Aggregation-induced emission of 1-methyl-1,2,3,4,5-pentaphenylsilole

Asymmetric phenothiazine derivatives modified with diphenylamine and carbazole: Photophysical properties and hypochlorite sensing

This study reports the design, synthesis, and characterization of four asymmetric donor-acceptor (D-A) fluorescent molecules-1CAR, 1DIP, 1OOCAR, and 1OODIP-featuring phenothiazine (PTZ), diphenylamine (DIP), and carbazole (CAR) as electron donors. By oxidizing the sulfur atom in PTZ and modifying the molecular structure at the 3-position, we systematically investigated the influence of structural variations on photophysical properties. These compounds exhibit distinct solvatochromic behavior, aggregation-induced enhanced emission (AIEE), and mechanofluorochromism (MFC). Solvent-dependent fluorescence studies revealed significant red shifts with increasing polarity, confirming strong intramolecular charge transfer (ICT) characteristics, as further supported by Lippert-Mataga analysis. In aggregated states, 1CAR and 1DIP displayed remarkable AIEE, with fluorescence intensity enhancements of up to 84.1- and 9.7-fold, respectively, whereas 1OOCAR exhibited aggregation-caused quenching (ACQ) due to structural constraints. Solid-state fluorescence analysis highlighted the impact of PTZ oxidation on emission characteristics, demonstrating its critical role in tuning fluorescence properties. Additionally, the sensing capabilities of 1CAR and 1DIP toward hypochlorite ions (ClO-) were explored through UV-Vis and fluorescence titration experiments, revealing substantial fluorescence quenching with increasing ClO- concentrations. The detection limits reached as low as 0.68 µM, underscoring their high sensitivity and selectivity. This research offers important perspectives for the rational design of multifunctional fluorescent materials for applications in chemosensing and environmental monitoring.

Boosting responses of fluorescent imaging probes toward sulfur dioxide through engineering side chain length

Development of fluorescent probes with high sensitivity and specificity is always desirable, yet, challenging. Conventionally, improving the responses of probes relied on optimizing the reactivities of recognition sites, either by increasing the binding affinity or reaction rates. Herein, we found the sensitivity and response kinetics could be improved by changing the aggregation behaviors of probes. As a proof-of-concept, benzothiazole derivatives with different side chain lengths were prepared and the enhanced responses toward sulfur dioxide (SO2) were observed for the probe with longer side chain. We demonstrated that the long side chain facilitates formation of tightly aggregates, which possessed higher positive charges and susceptible recognition sites as compared with probes possessing short side chains, resulting in better sensitivity and faster responses. In addition, we also demonstrated the generality of such design protocols with probes displaying aggregation induced emission (AIE) properties. Thus, the proposed side chain engineering strategy provides new paradigm for probe design.

Regulating aggregation and optical properties of rigid-flexible ligand via metal coordination for multifunctional applications

Non-covalent interactions typically drive molecular aggregation, but precisely controlling supramolecular interactions to regulate molecular stacking configurations and expand practical applications remains challenging. Herein, we design and synthesize a rigid-flexible ligand Tpy-Py, incorporating one terpyridine (Tpy) and two pyrenes (Py) moieties. Whose aggregation state is regulated by metal coordination, thereby significantly modulating its optical properties. Tpy-Py exists as monomers in solution and forms excimers in the solid state, with emission shifting from blue to green. Single-crystal analysis reveals that Tpy-Py molecules form H- and J-aggregates via π-π stacking in the crystal, while coordination with Zn2+ and Cu2+ further tunes the molecular packing, leading to red-shifted emission or quenching. Moreover, the photochromic properties of Tpy-Py are effectively utilized in fingerprint detection, anti-counterfeiting, and visual detection of heavy metal ions. This work provides a new approach for regulating aggregation via non-covalent interactions and highlights the potential of Tpy-Py in multifunctional applications.

Rational design of dual-state emission fluorophores for sensing nitro explosives by using sulfone unit as an electron acceptor in D-A system

Dual-state emission (DSE) fluorescent molecules have become the preferred type in designing sensing fluorescent molecules due to the virtue of their bright emission in both solid and liquid states. In this study, five D-A molecules were successfully designed and synthesized according to the design concept that structural modification of D-A molecules can lead to DSE molecules. Among them, the balance between the electron donor with a strong electron donation capacity and the twisted conformation in the whole molecule makes the compounds 3c-3e DSE molecules with excellent optical performances, showing significant solvatochromic effects and large Stoke shifts. In addition, the feasibility of the sulfone unit as an electron acceptor in the D-A structure is also verified, extending the application of sulfone group in the field of fluorescence. Interestingly, the fluorescence of 3c can exhibit sensitive and selective quenching of nitro aromatic compounds (NACs) under the synergistic mechanism of fluorescence resonance energy transfer (FRET) and photoinduced electron transfer (PET), with LOD as low as 10-8 M and KSV as high as 104 M-1. Furthermore, the selective, efficient, and sensitive detection of NACs by DSE fluorescent molecule 3c in real aqueous samples and loaded on test strips has demonstrated the potential of its practical applications.

Aggregation-induced emission-based aptasensors for the detection of various targets: Recent progress

The advancement of aptasensors utilizing aggregation-induced emission (AIE) has progressed remarkably in recent years, owing to various unique benefits provided by aggregation-induced emission luminogens (AIEgens) as a novel category of fluorescent substances and aptamers as exceptional recognition components. AIE refers to a photophysical phenomenon identified in certain luminogens that show minimal or absent emission in dilute solutions, yet display considerable emission when in aggregate or solid states. Fluorescent sensing is an effective technique for the detection of various targets; however, many traditional dyes frequently demonstrate an aggregation-caused quenching (ACQ) effect in solid form, which limits their applicability on a larger scale. In contrast, fluorescent probes that leverage AIE characteristics have garnered considerable interest, owing to their elevated fluorescence quantum yields and ease of fabrication. This review discusses the application of various AIEgens in the design of diverse sensitive and selective AIE-based aptasensors for monitoring various targets, with a particular focus on recent advances. The AIE-based aptasensors exploit the supreme affinity of the aptamers to their targets and the remarkable properties of AIEgen, including its photostability and high quantum yield, and the interaction between AIEgen and DNA. The objective is to acquaint researchers with the various categories of materials exhibiting AIE characteristics and their potential applications in the creation of different aptasensors, enabling them to introduce novel kinds of innovative AIEgens and AIE-integrated aptasensors.

Core-shell structured gold nanoparticle-AIEgen nanohybrids for enhanced dual-mode lateral flow immunoassay of fumonisin B1

Herein, we report the design and synthesis of bifunctional colorimetric and fluorescent nanohybrids (Au-AIENPs) through the co-assembly of oleylamine-modified gold nanoparticles (OA-AuNPs) and aggregation-induced emission luminogens (AIEgen). Due to the distinct compatibility of the components, the resulting Au-AIENPs form a core-shell nanostructure, with the AIEgen creating a fluorescent core and the OA-AuNPs uniformly dispersing on the shell. This spatial separation of AIEgen and OA-AuNPs optimizes the colorimetric signal while preserving a strong fluorescence output. Leveraging the intrinsic dual functionality of Au-AIENPs as dual-mode signal reporters, we demonstrate their potential for rapid, naked-eye visualization and fluorescent quantitative detection of fumonisin B1 (FB1) on the lateral flow immunoassay (LFIA) platform (Au-AIENPs-LFIA). Under optimal conditions, the developed Au-AIENPs-LFIA test strip achieved high sensitivity for FB1 qualitative detection, with a visual limit of detection (LOD) of 0.056 ng/mL, and exhibited ultrasensitivity for FB1 quantitative detection, with an LOD of 0.03 ng/mL. In conclusion, the proposed Au-AIENPs offer an ideal combination of visual compatibility and high sensitivity, providing significant practical implications for expanding LFIA applications, particularly in resource-limited settings.

