Aggregation-induced Emission Research Articles

3‐Hydroxy‐2‐naphthohydrazide: A Commercially Available Compound for Fluorescence Sensing of Ortho‐Vanillin and Vanillin

ABSTRACTVanillin and ortho‐vanillin are the most important flavoring additives used in the food industry at a large scale. Herein, the aggregation‐induced emission (AIE) behavior of commercially available 3‐hydroxy‐2‐naphthohydrazide (3HN) was explored and applied for the detection of vanillin and ortho‐vanillin. The weakly fluorescent 3HN in DMSO showed fluorescence enhancement at 500 nm with the increase in HEPES or PBS buffer (pH 7.4) fractions in DMSO. The 3HN in DMSO containing 30% HEPES buffer is used as Probe 1 for the selective detection of ortho‐vanillin. Probe 1 showed a new fluorescence emission at 415 nm for ortho‐vanillin without altering the probe emission at 500 nm. With high specificity, Probe 1 can detect ortho‐vanillin down to 0.3 μM. In contrast, 3HN in DMSO containing 20% PBS buffer is used as Probe 2 for the selective turn‐off detection of vanillin. The green fluorescence emission of Probe 2 at 500 nm is selectively quenched by vanillin with a detection limit of 0.8 μM. Finally, the analytical novelty of the developed probes was examined by quantifying ortho‐vanillin and vanillin in spiked food samples with good recovery percentages.

Bovine serum albumin framed activatable NIR AIE photosensitizer for targeted tumor therapy

Organic near-infrared (NIR) photosensitizers (PS) largely facilitate photodynamic therapy (PDT). To overcome aggregation induced quenching and diminishment of reactive oxygen species (ROS) generation capability of NIR-PS, aggregation-induced emission (AIE) effect groups have been introduced to generate NIR AIE photosensitizers. However, currently reported NIR AIE photosensitizers all take “always-on” activity that may cause systemic phototoxic side effects. Tumor microenvironment activatable NIR AIE photosensitizers have not been reported. Here we develop an activatable NIR AIE PS nanoparticle (a-NA-PSNP) for near-infrared-II (NIR-II) fluorescence (FL) imaging-guided PDT under 808 nm excitation. NIR AIE photosensitizer (N-PS) is designed and frames with cysteine (Cys)/glutathione (GSH) responsive charge transfer complex (CTC) in bovine serum albumin (BSA) to obtain a-NA-PSNP. With the aggregated state in BSA, N-PS shows high quantum yield with good photostability. As an energy acceptor, CTC quenchs NIR-II fluorescence and ROS production capability of a-NA-PSNP in normal cells and tissues. CTC is decomposed in response to tumor microenvironment Cys/GSH, therefore recovers NIR-II fluorescence of a-NA-PSNP and efficiently generates ROS under 808 nm light irradiation. The depletion of Cys/GSH also regulates tumor intracellular reductive environment to further facilitate PDT. Both in vitro and in vivo results confirmed the tumor microenvironment selective and efficient activation of a-NA-PSNP, indicating its potential in cancer therapy.

Polyfluorene-based Conjugated Nanocomposites with In-situ Gold Nanoparticles: Synthesis via Rational Chemical Passivation and Characterization of Supramolecular Fibrillar Structures

