In vivo fluorescent monitoring of physiological processes with high‐fidelity is essential in disease diagnosis and biological research, but faces extreme challenges due to aggregation‐caused ...quenching (ACQ) and short‐wavelength fluorescence. The development of high‐performance and long‐wavelength aggregation‐induced emission (AIE) fluorophores is in high demand for precise optical bioimaging. The chromophore quinoline‐malononitrile (QM) has recently emerged as a new class of AIE building block that possesses several notable features, such as red to near‐infrared (NIR) emission, high brightness, marked photostability, and good biocompatibility. In this minireview, we summarize some recent advances of our established AIE building block of QM, focusing on the AIE mechanism, regulation of emission wavelength and morphology, the facile scale‐up and fast preparation for AIE nanoparticles, as well as potential biomedical imaging applications.
In this Minireview, recent advances related to the aggregation‐induced emission (AIE) building block quinoline‐malononitrile are summarized. It focuses on the AIE mechanism, regulation of emission wavelength and morphology, the facile scale‐up and fast preparation for AIE nanoparticles, and potential biomedical imaging applications.
Developing dopant‐free hole transporting materials (HTMs) is of vital importance for addressing the notorious stability issue of perovskite solar cells (PSCs). However, efficient dopant‐free HTMs are ...scarce. Herein, we improve the performance of dopant‐free HTMs featuring with a quinoxaline core via rational π‐extension. Upon incorporating rotatable or chemically fixed thienyl substitutes on the pyrazine ring, the resulting molecular HTMs TQ3 and TQ4 show completely different molecular arrangement as well as charge transporting capabilities. Comparing with TQ3, the coplanar π‐extended quinoxaline based TQ4 endows enriched intermolecular interactions and stronger π–π stacking, thus achieving a higher hole mobility of 2.08×10−4 cm2 V−1 s−1. It also shows matched energy levels and high thermal stability for application in PSCs. Planar n‐i‐p structured PSCs employing dopant‐free TQ4 as HTM exhibits power conversion efficiency (PCE) over 21 % with excellent long‐term stability.
Quinoxaline derivatives, featuring with rotatable and chemically fixed thienyl substitutes, are introduced as the core for constructing dopant‐free hole transporting materials (HTMs). The coplanar π‐extended quinoxaline‐based HTM TQ4 achieves the best photovoltaic performance (exceed 21 %) among planar n‐i‐p structured dopant‐free perovskite solar cells.
Unprecedented dual aggregation‐induced emission (AIE) behavior based on a steric‐hindrance photochromic system is presented, with incorporation one or two bulky aryl groups, resulting in different ...flexibleness. The dual AIE behavior of open and closed isomers can be explained by restriction of intramolecular rotation (RIR), restriction of intramolecular vibration (RIV), and intermolecular stacking. The large bulky benzothiophene causes restricted rotation, enhancing the emission of open form in solution and weak π–π molecular packing, thereby efficiently enhancing the luminescence performance in the solid state. With incorporation of two large bulky benzothiophene groups, BBTE possesses the most outstanding AIE activity, undergoing highly efficient and reversible off‐to‐on fluorescence in film upon alternating UV and visible light irradiation along with excellent fatigue resistance. The off‐to‐on fluorescent photoswitch is successfully established in super resolution imaging.
Dual AIE behavior: The steric‐hindrance photochromic system efficiently regulates the intramolecular rotational/vibrational magnitude and intermolecular stacking to tune aggregation‐induced emission (AIE) activity. The off‐to‐on fluorescent photoswitch is successfully established in super resolution imaging.
Inverted‐structured perovskite solar cells (PSCs) mostly employ poly‐triarylamines (PTAAs) as hole‐transporting materials (HTMs), which generally result in low‐quality buried interface due to their ...hydrophobic nature, shallow HOMO levels, and absence of passivation groups. Herein, the authors molecularly engineer the structure of PTAA via removing alkyl groups and incorporating a multifunctional pyridine unit, which not only regulates energy levels and surface wettability, but also passivates interfacial trap‐states, thus addressing above‐mentioned issues simultaneously. By altering the linking‐site on pyridine unit from ortho‐ (o‐PY) to meta‐ (m‐PY) and para‐position (p‐PY), they observed a gradually improved hydrophilicity and passivation efficacy, mainly owing to increased exposure of the pyridine‐nitrogen as well as its lone electron pair, which enhances the contact and interactions with perovskite. The open‐circuit voltage and power conversion efficiency (PCE) of inverted‐structured PSCs based on these HTMs increased with the same trend. Consequently, the optimal p‐PY as HTM enables facile deposition of uniform perovskite films without complicated interlayer optimizations, delivering a remarkably high PCE exceeding 22% (0.09 cm2). Moreover, when enlarging device area tenfold, a comparable PCE of over 20% (1 cm2) can be obtained. These results are among the highest efficiencies for inverted PSCs, demonstrating the high potential of p‐PY for future applications.