Highly selective peptide-based fluorescent probe with aggregation induced emission (AIE) for detection of chondroitin sulfate and its application in living cells and zebrafish imaging

Chondroitin sulfate (CS), as a kind of acid mucosaccharide with natural activity, has shown various physiological activities in human body due to its advantages of high biocompatibility, good degradability and little side effects. Herein, a novel and simple peptide probe (TPE-ASRH) based on tetraphenylethene (TPE) and tetrapeptide (Ala-Ser-Arg-His-NH2) was designed and synthesized. TPE-ASRH displayed remarkable aggregation induced emission (AIE) characteristic in DMSO/water binary mixture. Based on electrostatic attraction, TPE-ASRH displayed highly selective and sensitive detection to chondroitin sulfate with large Stokes shift (156 nm), and the limit of detection (LOD) for chondroitin sulfate was calculated to be 0.11 nM based on 3σ/k. In addition, the colour change of TPE-ASRH was observed significantly from midnightblue to steelblue after adding chondroitin sulfate using naked eyes under 365 nm UV irradiation. Meanwhile, TPE-ASRH was able to achieve a rapid response to chondroitin sulfate (less than 30 s) with a pH response range of 3-12, which indicated that TPE-ASRH can detect chondroitin sulfate rapidly under physiological conditions. The response mechanism of TPE-ASRH to chondroitin sulfate was demonstrated using Zeta particle size and potential, UV-vis titration spectroscopy, FTIR spectra and CD spectroscopy. Most importantly, TPE-ASRH revealed the considerably low cytotoxic effects and good biological permeability, and was successfully applied to image chondroitin sulfate in living cells and zebrafish.

NIR-II AIEgen nanocomplex with suppressed nonradiative decay and intersystem crossing for high-contrast mesenteric vascular imaging

The prompt assessment of the mesenteric vasculature is crucial for the diagnosis of lethal mesenteric ischemia, underscoring the need for real-time mesenteric vascular imaging using small organic molecules that radiate fluorescence within the second near-infrared spectrum (NIR-II) due to its deep penetration and elevated signal-to-background ratio (SBR), which have been rarely reported. Unfortunately, numerous NIR-II dyes exhibit low quantum yields (QYs) when employed in practical applications, highlighting the need for QY enhancement. For this research, a NIR-II fluorescent AIEgen, termed TPETPA-TQT, was rationally designed by incorporating tetraphenylethylene (TPE)-fused triphenylamine (TPA) into the robust, high QY core of 6,7-di(thiophen-2-yl)-[1,2,5]thiadiazolo[3,4-g]quinoxaline (TQT). We further encapsulated this dye within F127 to form the TPETPA-TQT F127 nanocomplex, which exhibits a 6.5-fold enhancement in fluorescence intensity over the TPA-TQT dye encapsulated with DSPE-PEG2000, attributed to the suppression of molecular nonradiative decay and intersystem crossing. The abdominal vasculature and microvessels on the intestinal wall surface, as narrow as 0.41 mm, can real-time visualization using TPETPA-TQT F127 nanocomplex, and exhibit a 94 % improvement of SBR versus ICG. Our findings will push forward the progress of high-brightness NIR-II contrast agents for enhanced mesenteric vasculature imaging and mesenteric ischemia diagnosis.

Multi-dimensional donor engineering of NIR-II AIEgens for multimodal phototheranostics of orthotopic breast cancer

"One-for-all" multimodal phototheranostic agents, which integrate multiple photodiagnostic and phototherapeutic functionalities into a single component, have emerged as promising platforms for advancing cancer treatment. Among these, agents featuring second near-infrared (NIR-II) emission are particularly appealing due to their superior tissue penetration depth and high signal-to-background ratio (SBR). However, most reported NIR-II fluorophores suffer from severely imbalanced radiative and non-radiative excited-state energy dissipation in biological environments, resulting in extremely low fluorescence quantum yields (QYs) and limited diagnostic efficacy. This highlights the urgent need for innovative molecular design strategies to develop high-performance NIR-II "one-for-all" multimodal phototheranostic agents. Herein, we present, for the first time, a multi-dimensional donor engineering protocol that optimizes donor design at the molecular, aggregated, and solvent-interaction levels. By introducing 2,4,4-trimethylpentan-2-yl groups into the diphenylamine indeno[1,2-b]thiophene donor unit, we developed a donor-acceptor-donor (D-A-D) type NIR-II aggregation-induced emission-active luminogen (AIEgen), i.e. OPITBT. When formulated into nanoparticles (NPs), OPITBT NPs exhibited a 16-fold enhancement in fluorescence QY compared to OPITBT in tetrahydrofuran, along with excellent photothermal conversion efficiency (PCE) and acceptable type-I reactive oxygen species (ROS) generation. When further fabricated into tumor-targeting NPs, the resulted OPITBT-R NPs effectively eliminated orthotopic breast cancer through fluorescence-photoacoustic-photothermal multimodal imaging-guided photodynamic-photothermal synergistic therapy under single 808 nm laser irradiation. Notably, the exceptional NIR-II fluorescence brightness of OPITBT-R NPs enables high-resolution NIR-IIb whole-body vascular imaging in living mice. This work provides a versatile strategy to enhance radiative dissipation of NIR-II fluorophores for balanced phototheranostic performance and advances the development of "one-for-all" phototheranostic systems.

Tetraphenylethene-based covalent organic polymers with tunable Electrochemiluminescence for ultrasensitive detection of tetracycline

Tetracycline overuse has become significant threat to human health and ecological security. Therefore, it is urgent to develop an ultrasensitive and highly selective biosensor for fast, trace and precise detection of tetracycline. Herein, we developed an electrochemiluminescence (ECL) biosensing platform for tetracycline detection through using 1,1,2,2-tetrakis(4-(pyridin-4-yl)phenyl)ethene-1,4-bis(bromomethyl)benzene (TPPE-BBMB) covalent organic polymers (COPs). The as-developed ECL biosensor had rapid response, high sensitivity, wide linear range (0.05-20 μM), low limit of detection (2.26 nM), long-term stability and recyclability. The TPPE-BBMB COPs exhibited strong fluorescence (FL) and ECL emission, the maximal ECL efficiency of which was 9-fold higher than Ru(bpy)32+. The ultrasensitive ECL biosensor has successfully been applied to detect tetracycline in real samples, including milk, lake water and soil samples, which had good recovery rate of more than 93 %. Therefore, the ultrasensitive and highly selective ECL biosensor constructed by TPPE-BBMB COPs will have great potential for trace detection of other such antibiotics.

Enhanced generation of reactive oxygen species and membrane intercalation potency of berberine-based conjugates for efficient photodynamic inactivation against foodborne bacteria

Dual-functional photosensitizers (PSs) with enhanced reactive oxygen species generation based on natural aggregation-induced emission (AIE) luminogen and membrane-intercalating ability were fabricated. Specifically, the AIE property of berberine (BBR) was achieved by encapsulating it into the carboxymethyl-β-cyclodextrin (CMCD) cavity to restrict its molecular motion. Meanwhile, the CMCD was decorated with transacting activator of transduction (TAT) peptide to realize the membrane-intercalating function. On this basis, the fabricated BBR/CMCD/TAT conjugates exhibited superior PDI efficiency (>8 Log CFU mL-1) against foodborne bacteria by inducing severe membrane damages. Transcriptomic analysis revealed that the BBR/CMCD/TAT-mediated PDI significantly blocked the biosynthesis of peptidoglycan and lipopolysaccharide, and compromised the energy production pathways, eventually causing cell death. Furthermore, the BBR/CMCD/TAT-mediated PDI efficiently inactivated ∼99 % bacteria on salmon fillets throughout the storage period, consequently extending the shelf life by 3 days. These findings highlight the promising application of dual-functional PS-mediated PDI in combating bacteria and ensuring food microbiological safety.

