Aggregation-induced Emissions Research Articles

Unlocking the Luminescent Potential of Fish-Scale-Derived Carbon Nanoparticles for Multicolor Conversion.

This study introduces a novel approach to addressing environmental issues by developing fish-scale carbon nanoparticles (FSCNPs) with a wide range of colors from discarded fish scales. The process involves hydrothermally synthesizing raw tamban (Sardinella) fish scales sourced from Universal Canning, Inc. in Zamboanga City, Philippines. The optimization of the synthesis was achieved using the response surface methodology with a Box-Behnken design. The resulting FSCNPs exhibited unique structural and chemical properties akin to carbonized polymer dots, enhancing their versatility. The solid-state fluorescence of these nanoparticles can be modulated by varying their concentration in a polyvinylpyrrolidone matrix, yielding colors such as blue, green, yellow, and red-orange with Commission Internationale de l'Eclairage coordinates of (0.23, 0.38), (0.32, 0.43), (0.37, 0.43), and (0.46, 0.48), respectively. An analysis of the luminescence mechanism highlights cross-linking emissions, aggregation-induced emissions, and non-covalent interactions, which contribute to concentration-dependent fluorescence and tunable emission colors. These optical characteristics suggest that FSCNPs have significant potential for diverse applications, particularly in opto-electronic devices.

Review on Synthesis of 2-(2-Hydroxyaryl) Benzothiazoles (HBT) for Excited-State Intra-molecular Proton Transfer (ESIPT)-Based Detection of Ions and Biomolecules.

In this review, we present a systematic and comprehensive summary of the recent developments in the synthetic strategies of 2-(2-hydroxyarylsubstituted)-benzothiazole (HBT) framework along with incorporation of various substituents on phenolic and benzothiazole rings which affect the emission process. The literature, spanning the years 2015-2024, on excited-state intramolecular proton transfer (ESIPT)-based studies of HBT derivatives comprising the effects of solvent polarity, substituents, and extended conjugation on fluorophores has been searched. ESIPT, intramolecular charge transfer, and aggregation-induced emissions enable these fluorescent probes to specifically interact with analytes, thereby altering their luminescence characteristics to achieve analyte detection. These fluorescent probes exhibit large Stokes shifts, high quantum yields, and excellent color transitions. Finally, the applications of HBTs as ESIPT-based fluorescent probes for the detection of cations, anions, and biomolecules have been summarized. We anticipate that this review will provide a comprehensive overview of the current state of research in this field and encourage researchers to develop novel ESIPT-based fluorophores with new applications.

Metasurface Platform Incorporating Aggregation Induced Emission Based Biosensor for Enhanced Human Serum Albumin Detection

AbstractMetasurfaces exhibit excellent optical performance to enhance the light–matter interaction of target molecules in biosensing based on its well‐optimized nanostructured unit cells. In the meantime, fluorescence (FL) biosensors with aggregation induced emissions (AIE) features also demonstrate outstanding performance in biomarker detection due to their fast response, high selectivity, and low background noise. Nevertheless, extremely low‐level analytes are difficult to detect in practical applications since complex urine samples include a number of uncontrolled variables such as impurities, autofluorescence, other urine components, etc. At present, improving optical signal sensitivity of human serum albumin (HSA) detection is always a big challenge to overcome such interference in human urine scenarios. In this work, first an AIE‐based FL biosensor TPE‐4TA is combined with an all‐dielectric metasurface platform to achieve quantitative detection of trace HSA in urine by utilizing biofunctionalization protocols on the silicon (Si) nanostructures. The results indicate significant FL enhancement in the metasurface platform that offers a promising pathway for improving biomarker detection in the future.

Exploration of Novel Meso-C═N-BODIPY-Based AIE Fluorescent Rotors with Large Stokes Shifts for Organelle-Viscosity Imaging.

