Aggregation-induced Emission Dye Research Articles

Textile-Based Adsorption Sensor via Mixed Solvent Dyeing with Aggregation-Induced Emission Dyes.

This study demonstrates a novel methodology for developing a textile-based adsorption sensor via mixed solvent dyeing with aggregation-induced emission (AIE) dyes on recycled fabrics. AIE dyes were incorporated into the fabrics using a mixed solvent dyeing method with a co-solvent mixture of H2O and organic solvents. This method imparted unique fluorescence properties to fabrics, altering fluorescence intensity or wavelength based on whether the AIE dye molecules were in an isolated or aggregated state on the fabrics. The precise control of the H2O fraction to organic solvent during dyeing was crucial for influencing fluorescence intensity and sensing characteristics. These dyed fabrics exhibited reactive thermochromic and vaporchromic properties, with changes in fluorescence intensity corresponding to variations in temperature and exposure to volatile organic solvents (VOCs). Their superior characteristics, including a repetitive fluorescence switching property and resistance to photo-bleaching, enhance their practicality across various applications. Consequently, the smart fabrics dyed with AIE dye not only find applications in clothing and fashion design but demonstrate versatility in various fields, extending to sensing temperature, humidity, and hazardous chemicals.

A 3D nanoscale optical disk memory with petabit capacity.

High-capacity storage technologies are needed to meet our ever-growing data demands1,2. However, data centres based on major storage technologies such as semiconductor flash devices and hard disk drives have high energy burdens, high operation costs and short lifespans2,3. Optical data storage (ODS) presents a promising solution for cost-effective long-term archival data storage. Nonetheless, ODS has been limited by its low capacity and the challenge of increasing its areal density4,5. Here, to address these issues, we increase the capacity of ODS to the petabit level by extending the planar recording architecture to three dimensions with hundreds of layers, meanwhile breaking the optical diffraction limit barrier of the recorded spots. We develop an optical recording medium based on a photoresist film doped with aggregation-induced emission dye, which can be optically stimulated by femtosecond laser beams. This film is highly transparent and uniform, and the aggregation-induced emission phenomenon provides the storage mechanism. It can also be inhibited by another deactivating beam, resulting in a recording spot with a super-resolution scale. This technology makes it possible to achieve exabit-level storage by stacking nanoscale disks into arrays, which is essential in big data centres with limited space.

Development of NIR-II small animal living fluorescence imaging system

Fluorescence imaging technology can dynamically monitor gene and cell changing in live animals in real-time, with advantages such as high sensitivity, high resolution, and non-invasion. In recent years, it has been widely used in tumor research, gene expression research, drug development research, etc. The imaging wavelength of traditional fluorescence imaging technology falls in the visible and near-infrared-I region. Due to the absorption and scattering effects of light propagation in biological tissues, and the inherent fluorescence of biological tissues, traditional fluorescence imaging techniques still have significant limitations in penetration depth and image signal-to-noise ratio. In this work, a highly integrated near-infrared-II (NIR-II, 900—1880 nm) small animal living fluorescence imaging system is developed by taking the advantages of NIR-II fluorescence imaging technology, such as low absorption, low scattering, and deep penetration depth in biological tissues. And a method of enhancing and correcting fluorescence image is proposed to optimize fluorescence images. In this work, the biological tissue simulation experiments and live animal experiments are conducted to test the performance and imaging effect of the system. The experimental results show that the system has the advantages of deep penetration depth, high signal-to-noise ratio, and high sensitivity. Combined with commercial indocyanine green reagents and aggregation-induced emission dyes, this system can monitor the distribution of blood vessels in real time and continuously monitor deep tissues and organs in mice, and conduct the dynamically monitoring research in living mice in a conscious state. This helps to promote tumor research and drug development research in the field of biomedical imaging to enter a new stage.