AIE luminogens based on 9, 10-dithienylanthracene with a D-A-D structure: Design, synthesis and application in cell imaging

Three novel D-A-D-structured emitters derived from 9, 10-dithienylanthracene derivatives (DTAs) were synthesized and characterized. These DTAs consist of substituted 9-phenyl-9H-carbazole (BPCB-DTA), triphenylamine (BTPA-DTA) and N, N-dimethylaniline (BDMA-DTA) as donor units, with the phenylacetonitrile group serving as the acceptor. The impact of steric hindrance and electronic effect of the substituents on the optical properties has been thoroughly discussed. All DTAs exhibited aggregation-induced emission, except for BDMA-DTA, which displayed gradual fluorescence quenching as the water fraction increased from 0 to 90 %. Scanning electron microscope analysis revealed that aggregates formed morphologically regular nanorods due to the self-assembled process. Moreover, BPCB-DTA and BTPA-DTA demonstrated reversible mechanofluorochromic and vapochromic luminescence behaviors with a high color contrast mechanofluorochromism ranging from yellow to bright green coloration. These results suggest that large volume and non-coplanar fluorophores play a crucial role in constructing DTA-type AIE dyes. Additionally, fluorescence imaging experiments conducted on HeLa cells confirmed the bio-imaging capabilities of these DTAs.

An organic emitter with enhanced fluorescence modulation, high emission efficiency, multicolor tunability in solution and solid states, and dual-channel sensing for selective cyanide detection

For many industrial application, there arise a demand for multistate with multicolor emissive materials due to its substantial applications than fluorophore shows emission in single state. Therefore, in this work donor-acceptor-donor' (D-A-D') based three organic emitters (DSE1-DSE3) were synthesized. A substituted phenyl ring and cyano vinyl unit are used to manage molecular geometry and steric hindrance to reduce the gap between AIE and ACQ, resulting in an improved dual-state emission. Solid state emission maxima for all chemicals were red shifted compared to solution state. Additionally, quantum yields and excited state fluorescence lifetime were higher in the solid state. Because of their donor-acceptor pattern, all of the dyes show positive solvatochromism. As the solvent polarity increases, the emission maxima of DSE1-DSE3 redshift gradually. These emitter probe DSE1-DSE3 showed redshift in aggregation emission (ACRE) in water which is considered to be a poor solvent, this is supported by DLS and SEM analysis. Meanwhile, the compound DSE1-DSE3 can detect cyanide ion selectivity over other competing anions via the absorbance and fluorescence channels. Under the effect of electron accepting cyano groups, the vinyl C = C bond was easily reacted by nucleophilic CN- which disturb the conjugated bridge of the compounds and prevented the ICT process between the donor and acceptor. The addition of cyanide ions to the compounds DSE1-DSE3 resulted in a significant red shift in absorbance and a total quenching of fluorescence intensity. For real life application, the probe successfully detects cyanide ion in various water samples. Besides, the developed DSE3-encapsulated polysulfone (PSF) capsule kit effectively sense cyanide ion in water.

Nonclassical Hydrogen Bond-Based Efficient Solid-State Organic Emitters Enabled by a Synergistic Anion and Mechanical Bond Effect

Traditional fluorophores often face aggregation-caused quenching (ACQ), limiting their efficacy in high-concentration applications. We demonstrate that a combined effect of anion and mechanical bond can significantly increase fluorescence intensity, up to 14-fold, and a quantum yield of 97.0%. A large number of crystal analyses reveal that this enhancement is primarily driven by nonclassical hydrogen bonds, which stabilize the structure and restrict molecular motion. The versatility of this synergistic effect opens up new avenues for applications, including circularly polarized luminescence (CPL) facilitated by chiral anions and the development of a fluorescence switchable rotaxane shuttle-based stimuli-responsive material.

Cationic AIEgens with large rigid π-planes: Specific bacterial imaging and treatment of drug-resistant bacterial infections

In this study, four D-π-A type cationic photosensitisers with aggregation-induced emission (AIE) properties were developed based on the electron-donating group triphenylamine and pyrene molecules acting as auxiliary electron donors and main π-bridges, as well as pyridinium salts of different charge numbers acting as electron acceptors: TPP1, MeOTPP1, TPP2 and MeOTPP2. The introduction of pyrene endowed the AIE photosensitizers with a high solid fluorescence quantum yield and long fluorescence lifetime. All four photosensitizer molecules were able to efficiently generate type I (·OH) and type II (1O2) under white light irradiation, achieving efficient inactivation of methicillin-resistant Staphylococcus aureus (MRSA) at low concentrations, and TPP1 and TPP2 successfully promoted wound healing in MRSA-infected mice. The introduction of a methoxy group effectively enhanced the intramolecular charge transfer effect, achieved longer wavelength absorption and fluorescence emission redshift, and effectively reduced ΔEst thereby promoting ROS (Reactive Oxygen Species) generation. However, after the introduction of the methoxy group, the CAC (Critical Aggregate Concentration) of MeOTPP1 and MeOTPP2 became smaller and the hydrophobicity was enhanced, which affected the interaction with bacteria. In fact, the photodynamic antimicrobial activity and imaging ability against bacteria were reduced. TPP2 achieves efficient killing of MRSA and MDR E.coli (Multidrug-resistant Escherichia coli) by disrupting the bacterial cell membrane due to its high photosensitization efficiency, two positive charges and very high CAC value. Under light (40 mW·cm-2), only 1 μM of TPP2 inactivated 87 % of MRSA, followed by TPP1, which inactivated 59 %, while MeOTPP1 and MeOTPP2 showed no significant antibacterial activity at this concentration. At a concentration of 10 μM, TPP2 deactivated more than 95 % of MDR E.coli, TPP1 deactivated about 41 %, and MeOTPP1 and MeOTPP2 had no antimicrobial activity against MDR E.coli at this concentration. In addition, TPP1, MeOTPP1 and TPP2 were able to rapidly identify MRSA and MDR E.coli under the irradiation of 365 nm UV light, which provides a visual method for the rapid identification of MRSA and MDR E.coli.

Recent advances in fluorescent nanomaterials designed for biomarker detection and imaging

The highly sensitive detection and imaging of biomarkers are critical for early diagnosis, treatment, and prognosis monitoring. The unique size and structure of fluorescent nanomaterials provide key benefits such as excellent photostability, high fluorescence quantum yield, and tunable excitation and emission wavelengths. These properties have led to the widespread application of nanomaterials in fluorescent biomarkers detection and imaging. In this review, we began by introducing the composition of fluorescent probes and discussing the underlying sensing mechanisms. We then summarized recent advances in the use of fluorescent nanomaterials such as quantum dots (QDs), metal nanoclusters (MNCs), carbon dots (CDs), and metal-organic frameworks (MOFs) for biomarker detection and imaging. Additionally, we highlighted the applications of fluorescent nanomaterials in the detection and imaging of small molecules, biomacromolecules, and various biomarkers, including metal ions, bacteria, and circulating tumor cells (CTCs). The challenges and future prospects of fluorescent nanomaterials in biomarker detection and imaging were also discussed. We anticipate that fluorescent nanomaterials will have profound implications for clinical biomarker detection and imaging, with considerable application in both academic research and industrial applications.

In Vitro and In Live-Cell Rapid Hydrazine Detection by Disaggregation of the AIEgen Microstructure

In this study, efficient hydrazine detectors are developed using disaggregation of AIEgen microstructures. A new class of 2,4,6-triphenylaniline-based AIEgens are designed to alter the optoelectronic properties in different aggregated states. These 2,4,6-triphenylaniline-based molecules (SB1, SB2, and SB3) are self-assembled in the aqueous medium as well as in physiological condition, creating distinct microdomains and effectively showing tunable aggregation- induced emission (AIE) properties. The aggregation behavior was extensively investigated using advanced spectroscopic and microscopic techniques, by modulating the water content in acetonitrile solution. The aggregated state of SB3 emerged as the most sensitive hydrazine detector, achieving an exceptional detection limit of 0.054 µM, outperforming compounds SB1 (2.8 µM) and SB2 (2.2 µM). This attributed to hydrogen bond induced disaggregation of AIEgen aggregates, resulting in a pronounced turn-on fluorescence response by intramolecular charge transfer (ICT). Not only aqueous hydrazine or hydrazine vapor detection, but also the SB3 permeate cell membrane, localize in the perinuclear area, and detect intracellular hydrazine with great specificity. This on-site and real-time fluorogenic hydrazine detection have prospective applications in monitoring the environment and biomedical imaging.