The research on fluorescent rotors for viscosity has attracted extensive interest to better comprehend the close relationships of microviscosity variations with related diseases. Although scientists have made great efforts, fluorescent probes for cellular viscosity with both aggregation-induced emissions (AIEs) and large Stokes shifts to improve sensing properties have rarely been reported. Herein, we first report four new meso-C═N-substituted BODIPY-based rotors with large Stokes shifts, investigate their viscosity/AIE characteristics, and perform cellular imaging of the viscosity in subcellular organelles. Interestingly, the meso-C═N-phenyl group-substituted probe 6 showed an obvious 594 nm fluorescence enhancement in glycerol and a moderate 650 nm red AIE emission in water. Further, on attaching CF3 to the phenyl group, a similar phenomenon was observed for 7 with red-shifted emissions, attributed to the introduction of a phenyl group, which plays a key role in the red AIE emissions and large Stokes shifts. Comparatively, for phenyl-group-free probes, both the meso-C═N-trifluoroethyl group and thiazole-substituted probes (8 and 9) exhibited good viscosity-responsive properties, while no AIE was observed due to the absence of phenyl groups. For cellular experiments, 6 and 9 showed good lysosomal and mitochondrial targeting properties, respectively, and were further successfully used for imaging viscosity through the preincubation of monensin and lipopolysaccharide (LPS), indicating that C═N polar groups potentially work as rotatable moieties and organelle-targeting groups, and the targeting difference might be ascribed to increased charges of thiazole. Therefore, in this study, we investigated the structural relationships of four meso-C═N BODIPY-based rotors with respect to their viscosity/AIE characteristics, subcellular-targeting ability, and cellular imaging for viscosity, potentially serving as AIE fluorescent probes with large Stokes shifts for subcellular viscosity imaging.

Insights on salting-out triggering aggregation-induced emission in nitrogen-doped graphene quantum dots

A straightforward methodology for obtaining Nitrogen-doped Graphene Quantum Dots (N-GQDs) with aggregation-induced emission (AIE) using salting-out purification processes is presented in this work. Various salts, including NaCl at concentrations of 50 mM, were found to be effective for stratification of graphene-based materials (GBMs) by salting-out treatments. These salts were shown to be safer, more cost-effective, and environmentally sustainable alternatives to (NH4)2SO4 reported in previous works. Remarkably, this method demonstrated the ability to promote the self-assembly of N-GQDs into stable J-aggregates-like arrays with an average fluorescence decay time of ca. 4 ns and absolute quantum yield with values of 3.5 % and 6.9 % for 100 mM and 2 M, respectively. In contrast to a typical quenching effect caused by π-stacking, these arrays exhibited aggregation-induced emissions, as evidenced by the presence of new excitation and emission bands at 532 and 600 nm, respectively. The scalability of the process, along with the absence of additional purification steps, renders these results of great scientific and technological interest. Furthermore, the modulable fluorescence, size, and stability of these GBMs suggest their potential application in energy cells, sensors, and biomedical imaging.

Push-Pull Bridged Distyrylbenzene with Highly Bright Solid-State Red-Orange Aggregation-Induced Emission.

Multiple emission colors in solid-state organic fluorophores with the same main skeleton are essential for improving the performance of light-emitting devices/materials. Specifically, emission in the red/near-infrared region is of great importance in the biological field. Previously, we developed di-bridged-distyrylbenzene DBDB[7] with high-brightness solid-state blue and aggregation-induced emissions (AIE) by introducing the bridging structures of a seven-membered ring into the vinylene groups of distyrylbenzene (DSB). Herein, we synthesize MNDBDMeODB[7] (1), which features substituted methoxy and malononitrile groups as donor and acceptor groups, respectively, in DBDB[7]. In solvents more polar than THF, MNDSDMeOB (3), which has the same main skeleton as 1 but without bridges, shows no emission in the solid state, whereas 1 exhibits highly bright red-orange emission in the solid state owing to the suppression of intermolecular electronic interactions by the bridges and the AIE property. We also synthesize MNDSD(EHO)B (2) in which the methoxy groups of 3 are replaced by ethylhexyloxy groups, thus disrupting the crystallinity of the molecule. 2 exhibits positive fluorescence solvatochromism and has a high fluorescence quantum yield in the solid state as a red-emitting DSB derivative. The solid-state emission properties of 1 and 2 will improve the applicability of DSBs and functionalities of light-emitting devices/materials.