We present a rational and innovative chemical approach for synthesizing and characterizing conjugated polymer nanocomposites as direct passivation of gold nanoparticles (AuNPs), highlighting intrinsic morphologies and distinct photophysical properties in the solid state. The pioneering synthesis of polyfluorene with thiol, LaPPS79.10, revolutionized its application as a direct passivator of AuNPs, resulting in stable nanocomposites with the capacity for storage in the dry state and subsequent redispersion in organic solvent. The presence of AuNPs with average diameters of 3.5 ± 1.3 nm induced the formation of an interconnected fibrillar supramolecular network (ribbon-like) and several microdomains in the nanocomposite (LaPPS79.10+AuNPs), correlated by XRD, TEM and SEM measurements. Characterization of the polyfluorene precursor derivative, LaPPS10, revealed bundle-like morphologies with aggregation-induced emission (AIE). Introducing thiol groups into the intermediate structure induced polymer chain organization (LaPPS79.10), leading to unique straw-like and lenticular bundle morphologies, disrupting the non-planar π-π packing and quenching the emission, a case of aggregation-caused quenching (ACQ). In LaPPS79.10+AuNPs, the proximity of the π system to the Au localized surface plasmon resonance (LSPR) resulted in high absorption, negligible self-absorption, and efficient emission quenching, as well as improved thermal resistance compared to the original polymer. The unprecedented discovery of the properties resulting from the electronic interaction between the π system of the AuNPs passivating polymer and the effects of plasmonic resonance represents a significant advance in nanoscience, opening new perspectives for exciting applications in organic photovoltaic devices and metamaterials.

Multifunctional N-fused fluorescent probes for detection of iron ions and nitro explosives

In this work, two novel probes 4a and 4b were synthesized through Suzuki-Miyaura coupling reaction, whose structures were further confirmed by 1H NMR, 13C NMR, high-resolution mass spectrometry (HRMS) and X-ray single crystal diffraction. The optical properties of the obtained molecules were investigated accordingly. Owing to different bridging fluorophores, there are certain differences in optical performance and detection ability between the two synthesized compounds. Especially, due to the subtle difference in orbitals energy and electron distribution displayed by the DFT calculations, 4a possesses the characteristics of dual-state emission (DSE) molecule, while 4b is an aggregation-induced emission (AIE) molecule. Interestingly, these two molecules can be developed into multifunctional detection probes, successfully applied for the fluorescence recognition of iron ions and common nitroaromatic compounds (NACs). At the same time, the probe molecules can also be applied to the detection of NACs in aqueous environment. What’s more, they can also be loaded on test strips and thin-films for fluorescence identification of NACs, thus being expected to be developed into portable detection tools for NACs.

Anticancer behavior of cyclometallated iridium(III)-tributyltin(IV) carboxylate schiff base complexes with aggregation-induced emission

Cyclometallated iridium(III) and organotin(IV) carboxylate complexes have shown potential application value in the field of anticancer. However, the widespread aggregation-caused quenching (ACQ) effect of these complexes is not conducive to the exploration of their targeting and anticancer mechanism, and the idea of aggregation-induced emission (AIE) effect can effectively solve this problem. Then, AIE-activated cyclometallated iridium(III)-tributyltin(IV) carboxylate Schiff base complexes were designed and prepared in this study. Complexes exhibited AIE effect in highly concentrated solution or aggregative state, which facilitated the investigation of subcellular tissue targeting (mitochondria) and cell morphology. Compared with cyclometallated iridium(III) complex and tributyltin(IV) carboxylate monomers, these complexes showed the better in-vitro anti-proliferative activity toward A549 cells, confirming the favorable synergistic anticancer activity. Even for A549/DDP (cisplatin-resistance) cells, these complexes also exhibited the better activity. In addition, complexes showed a mitochondrial apoptotic pathway. Therefore, cyclometallated iridium(III)-tributyltin(IV) carboxylate Schiff base complexes can be used as the potential substitutes for platinum-based drugs and gain further application.

Tuning the photophysical and NLO properties of β-diketonates derived from coumarin-triphenylamine-chalcones: effect of the BF2 group.