Multi-Stimuli Responsive Tripodal Phenothiazine Derivatives and Their Applications in Monitoring Fish Spoilage, Anti-counterfeiting Writing, and Visualization of Latent Fingerprints

In this work, we designed and synthesized D-A type tripodal phenothiazine derivatives to examine the influence of different functional groups on the photophysical properties and response to external stimuli. The compounds show emission in both solution and solid-state. Intramolecular charge transfer (ICT) characteristics are evidenced by the fluorescence studies revealing positive solvatochromism in compounds. The compounds are highly thermally stable with low optical band gaps (2.1-2.55 eV). Compounds 3a-3c displayed excellent aggregation-induced emission enhancement (AIEE) phenomena in CH3CN/DMSO and water mixtures. Compound 3e could detect moisture in three solvents, namely THF, CH3CN, and DMSO, with the lowest detection limit of 0.018% in DMSO. The compounds show reversible acidochromism in solution and solid-state, where compound 3e containing pyridyl shows the lowest detection limit for TFA of 0.59 ppm among others. The 'ON-OFF-ON' response to TFA/TEA stimulation has been utilized for the construction of the truth table and the outcome corresponds to the IMPLICATION logic gate. The sensitive response of compound 3e to amine vapors has been utilized for monitoring food spoilage. The compounds also show mechanofluorochromism, and the phase transformation was analyzed by powder X-ray diffraction studies. These compounds are potential candidates for multi-level anti-counterfeiting applications and latent fingerprint sensing. Acidochromism; Aggregation-induced emission enhancement (AIEE); Anti-counterfeiting; IMPLICATION logic gate; Mechanofluorochromism.

Developing Dual-State Emission Berberine Derivatives as Theranostic Agents by Reducing Nonradiative Transition Pathways

Berberine, an antibacterial natural product, shows promise as a theranostic agent. However, berberine exhibits moderate antibacterial efficacy and limited water solubility, restricting its clinical application. In this study, we discovered that a berberine derivative B-12 exhibits dual-state emission (DSE) characteristics, and its photodynamic antibacterial activity is significantly higher than that of berberine and methylene blue. The mechanistic studies suggested that substitution with a single methoxy group at the C-3 position reduces the intramolecular electron transfer and increases the energy gap between singlet and triplet excited states, which reduces nonradiative transition pathways and improves the fluorescence quantum yield. The C-3 methoxy group also contributes to higher ROS production due to the longer lifetime of the excited state. Through bioimaging, B-12 was able to discriminate between Gram-positive and Gram-negative bacteria. Notably, this study offers valuable insights for designing photodynamic and DSE-active berberine derivatives, highlighting the potential of these derivatives as theranostic agents.

Mapping human fingerprint beyond level-3 based on an amphiphilic aggregation-induced emission luminogen and the construction of intelligent platform for personal identification

BACKGROUND

Fluorescence imaging agents have been benefiting tremendously from tailor-made aggregation-induced emission (AIE) luminogens, owing to their high on-off ratio, large signal contrast, low background noise as well as the resistance to photobleaching. In the domain of fingerprint imaging, AIE luminogens are beginning to exhibit an advantage owing to the aforementioned superiorities.

RESULTS

We present an amphiphilic benzoic-acid salicylaldehyde AIE luminogen AIE-BASB, and outline its water sensitivity, self-assembly behavior as well as fingerprint imaging properties. AIE-BASB self-assembles into nanoscale textures when fabricated into a drop-casting film but undergoes a disassembly process in response to trace water on fingertip upon physical-contacting. Owing to the biological textures on the skin, fingerprint image can be clearly recorded by AIE-BASB film, which reveals detailed microscopic features of fingerprint information ranging from level-1 to level-3. Furthermore, it allows accurate measurements of the sizes, shapes, centroids, and areas of the sweat pores, which leads the fingerprint information into the next level. In addition, we develop an intelligent system based on AIE-BASB by integrating hardware and software modules, which is capable of recording and identifying fingerprint. After inputting fingerprint segments in trial operation, this intelligent system makes identification by calculation of the categorical probability, and successfully predicts the classification of the undefined fingerprint segments, implying 100 % accuracy in fingerprint identification.

SIGNIFICANCE

We predict that AIE-BASB may facilitate the development of new biometric technologies, which have broad applications in the domain of artificial intelligence, including machine tactility, target perception and object-machine interaction.

Interpretable prediction of aggregation-induced emission molecules based on graph neural networks

We developed an interpretable graph neural network (96.4% accuracy) for AIEgen identification, revealing 24 characteristic functional groups. Based on these insights, two virtual library strategies (self-fragment and donor-acceptor docking) were proposed and predicted four experimentally confirmed AIEgens successfully, which establishes a rational design framework for AIE materials.

Artificial Light-Harvesting Pt(II) Amine Cage and Its Application as Security Ink

A new platinum (II)-triphenylamine tetra aldehyde-based barrel-shaped rectangular covalent cage was prepared using dynamic imine condensation and subsequent reduction. The cage was found to exhibit aggregation-induced emission behavior in 60% water in THF solvent composition and the AIE property was successively utilized to achieve excellent sequential light-harvesting behavior in aggregate form in the presence of acceptors such as Eosin Y and Nile Red. Moreover, the light-harvesting capability was employed to prepare a new type of security ink whose potential was demonstrated using TLC plates and commercial banknotes.

Detection of Latent Fingerprints with Simple AIE-Active p-Phenylenediamine Schiff Bases

Detection of latent fingerprints (LFPs) is pivotal in recognizing the individuals involved in the crime. To achieve this, many attempts have been made to obtain highly sensitive fluorophores with low adhesiveness; however, this remains a challenge. The present research explores the synthesis and application of aggregation-induced emission active phenylenediamine-based Schiff bases 3a and 3b for latent fingerprint detection. The Schiff base, exhibiting enhanced fluorescence upon aggregation, demonstrates remarkable sensitivity and selectivity towards latent fingerprints. The synthesized compounds offer a unique approach, capitalizing on the aggregation-induced enhanced emission phenomenon, providing clear and vivid visualization of latent fingerprints on various surfaces, including rubber, plastic, glass, metals, aluminum foil, and ceramics. A simple powder dusting method was utilized to visualize the latent fingerprints. This technique successfully produced high-resolution images, giving all the 1-3 levels of specifications of the developed fingerprints. The photostability of the synthesized molecule was also evaluated by checking the emission produced by the compounds after storing them for a longer period under ambient conditions. The AIE Active Phenylenediamine-based Schiff bases provide a simple tool to visualize LFPs. The CIE (x, y) coordinates for 3a and 3b were (0.416, 0.556) and (0.317, 0.452), respectively, indicating green-yellow emission under UV 365 nm illumination.

A novel fluorescent nanoprobe based on platinum nanoclusters with the characteristic of aggregation-induced emission for the detection of Cu2+ and D-penicillamine

In this work, platinum nanocluster (Pt NCs) with AIE property using L-glutathione (L-GSH) as the protecting ligand are reported. The solid-state photoluminescence quantum yields of obtained Pt NCs powder is as high as 8.0 %. The as-prepared Pt NCs exhibited solvent-induced emission. Specifically, they exhibited gradually enhanced red fluorescent emission as the volume ratio of ethanol to H2O increases. Additionally, the obtained Pt NCs presented excellent stability and resistance to photobleaching in the mixed solvent of ethanol and H2O. Based on the fluorescent quenching effect of Pt NCs induced by Cu2+ and the strong coordination interaction between Cu2+ and thiol group of D-penicillamine (D-Pen), a novel "off-on" fluorescent nanoprobe was proposed for quantifying the labelling amount percentage of commercially available D-penicillamine tablets. Experimental results demonstrated the fluorescent quenching from our proposed Pt NCs-based nanoprobe was linearly correlated with Cu2+ concentration within the range from 1 to 28 μM, with a limit of detect (LOD) of 0.13 μM. Besides, upon addition of D-Pen into a mixed system containing Pt NCs and Cu2+, fluorescent intensities of Pt NCs were recovered and exhibited concentration-dependent responses within a concentration of D-Pen from 1 to 120 μM, with an LOD of 0.058 μM. Spiked sample experiment validated that our proposed nanoprobe possessed an outstanding accuracy, which expands the potential application of metal nanoclusters exhibiting AIE effects in pharmaceutical analysis.