Polycrystalline monophenyl solid emitters with amplified spontaneous emission

There are many reports of small molecules exhibiting amplification spontaneous emission laser properties, but there are few reports of single benzene rings exhibiting laser properties while achieving high solid state emission from polycrystalline states. This work takes two very simple organic molecules and constructs an efficient single benzene ring solid state emitter. The crystal laser properties are based on aggregation‐induced emissions (AIE) generated through an excited‐state intramolecular proton transfer reaction (ESIPT).

Coal humus acid functionalized high stability fluorescent copper nanoclusters for tumor identification by sequential off-on-off monitoring tryptophan and Hg2.

The abnormalities of Tryptophan (Trp) and mercury ions (Hg2+) not only easily activate diseases, including mental illness and cancer, but also seriously affect human wellbeing. Fluorescent sensors are profoundly attractive options for identifying amino acids and ions; however, most sensors remain challenging due to the multipliable cost and deviation from the asynchronous quenching detection. In particular, fluorescent copper nanoclusters with high stability that quantitatively monitoring Trp and Hg2+ successively have seldom been reported. Herein, we employ coal humus acid (CHA) as a protective ligand and successfully construct weak cyan fluorescent copper nanoclusters (CHA-CuNCs) by a rapid, environmentally benign and cost-effective method. Significantly, the fluorescence of CHA-CuNCs is obviously improved by introducing Trp, because the indole group of Trp enhances the radiative recombination and aggregation-induced emissions. Interestingly, CHA-CuNCs not only realizes the highly selective and specific detection of Trp with a linear range of 25-200μM and a detection limit of 0.043μM based on the turn-on fluorescence strategy, but also quickly achieves the consecutive turn-off detection of Hg2+ due to the chelation interaction between Hg2+ and pyrrole heterocycle in Trp. Moreover, this method is successfully applied in the analysis of Trp and Hg2+ in real samples. Furthermore, the confocal fluorescent imaging of tumor cells demonstrates that CHA-CuNCs can be used for bioimaging and cancer cell recognition with Trp and Hg2+ abnormalities. These findings provide new guidance for the eco-friendly synthesis of CuNCs with eminent sequential off-on-off optical sensing property, indicating good prospects in biosensing and clinical medicine applications.

Pyrene-Based Fluorescent Probe for “Off-on-Off” Sequential Detection of Cu2+ and CN− with HeLa Cells Imaging

The novel pyrene-appended Schiff base probe L with aggregation-induced emissions (AIE) relevant to an increase in water fractions (0–90%) is synthesized and applied in sequentially detecting Cu2+ and CN−. The pyrene-based probe L firstly induces the excimer formation in the presence of Cu2+. However, the process can be reversed by sequentially adding CN−, which is demonstrated using the fluorescence “Off-On-Off” response in semi-aqueous media ethanol water (v/v = 7/3) under physiological pH (5 mM HEPES, pH 7.0). The Job’s plot, mass analysis, 1H NMR titrations, and density functional theory (DFT) interrogations confirm the 2:1 stoichiometry of excimer complex L–Cu2+-L*, preferential binding atoms, and CN− tuned complex reversibility. Based on the photoluminescence (PL) titration, the association constant of L to Cu2+ is determined as 4.95 × 106 M−1. From standard deviation and linear fittings, the detection limits (LODs) of Cu2+ and CN− are estimated as 219 nM and 580 nM, respectively. The practicality of Cu2+ and CN− detection is demonstrated using a TLC plate and a blended polymer membrane through which significant color changes under a UV lamp can be monitored. Moreover, utility of the designed probe L towards biological application with low toxicity is demonstrated by detecting Cu2+ and CN− inside HeLa cells. The responses of the probe to Cu(II) ions were also verified using living HeLa cells imaging.