Biotin receptor and mitochondria dual targeted AIE photosensitizer for fluorescence imaging guided photodynamic anticancer therapy

Rational design of organelle targeted therapeutic platform in where the drug can be targeted to destroy tumor cells as much as possible, is one of the effective ways to improve the therapeutic outcomes and minimize the cytotoxicity to normal cells. Here, photosensitizer TSPy-B with aggregation-induced emission (AIE) feature, biotin receptor and mitochondria dual-targeted capability, and high reactive oxygen species (ROS) generation efficiency was designed for fluorescence imaging guided photodynamic therapy (PDT) by linking biotin group to D-π-A type AIE dyes via ester bonds. Notably, cell imaging experiments showed that TSPy-B could selectively target tumor cells with biotin receptor overexpression and further exhibit mitochondria targeting ability. The in vitro anticancer mechanism confirmed that after cell internalization, TSPy-B localized in the mitochondrial site and produced ROS resulting in mitochondrial dysfunction and cell death. ROS generation experiments showed that TSPy-B could simultaneously produce 1O2 and highly toxic free radicals which not depended on the oxygen level of solid tumor. The cell killing effect of TSPy-B was also confirmed in hypoxic culture model. In vivo photodynamic therapy experiments demonstrated that TSPy-B could effectively inhibit tumor growth and had good biological safety. This work provides a choice for development of highly targeted photosensitizers for clinical fluorescence imaging guided PDT.

Improved brightness of multiarylpyrroles in the near-infrared region via coordination-induced supramolecular system

Organic fluorescent dyes that emit in the near-infrared region offer many benefits in biological imaging; nevertheless, their low fluorescence quantum yield remains problematic. In this study, we synthesized an aggregation-induced emission dye from multiarylpyrroles (MAPs) and continuously increased the fluorescence intensity by coordinating the MAPs with tris(pentafluorophenyl)borane (BCF). The coordination between MAPs and BCF improved the fluorescence quantum yields without changing the emission wavelength by increasing the intramolecular interactions and restricting the molecular motion. Moreover, experimental and theoretical calculations verified that the ability to produce reactive oxygen species decreased after coordination, which was beneficial for long-term fluorescence imaging tracking. The coordination between near-infrared dyes and BCF not only provides general guidance for improving the quantum yield but also regulates the charge transfer between the singlet and triplet states, which influences the production of reactive oxygen species.

Aggregation-Induced Stimulated Emission of 100% Dye Microspheres.

Dyes with aggregation-induced emission (AIE) properties have gained interests due to their bright luminescence in solid-state aggregates. While fluorescence from AIE dyes have been widely exploited, relatively little is known about aggregation-induced stimulated emission. Here, we investigated stimulated emission of tetraphenylethene (TPE)-based organoboron AIE dyes, TPEQBN, in thin films and in microcavity lasers. Using femtosecond pump-probe spectroscopy, gain coefficients up to 230 cm-1 at 500 nm were measured. Using rate equations, we analyzed concentration- and pump-dependent gain dynamics as well as laser build up dynamics. During laser oscillation, radiative stimulated emission allows high instantaneous quantum yield greater than 90% to be achieved. We fabricated solid-state microspheres made of 100% AIE dyes via microfluidic emulsion and solvent evaporation method. Coupled with high gain and high refractive index of 1.76, microspheres as small as 2 μm in diameter showed lasing by nanosecond pumping with a threshold of ~10 pJ μm-2. Polymer coated, but not bare, microspheres were internalized by live cells and generated narrowband cavity mode emission from within the cytoplasm. Our work shows the potential of AIE dyes as laser materials.

A Target-Triggered Emission Enhancement Strategy Based on a Y-Shaped DNA Fluorescent Nanoprobe with Aggregation-Induced Emission Characteristic for microRNA Imaging in Living Cells.

DNA self-assembled fluorescent nanoprobes have been developed for bio-imaging owing to their high resistance to enzyme degradation and great cellular uptake capacity. In this work, we designed a new Y-shaped DNA fluorescent nanoprobe (YFNP) with aggregation-induced emission (AIE) characteristic for microRNA imaging in living cells. With the modification of the AIE dye, the constructed YFNP had a relatively low background fluorescence. However, the YFNP could emit a strong fluorescence due to the generation of microRNA-triggered AIE effect in the presence of target microRNA. Based on the proposed target-triggered emission enhancement strategy, microRNA-21 was detected sensitively and specifically with a detection limit of 122.8 pM. The designed YFNP showed higher bio-stability and cell uptake than the single-stranded DNA fluorescent probe, which has been successfully applied for microRNA imaging in living cells. More importantly, the microRNA-triggered dendrimer structure could be formed after the recognition of target microRNA, achieving a reliable microRNA imaging with a high spatiotemporal resolution. We expect that the proposed YFNP will become a promising candidate for bio-sensing and bio-imaging.