The first example of white-light emission based on pyrimido[4',5':4,5]thieno[2,3-d]pyrimidine moiety: Synthesis, photophysical, and antimicrobial studies

A series of new AIE systems based on the pyrimidothienopyrimidine skeleton were efficiently synthesized and fully characterized. These compounds exhibited weak emission in solution but strong solid-state fluorescence with a red shift. Notably, compound 16 displayed unique white-light emission from a single-component system and tunable emission colors in DMF/water mixtures. This dual emission behavior, arising from AIE and excimer formation, is unprecedented for pyrimidothienopyrimidine derivatives. Although compounds 9a and 9b exhibited AIEE behavior, compounds 15c and 18 demonstrated AIE behavior, with significantly enhanced fluorescence intensity upon water addition. Moreover, most synthesized compounds exhibited moderate to strong antimicrobial activity against various bacterial and fungal strains, suggesting their potential for biological applications.

High-contrast tricolored mechanofluorochromism of a novel gold(I)-based AIEgen achieved through the phosphino-type auxiliary ligand modulation strategy

Two novel tetraphenylethylene-functionalized carbazole-based gold(I) complexes with phosphino-type auxiliary ligands are ingeniously designed and prepared. Significantly, this is the first time that two newly developed gold(I) complexes possessing phosphino ligands can simultaneously show aggregation-induced emission (AIE) and tricolor mechanofluorochromic properties. Furthermore, the gold(I)-bearing AIEgen with a triphenylphosphine auxiliary ligand exhibits a force-induced high-contrast three-color fluorescence switching feature.

Fluorescent Carbazole-Derived Aza[5]Helicenes: Synthesis, Functionalization, and Characterization

5,8-Dihydroindolo[2,3-c]carbazole (ICz), 9H-cinnolino[3,4-c]carbazole (CnCz), and variously alkyl-, alkenyl-, and aryl-substituted indolo[2,3-k]- and -[3,2-a]phenanthridines (IPs) were synthesized using an ortho fusion strategy with Suzuki cross couplings, intramolecular nitrene insertions, diazo couplings, and Morgan-Walls cyclizations as key reactions. The IPs were additionally transformed into organoboranes and helicene conjugates with tetraphenylethylene derivatives. The compounds fluoresce with large Stokes shifts, exhibit strong acidochromism, and show a good to excellent aggregation-induced emission. Their helical structure was elucidated by x-ray crystallographic analysis and by quantum chemical calculations. HOMO-LUMO gaps of 3.96-4.06 eV and S1-T1 gaps were calculated, with CnCz showing a small singlet-triplet inversion. Relative pKa values of 6.65-9.55 were estimated for the different types of azahelicenes.

Computational Design Strategy for Aggregation-Induced Emission Luminogens: Modulating the S1/S0 Minimum Energy Conical Intersection of Anthracene Derivatives through Substituent Effects

Aggregation-induced emission (AIE) has become a key focus in luminescent material development, with substituent modulation being a critical strategy for expanding AIE systems. The S1/S0 minimum energy conical intersection (MECI) significantly influences molecular photophysical properties, making it essential for understanding the AIE phenomenon. Here, we employ anthracene derivatives, known for their chemical versatility and applications in organic light-emitting diodes (OLEDs), to systematically investigate the effects of substituents on the S1/S0-MECI. We select 22 anthracene derivatives with varied electron-donating and electron-withdrawing substituents and explore their impacts on the S1/S0-MECI relative energy and molecular structure. Our findings reveal that strong electron-donating or electron-withdrawing groups at the C9-position effectively lower the S1/S0-MECI relative energy of the gaseous phase singly substituted anthracene derivatives, thus enhancing the AIE phenomenon of such molecules. Additionally, doubly substituted derivatives on the same ring also slightly reduce the S1/S0-MECI relative energy of the isolated molecule. Based on these insights, we propose a novel AIE molecular design strategy focusing on modulating S1/S0-MECI through strategic substituent selection, leading to the identification of 24 AIEgens candidates among 81 anthracene derivatives. In summary, our study provides a systematic approach to designing AIE molecules by modulating the S1/S0-MECI through a substituent effect. The validity of this strategy is confirmed using the 9-tBu-Ant molecule with quantitative calculations.

Synergistic Integration of Aggregation-Induced Emission and FRET Mechanisms in Conjugated Polymers via Molecular Engineering for Ultrasensitive, Rapid, and Discriminative Detection of Perfluoroalkyl Substances

The global contamination of water bodies by persistent organic pollutants (perfluoroalkyl substances (PFAS)) has generated significant societal concern, emphasizing the urgent need for smart strategies for their rapid, ultratrace, and on-site detection. Conjugated polymers (CPs) are exceptional fluorescence sensing materials with signal-amplification properties, yet their performance is often hindered by a conventional aggregation-caused quenching (ACQ) effect. Herein, we present two acceptor-engineered aggregation-induced emission (AIE)-active CPs (FTD-MI and FTD-C8-MI) integrated with efficient Förster resonance energy transfer (FRET) mechanisms for ultralow detection of PFAS. FTD-MI exhibits a turn-off (cyan to dark) fluorescence response, while FTD-C8-MI shows a ratiometric (cyan to red) response to PFAS due to the synergistic effect of AIE and efficient interchain FRET, facilitated by electrostatic and hydrophobic interactions upon binding. Both CPs demonstrate excellent sensitivity at the subnanomolar level toward the most abundant PFAS, perfluorooctanoic acid (PFOA), and perfluorooctanesulfonic acid (PFOS). The sensing mechanism has been thoroughly investigated by both experimental and simulation studies. Additionally, an optical sensor array coupled with machine learning algorithms is established for the discriminative detection of six types of PFAS. Finally, a portable smartphone platform with a custom-designed "app" was developed for real-time, on-site, and semiquantitative analysis of PFAS in actual water samples. Thus, by providing a sensitive, portable, cost-effective, and user-friendly solution, this work offers a powerful tool for monitoring PFAS pollution, ensuring water safety, and reducing risks to public health.

Fluorescent Chromophore Construction via Through-Space Conjugation of Caprolactam and Itaconic Acid: Mechanistic Validation Enabled by 3D-Printed Architectures

Fluorescence characteristics are generally attributed to conjugated molecular structures. Substances exhibiting chromatic or fluorescent effects hold significant application value in functional coatings, biochemical detection, anti-counterfeiting technologies, and pharmaceutical tracking due to their distinctive optical identification properties. Although numerous fluorescent materials have been developed, research on fluorescence mechanisms in low-molecular-weight substances remains insufficient. This study serendipitously discovered that a simple thermal mixing reaction between caprolactam (CPL) and itaconic acid (ITA) can produce a fluorescent-colored metastable colloidal system. The colloid exhibits exceptional stability at ambient temperature, maintaining noncrystalline status or forming novel butterfly/leaf-like crystal structures upon cooling, with reversible colloidal characteristics through thermal cycling. Through comprehensive characterization using fourier transform infrared spectroscopy (FT-IR), nuclear magnetic resonance (NMR), high-performance liquid chromatography (HPLC), and polarized optical microscopy, we elucidated the chromatic and fluorescent mechanisms: intermolecular hydrogen bonding networks facilitate the construction of spatial conjugation systems containing unsaturated groups, achieving photoluminescence via π-electron orbital transitions. The reliability of fluorescence color generation mechanism was confirmed by 3D printing side. This material exhibits excellent solubility in common solvents and shows promising potential for developing fluorescent composites through polymer matrix incorporation.

Uniform Half-Substituted Chiral Arylcycloparaphenylene: Synthesis, Crystal Structure, and Chiroptical Properties

The strategic implementation of aryl-functionalization in every phenyl group in organic architectures presents a transformative approach to constructing novel molecular nanocarbon materials. In this present work, we demonstrate the first synthesis of a uniform and chiral half-aryl substituted cycloparaphenylene (CPP), [6]CPP-12tBuPh. Single-crystal X-ray diffraction analysis unambiguously confirms its hoop-shaped structure and the existence of planar chirality arising from stereochemically distinct substituent orientations. The resolved pS and pR enantiomers display mirror-imaged circular dichroism (CD) signals and a high luminescence dissymmetry factor (|glum| = 2.6 × 10⁻2). Photophysical characterization reveals the emergence of aggregation-induced emission (AIE) behavior, with pure [6]CPP-12tBuPh powder sample exhibiting intense orange fluorescence.

