsiveness, showing numerous potential applications for encapsulation and controlled release

White-Light Emission of a Binary Light-Harvesting Platform Based on an Amphiphilic Organic Cage

White-light emissive materials with stable photophysical properties are of great importance for their potential applications in information display, fluorescent sensors, and optical-recording systems. Herein, an amphiphilic tetraphenylpyrazine (TPP)-based cage compound (TPP-Cage) was facilely synthesized by reaction of propeller-like TPP with aggregation-induced emission characteristics and triglycol monomethyl ether-substituted triazine. By immobilizing the twisted conformation of TPP, TPP-Cage showed obvious helical chirality in the solution and aggregated state. TPP-Cage emits strong deep blue fluorescence in solution due to the restriction of intramolecular rotation of the TPP unit. Its amphiphilic nature enables it to serve as an excellent light-harvesting platform to encapsulate diketopyrrolopyrrole (DPP) with aggregation-caused quenching effect in its hydrophobic cavity in aqueous medium, forming the DPP@TPP-Cage complex. Such inclusion prevents π–π stacking of DPP enabling it to emit strong yellow-light emission in the aggregated state. Due to the complementary emission colors of TPP-Cage and DPP, DPP@TPP-Cage exhibited stable white-light emission in the aggregated state and poly­(ethylene glycol) film. This work not only introduces a promising strategy for development of chiral compounds through immobilization of propeller-like achiral molecules but also provides a prospective pathway for white-light emission based on supramolecular assembly

A “Simple” Donor-Acceptor AIEgen with Multi-Stimuli Responsive Behavior

At present, there is still an urgent demand for novel smart materials that can achieve a diverse range of practical applications in synthetic material area. Herein, we developed a simple but versatile aggregation-induced emission luminogen (1) with a donor-acceptor structure and pronounced intramolecular charge transfer property. Compound 1 showed a remarkable color change in sensitive response to polarity change making it to serve as a promising imaging probe for detecting environmental polarity in cells and selective visualization of lipid droplets in live tissues. Additionally, this compound exhibited a wide range of thermoresponsive behavior with ratiometric luminescence change and noticeable fluorescence color switching. It also can respond to anisotropic shearing force and isotropic hydrostatic pressure with prominent but contrast luminescence conversion due to the distinct disturbance of the weak intermolecular interactions and charge transfer processes. Meanwhile, compound 1 was sensitive to external electric stimulus and displayed reversibly three-color switched electrochromism and on-to-off electroluminochromism. Such property allowed the fabrication of high-performance non-doped OLED with a high external quantum efficiency of 5.22%. The present results may offer an important guideline for multifunctional molecular design and provide an important step forward to expand the real-life applications of AIE-active smart materials.</p

Metallophilicity-Induced Clusterization: Single-Component White-Light Clusteroluminescence with Stimuli Responses

The single-component white-light-emitting materials play an essential role in the next-generation solid-state lighting technology. Herein, linear gold(I) complex TPPGPA with conglobate trimer configuration trigged by aurophilic interactions in crystalline state was prepared to emit dual phosphorescent white-light emission, which also exhibited multi-stimuli responsive luminescent properties including thermochromism and mechanochromism. Specifically, the molecular packing mode and aurophilic interactions regulation were subtly taken as a functional relationship of the experimental correlation with emission. The results showed that the regulated aurophilic interactions and restriction of molecular motion were determined to be the precipitating factor and as a function of the wavelength and intensity, which is significant for the design guide about intelligent stimuli-responsive white-light emissive luminescent materials. Furthermore, their application in temperature-responsive white-light illumination was successfully demonstrated. </p

Ionization and Anion−π⁺ Interaction: A New Strategy for Structural Design of Aggregation-Induced Emission Luminogens

Recent years have witnessed the significant role of anion−π⁺ interactions in many areas, which potentially brings the opportunity for the development of aggregation-induced emission (AIE) systems. Here, a new strategy that utilized anion−π⁺ interactions to block detrimental π–π stacking was first proposed to develop inherent-charged AIE systems. Two AIE-active luminogens, namely, 1,2,3,4-tetraphenyloxazolium (TPO-P) and 2,3,5-triphenyloxazolium (TriPO-PN), were successfully synthesized. Comprehensive techniques such as single-crystal analysis, theoretical calculation, and conductivity measurement were used to illustrate the effects of anion−π⁺ interactions on the AIE feature. Their analogues tetraphenylfuran (TPF) and 2,4,5-triphenyloxazole (TriPO-C) without anion−π⁺ interactions suffered from the aggregation-caused emission quenching in the aggregate state, demonstrating the important role of anion−π⁺ interactions in suppressing π–π stacking. TriPO-PN was biocompatible and could specifically target lysosome in fluorescence turn-on and wash-free manners. This suggested that it was a promising contrast agent for bioimaging