"Synergistic effect" based novel and ultrasensitive approach for the detection of serotonin using DEM-modulated bimetallic nanosheets.

Neurotransmitters have been of immense scientific interest due to their importance as human-health biomarkers. Several reports suggest necessary improvisations in the sensing capabilities of these neurotransmitters. Herein, the authors report a novel synthesis methodology for bimetallic aluminum-tungsten (Al-W) nanosheets, with the hybrid nanostructure showing high specificity toward serotonin neurotransmitters. The inspiration to design hybrid metallic nanosheets depends on the inherited optical properties of the parent precursors. The interstate conversion (ISC) between Al-W nanosheets promoted photoluminescent behavior with serotonin. The PL study shows that serotonin drastically enhanced λem at 335 nm. The importance of emission below the visible spectrum is to modulate any possible aggregation-induced emissions, which earlier troubled analytical chemists. The understanding of the selective detection of serotonin from a group of similar neurotransmitters is discussed with nanomolar quantification. The quantified detection limit using Al-W nanosheets is 0.05 nm with high linearity (R2 = 0.9906). Furthermore, real-world quantification studies have been performed on human urine and serum samples with R2 of 0.9938 and 0.9801, respectively.

Aggregation-induced emission and reversible high-contrast mechanofluorochromic behavior of dicyanoethylenes modified by xanthene and carbazole

Two novel donor-acceptor type molecules, XA-CE-CAR and XA-CE-BCAR, were created and synthesized using xanthene, carbazole and dicyanoethylene. The two luminophores possessed effective emissions in the solid-state with the respective fluorescence efficiencies of 0.256 and 0.238 and showed distinct aggregation-induced emissions. Particularly, XA-CE-CAR and XA-CE-BCAR exhibited high-contrast mechanofluorochromic (MFC) characteristics. When the as-prepared powders of the two compounds underwent grinding, the colors of emission shifted from yellow-green to yellow and then orange-yellow, respectively. Accordingly, the emission peaks of the two samples were red-shifted from 500 to 505 nm to 563 and 581 nm, respectively. Moreover, after dichloromethane vapor fuming, the emission colors and wavelengths of the ground powders were restored to conditions that were similar to those of the as-prepared powders. Powder X-ray diffraction revealed that the transformation between the crystalline and amorphous states following external stimuli was responsible for the MFC characteristics of XA-CE-CAR and XA-CE-BCAR. The reduced gap between bands resulting from the planar intramolecular charge transfer as well as an increase in π–π interactions, exciton coupling, and orbital overlap between neighboring molecules are the reasons for the redshifts in the photoluminescence spectra following grinding.

Palladium-Catalyzed Cascade Reaction in Water to Imidazo[1,2-a]pyridazines as Switchable DSEgens, AIEgens, and ACQgens.

Dual-state emission (DSE) luminophores exhibit strong emissions in both solution and solid states, filling the gaps between aggregation-induced emissions (AIE) and aggregation-caused quenching (ACQ). However, limited design concepts and complicated synthetic strategies restrict the discovery of novel DSE molecules. Developing efficient and green methodologies to access novel DSE scaffolds via rational design remains highly desirable. In this work, we report a water-promoted Pd-catalyzed cascade reaction for the synthesis of multi-substituted imidazo[1,2-a]pyridazine derivatives with DSE properties. The intramolecular interactions of the neighboring benzene rings restrict molecular motion, leading to emissions in the solid state (quantum yield: 11 %), and the newly constructed core structure of imidazo[1,2-a]pyridazine ensures considerable planarity, allowing for emissions in solution. Further removal of the neighboring phenyl groups resulted in ACQgens, while additional methyl groups led to AIEgens. Subsequent live cell imaging investigations suggested that the novel DSEgens could serve as specific lipid droplet (LD) probes in a wide concentration range.