Heteroaryl-Substituted Bis-Anils: Aggregation-Induced Emission (AIE) Derivatives with Tunable ESIPT Emission Color and pH Sensitivity.

The two-step synthesis, structural, and photophysical properties of a series of heteroaryl-substituted bis-anil derivatives presenting aggregation-induced emission (AIE) coupled with an excited-state intramolecular proton transfer (ESIPT) process is described. The fluorescence color of the aggregates can be fine tuned by changing the electronic nature of the peripheral substitution, leading to a wide range of emission wavelengths (from green to the near infra-red). Moreover, upon introduction of strong electron-withdrawing groups such as cyano (CN), a competition between ESIPT and deprotonation is observed leading to the emission of the anionic species at low water percentage. This observation led to the synthesis of an additional mixed AIE fluorophore, functionalized by methoxy groups on one side and cyano groups on the other side. Upon addition of water, this dye displays first anionic emission, followed by typical AIE/ESIPT red fluorescence upon formation of the aggregates. TD-DFT calculations on selected AIE dyes were performed to rationalize the nature of the emissive transitions in these derivatives.

Boronic acid derived salicylidenehydrazinopyridine (BOSPY) complexes with aggregation-induced emission for fluorescence imaging of cellular organelles

A series of boronic acid derived salicylidenehydrazinopyridine complexes have been synthesized from the condensation of 2-hydrazinopyridine or 2-hydrazinoquinoline and salicylaldehyde then followed by complexation with various boronic acids. Their X-ray structures demonstrate that the boron atoms adopt a tetrahedral geometry and the aryl substituents from arylboric acids along the vertical axis gave the molecule stereotactic structure and induced molecular chirality. These dyes have good solubility on organic solvents due to the nonplanar curved structure and the presence of axial-substituted groups that provide steric protection. They have strong visible-light absorption, weak emission and large Stoke shifts in organic solvents. Interestingly, molecular aggregates of these new boron complexes experienced the transformation from H-type aggregation to J-type aggregation and exhibited strong aggregation-induced emission (AIE) activities. These novel AIE dyes showed great potential as bioimaging dyes, and two complexes were mainly distributed in lipid droplets of cells in colocalization experiments.

Stimuli-Responsive Electrospun Fluorescent Fibers Augmented with Aggregation-Induced Emission (AIE) for Smart Applications.

This review addresses the latest advancements in the integration of aggregation-induced emission (AIE) materials with polymer electrospinning, to accomplish fine-scale electrospun fibers with tunable photophysical and photochemical properties. Micro- and nanoscale fibers augmented with AIE dyes (termed AIEgens) are bespoke composite systems that can overcome the limitation posed by aggregation-caused quenching, a critical deficiency of conventional luminescent materials. This review comprises three parts. First, the reader is exposed to the basic concepts of AIE and the fundamental mechanisms underpinning the restriction of intermolecular motions. This is followed by an introduction to electrospinning techniques pertinent to AIE-based fibers, and the core parameters for controlling fiber architecture and resultant properties. Second, exemplars are drawn from latest research to demonstrate how electrospun nanofibers and porous films incorporating modified AIEgens (especially tetraphenylethylene and triphenylamine derivatives) can yield enhanced photostability, photothermal properties, photoefficiency (quantum yield), and improved device sensitivity. Advanced applications are drawn from several promising sectors, encompassing optoelectronics, drug delivery and biology, chemosensors and mechanochromic sensors, and innovative photothermal devices, among others. Finally, the outstanding challenges together with potential opportunities in the nascent field of electrospun AIE-active fibers are presented, for stimulating frontier research and explorations in this exciting field.

