Aggregation-induced Emission Units Research Articles

Molecular engineering of AIE-active boron clustoluminogens for enhanced boron neutron capture therapy.

The development of boron delivery agents bearing an imaging capability is crucial for boron neutron capture therapy (BNCT), yet it has been rarely explored. Here we present a new type of boron delivery agent that integrates aggregation-induced emission (AIE)-active imaging and a carborane cluster for the first time. In doing so, the new boron delivery agents have been rationally designed by incorporating a high boron content unit of a carborane cluster, an erlotinib targeting unit towards lung cancer cells, and a donor-acceptor type AIE unit bearing naphthalimide. The new boron delivery agents demonstrate both excellent AIE properties for imaging purposes and highly selective accumulation in tumors. For example, at a boron delivery agent dose of 15 mg kg-1, the boron amount reaches over 20 μg g-1, and both tumor/blood (T/B) and tumor/normal cell (T/N) ratios reach 20-30 times higher than those required by BNCT. The neutron irradiation experiments demonstrate highly efficient tumor growth suppression without any observable physical tissue damage and abnormal behavior in vivo. This study not only expands the application scopes of both AIE-active molecules and boron clusters, but also provides a new molecular engineering strategy for a deep-penetrating cancer therapeutic protocol based on BNCT.

Furan‐modified thiadiazolo quinoxaline as an electron acceptor for constructing second near‐infrared aggregation‐induced emission fluorophores for beyond 1300 nm fluorescence/photoacoustic imaging and photothermal therapy

AbstractCreation of new fluorophores is important for understanding the structure–property relationship, by which the required optical properties are likely to be attained. Herein, through theory calculation, it is found that furan‐modified thiadiazolo quinoxaline acting as an electron acceptor can endow donor–acceptor–donor (D–A–D) type second near‐infrared (NIR‐II) fluorophores with longer emission wavelength than the other thiadiazolo quinoxaline‐based acceptors containing pyridine, pyrrole, thiophene, and phenyl groups, respectively. On the basis of this theoretical prediction, a D–A–D type NIR‐II fluorophore with 6,7‐di(furan‐2‐yl)‐[1,2,5]thiadiazolo[3,4‐g] quinoxaline (DFTQ) as the acceptor and dithieno[3,2‐b:2′,3′‐d]pyrrole (DTP) as the donor is designed and synthesized, and the aggregation‐induced emission (AIE) function is further achieved by introducing the AIE units of tetraphenylethylene (TPE) and triphenylamine (TPA), respectively, totally forming three NIR‐II fluorophores DFTQ–DTP, DFTQ–DTPE, and DFTQ–DTPA. For biological applications, the fluorophores are encapsulated by amphiphilic DSPE–PEG2000 to generate water‐dispersible nanoparticles (NPs). Almost the whole emission of each of the NPs falls into the NIR‐II spectral range, with part emission beyond 1300 nm. By using DFTQ–DTPA NPs as the contrast and photothermal therapy (PTT) agent, high‐resolution in vivo fluorescence imaging is achieved in the greater than 1300 nm window, and their good performance in photoacoustic imaging and high tumor PTT efficacy in tumor‐bearing mice are also demonstrated. Taken together, this work mainly provides a strong electron acceptor for constructing long‐emitting fluorophores, and by using the electron acceptor, a AIE fluorophore with desirable quantum yield (QY) and photothermal conversion efficienciy (PCE) is synthesized and demonstrated to be promising in fluorescence/photoacoustic imaging and PTT.

Dextran-Cholesterol Carrier Encapsulated Efficient Photosensitizer for the Photodynamic Killing of Cancer Cells.

Selective photodynamic therapy (PDT) for cancer cells is more efficient and much safer. Most selective PDTs are realized by antigene-biomarker or peptide-biomarker interactions. Here, we modified dextran with hydrophobic cholesterol as a photosensitizer carrier to selectively target cancer cells, including colon cancer cells, and fulfilled selective PDT. The photosensitizer was designed with regular Aggregation-Induced Emission (AIE) units, including triphenylamine and 2-(3-cyano-4,5,5-trimethylfuran-2-ylidene)propanedinitrile. The AIE units can help to decrease the quenching effect in the aggregate state. The efficiency of the photosensitizer is further improved via the heavy atom effect after bromination modification. We found that the obtained photosensitizer nanoparticles could selectively target and ablate cancer cells after encapsulation into the dextran-cholesterol carrier. This study indicates that the polysaccharide-based carrier may have potential for cancer-targeting therapy beyond expectations.

