Aggregation-induced Emission Materials Research Articles

Sustainable aggregation-induced emission material based on pectin-l-lysine: Potential antibacterial and monitoring in food spoilage

The demand of smart food detection system which in detecting food spoilage is increasing. In this work, a new type of aggregation-induced emission (AIE) compound was synthesized based on pectin (P) and l-lysine (Lys). P-Lys is an AIE active compound which has the advantages of simple synthesis, easy modification and processability, it also has good water solubility and biocompatibility. Moreover, P-Lys has potential application in detecting Fe3+ (oxidation from Fe2+) and bacterial in monitoring pork spoilage. In addition, P-Lys also has spectral antibacterial properties which can prevent pork spoilage. The research results shown that P-Lys, as a new type of food testing agent has a useful future in monitoring and protecting the freshness of food.

Y‐Shaped Pyrene‐Based Aggregation‐Induced Emission Blue Emitters for High‐Performance OLED Devices

AbstractThe proposed concept of aggregation‐induced emission (AIE) has offered an efficient strategy to design high‐performance luminescent materials. Herein, three blue emitters containing a pyrene core decorated with either triphenylamine or tetraphenylethylene units are presented. The designed compoundsPy‐TPAandPy‐2TPEare AIE or active materials with blue emission from 464 to 478 nm in the solid state, whereasPy‐2TPAis not. Moreover, the enhanced thermal stability of compoundsPy‐TPAandPy‐2TPEallows for their utilization as emitter layers for the fabrication of blue organic light‐emitting diode (OLED) devices. The devices exhibit excellent electroluminescence emission with maximum λmax emin the range 456–482 nm with a maximum external quantum efficiency of 7.27%, high exciton utilization efficiency (77.3%), and low turn‐on voltage (≤3.1 V), as well as low‐efficiency roll‐off. Theoretical calculations reveal that the high exciton utilization efficiency (ƞr) originates from the triplet excitons at T2to the lowest single excited (S1) state via a reverse intersystem crossing process following the principle of the “hot exciton” mechanism. This article not only provides powerful evidence revealing the advantages of pyrene‐based AIEgens for OLED applications, but also offers a new approach for designing pyrene‐based “hot exciton” materials for next‐generation OLEDs.

H2O brace molecules to slip stack: Transform ACQ to AIE for latent fingerprints recognition

Aggregation-induced emission (AIE) materials have received a lot of attention in recent years, however, it remains a great challenge to develop a facile method for the conversion of aggregation-caused quenching (ACQ) molecules to AIE. In this paper, the ACQ molecule, 3,5-diacetyl-1,4-dihydro-2,6-lutidine (DDL), is successfully transformed from face-to-face stacking to slip stacking under the induction of H2O, achieving the transformation of ACQ molecule to AIE. Experimental analysis and theoretical calculations show that H2O is inserted into DDL molecules through hydrogen bonds, and its spatial configuration makes an angle between the H2O and DDL planes, thus increasing the horizontal and vertical distances between adjacent DDL molecules, so that DDL is arranged in a slip stacking pattern. Meanwhile, hydrogen bonds fix the DDL molecules in a relatively rigid structure, leading to the generation of other weak interactions, which further restrict the molecular motion and reduce the non-radiative transitions, so that the DDL possesses the AIE property, and the quantum yield increases from 0.95 % to 25.60 %. Based on the high fluorescence intensity of DDL-H2O, it has been successfully applied to the first-, second- and tertiary-level structures of latent fingerprints (LFPs) identification, which provides more possibilities for the practical application of ACQ molecules.

Natural products with aggregation-induced emission properties: from discovery to their multifunctional applications

<p indent="0mm">Aggregation-induced emission (AIE) materials derived from natural products have the advantages of non-synthetic, good biocompatibility, natural degradation and pharmacological activity, and are gradually becoming a powerful tool in environmental monitoring, biological imaging and disease diagnosis. Here, we review AIE materials discovered from natural products, including alkaloids such as berberine, flavonoid polyphenols such as quercetin, non-flavonoid polyphenols such as tannic acid, and other natural compounds such as saponins and vitamins. AIE mechanisms of these materials include restriction of intramolecular/intermolecular motion (RIM), torsional intramolecular charge transfer (TICT), excited state intramolecular proton transfer (ESIPT), J-aggregate and clusterization-triggered emission (CTE). Based on remarkable AIE properties, these natural products show great potential in the fields of pH, ion and biomarker sensing, cell imaging and biological diagnosis and treatment. This paper is expected to deepen the understanding of aggregation-induced luminescence, inspire the exploration of AIE molecules from natural products and develop new applications.