Herein the synthesis of three difluoroboron β-diketonate complexes (7a-c) and one chalcone (7d) with coumarin and triphenylamine fragments is described. The effect of the inclusion of the difluoroboron (BF2) group and a phenyl linker on the photophysical properties, intramolecular charge transfer (ICT) and nonlinear optical (NLO) properties was studied. These dyes exhibited excellent ICT properties due to their A-π-D and D-π-A-π-D type push-pull configuration. Thus, all compounds presented a strong solvatochromism, given the absorption and emission maxima shifted to red because of the increase in the polarity of the medium. In addition to this, 7a-d showed the formation of a twisted intramolecular charge transfer (TICT) state, which quenched fluorescence in polar solvents. Compounds 7a, 7b and 7d exhibited aggregation-induced emission (AIE) in MeCN/H2O mixtures, while 7c did not have this behavior. In addition, all compounds showed emission in the solid state. Using DFT and TD-DFT calculations, the molecular geometries of the ground state S0 and the first excited state S1 were elucidated, which confirmed the formation of a TICT state. Furthermore, the theoretical and experimental absorption electronic transitions were correlated by testing different functionals: B3LYP, CAM-B3LYP, PBE0, wB97XD, HSEH1PBE and M062X. Frontier molecular orbitals (FOMs) and molecular electrostatic potentials (MEPs) supported the ICT from the donor to the acceptor group. The global reactivity descriptors were studied and the NLO properties were predicted by calculating first (βtot) and second-order (γave) hyperpolarizabilities, revealing that 7a-d would present promising NLO behavior.

Ultrafast dynamics and electroluminescence performance of a novel tetraphenylethylene-based aggregation induced emission luminogen

Efficient emission and confined molecular conjugation in aggregated/solid form, are two beneficial characteristics of blue organic light-emitting materials (OLEMs). Aggregation-induced emission molecules (AIEgens) have evolved as auspicious OLEMs that possess these properties. Herein, we discover an innovative sky-blue tetraphenylethene-based AIEgen, 4′,4‴-(1-phenyl-2-(4-(1,2,2-triphenylvinyl)phenyl)-1H-imidazole-4,5-diyl)bis(N,N-diphenyl-[1,1′-biphenyl]-4-amine) (2TPA-ITPE), with high thermal stability. By employing this AIEgen as a non-doped emitter, the constructed organic light-emitting diode demonstrates a maximum external quantum efficiency of 3.35 % with a power efficiency of 4.1 lm/W and high luminescence of 15896.92 cd/m2 2TPA-ITPE exhibits a weak donor-acceptor character. Moreover, to probe the photo-physical nature of this AIEgen, its excited-state dynamics are examined through ultrafast transient absorption spectroscopy (TAS). The TAS results of this OLEM unveil the generation of a resonant structure species owing to the elongation of C=C double bond. The excited state dynamics reveal that 2TPA-ITPE undergoes three processes after excitation (internal conversion, C=C elongation and vibrational cooling). These findings offer innovative insights into the ultrafast mechanisms underlying excited TPE-based OLEMs.

AIEgens-based luminescent metal-organic frameworks as novel electrochemiluminescence emitters Integrated with co-reaction amplification strategy for CA15-3 detection

A current research focus in the field of electrochemiluminescence (ECL) is the development of novel high-performance emitters. Herein, we reported the synthesis of a zirconium-based metal–organic framework (Zr-TBAPy-MOF) using the aggregation-induced emission luminogens (AIEgens) 1,3,6,8-tetra(4-carboxyphenyl)pyrene (H4TBAPy) as ligands and Zr6-clusters as nodes. The resulting AIE-active luminescent MOF (AIE-LMOF) exhibited superior ECL properties and was used as an ECL emitter to construct a high-sensitivity ECL immunosensor. Conceptual experiments demonstrated that Zr-TBAPy-MOF showed significantly stronger ECL emission compared to both the monomers and aggregates of H4TBAPy, attributed to the effective restriction of intramolecular motion (RIM). On the sensor substrate, we designed an Au@ZnO/Cu2O nanocomposite as a co-reactant accelerator. This significantly promoted the generation of sulfate radicals (SO4•−) from persulfate (S2O82−) through the sustainable switching of Cu+/Cu2+ oxidation states in copper oxide (Cu2O). Additionally, zinc oxide (ZnO), which had excellent electrochemical properties, further enhanced the catalytic activity of the materials. Leveraging these advantages, we developed a sandwich-type ECL immunosensor for the ultrasensitive detection of carbohydrate antigen 15–3 (CA15-3), demonstrating a wide sensitive range (0.001 − 100 U/mL) and a low detection limit (0.0007 U/mL). Overall, this work paves the way for the development of efficient ECL luminophores with significant potential in the field of immunoassays for the early diagnosis of disease.