Discriminative Detection of Aliphatic, Electron‐Rich and Electron‐Deficient Aromatic Volatile Organic Contaminants Using Conjugated Polymeric Fluorescent Nanoaggregates with Aggregation Induced Emission Characteristics

AbstractDiscrimination of aromatic, aliphatic volatile organic compounds (VOCs) with high sensitivity and easy operational techniques is important due to related environmental implications. Herein the development of fluorescent conjugated polymers is reported, consisting of donor–acceptor pairs and their nanoaggregates as fluorophores with differential emission behavior in the presence of aromatic, aliphatic VOCs and electron‐deficient VOCs both in aqueous solution and solid state. The polymeric network consists of fluorene moiety with dangling alkyl groups as donors and aggregation‐induced emission (AIE) active tetraphenylethylene (TPE) unit as an acceptor. The corresponding fluorescent nanoaggregates exhibit enhancement in the emission intensity owing to restriction in intramolecular motion of AIE unit in the presence of aliphatic VOCs, whereas the fluorescence enhancement is accompanied by a bathochromic shift in emission maxima in the case of aromatic VOCs owing to the conformational change in the phenyl rings of TPE unit. On the other hand, the fluorescence of nanoaggregates quenches in the presence of an electron‐deficient VOC through a possible nonradiative electron transfer. Detailed mechanistic studies are corroborated through a variety of spectroscopic, density functional theory calculations, and theoretical simulations. The discriminatory response of the polymeric nanoaggregates toward a different kind of VOCs can also be observed visually in the thin‐film state.

Polymer-based chemical-nose systems for optical-pattern recognition of gut microbiota.

Gut-microbiota analysis has been recognized as crucial in health management and disease treatment. Metagenomics, a current standard examination method for the gut microbiome, is effective but requires both expertise and significant amounts of general resources. Here, we show highly accessible sensing systems based on the so-called chemical-nose strategy to transduce the characteristics of microbiota into fluorescence patterns. The fluorescence patterns, generated by twelve block copolymers with aggregation-induced emission (AIE) units, were analyzed using pattern-recognition algorithms, which identified 16 intestinal bacterial strains in a way that correlates with their genome-based taxonomic classification. Importantly, the chemical noses classified artificial models of obesity-associated gut microbiota, and further succeeded in detecting sleep disorder in mice through comparative analysis of normal and abnormal mouse gut microbiota. Our techniques thus allow analyzing complex bacterial samples far more quickly, simply, and inexpensively than common metagenome-based methods, which offers a powerful and complementary tool for the practical analysis of the gut microbiome.

Chiral assembly of organic luminogens with aggregation-induced emission.

Chirality is important to chemistry, biology and optoelectronic materials. The study on chirality has lasted for more than 170 years since its discovery. Recently, chiral materials with aggregation-induced emission (AIE) have attracted increasing interest because of their fascinating photophysical properties. In this review, we discussed the recent development of chiral materials with AIE properties, including their molecular structures, self-assembly and functions. Generally, the most effective strategy to design a chiral AIE luminogen (AIEgen) is to attach a chiral scaffold to an AIE-active fluorophore through covalent bonds. Moreover, some propeller-like or shell-like AIEgens without chiral units exhibit latent chirality upon mirror image symmetry breaking. The chirality of achiral AIEgens can also be induced by some optically active molecules through non-covalent interactions. The introduction of an AIE unit into chiral materials can enhance the efficiency of their circularly polarized luminescence (CPL) in the solid state and the dissymmetric factors of their helical architectures formed through self-assembly. Thus, highly efficient circularly polarized organic light-emitting diodes (CPOLEDs) with AIE characteristics are developed and show great potential in 3D displays. Chiral AIEgens are also widely utilized as “turn on” sensors for rapid enantioselective determination of chiral reagents. It is anticipated that the present review can entice readers to realize the importance of chirality and attract much more chemists to contribute their efforts to chirality and AIE study.

Restriction of Conformation Transformation in Excited State: An Aggregation-Induced Emission Building Block Based on Stable Exocyclic C=N Group.

SummaryThe development of aggregation-induced emission (AIE) building block and deciphering its luminescence mechanism are of great significance. Here a feasible strategy for the construction of AIE unit based on E-Z isomerization (EZI) of exocyclic C=N double bond is proposed. Taking [1,2,4]thiadiazole[4,3-a]pyridine (TZP) derivative as an example, its aryl-substituted derivative (TZPP) shows obvious AIE character. The analysis of spectral data and theoretical calculations indicates that fast structural relaxation of TZPP in the emissive state plays a key role in a low fluorescence quantum yield in dilute solution, which should be caused by the small energy gap between locally excited (LE) state and twisted intramolecular charge transfer state. When in solid state, the bright emission with LE state characteristic reappears due to the large shift barrier of geometry transformation. As a potential building block for AIEgens with special heterocyclic structure, these findings would open up opportunities for developing various functional materials.