Aggregation-induced emission of active nanoparticles based on konjac glucomannan: Fabrication, properties, and applications

Recently, the design of aggregation-induced emission (AIE) materials with good water-solubility and biocompatibility has attracted much attention. In this work, amphiphilic AIE-active nanoparticles (KGM-TPE) were synthesized by a facile Schiff base condensation of oxidized konjac glucomannan with amino-tetraphenylethylene. The final KGM-TPE had good water dispersibility and could self-assemble into nanoparticles with average diameters ranging from 100 to 200 nm. A cytotoxicity test showed that the cell survival was approximately 90% even when the concentration of KGM-TPE reached 150 μg/mL, indicating that KGM-TPE possessed good biocompatibility. In addition, the excellent cell imaging and good anti-counterfeiting function results of KGM-TPE indicated that this material has great potential in the fields of biomedicine and anti-counterfeiting.

Preparation of AIE Functional Single-Chain Polymer Nanoparticles and Their Application in H2 O2 Detection through Intermolecular Heavy-Atom Effect.

Single-chain polymer nanoparticles (SCNPs) are soft matter constructed by intrachain crosslinks, with promising prospects in detection and catalysis. Herein, a fluorescent core (SCNPs) with aggregation-induced emission (AIE) is prepared, applying for H2 O2 detection through intermolecular heavy-atom effect. In detail, the SCNPs precursors are synthesized by ring-opening copolymerization. Then the SCNPs are prepared by intramolecularly cross-linking via olefin metathesis. Imitating the structure of AIE dots, SCNPs are encapsulated by H2 O2 -responsive polymers. Probably due to the stable secondary structure of SCNPs, the obtained micelles show stable fluorescence performance. Furthermore, as the heavy-atom, tellurium is introduced into the carriers to construct the heavy-atom effect. In this micelle-based system, the SCNPs act as the fluorescent core, and the stimuli-responsive polymer acts as the carrier and the fluorescent switch. The hydrophilicity of the tellurium-containing segment is affected by the concentration of H2 O2 , resulting in a change in the distance from the SCNPs, which ultimately leads to a change in the fluorescence intensity. Furthermore, tellurium is particularly sensitive to H2 O2 , which can detect low concentrations of H2 O2 . The SCNPs are merged with AIE materials, with the hope of exploring new probe designs.

Blue light-emitting electrochemical cells incorporating aggregation-induced emission small molecules

The light-emitting electrochemical cells (LECs) have received extensive attention from researchers in recent years due to their simple single-layer structure, air-stable metal electrodes, and low manufacturing cost. So far, reports on the use of LEC active layer emitter materials have mainly focused on ionic transition metal complexes (iTMCs) and conjugated polymers (CPs). The application of the above materials in blue LECs is restricted due to high cost, complicated synthesis process, and poor stability, which results in the slow development of blue LECs. A novel blue LECs device based on aggregation-induced emission (AIE) small molecule (2,3-diphenylbenzo[b]thiophene S, S-sulfur dioxide, DP-BTO) with a peak luminance of 36.58 cd/m2, a CEmax of 1.14 cd/A, and an EQEmax of 0.46% was reported in this work. The blue light emission centered at ~460 nm was exhibited at a voltage above 6 V. This work successfully constructed blue light-emitting LECs devices based on AIE materials, opening up a new research avenue for the application of AIE materials in the field of thin-film device development.

Chitosan-salicylide Schiff base with aggregation-induced emission property and its multiple applications

Aggregation-induced emission (AIE) active compounds are fascinated due to their unique properties of limiting intramolecular rotation, and they have been developed in the biomedical fields. In this work, AIE material based on the Schiff base compound of chitosan (Cs) and salicylaldehyde (SA) was designed and synthesized. Cs-SA emits weak light in dilute aqueous solution, and emits bright light in concentrated solution and solid, showing obvious AIE performance. In addition, Cs-SA can also be used as a biosensor to detect Fe3+, and Cu2+, it has good bioimaging behavior. In addition, it can also be used as biosensor to quantitatively detect gram-positive bacteria and gram-negative bacteria, Moreover, Cs-SA shows excellent broad spectrum antibacterial performance in inhibiting E. coli and S. aureus.