Aggregation-induced emission luminogens for intracellular bacteria imaging and elimination

Intracellular bacterial infections are a serious threat to human health due to their ability to escape immunity and develop drug resistance. Recent attention has been devoted to identifying and ablating intracellular bacteria with fluorescence probes. Aggregation-induced emission luminogens (AIEgens) photosensitizers as fluorescence probes possess excellent photostability and rapid response, which have emerged as powerful fluorescent tools for intracellular bacterial detection and antibacterial therapy. This review is intended to highlight the current advances in AIEgens on intracellular bacteria imaging and elimination, which covers topics from intracellular AIE mechanism, intracellular bacteria imaging of AIEgens to the elimination of intracellular bacteria with AIEgens. AIEgens utilized different interactions to detect intracellular bacteria, emitting bright light due to restricted intramolecular movement to visualize intracellular bacteria. Photosensitive AIEgens generate reactive oxygen species (ROS) in the aggregate state to elimate intracellular bacteria. Moreover, the prospects and application of AIEgens in intracellular bacteria imaging and elimination are also discussed, which provides insights for the development of AIE-based diagnostic and therapeutic materials and technologies.

Sensor array and color-coded test paper tongue based on multivariate cross-responsive AIEgen functionalized bimetallic lanthanide infinite coordination polymers: Toward smart identification and systematic analysis of antibiotics

Building and improving the monitoring technology system for newly emerging contaminants with a positive attitude is the first step to enhance governance capacity, which is in good accordance with the requirements of worldwide sustainable development strategy nowadays. With the urgent needs of smart identification and simultaneous detection of multiple antibiotics co-existing in the aquatic system in mind, we intentionally synthesized the aggregation-induced emission luminogen (AIEgen) functionalized bimetallic lanthanide infinite coordination polymers (TPE-TS@Tb/Eu-AMP ICPs) series. The intrinsic physical and chemical properties of target antibiotics (flumequine, four kinds of tetracyclines, and sulfadiazine) triggered the complex chemical recognition reactions of TPE-TS@Tb/Eu-AMP ICPs series to give birth to multivariate cross-responses. Based on these theoretical-oriented sensing elements and rationally selected smart statistical tools, the “lab-on-TPE-TS@Tb/Eu-AMP ICPs” antibiotic sensor array is established with superior analytical performance. Moreover, the unique optical dominance of TPE-TS@Tb/Eu-AMP ICPs series on solid substrate enabled the subsequent exploitation of test paper tongue (TPT) with simultaneously altered RGB values as elements. Being further coded by the excitation modulation on commercial dark box UV-lamp, even promoted analytical behaviors of the TPT can be realized for the first time. With the aid of the smartphone, robust pattern recognition and accurate systematic analysis of antibiotics in the actual environmental samples were achieved by our sensor array and color-coded TPT, which may provide important scientific supports and technical reserves for the antibiotic control actions in future.

Fluorescent Porous Materials Based on Aggregation-induced Emission for Biomedical Applications.

Fluorescent porous materials based on aggregation-induced emission (AIE) are growing into a sparkling frontier in biomedical applications. Exploring those materials represents a win-win integration and has recently progressed at a rapid pace, mainly benefiting from intrinsic advantages including tunable pore size and structure, strong guest molecule encapsulation ability, superior biocompatibility, and photophysical outcomes. With the great significance and rapid progress in this area, this review provides an integrated picture on AIE luminogen-based porous materials. It encompasses inorganic, organic, and inorganic-organic porous materials, exploring fundamental concepts and the relationship between AIE performance and material design and highlighting significant breakthroughs and the latest trends in biomedical applications. In addition, some critical challenges and future perspectives in the development of AIE luminogen-based porous materials are also discussed.