Coemissive luminescent nanoparticles combining aggregation-induced emission and quenching dyes prepared in continuous flow

Achieving an ideal light-harvesting system at a low cost remains a challenge. Herein, we report the synthesis of a hybrid dye system based on tetraphenylene (TPE) encapsulated organic dyes in a continuous flow microreactor. The composite dye nanoparticles (NPs) are synthesized based on supramolecular self-assembly to achieve the co-emission of aggregation-induced emission dyes and aggregation-caused quenching dyes (CEAA). Numerical simulations and molecular spectroscopy were used to investigate the synthesis mechanism of the CEAA dyes. Nanoparticles of CEAA dyes provide a platform for efficient cascade Förster resonance energy transfer (FRET). Composite dye nanoparticles of TPE and Nile red (NiR) are synthesized for an ideal light-harvesting system using coumarin 6 (C-6) as an energy intermediate. The light-harvesting system has a considerable red-shift distance (~126 nm), high energy-transfer efficiency (ΦET) of 99.37%, and an antenna effect of 26.23. Finally, the versatility of the preparation method and the diversity of CEAA dyes are demonstrated.

Nonlinear optical properties of AIE doped PMMA thin film upon restriction of intramolecular motion

Aggregation Induced Emission (AIE) is an interesting Photophysical phenomenon in which a series of molecules non-emissive in solution state become fluorescent upon aggregation or by structural rigidification. Restriction of intramolecular motion (RIM) is the basic principle of this phenomenon. Nonlinear absorption properties of AIE dye named Tertraphenylethylene (TPE) in Anisole and doping it in PMMA matrix is studied using Open Apperture (OA) Z-scan technique. OA Z-scan trace of TPE in anisole showed RSA in SA behaviour due to two photon induced excited state absorption while TPE doped PMMA film showed RSA behaviour with two photon absorption (TPA) as an underlying mechanism. Five level energy model is used to understand this change in nonlinearity. Optical limiting threshold shows only a slight change upon RIM.

Highly Tunable Circularly Polarized Emission of an Aggregation-Induced Emission Dye Using Helical Nano- and Microfilaments as Supramolecular Chiral Templates.

Aggregation-induced emission (AIE)-based circularly polarized luminescence (CPL) has been recognized as a promising pathway for developing chiroptical materials with high luminescence dissymmetry factors (|glum|). Here, we propose a method for the construction of a thermally tunable CPL-active system based on a supramolecular self-assembly approach that utilizes helical nano- or microfilament templates in conjunction with an AIE dye. The CPL properties of the ensuing ensembles are predominantly determined by the intrinsic geometric differences among the various filament templates such as their overall dimensions (width, height, and helical pitch) and the area fraction of the exposed aromatic segments or sublayers. The proposed mechanism is based on the collective data acquired by absorption, steady state and time-resolved fluorescence, absolute quantum yield, and CPL measurements. The highest |glum| value for the most promising dual-modulated helical nanofilament templates in the present series was further enhanced, reaching up to |glum| = 0.25 by confinement in the appropriate diameter of anodized aluminum oxide (AAO) nanochannels. It is envisioned that this methodology will afford new insights into the design of temperature-rate indicators or anti-counterfeiting tags using a combination of structural color by the nano- and microfilament templates and the AIE property of the guest dye.

Engineering light-initiated afterglow lateral flow immunoassay for infectious disease diagnostics

The pandemic of highly contagious diseases has put forward urgent requirements for high sensitivity and adaptive capacity of point-of-care testing (POCT). Herein, for the first time, we report an aggregation-induced emission (AIE) dye-energized light-initiated afterglow nanoprobes (named LiAGNPs), implemented onto a lateral flow immunoassay (LFIA) test strip, for diagnosis of two highly contagious diseases, human immunodeficiency virus (HIV) and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) as model validation. The primary working mechanism relies on the cyclically generated singlet oxygen (1O2)-triggered time-resolved luminescent signals of LiAGNPs in which AIE dyes (TTMN) and chemiluminescent substrates (SO) are loaded. The designed LiAGNPs were found 2-fold and 32-fold sensitive than the currently used Eu(III)-based time-resolved fluorescent nanoparticles and gold nanoparticles in lateral flow immunoassay (LFIA), respectively. In addition, the extra optical behaviors of nude color and fluorescence of LiAGNPs enable the LFIA platform with the capability of the naked eye and fluorescent detection to satisfy the applications under varying scenarios. In short, the versatile LiAGNPs have great potential as a novel time-resolved reporter in enhancing detection sensitivity and application flexibility with LFIA platform for rapid but sensitive infectious disease diagnostics.