Sensitive discrimination of hazardous explosives by a sensor array based on siloles with aggregate-induced emission

The utilization of cationic amidinourea as side chain of fluorophore has rarely been reported, which might be an efficient and feasible strategy for detecting hazardous explosives. In this work, we present an organic sensor bearing a cationic amidinourea group-specifically, silole UMPS-synthesized via a rapid and convenient method. Its analogues with novel and symmetric structures were also reported. One is neutral and the other two carry hydrocarbon side chains that are positively charged. All four derivatives exhibit aggregation-induced emission and were employed for the detection of nitroaromatic explosives in water. These silole-based derivatives demonstrate excellent sensitivity and effective discriminatory capabilities in detecting explosives. We constructed a cross-reactive sensor array consisting of four derivatives, enabling the differentiation of nine closely related nitro explosives through linear discriminant analysis (LDA). This sensor array not only effectively distinguishes individual explosives of different concentrations and complex explosive mixtures, but also has the capability to identify individual explosives in real water samples with the assistance of machine learning algorithms. Moreover, two siloles were fabricated into test strips for sensing nitroaromatics in practical applications. We anticipate that the current work will pave the way for the development of cation sensors and provide a convenient detection platform for environmental analysis.

Advances in chiral luminescent liquid crystals (CLLCs): from molecular design to applications

Research on circularly polarized luminescent (CPL) materials has evolved into a hot research topic because of their potential application prospects in the optoelectronics and chiroptical fields. Achieving a high glum value and high quantum efficiency is essential and challenging in CPL research. To date, various material design strategies, such as chiral organic small molecules, CPL polymers, chiral lanthanide complexes, chiral liquid crystals and supramolecular self-assembly, have been proposed to achieve a CPL emitter with a high glum value. Among them, chiral luminescent liquid crystals (CLLCs) are recognized as a key approach for achieving CPL materials with a high glum factor owing to their exceptional optical properties and flexibility. In this review, we focused on the various synthesis methods employed for developing CLLCs, their properties and their potential applications. The synthesis section discusses various approaches employed to design chiral luminescent liquid crystals, including (i) doping systems for incorporating chiral dopants into achiral liquid crystalline hosts and (ii) nondoping methods for preparing AIE active chiral luminescent liquid crystalline materials. The section on properties highlights how chirality influences the optical, electronic and structural characteristics of CLLCs. Finally, we discuss the diverse applications of CLLCs from photonics and chiral switching to optoelectronic devices and beyond. This review provides new insights into recent research developments and future opportunities in this booming research field. We anticipate that this review could offer a clear picture of the interesting properties of chiral luminescent liquid crystal materials and inspire more researchers to work in this potential area.

Optically pH-Sensing in smart wound dressings towards real-time monitoring of wound states: A review

BACKGROUND

Over the recent years, the investigations on wound dressings have been undergoing significant evolution, and now smart dressings with the function of the real-time monitoring of the wound states have been recognized as one of the most advanced treatment modalities. Among a variety of wound-related biomarkers, pH represents a promising candidate for in situ supervising the wound healing status. In this regard, a variety of optically pH sensing agents have been widely incorporated into different types of wound dressings.

RESULTS

Herein, we first presented an overview of the advanced wound dressings, especially those commonly used in wound pH sensing. Then, a comprehensive summary of the optical pH sensing agents that could be incorporated into the wound dressings for detecting the pH alteration on the wound bed was described in detail. These materials were classified into colorimetric dyes (i.e., synthetic and plant-based dyes) and fluorescent probes (i.e., small-molecular fluorescein and fluorescent nanomaterials). Each type of pH sensing agent was fully discussed with advantages and limitations for monitoring the wound pH alteration, as well as typical examples of practical applications. To well interpret messages produced by the color-coding dressings, the approaches for defining and communicating color were also summarized, and a proof-of-concept, the smartphone-based remote supervision was particularly highlighted.

SIGNIFICANCE

This review provides a comprehensive overview of the utilization of optically pH sensing in advanced wound dressings for the real-time monitoring of the wound states. It was expected to be an informative source for the exploitation of novel diagnostic dressings for wound management, and also a reference the for application of these materials in the biosensing of other physiological or pathological fluids.

Supramolecular artificial light-harvesting systems incorporating aggregation-induced emissive components: from fabrication to efficient energy conversion

The harvesting and utilization of light energy have increasingly captivated researchers. The construction of artificial light harvesting systems (ALHSs) through supramolecular assemblies has emerged as a prominent approach. Following the discovery of the aggregation-induced emission (AIE) phenomenon, AIE luminogens (AIEgens) have been extensively employed to develop ALHSs, in which these molecules are assembled into nanoparticles or nanoaggregates to enhance energy transfer efficiency. In this review, we summarize recent research advances in supramolecular ALHSs based on AIEgens, including some representative examples reported by our research group and others. In particular, different design strategies for ALHSs formed by self-assembly of host-guest complexes and other building blocks such as macrocyclic and amphiphilic molecules have been discussed over the past three years. For host-guest complexes with AIE activity, we analyze the design principles of AIE-active hosts or guests, and how their self-assembly influences the efficiency of ALHSs. For AIE-active macrocycles or amphiphiles that do not form host-guest complexes, we discuss how they can independently self-assemble into ALHSs. Finally, future research directions for the utilization of AIEgens in the development of ALHSs are discussed.

Aggregation-induced emission-twisted intramolecular charge transfer-activated fluorescent probe for analyzing mitochondrial viscosity in cells and zebrafish

Mitochondria are crucial energy-supplying organelles that support cellular activities and play vital roles in cell metabolism, aging, autophagy, and apoptosis. Abnormal viscosity can alter the mitochondrial microenvironment, disrupt normal mitochondrial function, and lead to disease. To address this, we designed and developed two aggregation-induced emission-twisted intramolecular charge transfer fluorescent probes, namely, (E)-1,1,3-trimethyl-2-(4-(1,2,2-triphenylvinyl)styryl)-1H-benzo[e]indol-3-ium (HSL-1) and (E)-2-(4-(di-p-tolylamino)styryl)-1,3,3-trimethyl-1H-benzo[e]indol-3-ium (HSL-2). In vitro fluorescence detection revealed that both HSL-1 and HSL-2 were sensitive to viscosity and demonstrated a strong log-linear relationship, with linear coefficients of 0.982 and 0.980, respectively. Notably, the responses of HSL-1 and HSL-2 to viscosity changes were unaffected by pH, polarity, or interfering ions. HSL-1 exhibited stronger resistance to background interference than HSL-2 and significantly enhanced fluorescence intensity; thus, it was selected for cell experiments and animal fluorescence intensity assessments. Furthermore, HSL-1 showed excellent biocompatibility, enabling real-time detection of mitochondrial viscosity changes and identification of viscosity abnormalities triggered by mitophagy in HeLa cells. It could also monitor changes in mitochondrial viscosity in zebrafish. In conclusion, HSL-1 is a valuable tool for studying viscosity and understanding diseases associated with abnormal mitochondrial viscosity.

Stereoselective synthesis of heterocyclic tetraphenylethylene analogues with configuration-dependent solid-state luminescence

While nowadays ubiquitous in a variety of optoelectronic applications, fluorophores displaying aggregation induced emission (AIE) and in particular those constructed around the tetraphenylethylene (TPE) core suffer severe limitations. In particular, it has been reported in many instances that stereoconfiguration around the central double bond may severely impact the solid-state luminescence properties (maximal emission wavelength and fluorescence quantum yield). Stereoselective synthesis of extended TPE cores remains challenging, and separation of diastereoisomer mixtures is generally tedious. In this paper, we introduce ditriazolostilbene moities (DTS) as an alternative to TPE. DTS offers two significant advantages over its TPE counterpart: firstly, a fully stereoselective synthesis of the (E)-isomer, and secondly, the use of a copper-catalyzed azide-alkyne cycloaddition (CuAAc) reaction in the final step, which simplifies access to novel derivatives. We illustrate the benefits of this approach using stereopure and (E) and (Z)-aggregates, powders and crystals of the molecule and show that emission properties are considerably dependent on their stereoconfiguration.