Aggregation-Induced Emission and Circularly Polarized Luminescence Duality in Tetracationic Binaphthyl-Based Cyclophanes.

Here, we report an approach to the synthesis of highly charged enantiopure cyclophanes by the insertion of axially chiral enantiomeric binaphthyl fluorophores into the constitutions of pyridinium-based macrocycles. Remarkably, these fluorescent tetracationic cyclophanes exhibit a significant AIE compared to their neutral optically active binaphthyl precursors. A combination of theoretical calculations and time-resolved spectroscopy reveal that the AIE originates from limited torsional vibrations associated with the axes of chirality present in the chiral enantiomeric binaphthyl units and the fine-tuning of their electronic landscape when incorporated within the cyclophane structure. Furthermore, these highly charged enantiopure cyclophanes display CPL responses both in solution and in the aggregated state. This unique duality of AIE and CPL in these tetracationic cyclophanes is destined to be of major importance in future development of photonic devices and bio-applications.

Multifunctional fluorescent gold nanoclusters with enhanced aggregation-induced emissions (AIEs) and excellent antibacterial effect for bacterial imaging and wound healing.

To explore new alternatives to combat increasing risk of bacterial infection, in this work, a cationic antimicrobial peptide (HHC10) and glutathione (GSH) co-ligand protected ultra-small gold nanoclusters (Au NCs) was constructed by a simple one-pot method. The intrinsic luminescent property of GSH-protected Au NCs (AuxGSH) endowed enhanced aggregation-induced emissions (AIEs) of co-ligand-protected Au NCs (AuxGSH-HHC10), which exhibited a very strong orange luminescence. Based on the AIE effect, for one thing, AuxGSH could be applied to rapidly and selectively detect Gram-positive bacteria. For another, AuxGSH-HHC10 exhibited potential for multicolor imaging of both Gram-negative and Gram-positive bacteria. Besides, as-synthesized AuxGSH-HHC10 could act as potent nanoantibiotics against both Gram-negative and Gram-positive bacteria, which could not only avoid drug tolerance but also be effective toward drug-resistance bacteria. The antibacterial mechanism indicated that the synergetic effect of the generation of reactive oxygen species (ROS), binding with DNA, and broad-spectrum antibacterial activity of HHC10 led to the membrane damage, depolarization, and interference of biological function, thus enhancing the antibacterial effect. More importantly, such an Au NCs could realize excellent therapeutic outcomes for wound healing in vivo, and showed good biocompatibility and biosafety toward health tissues. The results will provide a great potential for the application of Au NCs for imaging-guided antibacterial platform.

Oligotriarylamine-Extended Organoboranes with Tunable Electron-Donating Strength by Changing the Number of Donor Units.

Triarylborane (Ar3B) and triarylamine (Ar3N) have been widely employed to construct electronically different donor-acceptor (D-A) systems. Herein, we describe a series of A-D-A-type luminescent organoboranes L-B2Nn (n = 1, 3, 5) that show an increased number of Ar3N units as electron donors and two terminal Ar3B as acceptors. When the Ar3N moieties were extended from one to five units, their electron-donating strength was gradually enhanced and the highest occupied molecular orbital (HOMO)-lowest unoccupied molecular orbital (LUMO) energy gaps could also be tuned, which was further reflected in the red-shifted emissions from blue (λem = 458 nm) to orange (λem = 595 nm) with a decrease in Egap(elect) from 3.19 to 2.61 eV. L-B2N5 showed a huge Stokes shift (∼14 057 cm-1) and a considerably bright emission with an enhanced solid-state quantum efficiency (ΦS = 98%) compared with the other members. L-B2N3 and L-B2N5 exhibited aggregation-induced emissions (AIEs), and an apparent solvatochromic shift was also observed in the emission spectra as the solvent was changed from hexane to tetrahydrofuran (THF) (430 → 595 nm). In addition, the donor-acceptor charge-transfer character in these organoboranes caused a thermally responsive emission over a broad range.