Novel triazole-based AIE materials: Dual-functional, highly sensitive and selective fluorescence probe

Two novel aggregation-induced emission (AIE) blue-emission materials 4-N-(naphthalen-l-yl)-3,5-bis(4-diphenylamine) phenyl-4H-1,2,4-triazole (TPA-TAZ-TPA) and 4-N-(naphthalen-l-yl)-3-(4-diphenlamin)phenyl-4H-1,2,4-triazole (TPA-TAZ-Ph) were designed and synthesized. TPA-TAZ-TPA is a donor (D) - acceptor (A) - D type molecule, and TPA-TAZ-Ph is a D-A type molecule. Even both of them had not typical AIE units, they still possessed excellent AIE properties. Further, their spin-coated films were used as the fluorescence film probes for DNT vapor with rapid response, high sensitivity and selectivity. Additionally, they exhibited significant fluorescence quenching and color responses toward Fe3+ in aqueous solution, which suggested them fluorometric/colorimetric dual-channel probe to Fe3+.

Tetraphenylpyrazine Based AIE Luminogens: Unique Excited State Decay and Its Application in Deep‐Blue Light‐Emitting Diodes

AbstractCarbazole‐modified tetraphenylpyrazine (TPP) derivatives TPP‐Cz, TPP‐PhCz, TPP‐2Cz, and TPP‐2PhCz are prepared with different patterns by inserting a π‐bridge and adopting two‐armed forms to produce aggregation‐induced emission (AIE)‐type deep‐blue emitters for organic light‐emitting diode (OLED) applications. Systematic spectral analysis and detailed theoretical calculation of these TPP derivatives reveal their special excited state behaviors. Unlike the traditional AIE unit, which features enhanced emission from solution to aggregate with the nonradiative decay channel blocked, a tenfold increase in the radiative decay rate of these TPP‐based AIE luminogens (AIEgens) is observed from the solution to film states. The formation of a stable quinone conformation of the TPP center and its peripheral phenyl group in the excited state is the main reason for this behavior. The distribution changes in the total reorganization energy are further integrated, and a feasible molecular design strategy is proposed for the TPP family. Nondoped OLEDs are fabricated, and the AIEgens exhibit good performance with valuable blue emission (x + y < 0.3). The TPP‐Cz‐based optimized devices exhibit more stable external quantum efficiencies and an ideal roll‐off with unchanged Commission Internationale de l'Elcairage (CIE) coordinates of (0.16, 0.11). These findings demonstrate the great potential of TPP with its unique excited state characteristics as a deep‐blue AIEgen.

A rapid-response fluorescent film probe to DNT based on novel AIE materials

New aggregation-induced emission (AIE) materials 4 - (3, 5- bis (4′-(1, 2, 2-triphenylvinyl)-[1, 1′-biphenyl]-4-yl)-4H-1, 2, 4-triazol-4-yl)-N, N-diphenylaniline (BTT) and 9-(4-(3, 5-bis(4′-(1, 2, 2-triphenylvinyl)-[1, 1′-biphenyl]-4-yl)- 4H-1, 2, 4-triazol-4-yl) phenyl)-9H-carbazole (BPT) are designed and synthesized, which contain triazole, tetraphenylethylene and electron donating units. Further, their spin-coated films are used as fluorescent probes to detect 2, 4-dinitrotoluene (DNT) vapor with rapid fluorescence response, high sensitivity, high selectivity and reutilization. Moreover, by comparing BTT and BPT with other similar molecules without AIE properties, the extrusive sensing performances of BTT and BPT can be attributed to the introduction of AIE units.

Recent Application Progress on Aggregation-Induced Emission

Luminescence of conventional fluorophores often becomes weakened or quenched at high concentration or solid state. In contrast, some are non-luminescent in solution but highly emissive in the aggregate or solid state, so called “aggregation-induced emission (AIE)”, which might be resulted from the restriction of intramolecular rotation (RIR) and changes in aggregate morphology. Herein, the latest progress on AIE since 2008 is reviewed, such as: (i) developing chemoor bio-sensors for detecting ions, gas, small molecules, explosives, proteins, enzymes and so on; (ii) incorporating the AIE unit to realize highly luminescent solid emitters, especially for OLEDs (organic light-emitting diodes); (iii) tuning the aggregation morphology to construct reversible multi-responsive materials stimulated by pressure, heat or solvent vapor; (iv) due to the biocompatibility of aggregate nanoparticles, developing hybrid materials including fluorescent silica nanoparticles, polymeric micelles and electrolytes for applications in cell imaging, structure analysis and bioassay.

Fluorescent detection of heparin by a cationic conjugated polyfluorene probe containing aggregation-induced emission units

A novel conjugated cationic polyfluorene containing aminated tetraphenylethene (ATPE) unit is developed as a sensitive and selective fluorescence probe for heparin detection based on the combination of aggregation-induced emissive property of the ATPE units and the FRET process from the blue-emissive polyfluorene segments to the yellow-emissive ATPE units. The addition of anionic heparin will lead to the formation of heparin/polymer complexes, and turn on the aggregation-induced yellow emission of the ATPE units. A good linear relationship is found between the yellow emission intensity of the ATPE units and the heparin concentrations with a limit of detection of 30 nM in aqueous buffer.