Fiber Optic-Mediated Type I Photodynamic Therapy of Brain Glioblastoma Based on an Aggregation-Induced Emission Photosensitizer.

Glioblastoma (GBM) is one of the most lethal human malignancies. The current standard-of-care is highly invasive with strong toxic side effects, leading to poor prognosis and high mortality. As a safe and effective clinical approach, photodynamic therapy (PDT) has emerged as a suitable option for GBM. Nevertheless, its implementation is significantly impeded by the limits of light penetration depth and the firm reliance on oxygen. To overcome these challenges, herein, a promising strategy that harnesses a modified optical fiber and less oxygen-dependent Type I aggregation-induced emission (AIE) photosensitizer (PS) is developed for the first time to realize in vivo GBM treatments. The proposed AIE PS, namely TTTMN, characterized by a highly twisted molecular architecture and a bulky spacer, exhibits enhanced near-infrared emission and strong production of hydroxyl and superoxide radicals at the aggregated state, thus affording efficient fluorescence imaging-guided PDT once formulated into nanoparticles. The inhibition of orthotopic and subcutaneous GBM xenografts provides compelling evidence of the treatment efficacy of Type I PDT irradiated through a tumor-inserted optical fiber. These findings highlight the substantially improved therapeutic outcomes achieved through fiber optic-mediated Type I PDT, positioning it as a promising therapeutic modality for GBM.

A novel long-alkyl-chained Schiff bases supramolecular Self assembled material for ultrasensitive detection of Fe3+ and Cu2+

Herein, a novel supramolecular gel, OGW, is successfully synthesized by the rational introduction of long alkyl chains and Schiff base groups. Strikingly, OGW exhibits a bright blue-white aggregation-induced emission under UV light and and was utilized as a chemosensor for the detection of Fe3+ and Cu2+. The lowest detection limits were determined to be 5.37 × 10–8 M and 5.18 × 10–8 M, respectively. The gel OGW was systematically characterized by SEM, FTIR, XRD, XPS, rheological measurements, and fluorescence spectroscopy. Additionally, the prepared OGW-based film was employed as an excellent fluorescent writing material for the detection of Fe3+ and Cu2+.

Organic Nanomaterials Based on Aza-Boron Dipyrromethene with Aggregation-Induced Emission for NIR-II Fluorescence Imaging-Guided Photothermal Therapy

Organic Nanomaterials Based on Aza-Boron Dipyrromethene with Aggregation-Induced Emission for NIR-II Fluorescence Imaging-Guided Photothermal Therapy

Suzuki-Miyaura coupling reaction: Blue-yellow emitting AIE active dyes for organic electronics

A series of eight novel donor‒acceptor (D─A) based 2,3-di(thiophen-2-yl)quinoxaline derivatives 2–9 were prepared by modulating donor species on quinoxaline core with Palladium catalyzed Suzuki–Miyaura ‘C–C bond’ coupling reaction. The synthesized molecules were fully characterized and studied for impact of D–A interaction on opto-electrochemical properties. Absorption spectra of 2–9 display intramolecular charge transfer (ICT) transitions in the range of 388–414 nm. Dyes shows positive solvatochromism and emit in blue‒yellow region with emission maxima 444−550 nm on excitation at their respective ICT maxima in toluene, chloroform, DCM, DMSO and neat solid film. Further, solid state emission was studied for aggregation‒induced emission (AIE) effect in THF–water system due to the nanoparticles formation, as confirmed by FEG‒SEM technique. The HOMO and LUMO energy level for compounds 2–9 were measured by cyclic voltammetry and found in the range of −5.15 to −5.94 eV and −2.81 to −3.39 eV. Theoretical studies of molecules were also carried out by using DFT and TD‒DFT calculations. The comparable HOMO and LUMO energy levels with reported ambipolar materials and efficient solid-state emission make synthesized compounds potential candidate for solid state emissive, ambipolar charge transporting materials in organic electronics.