Enantioselective determination of chiral acids and amino acids by chiral receptors with aggregation-induced emissions

The chiral AIEgens showed satisfying enantiomer discrimination not only for amino acids but also for chiral acids.

Insight into dual fluorescence effects induced by molecular aggregation occurring in membrane model systems containing 1,3,4-thiadiazole derivatives

This work reports on biophysical insights into the excited state intramolecular proton transfer (ESIPT) processes taking place in three 1,3,4-thiadiazole derivatives that served as model compounds, on which electronic absorption, fluorescence, Fourier-transform infrared spectroscopy (FTIR), surface plasmon resonance (SPR) and electrochemical impedance spectroscopy (EIS) studies were performed. The fluorescence spectra recorded in various solvents revealed an interesting dual fluorescence effect. In molecules in their monomeric form, the effect is associated with the ESIPT phenomenon, and may be further enhanced by aggregation-related effects, such as aggregation-induced emissions. Other spectroscopic studies on the selected molecules in a liposomal medium as a model revealed that, in a biomimetic environment, they can exist in both monomeric and aggregated forms. In both cases, however, the effects observed are closely related to the lipid’s main phase transition temperature and the structure of the molecule. Introduction of specific substituents to the phenyl moiety either allows or prevents proton transfer from occurring in the excited state. The hydrophobicity changes in a lipid environment may result in an emergence of specific molecular forms and therefore either facilitate or hinder ESIPT processes. SPR and EIS confirmed the significant hydrophobicity changes in the model lipid systems, while FTIR measurements revealed a notable influence of 1,3,4-thiadiazoles on the fluidity of liposomal membranes. The results obtained clearly show that the thiadiazole derivatives are very good model molecules for studying hydrophobic-hydrophilic environments, and particularly with polymers or liposomes used as drug delivery systems.

Tetraphenylethene-decorated difluoroboron β-diketonates with terminal chiral α-phenylethylamine: Aggregation-induced emission, circularly polarized luminescence and mechanofluochromism

Incorporating tetraphenylethene (TPE) group and enantiopure α-phenylethylamine (α-PEA), a facile synthetic approach to chiral β-diketone ligands (R/S)-3 and their respective boron complexes (R/S)-4 has been developed. Aggregation-induced emissions (AIE) are observed for both (R/S)-3 and (R/S)-4. Benefiting from self-assembly, obvious circular dichroism (CD) and circularly polarized luminescence (CPL) signals are observed for both the ligands and boron complexes. The nanoassemblies of (R/S)-4 exhibit strong emission (ΦF > 30%) and high contrast mechanofluorochromism (MFC) from orange-yellow to red after grinding. The ground-state geometries, chiroptical properties for (R/S)-3 and (R/S)-4 have been validated by TDDFT calculations. It is demonstrated that effective electronic communications through π-conjugation among the individual fluorescent units and chiral centers are very crucial.

Aggregation-induced emissions in the mesogenic BF2 complexes of aroylhydrazines

PL peak intensity of 1a-BF2 (n = 12) versus fw of THF/H2O in pure THF (fw = 0) and THF/water with a specific fw. The concentration is 10 μM and PL emission was excited at 376 nm. Photos were taken under UV illumination.

Multifunctional Fluorescent Gold Nanoclusters with Enhanced Aggregation-Induced Emissions (AIEs) and Excellent Antibacterial Effect for Bacterial Imaging and Wound Healing

Multifunctional Fluorescent Gold Nanoclusters with Enhanced Aggregation-Induced Emissions (AIEs) and Excellent Antibacterial Effect for Bacterial Imaging and Wound Healing