Specific Tumor Cell Detection by a Metabolically Targeted Aggregation-Induced Emission-Based Gold Nanoprobe.

Detection of circulating tumor cells (CTCs) could be widely used for early diagnosis and real-time monitoring of tumor progression in liquid biopsy samples. Compared with normal cells, tumor cells exhibit relatively strong negative surface charges due to the high rate of glycolysis. In this study, a cationic fluorescence “turn-on” aggregation-induced emission (AIE) nanoprobe based on gold nanorods (GNRs) was designed and tested to detect tumor cells specifically. In brief, tetraphenylethene (TPE), an AIE dye, was conjugated to the cationic polymer polyethylenimine (PEI) yielding TPEI. TPEI-PEG-SH was obtained by further functionalizing TPEI with a thiol group. TPEI-PEG-SH was grafted to the surface of GNRs, yielding the cationic AIE nanoprobe, named as GNRs-PEG-TPEI. The nanoprobe was characterized to have a uniform particle size of 172 nm, a strong positive surface charge (+54.87 mV), and a surface modification load of ∼40%. The in vitro stability of GNRs-PEG-TPEI was verified. The cellular imaging results demonstrated that the nanoprobe could efficiently recognize several types of tumor cells including MCF-7, HepG2, and Caco-2 while exhibiting specific fluorescence signals only after interacting with tumor cells and minimal background interference. In addition, the study investigated the toxicity of the nanoprobe to the captured cells and proved the safety of the nanoprobe. In conclusion, a specific and efficient nanoprobe was developed for capture and detection of different types of tumor cells based on their unique metabolic characteristics. It holds great promise for achieving early diagnosis and monitoring the tumor progression by detecting the CTCs in clinical liquid biopsy samples.

Tetraphenylethylene-Incorporated Macrocycles and Nanocages: Construction and Applications

Dyes exhibiting aggregation-induced emission (AIE) properties can efficiently circumvent the aggregation-caused quenching phenomenon presented in conventional fluorophores in their solid state. As one of the AIE dyes, tetraphenylethylene (TPE) has attracted tremendous attention because of its concise synthesis, stability, at least four reaction sites, and so on, making it a splendid building block for macrocycles and nanocages. In TPE-incorporated macrocycles and nanocages, the AIE effect can be not only preserved but also enhanced as a result of the geometrical constraint of the otherwise rotatable phenylene rings in the TPE units, which endows them with various applications involving the encapsulation and detection of explosives and dyes. This review surveys the recent developments of TPE-incorporated macrocycles and nanocages all the way from the perspective of synthetic strategies involving dynamic covalent chemistry, covalent bonding, and metal coordination to their potential applications in explosives detection, chemical sensing, cell imaging, and catalysis. Finally, we summarize the state-of-the-art status and challenges in this area, which we hope will guide future investigations.

Synthesis and Characterization of Diketopyrrolopyrrole-Based Aggregation-Induced Emission Nanoparticles for Bioimaging.

Conventional fluorescent dyes have the property of decreasing fluorescence due to aggregation-caused quenching effects at high concentrations, whereas aggregation-induced emission dyes have the property of increasing fluorescence as they aggregate with each other. In this study, diketopyrrolopyrrole-based long-wavelength aggregation-induced emission dyes were used to prepare biocompatible nanoparticles suitable for bioimaging. Aggregation-induced emission nanoparticles with the best morphology and photoluminescence intensity were obtained through a fast, simple preparation method using an ultrasonicator. The optimally prepared nanoparticles from 3,6-bis(4-((E)-4-(bis(40-(1,2,2-triphenylvinyl)-[1,10-biphenyl]-4-yl)amino)styryl)phenyl)-2,5-dihexyl-2,5-dihydropyrrolo[3,4-c]pyrrole-1,4-dione (DP-R2) with two functional groups having aggregation-induced emission properties and additional donating groups at the end of the triphenylamine groups were considered to have the greatest potential as a fluorescent probe for bioimaging. Furthermore, it was found that the tendency for aggregation-induced emission, which was apparent for the dye itself, became much more marked after the dyes were incorporated within nanoparticles. While the photoluminescence intensities of the dyes were observed to decrease rapidly over time, the prepared nanoparticles encapsulated within the biocompatible polymers maintained their initial optical properties very well. Lastly, when the cell viability test was conducted, excellent biocompatibility was demonstrated for each of the prepared nanoparticles.