Photo‐Enhanced‐Coordination Triggered Unprecedented Bistable AIE for Long‐Term Optical Memories

AbstractPhoto‐triggered chromism has emerged as critically important in materials for advanced soft photonic devices. The conventional photochromic units with reversible color change between two isomers are unstable either thermally or photochemically, which is an important challenge for long‐standing optical devices. Here, a novel photo‐enhanced coordination mechanism leading to stable chromism is reported. Upon tethering the aggregation‐induced emission (AIE) moiety diphenyldibenzofulvene (PBF) to a dicarboxylic pyridine group, photo‐irradiation triggers the coordination transition between the carbonate groups and Mg2+ from bidentate to the more stable bridging mode, which further influences the conformation of the remote PBF group, leading to transition of the emission color from cyan to yellow. Under ambient conditions, both coordinating isomers display excellent thermal and photochemical stability. As a result, the photo writings on the films based on the coordinating AIE materials exhibit the long‐term stability, which barely fades even upon heating, vapor fuming, or day‐light exposure. This photo‐enhanced‐coordination enabled bistable chromism is expected to open a new vista in the study of chromism and high durable optical memories.

Aggregation-Induced Emission Boosting the Study of Polymer Science.

The past one hundred years have witnessed the great development of polymer science. The advancement of polymer science is closely related with the development of characterization techniques and methods, from viscometry in molecular weight determination to advanced techniques including differential scanning calorimetry, nuclear magnetic resonance, and scanning electron microscopy. However, these techniques are normally constrained to tedious sample preparation, high costs, harsh experimental conditions, or ex situ characterization. Fluorescence technology has the merits of high sensitivity and direct visualization. Contrary to conventional aggregation-causing quenching fluorophores, those dyes with aggregation-induced emission (AIE) characteristics show high emission efficiency in aggregate states. Based on the restriction of intramolecular motions for AIE properties, the AIE materials are very sensitive to the surrounding microenvironments owing to the twisted propeller-like structures and therefore offer great potential in the study of polymers. The AIE concept has been successfully used in polymer science and provides a deeper understanding on polymer structure and properties. In this review, the applications of AIEgens in polymer science for visualizing polymerization, glass transition, dissolution, crystallization, gelation, self-assembly, phase separation, cracking, and self-healing are exemplified and summarized. Lastly, the challenges and perspectives in the study of polymer science using AIEgens are addressed.

Maltose: A natural disaccharide with aggregation-induced emission and room temperature phosphorescence and its multiple applications

In this study, a novel aggregation-induced emission (AIE) material of maltose (mal) was found. Due to mal has various oxygen clusters with a sufficiently rigid conformation, which makes the clustering-triggered emission (CTE) mechanism more rational. Since Fe3+ can quench the fluorescence of mal, thus, mal can be used as a biosensor to detect Fe3+. Furthermore, mal has room temperature phosphorescence. So, mal has broad application prospects in anti-counterfeiting display. In addition, due to mal is excitation-dependent, it can also be used as a three-color bioimaging.

Nanoconfinement of tetraphenylethylene in zeolitic metal-organic framework for turn-on mechanofluorochromic stress sensing

Mechanofluorochromic materials are of great significance for the fabrication of innovative sensors and optoelectronics. However, efficient mechanofluorochromic materials are rarely explored due to the deficiency of existing design strategies. Here, we demonstrate the incarceration of aggregation-induced emission (AIE) materials within metal-organic framework (MOF) single crystals to construct a composite system with turn-on mechanofluorochromism. A new type of AIE@MOF material was designed: integrating a zeolitic MOF (ZIF-71) and tetraphenylethylene (TPE, a topical AIE material) to generate a TPE@ZIF-71 system with exceptional turn-on type mechanofluorochromism. Using terahertz vibrational spectroscopy, we show the unique fluorochromism mainly emanates from the enhanced nanoconfinement effect exerted by ZIF-71 host on TPE guest under pressure. Compared with pure TPE, we demonstrate the nanoconfinement in AIE@MOF not only changes the TPE's turn-off type sensing behavior to a turn-on type, but boosts the original sensitivity markedly by tenfold. Significantly, because ZIF-71 prevents the spontaneous recrystallization of TPE upon unloading, this allows TPE@ZIF-71 to record the stress history. This is the first demonstration of the Guest@MOF system combining the concepts of AIE and MOF; its promising properties and potential engineering applications will stimulate new directions pertaining to luminescent stress sensors and smart optics.