A supramolecular fluorescent substance constructed by cucurbit [8]uril and triphenylamine derivate: AIE properties and application for the detection of 4-nitroaniline in aqueous system

Supramolecular substances with aggregation-induced emission (AIE) characteristics have been attracting increased attention. In this work, a supramolecular AIE fluorescent sensor was successfully constructed using a triphenylamine (TPA) derivative, 4,4',4''-(nitrilotris(benzene-4,1-diyl))tris(1-methylpyridin-1-ium) (TPA-PM), as the guest molecule, and Cucurbit[8]uril (Q[8]) as the host one. Physical characterizations, including UV-vis absorption, photoluminescence, 1H NMR, and Mass spectrometry (MS), proved the formation of a [2 + 3] supramolecular complex, TPA-PM2@Q[8]3. Compared with TPA-PM, the as-constructed TPA-PM2@Q[8]3 exhibited greatly enhanced fluorescence emission in aqueous solution, displaying significant AIE effect. Intriguingly, since 4-nitroaniline (4-NA) in aqueous solution could cause the dissociation of the host-guest complex, the strong fluorescence of TPA-PM2@Q[8]3 could be rapidly and highly selectively quenched by 4-NA in aqueous solution without interferences of other nitro-aromatic compounds and common ions. Additionally, the sensing capacity of TPA-PM2@Q[8]3 for 4-NA remained well in actual water samples, indicating its potential practical application.

Investigation of Aggregation Induced Emission Mechanism of Tetrabenzoheptafulvalene Derivative by Spin-Flip Time-Dependent Density Functional Theory (SF-TDDFT)

This study explores the mechanism of aggregation-induced emission (AIE) in the tetrabenzoheptafulvalene derivative, 10,10',11,11'-tetrahydro-5,5'-bidibenzo[a,d][7]annulenylidene (abbreviated as THBDBA) in tetrahydrofuran (THF) solution. THBDBA is AIE-active because in THF solution, it emits significantly less emission (or almost non-emissive) and the fluorescence quantum yield increases by 230 times in aggregate state. We adopted spin-flip time-dependent density functional theory (SF-TDDFT), widely acknowledged for its ability to locate the conical intersection (CI) in medium to large-sized molecules (due to its balanced and reliable description of both ground and excited states and ability to capture double excitation and multireference characters at low computational cost). The functional used is long-range corrected ωPBEh (i. e., LRC-ωPBEh). The strategies used are the excited state deactivation processes by taking into account the S1/S0 surface crossing, referred to as the 'minimum energy conical intersection' (MECI). Reduction of oscillator strength near the minimum energy gap (MEG) structure or CI is also another parameter used to study fluorescence quenching. For the monomer (i. e., in solution), our findings reveal a significant reduction in oscillator strength (f) for de-excitation near the MEG structure and CI, which led us to conclude that in solution, the flapping motion of the phenyl rings plays a vital role to reach the CI. In a smaller scale, a dimer system was chosen to represent the aggregate state. The higher energy gap as well as higher f-value at MEG structure with just the model dimer system indicates that in the actual aggregate (or the crystal) the MECI might be absent. This is because in the aggregate the flapping motion of the phenyl rings will be highly restricted (because of the steric and electrostatic confinements by a large number of monomers from all sides), thereby favoring radiative transitions for energy dissipation. This study consequently elucidates the AIE mechanism of the chosen tetrabenzoheptafulvalene derivative, shedding light on its photophysical properties.

A Novel Enhanced-Fluorescent Probe Based on DHLA-Stabilized Red-Emitting Copper Nanoclusters for Methimazole Detection Via Aggregation-Induced Emission Effect

Herein, an aqueous phase synthesis approach was presented for the fabrication of copper nanoclusters (Cu NCs) with aggregation-induced emission (AIE) property, utilizing lipoic acid and NaBH4 as ligands and reducing agent, respectively. The as-synthesized Cu NCs exhibit an average size of 3.0 ± 0.2 nm and demonstrate strong solid-state fluorescence upon excitation with UV light. However, when dissolved in water, no observable fluorescent emission is detected in the aqueous solution of Cu NCs. Remarkably, the addition of Methimazole induced a significant red fluorescence from the aqueous solution of Cu NCs. This unexpected phenomenon can be ascribed to the aggregation of negatively charged Cu NCs caused by electrostatic interaction with positively charged imidazole groups in Methimazole, resulting in enhanced fluorescence through AIE mechanism. Therefore, there exists an excellent linear correlation between the fluorescent intensities of Cu NCs aqueous solution and the concentration of Methimazole within a range of 0.1-1.5 mM with a low limit of detection of 82.2 µM. Importantly, the designed enhanced-fluorescent nanoprobe based on Cu NCs exhibits satisfactory performance in assaying commercially available Methimazole tablets, demonstrating its exceptional sensitivity, reliability, and accuracy.

High quantum yield copper nanoclusters integrated with nitrogen-doped carbon dots for off-on ratiometric fluorescence sensing of S2- and Zn2

Pursuing nanomaterials with high fluorescence quantum yields is of great significance in the fields of bioimaging, medical diagnosis, and food safety monitoring. This work reports on orange-emitting aggregation-induced emission (AIE) copper nanoclusters (Cu NCs) integrated with blue-emitting nitrogen-doped carbon dots (N-CDs), which enables highly sensitive detection of S2- and Zn2+ ions through an off-on ratiometric fluorescence method. The highly emissive Cu NCs was doped by Ce3+ with a high quantum yield of 51.30 % in aqueous solution. The S2- can induce fluorescence quenching of AIE Cu NCs/N-CDs from orange to blue, while Zn2+ can restore the orange fluorescence. The probe provided linear detection ranges of 0.5-170 μM for S2- and 0.05-200 μM for Zn2+, with detection limits of 0.17 μM and 0.02 μM, respectively. Moreover, a smartphone assistant ratiometric fluorescent test strips were developed for the rapid and visual detection of S2- and Zn2+. The AIE Cu NCs/N-CDs probe exhibited diverse fluorescence color responses, high fluorescence stability, and low cytotoxicity. The ratiometric system was successfully applied to the detection of S2- and Zn2+ in real water samples as well as in cellular and living imaging, demonstrating its potential in biochemical analysis and food safety monitoring.

Ultrasensitive Detection of Prostate Specific Antigen by an Unlabeled Fluorescence Aptasensor Based on the AIE Effect

The accurate and sensitive detection of prostate specific antigen (PSA) is vital for the early diagnosis and treatment of prostate cancer. To this end, an unlabeled fluorescent aptasensor was constructed by using a novel Compound B {1,1'-(1,4-phenylene) bis(3-ethyl-1H-imidazol-3-ium) iodide} with aggregation-induced emission (AIE) activity as a fluorescence signal and NH2-Fe3O4 particle as an adsorption platform. Compound B could combine with prostate specific antigen aptamers (PSA-Apt) to form a PSA-Apt/B complex, which further generated the AIE effect. Then, PSA was added to the PSA-Apt/B solution. PSA combined with PSA-Apt/B to form the PSA-Apt/B/PSA complex. Next, NH2-Fe3O4 magnetic particles were added to the solution. Given that PSA-Apt/B/PSA would no longer combine with NH2-Fe3O4 magnetic particles, the PSA-Apt/B/PSA complex remained in the supernate after magnet separation, and the supernate showed strong fluorescence (I). When no PSA was added to the PSA-Apt/B solution, PSA-Apt/B could combine with NH2-Fe3O4 magnetic particles and would be sucked into the bottom of the test tube by magnet, and the supernate would show weak fluorescence (I0). Result showed that the difference between the above-mentioned two fluorescence values (∆I = I - I0) had an excellent linear relationship with the PSA concentration within the concentration range of 0.01-10 ng/mL, and its limit of detection was 3 pg/mL (S/N = 3). In addition, the sensor has high accuracy and can be directly used to test PSA in actual serum samples.