Highly sensitive AIE-based mechanoresponsive luminescent polymer coatings for surface pressure imaging

• AIE-based mechanoresponsive luminescent polymer coatings for surface pressure imaging are prepared. • Phase transition of AIE dye is prohibited by polymer network to receive high mechanoluminescent reversibility. • Pressure sensitivity of the coatings is controlled by mechanical property of the polymer matrix. • The coatings realize the detection of surface pressure distribution in both hydrostatic and hydrodynamic applications. Herein, we report on a facile methodology for the development of aggregation induced emission (AIE)-based mechanoresponsive luminescent (MRL) polymer coatings with the characteristics of high sensitivity and high reversibility in 2D surface pressure imaging. Amorphous nitro-functionalized tetraphenyethylene was embedded into an elastomer substrate to prevent the crystallization of the dye and meanwhile to allow the conformational variation in response to the gradual deformation and relaxation of the polymer network. The strategy endows strain-mediated fluorescence enhancement and fast recovery of the material in compressive force loading–unloading cycles. The relationship between pressure and fluorescence intensity of the AIE-based MRL coatings was calibrated which showed adjustable sensitivity within kilopascal (kPa) to megapascal (MPa) range, according to the mechanical property of the polymer matrix. The coatings were capable for the detection of surface pressure distribution through non-contact optical observation technique in both static and dynamic processes. The high sensitivity realized the utility of AIE-based materials in the field of hydrodynamics and probably for other applications in industry.

Fast dual-beam alignment method for stimulated emission depletion microscopy using aggregation-induced emission dye resin

A stimulated emission depletion is capable of breaking the diffraction limit by exciting fluorescent molecules with a solid Gaussian beam and quenching the excited molecules with another donut beam through stimulated emission. The coincidence degree of these two beams in three dimensions will significantly influence the spatial resolution of the microscope. However, the conventional alignment approach based on raster scanning of gold nanoparticles by the two laser beams separately suffers from a mismatch between fluorescence and scattering modes. To circumvent the above problems, we demonstrate a fast alignment design by scanning the second beam over the fabricated sample, which is made of aggregation-induced emission (AIE) dye resin. The relative positions of solid and donut laser beams can be represented by the fluorescent AIE from the labeled spots in the dye resin. This design achieves ultra-high resolutions of 22 nm in the x/y relative displacement and 27 nm in the z relative displacement for fast spatial matching of the two laser beams. This study has potential applications in scenarios that require the spatial matching of multiple laser beams, and the field of views of different objectives, for example, in a microscope with high precision.

Engineering BODIPY-based near-infrared nanoparticles with large Stokes shifts and aggregation-induced emission characteristics for organelle specific bioimaging.

Lipid droplets (LDs) and lysosomes, as two important subcellular organelles, play specific and indispensable roles in various cellular processes. The development of efficient LD- and lysosome-specific fluorescent bio-probes is of great importance. However, current commercial lipid droplet- (LD) and lysosome-specific fluorescent specific bio-probes often suffer from the aggregation-caused quenching (ACQ) effect, short absorption and emission wavelengths, poor photostability and low specificity. Herein, a typical ACQ luminogen BODIPY was directly conjugated to strong electron donating triarylamine units at its α-positions, giving near-infrared (NIR) fluorescent materials TPAB and 2TPAB with aggregation-induced emission (AIE). Both TPAB and 2TPAB nanoparticles were obtained by self-assembly, and showed NIR emissions, large Stokes shifts, good photostability and two-photon absorption. These nanoparticles presented remarkable bioimaging performances and were shown to specifically localize in LDs or lysosomes, respectively, depending on the number of triarylamine units attached. They have been successfully used to detect endogenous LD overproduction, and monitor abnormal activities of LDs/lysosomes, as well as real-time track the lipophagy process in cells. Their far NIR emission and two-photon excitation further supported their promising bioimaging application for lipid droplet tracking in liver tissue and live zebrafish larvae. Our work here enriches BODIPY based NIR AIE dyes and provides organelle specific bio-probes which are superior to currently used commercial ones.