Restriction of intramolecular torsion induces abnormal blue-shifted fluorescence in the aggregate state

The aggregation-induced emission (AIE) effect and corresponding restriction of intramolecular motions strategy are important mechanisms for regulating the performance of novel organic light-emitting diode materials and constituent molecules, such as emission intensity and peak position. Nevertheless, molecules in the aggregate state usually yield a red-shifted fluorescence due to the π-π interaction enhancement. Here, we report a blue-shifted fluorescence mechanism induced by the restriction of intramolecular torsion in the aggregate state for an interesting excited-state intramolecular proton transfer fluorophore. A combined experimental and theoretical method is performed to investigate the excited state dynamics of the molecules in solvent and the aggregate state respectively. Multiple regression analysis reveals that the changes of reorganization energy caused by AIE effect induce the blue-shifted fluorescence. These findings contribute in several ways to our understanding of the AIE effect, and provide a new strategy to regulate the emission performance of AIE materials.

Construction of Mechanofluorochromic and Aggregation-Induced Emission Materials Based on 4-Substituted Isoquinoline Derivatives.

Although many organic mechanofluorochromic (MFC) materials have been reported, the design strategy and formation mechanism are still unclear, and thus some of their discoveries are based on chance or a result of blind screening of some compounds. Herein, we show a strategy for constructing MFC materials from a multisubstituted isoquinoline compound with excellent crystallinity. The introduction of bromine atom at 4-position realizes the morphological change from crystalline state to amorphous state under the stimulation of external pressure, but it is not enough to generate MFC phenomenon. Similarly, although naphthalene, benzofuran, and benzothiophene endow the resultant isoquinolines with twisted molecular conformations and aggregation-induced emission (AIE) activities, no obvious solid-state emission color changes are observed. However, the introduction of 2-benzylidenemalononitrile and (E)-2-cyano-3-phenylacrylate leads not only to the AIE activities of IQ-M and IQ-A, but also to their outstanding and reversible MFC properties. The MFC activities of these two derivatives are demonstrated to come from more twisted molecular conformations, larger deformation spaces, and stronger intramolecular charge transfer compared with the other isoquinolines. This work offers important reference value for the construction of MFC and AIE materials from traditional fluorophores.

Progress in glycosylated aggregation-induced emission materials

<p indent="0mm">Materials with aggregation-induced emission (AIE) effect have excellent optical properties and are widely utilized in chemical sensing, biological probes and other fields. Since most classic AIE fluorogens are hydrophobic, their application was restricted to some extent. In the past <sc>5 years</sc>, several glycosylated AIE-active fluorescent probes were synthesized by coupling the AIE cores with hydrophilic carbohydrates in our group and were used for detection of various biomolecules based on the special binding and reaction between these probes and analytes. These glycosylated AIE-active fluorescent probes with better water solubility and biocompatibility have low fluorescence background and low biological toxicity. This review summarized the recent progress on the glycosylated AIE-active fluorescent probes, hoping to expand the applications of AIE materials and provide effective tools for biochemistry research.

An unconventional nano-AIEgen originating from a natural plant polyphenol for multicolor bioimaging

Biocompatible aggregation-induced emission (AIE) materials from natural resources are of great interest for a variety of potential applications. Here, we report the unconventional AIE nature of the green tea polyphenol epigallocatechin gallate (EGCG), which is investigated by observing the disappearance and reoccurrence of fluorescence when EGCG is dissolved and recrystallized in aqueous solutions. The intermolecular through-space conjugation and structural rigidification induced by multiple intermolecular H-bonds play critical roles in the AIE phenomenon. This inspires the development of a multicolored, monodisperse, photostable, and non-toxic nano-AIE luminogen (nano-AIEgen), which is simply prepared by polyphenol-amine-based crosslinking in aqueous solutions, demonstrating great potential for living cell bioimaging. Our strategy to develop nano-AIEgens using AIE-active hydrophilic natural products—e.g., plant polyphenols, such as tannic acid, that exhibit similar AIE characteristics—can help push the boundary of the exploration of various novel, large-scale, biocompatible, water-soluble, and degradable AIE materials from natural resources. • AIE phenomenon for EGCG in the solid state • The AIE activity results from through-space conjugation by intermolecular H-bonds • The EGCG nano-AIEgens may be successfully used to image living cells As a plant polyphenol, epigallocatechin gallate is highly soluble in water and non-toxic. Here, Lu et al. demonstrate an interesting AIE phenomenon in common natural products and propose strategies for screening and developing hydrophilic AIEgens from natural products.