Solvent-induced modulation of sensitivity and selectivity in the self-assembly of tetracationic cyclophanes with cholesterol sulphate, sodium dodecyl sulfate, and sodium dodecyl benzene sulfonate: Observations of significant shifts

Cyclophane CP-1 demonstrates markedly distinct sensitivities toward Cholesterol sulfate (CH-S), Sodium Dodecyl Sulfate (SDS), and Sodium Dodecyl Benzene Sulfonate (SDBS) when the solvent is shifted minimally from a 95 % to a 98 % HEPES-DMSO mixture. In a 98:2 HEPES-DMSO mixture, CP-1 engages in highly selective self-assembly with CH-S, which is characterized by aggregation-induced emission enhancement (AIEE) in contrast to other steroidal sulfates such as pregnenolone sulfate (PRG-S), dehydroisoandrosterone sulfate (DIAND-S), taurocholic acid (TACH-S), and the surfactants SDS and SDBS. This assembly results in an approximate 40-fold increase in fluorescence intensity with three equivalents of CH-S and allows for the detection of concentrations as low as 200 nM under physiological conditions. Dynamic light scattering (DLS) studies illustrate the aggregation of CP-1 and CH-S, with the zeta potential of each shifting from negative values to nearly zero in a 1:2 CP-1:CH-S mixture, indicating self-assembly. This aggregation behavior is reversible, as demonstrated by a corresponding decrease and then increase in fluorescence intensity with temperature variations from 25 °C to 70 °C and back to 25 °C. Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) analyses show that CP-1 forms aggregates ranging from 100 to 180 nm, which increase to 150–250 nm upon interaction with CH-S. In a 95:5 HEPES-DMSO mixture, CP-1 exhibits a stronger AIEE response with SDS and SDBS compared to CH-S. Cyclophane CP-2, when dissolved in binary DMSO-water mixtures with water content exceeding 80 %, shows similar AIEE phenomena and undergoes selective fluorescence quenching with SDS and only a 50 % increase in fluorescence intensity with CH-S, irrespective of the HEPES concentration (95 % or 98 %).

Triphenylamine-Based Solid-State Emissive Fluorene Derivative with Aggregation-Induced Emission Enhancement Characteristics

Aggregation-induced emission (AIE) has garnered considerable attention in recent years. Understanding the mechanisms underlying AIE phenomena is crucial. Here, we present the design and synthesis of a novel fluorene derivative (4) based on triphenylamine, which exhibits typical AIE properties. The structure of it was totally characterized using FT-IR, MALDI-TOF mass analysis, elemental analysis, 1H, and 13C NMR spectroscopy. It displayed strong solid-state emission with diverse fluorescence characteristics. The AIE property of the compound was systematically studied using photoluminescence spectroscopy, revealing a distinct yellow light-emitting phenomenon. The solid-state luminescence showed a red shift of 148 nm compared to its luminescence in dilute dimethylformamide (DMF) solutions. Moreover, photophysical characteristics, including absorption and emission spectra, as well as fluorescence lifetime, were examined using UV–vis absorption and fluorescence emission spectroscopy. Compound (4) exhibited superior photosensitization abilities in both solid and solution states, with a notably enhanced effect observed in the solid state compared to the solution state.