The quality of buried interfaces in inverted perovskite solar cells is improved via constructing hole‐transporting materials with deep HOMO levels, high wetting, and passivation capabilities. By systematically regulating the linking‐site of pyridine unit, high efficiencies exceeding 22% (0.09 cm2) and 20% (1 cm2) are achieved.
Pancreatic cancer (PC) is one of the most devastating malignant tumors. However, fluorescence probes for early clinical diagnosis of PC often encounter difficulties in accuracy and penetrability. In ...this work, an enzyme‐activated aggregation‐induced‐emission (AIE) probe, QM–HSP–CPP, for high‐contrast fluorescence diagnosis of PC is developed by monitoring specific overexpressed enzyme Cathepsin E (CTSE). The probe is composed of an AIE fluorophore QM–COOH (QM = quinoline–malononitrile), CTSE‐triggered hydrophobic peptide (HSP), and hydrophilic biocompatible cell penetrating peptide (CPP). The CPP unit can well‐modulate the molecular dispersion properties, giving initial fluorescence‐off state in the aqueous biosystem, thus endowing high signal‐to‐noise ratio, and finally overcoming the poor targeting selectivity of traditional AIE probes. CPP can ensure cell/tissue penetrating ability, thus allowing on‐site monitoring of endogenous CTSE in PC cells, tissues, and living animal models. When the QM–HSP–CPP probe is specifically cleaved by CTSE, it can generate AIE signals in situ with high‐specificity and long‐term tracking ability, and successfully achieve intraoperative diagnosis of human PC sections, tracking PC in heterotopic nude mice models. The CTSE‐enzyme‐triggered AIEgens’ liberation strategy improves accuracy and addresses the penetration problem simultaneously, which can expand the database of multitudinous biocompatible AIE‐active probes, especially for establishing intraoperative pathological fluorescent diagnosis.
An amphiphilic AIE‐active probe is developed by integrating a biological penetration unit, a cell penetrating peptide, which realizes efficient cell‐penetration ability, with in situ generation of high‐fidelity AIE signals for long‐term tracking of the endogenous overexpressed Cathepsin E enzyme in human PC cells, achieving the intraoperative pathological diagnosis of pancreatic cancer section, and succeeding in tracking xenograft‐tumor‐bearing nude BALB/C mice.
High‐fidelity trapping of mitochondrial dynamic activity is critical to value cellular functions and forecast disease but lack of spatial–temporal probes. Given that commercial mitochondria probes ...suffering from low photostability, aggregation‐caused quenching effect, and limited signal‐to‐noise ratio from fluorescence “always on” in the process of targeting mitochondria, here, the rational design strategy of a novel aggregation‐induced emission (AIE) molecular motif and unique insight into the high‐fidelity targeting of mitochondria is reported, thereby illustrating the relationship between tailoring molecular aggregation state and mitochondrial targeting ability. This study focuses on how to exactly modulate the hydrophilicity and the aggregated state for realizing “off‐on” fluorescence, as well as matching the charge density to go across the cell membrane for mitochondrial targeting. Probe tricyano‐methylene‐pyridine (TCM‐1) exhibits an unprecedented high‐fidelity feedback on spatial–temporal mitochondrial information with several advantages such as “off‐on” near‐infrared characteristic, high targeting capacity, favorable biocompatibility, as well as excellent photostability. TCM‐1 also produces reactive oxygen species in situ for image‐guided photodynamic anticancer therapy. Through unraveling the relationship between tuning molecular aggregation behavior and organelle‐specific targeting ability, for the first time, a unique guide is provided in designing AIE‐active probes to explore the hydrophilicity and membrane potential for targeting subcellular organelles.