Development and application of Diels-Alder adducts displaying AIE properties

Exploring organic reactions to construct novel molecules with aggregation-induced emission (AIE) features is an essential branch of AIE research. The fast-paced application of AIE materials in various disciplines, including photoelectricity, molecular biology, medicine, and materials science, has led to an ever-growing need for new AIE molecules. Unlike the synthesis of most “earlier generations” of AIE fluorogens (AIEgens) that require tedious and harsh reactions, chemists now shift their synthetic focus to a selection of reliable and straightforward reactions. The Diels-Alder reaction has been overlooked in this field. Herein, we report a catalyst-free Diels-Alder reaction between 1,3-diphenylisobenzofuran and a series of electron-deficient alkynes to create AIEgens. Photophysical properties of our synthesized 1,3,4-triphenyl-1,4-dihydro-1,4-epoxynaphthalene (ENAP) derivatives are studied systematically, manifesting their AIE characteristics and structure-fluorescence property relationships. Finally, we highlight the diverse applications of some selected ENAP derivatives in latent fingerprint detection, cell imaging, and bacterial staining.

Tunable Aggregation-Induced Emission Fluorophore with the Assistance of the Self-Assembly of Block Copolymers by Controlling the Morphology and Secondary Conformation for Bioimaging.

Aggregation-induced emission (AIE) luminogens with highly tunable properties show great potential for many applications. In this study, we synthesized a new family of AIE-type poly(ethylene glycol)-block-poly(9-anthrylmethyl lysine) (PEG-b-PLys-An) diblock copolymers by taking advantage of amphiphilic self-assembly and rigid helical backbones. These copolymers can self-assemble into various assemblies through nanoprecipitation methods. The micelles using N,N-dimethylformamide (DMF) as a cosolvent present brighter fluorescence than the vesicles prepared from tetrahydrofuran (THF). We demonstrate that the decreased solubility of copolymers in DMF results in the formation of more compact micelles with more excimer formation during the self-assembly process, while better solvent THF favors the formation of vesicles with stretched core chains. In addition, the secondary conformation of the polypeptide block shows pronounced effects on the fluorescence property. We further show the internalization of the assemblies using two types of cells by cellular uptake experiments. By the delicate design of the block copolymer, we successfully prepare the morphology- and conformation-dependent AIE materials for potential biomedical applications.

Near-infrared aggregation-induced emission nanodots for early diagnosis of tongue squamous cell carcinoma and sentinel lymph node mapping.

Fluorescence imaging has been widely used in the biomedical field owing to its merits of high sensitivity, excellent accuracy, high biosafety, etc. However, despite the good performance of fluorescent materials in the diagnosis of subcutaneous tumors or some orthotopic tumors in mice, their potential clinical application for most orthotopic tumors in humans is still limited due to their weak tissue penetration ability and the high thickness of human tissues. Given that the human tongue can extend out of the mouth and is approximately 1 cm thick, the diagnosis of tongue squamous cell carcinoma (TSCC) by fluorescence has great potential for clinical applications. However, to the best of our knowledge, a few studies have been performed to detect tongue tumors using fluorescence imaging, and most of them are administered in a subcutaneous tumor-bearing mouse model and are based on fluorescent materials with aggregation-caused quenching effects. Herein, by developing DPA-TPE-DCM with intense near-infrared fluorescence emission in the aggregation state, aggregation-induced emission materials were used for the first time in the early diagnosis of orthotopic TSCC and sentinel lymph node (SLN) mapping in an immunocompetent mouse model of orthotopic TSCC with a high signal-to-background ratio of 10.2. Moreover, with the guidance of the fluorescence of DPA-TPE-DCM NPs, SLNs smaller than 2 mm in diameter were successfully excised. This study provides new insight and a method for the early diagnosis of TSCC in clinical practice and provides more possibilities to broaden the potential clinical applications of fluorescent materials.

Cation polymer-induced aggregation of water-soluble Au(I)-thiolate complexes and their photoluminescence properties.

Au(I)-thiolate complexes are a new class of aggregation-induced emission (AIE) material. Here we demonstrate a new aggregation strategy of water-soluble Au(I)-thiolate complexes induced by cationic polymers at optimized pH values. The generated AIE shows longer wavelengths than the emission induced by other methods.