Judicially Designed Boranil Analogue as Multi-Stimuli Material Displaying Rewritable Behavior

In this paper, we report a systematic investigation related to the solid-state emission and mechanochromic properties by using a series of judicially designed boranil analogues. Interestingly, subtle chemical modification around the boranil and the attached appendage, thereby regulating the steric clash and/or rotational possibility have been found to play a vital role in governing the functional outcome. While smaller and closely connected appendages to the boranil moiety (B-Ph, B-Py, B-TPA, and B-p-Ph) were found to be mechanochromically inactive or insignificant changes were observed, the bulkier appendage with spacer (B-p-TPA and B-p-PY) have shown reversible mechanochromic behavior having spectra shift of 21 and 17 nm, respectively. Furthermore, the potential of B-p-TPA as rewritable material was investigated and reported. In-depth studies related to structural elucidation, solution/solid phase spectroscopy, as well as theoretical calculations; were performed to support the observations.

A Novel NIR Fluorescence Probe with AIE Property to Image Viscosity in Nystatin-Induced Cell Model

As one of the most significant parameters in cellular microenvironment, viscosity levels could be used to determine the metabolic process of bioactive substances within cells. Abnormal viscosity levels are closely associated with a series of diseases. Therefore, the design and synthesis of fluorescent probes that can monitor changes of intracellular viscosity in real-time is of great significance for the study of disease development process. Here, a new viscosity-recognized NIR fluorescence probe W1 based on quinoline-malonitrile is synthesized, and it is not susceptible to interference substances. Besides, AIE probe W1 shows fast response, excellent photostability, low cytotoxicity, good linear relationship between fluorescence intensity value and viscosity. Based on the above advantages, probe W1 is used to image the change of viscosity level in the cell model induced by nystatin.

A chitosan-based fluorescence probe for the detection of nitrite in food samples

Polysaccharides, as a natural biomolecule, are abundantly available in nature and have good bioactivity. They contain several functional groups such as hydroxyl, carboxyl, and amino groups, which can exhibit different fluorescent property after modification. In this work, the chitosan (CS) was selected as a raw material and grafted with methotrexate (MTX) to prepare a nitrite sensor. The sensing material exhibited obvious aggregation-induced emission (AIE) properties and could react with nitrite under acidic conditions to form diazo compounds that could enhance fluorescence. This "enhanced-luminescent" mode fluorescence probe for nitrite (NO2-) displayed superior sensing performance, such as excellent sensitivity, good selectivity, a low detection limit (0.22 μM) and wide detection range from 0 to 120 μM. Moreover, this sensor was effectively applied to detect nitrite in sausage samples. Finally, CS-MTX also showed excellent biocompatibility, good water solubility and outstanding antibacterial performance against Gram-positive Staphylococcus aureus (S. aureus) and Gram-negative Escherichia coli (E. coli). These results demonstrated that it may be a potent multifunctional material for nitrite detection and anti-bacteria in food industry.

Red Fluorescent Molecule with Aggregation-Induced Emission Based on Dehydroabietic Acid Diarylamine for Bioimaging

In this paper, molecules with AIE red light properties were designed by coupling dehydroabietic acid diarylamine and 2,3-diphenylfumaronitrile, which were designated 2DTPA-CN and 2TPA-CN. The emission wavelengths were 683 nm and 701 nm, respectively. The 2DTPA-CN and 2TPA-CN showed typical AIE characteristics with large Stokes shifts of 7.4 × 104 cm-1 and 6.7 × 104 cm-1, respectively. The obvious solvatochromism and electron cloud distributions of HOMO/LUMO in the ground and excited states both reveal the intramolecular charge transfer (ICT) effect. The 2DTPA-CN, boasting exceptional biocompatibility, was successfully prepared into nanoparticles (NPs), which were applied to tumor cell imaging, showing good bioimaging effects both in vitro imaging in live cells and in vivo imaging in live mice. The results demonstrated that it possesses significant potential as an effective bioimaging reagent for the detection of tumor cells. Furthermore, the incorporation of 2,3-diphenylfumaronitrile moieties to dehydroabietic acid diarylamine emerged as a proficient approach to broaden the emission wavelengths of rosin-based fluorescent materials.

Anion-π interaction guided switchable TADF and low-temperature phosphorescence in phosphonium salts for multiplexed anti-counterfeiting

Anion-π+ interactions have gained continuous attention in diverse organic aggregates, as they can effectively alter emission behavior. Herein, the anion-π+ interaction is introduced to phosphonium salts, which exhibit tunable thermally activated delayed fluorescence and phosphorescence emission. Intriguingly, the emission spectra evolve from deep-blue to yellow emission by regulation of the anion-π+ interaction strength through varying the anions, such as BF4 -, CF3SO3 -, PF6 -, and NO3, accompanied by adjustable luminescent decay times from milliseconds to several seconds. Notably, bright blue emission with a high photoluminescence quantum yield near 100% is achieved when substituting the iodide ions with larger counter anions. The phosphonium iodide with strong anion-π+ interaction and heavy atom effect shows a high inter-system crossing rate, which inhibits the direct and prompt fluorescence emission. The anion-π+ interaction and twisted structure strongly suppress π-π stacking and afford ultra-high photoluminescence yields. Furthermore, the participation of polar solvent molecules results in the solvation and bathochromic-shift phenomenon of the solid-state phosphonium iodide due to the ionic polarized host-guest structure. This work provides new insights into the anion-π+ interaction in luminescent phosphonium aggregates.

Dual AIE and Visible-Light-Driven Photoswitchable Polymer for Super-resolution Imaging

Photochromic polymers and aggregation-induced emission (AIE) materials show great potential for many applications. To explore the synergy of both characteristics in polymer material areas, we reported the first synthesis of tetraphenylethylene (TPE)-diarylethene (DAE) polymer and its application as a super-resolution probe for imaging self-assembled cylindrical micelles of PSt38k-b-PEO11k. The polymer exhibits high fluorescence ON/OFF ratios, visible-light-driven photocycloreversion, and AIE properties. Compared with other DAE materials studied in super-resolution imaging, our polymer shows advantages of visible-light-driven photocycloreversion, higher resolution, higher fluorescence quantum yield, or higher thermal stability.

Application of aggregation-induced emission materials in gastrointestinal diseases

Aggregation-induced emission (AIE) is a phenomenon characterized by certain fluorescent molecules that exhibit weak or no luminescence in solution but demonstrate significantly enhanced luminescence upon aggregation. Accordingly, AIE materials have successfully addressed the limitations associated with aggregation-caused quenching effects and have made significant progress in the application of various fields of medicine in recent years. At present, the application of AIE materials in gastrointestinal (GI) diseases is mainly in GI imaging, diagnosis and treatment. In this review, we summarize the applications of AIE materials in GI pathogens and GI diseases, including inflammatory bowel disease and GI tumors, and outline combined treatment methods of AIE materials in GI tumor therapy.

Copper(I) Halide Complex Featuring Blue Thermally Activated Delayed Fluorescence and Aggregate Induced Emission for Efficient X-ray Scintillation and Imaging

Developing solution-processable and stable scintillators with high light yields, low detection limits and high imaging resolutions holds great significance for flexible X-ray imaging. However, attaining an optimal equilibrium among X-ray absorption capacity, exciton utilization efficiency, and decay lifetime of scintillators remains a substantial challenge. Here, a new Cu(I) halide complex was synthesized in a mild condition. It exhibits intense blue thermally activated delayed fluorescence (TADF), remarkable aggregation-induced emission (AIE) characteristic, as well as good water-oxygen stability and photochemical stability. Notably, the complex shows excellent radiation resistance and efficient radioluminescence (RL) with an ultra-low detection limit of 42.5 nGyairs-1. This superior scintillation performance can be attributed to the synergistic effect of effective X-ray absorption by the heavy Cu2I2 core, the high radiation-induced exciton utilization rate in TADF process, and the remarkable suppression of non-radiative transitions by the restriction of intramolecular motions in solid state. Furthermore, the favourable solution processability of the complex facilitates the successful fabrication of a flexible film, achieving high-quality X-ray imaging with a resolution of 17.3 lp mm-1. This work highlights the potential of hybrid Cu(I) halides with AIE-TADF effects for high-energy radiation detection and imaging, opening up new avenues for the exploration of cost-effective and high-performance scintillators.