A novel aggregation‐induced emission building block is connected with a triphenylphosphine group at substitution positions for the high‐fidelity targeting of mitochondria, where the molecular aggregation state is modulated for realizing the “off‐on” characteristic, and the charge density is matched for mitochondrial targeting. The report reveals the relationship between tuning molecular aggregation behavior and organelle‐specific targeting ability.
Aggregation induced emission (AIE) photosensitizers have attracted great attention due to their good performance in photodynamic therapy (PDT). However, the therapeutic effect of AIE photosensitizer ...is often highly dependent on the biological microenvironment because it is difficult to produce type I and type II reactive oxygen species (ROS) simultaneously. Herein, an electron‐rich anion‐π+ AIEgen Pys‐QM‐TT is reported, which is capable of highly generating type I and type II ROS and realizing near‐infrared fluorescence imaging synchronously. In the rational design of AIE photosensitizer, the strong electron‐donating triphenylamine unit, π‐bridge thiophene and electron‐withdrawing pyridinium salt unit can enhance the D–π–A behavior, thereby improving the intramolecular charge transfer effect and extending the wavelength. Meanwhile, the powerful D–π–A effect is supposed to reduce ∆ES‐T and promote the intersystem crossing processes, thus increasing the generation of ROS. In addition, the negatively charged anion in pyridinium salt group provides an electron‐rich environment for the excited photosensitizer, so as to promote electron transfer to generate type I ROS. Therefore, Pys‐QM‐TT can not only generate type I and type II ROS simultaneously with weak environmental dependence, but also effectively inhibit bacterial infections and ablate tumor tissue by promoting tumor cell apoptosis, inhibiting tumor cell proliferation and anti‐angiogenesis.
An electron‐rich anion‐π+ AIEgen Pys‐QM‐TT is constructed, which is capable of highly generating type I and type II ROS and realizing near‐infrared (NIR) fluorescence imaging synchronously, thus realizing efficient bacteria elimination and hypoxic tumor ablation.
With the purpose to achieve panchromatic absorption for constructing efficient dye-sensitized solar cells (DSSCs), the cosensitization approach of using two dyes with complementary absorption has ...been developed with great success. However, this approach usually requires time-consuming optimization of a number of parameters for controlling the ratio and distribution of the two coadsorbed dyes on TiO2 film, which limits the potentials of this strategy. We herein report an alternative approach for developing efficient DSSCs by designing a class of “concerted companion dyes” with two complementary dye components linked covalently. Thus, a newly synthesized organic dye Z2 was linked to a recently reported doubly strapped porphyrin dye XW51 through flexible chains with various lengths to afford XW60–XW63. These dyes exhibit excellent absorption and efficiencies in the range of 8.8%–11.7%. Notably, upon coadsorption with chenodeoxycholic acid, XW61 affords an impressive efficiency of 12.4%, a record for iodine electrolyte-based DSSCs, to the best of our knowledge. In addition, these dyes also exhibit the advantages of easy cell fabrication, simple optimization, as well as excellent photostability.
Chemical passivation is an effective approach to suppress the grain surface dominated charge recombination in perovskite solar cells (PSCs). However, the passivation effect is usually labile on ...perovskite crystal surface since most passivating agents are weakly anchored. Here, the use of a bidentate molecule, 2‐mercaptopyridine (2‐MP), to increase anchoring strength for improving the passivation efficacy and stability synchronously is demonstrated. Compared to monodentate counterparts of pyridine and p‐toluenethiol, 2‐MP passivation on CH3NH3PbI3 film results in twofold improvement of photoluminescence lifetime and remarkably enhanced tolerance to chlorobenzene washing and vacuum heating, which improve the power conversion efficiency of n–i–p planar structured PSCs from 18.35% to 20.28%, with open‐circuit voltage approaching 1.18 V. Moreover, the CH3NH3PbI3 films passivated with 2‐MP exhibit unprecedented humid‐stability that they can be exposed to saturated humidity for at least 5 h, mainly due to the passivation induced surface deactivation, which renders the unencapsulated devices retaining 93% of the initial efficiency after 60 days aging in air with relative humidity of 60–70%.
A specific bidentate molecule, 2‐mercaptopyridine, is demonstrated to substantially enhance anchoring strength at surface of metal halide perovskites, which improves the passivation efficacy and stability synchronously relative to monodentate counterparts. The highly stable bidentate anchoring based passivation on CH3NH3PbI3 not only advances power conversion efficiency from 18.35% to 20.28%, but also leads to a champion lifetime in humid air.
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