A dual-response fluorescent hemicyanine probe for the detection of mitochondrial hypochlorite and viscosity based on ESIPT/AIE and TICT

Viscosity and hypochlorite (ClO−) are two important factors affecting the physiological activity and function of mitochondria. Hypochlorite (ClO−) is a vital reactive oxygen species, and endogenous ClO− acts as an important germicidal oxidant in the immune system at low concentrations. While, fluctuations in viscosity can cause mitochondrial dysfunction that is linked to several diseases. We herein report on a hemicyanine-based probe (BDTB-PA) for the detection of hypochlorite (ClO−) and viscosity. The probe exhibits a very low fluorescence background in an aqueous solution due to twisted intramolecular charge transfer (TICT) and blocked excited-state intramolecular proton transfer (ESIPT). In a viscous solution, the TICT of the probe was inhibited, generating a strong emission at 580 nm. In contrast, upon treatment with ClO−, the phenylboronic acid pinacol ester group of probe BDTB-PA was removed, and the hydroxyl group was released, activating the ESIPT process. Coupled with its aggregation-induced emission (AIE) characteristics, the product of BDTB-PA with ClO− exhibited a distinct emission at 540 nm. As such a solution of the probe BDTB-PA exhibited a distinct fluorescent color change from colourless to green under UV light with the addition of ClO−. More importantly, probe BDTB-PA was used for monitoring ClO− and viscosity in the mitochondria of living cells, plants and zebrafish.

Design and synthesis of dicyanoethylene derivatives functionalized with carbazole possessing the properties of obvious aggregation-induced emission and reversible high-contrast mechanofluorochromism

This study devotes to the design, preparation, and examination of two novel D-A structured molecules, designated as CCEDBF and BCCEDBF, which are derived from carbazole unit, dicyanoethylene segment, and dibenzofuran unit. The distinctive D-A molecular architectures and highly twisted spatial configurations of these compounds facilitate pronounced intramolecular charge transfer (ICT) while also imparting robust solid-state luminescence, exhibiting emission efficiencies of 0.518 and 0.739, respectively, and notable aggregation-induced emission (AIE) with AIE factors of 43 and 30. Significantly, both CCEDBF and BCCEDBF demonstrate reversible mechanofluorochromic (MFC) behavior characterized by high fluorescence contrast. Mechanical grinding of the initial powders results in a shift in their emission colors, transitioning from green and yellow-green to yellow and orange-red, respectively, alongside a corresponding shift in emission peaks from 525 nm to 536 nm–558 nm and 597 nm. Powder X-ray diffraction (PXRD) examination of the initially synthesized, mechanically processed, and vaporized samples reveals that the observed fluorescence color change is due to a structural transformation between ordered crystalline and disordered amorphous configurations induced by the application of the external force. The red shift in photoluminescence (PL) spectra post-grinding is attributed to a reduced band gap, driven by factors such as extended π-conjugation length, enhanced planar intramolecular charge transfer (PICT) effect, strengthened π-π interactions and exciton coupling, as well as the increase in the orbitals overlap between neighboring molecular. Moreover, the presence or absence of tert-butyl substituents attaching to the 3- and 6-positions of the carbazole units significantly impacts the photophysical properties of these materials.

Asymmetric D-A-D’ type diphenylsulfone derivative modified by carbazole and tetraphenylethylene showing high solid-state luminescence efficiency, aggregation-induced emission and reversible mechanochromic luminescence

The new D-A-D’ type diphenylsulfone derivative TPE-DBS-Cz with carbazole and tetraphenylethylene units as the donors and diphenylsulfone moiety as the acceptor was prepared. Photophysical properties in solutions and theoretical calculations indicated that the D-A-D’ type molecule TPE-DBS-Cz adopted a highly twisted molecular conformation, obvious intramolecular charge transfer (ICT) and aggregation-induced emission (AIE) behaviors, which not only endowed it with high solid-state luminescence efficiency but also have an obvious fluorescent response to mechanical force. When applied by the grinding and fuming treatment, the emitting color was continuously switched between bright cyan and green. In other words, effective MCL behavior was obtained. The XRD, DSC, fluorescence lifetimes and the PL spectral analyses in different solid states indicated that the MCL nature of TPE-DBS-Cz was derived from the conversion of the crystalline and amorphous states. Moreover, the bathochromic-shift of the PL peak after grinding could be attributed to the degree of extended conjugation and the conformational planarization under external pressure.