Sulfur oxidation states manipulate excited state electronic configurations for constructing highly efficient organic type I photosensitizers.

The multiple relaxation processes of excited states are a bridge connecting molecular structures and properties, providing enormous application potential for organic luminogens. However, a systematic understanding and manipulation of the relationship between the molecular structure, excited state relaxation processes, and properties of organic luminogens is still lacking. Herein, we report a strategy for manipulating excited state electronic configurations through the regulation of the sulfur oxidation state to construct eminent organic type I PSs. Combined with the experimental results and theoretical calculations, we have successfully revealed the decisive role of high sulfur oxidation states in promoting ROS production capacity. Impressively, a higher sulfur oxidation state can reduce the singlet-triplet energy gap (ΔE ST), increase the matching degree of transition configurations, promote the changes of the excited state electronic configurations, and boost the effective ISC proportion by enhancing intramolecular interactions. Therefore, DBTS2O with the highest sulfur oxidation state exhibits the strongest type I ROS generation ability. Additionally, guided by our strategy, a water-soluble PS (2OA) is designed and synthesized, showing selective imaging capacity and photokilling ability against Gram-positive bacteria. This study broadens the horizons for both molecular design and mechanism study of high-performance organic type I PSs.

Asymmetric Structural Engineering of Hot-Exciton Emitters Achieving a Breakthrough in Non-Doped BT.2020 Blue OLEDs with a Record 9.5% External Quantum Efficiency.

High-efficiency non-doped deep-blue organic light-emitting diodes (OLEDs) meeting the standard of BT.2020 color gamut is desired but rarely reported. Herein, an asymmetric structural engineering based on crossed long-short axis (CLSA) strategy is developed to obtain three new deep-blue emitters (BICZ, PHDPYCZ, and PHPYCZ) with a hot-exciton characteristic. Compared to 2BuCz-CNCz featuring a symmetric single hole-transport framework, these asymmetric emitters with the introduction of different electron-transport units show the enhancement of photoluminescence efficiency and improvement of bipolar charge transport capacity. Further combined with high radiative exciton utilization efficiency and light outcoupling efficiency, the non-doped OLED based on PHPYCZ exhibits the best performance with an excellent current efficiency of 3.49%, a record-high maximum external quantum efficiency of 9.5%, and a CIE y coordinate of 0.049 approaching the BT.2020 blue point. The breakthrough obtained in this work can inspire the molecular design of deep-blue emitters for high-performance non-doped BT.2020 blue OLEDs.

Water-Involved Carbon-Nitrogen Triple-Bond Monomer Based Polymerization toward Processable Functional Polyamides under Ambient Conditions.

Polyamide plays a pivotal role in engineering thermoplastics. Constrained by the harsh conditions and arduous procedures for its industrial synthesis, developing facile synthesis of polyamides is still challengeable and holds profound significance. Herein, we successfully utilized water as one of the monomers to synthesize functional polyamides under ambient conditions. A powerful multicomponent polymerization of water, isocyanides, and chlorooximes was established in phosphate-buffered saline. Soluble and thermally stable polyamides with high weight-average molecular weights (up to 53900) were obtained in excellent yields (up to 95%). The polymerization exhibits unique polymerization-induced emission characteristics, successfully converting non-emissive monomers into unconventional emissive polymers. Notably, the resultant polyamides could undergo effective post-modification via the hydroxyl-yne click reaction. By incorporating various functional groups into the polyamide, its emission color could be fine-tuned from blue to green and to red. Remarkably, the refractive index (n) of the polyamide at 589 nm could be increased from 1.6173 to 1.7227 and the Δn could be unprecedentedly as high as 0.1054 for non-heavy atom-containing polymers after post-modification, and its micron-thick films exhibited excellent transparency in the visible region. Thus, this work not only establishes a powerful polymerization toward novel polyamides but also opens up an avenue for their versatile functionalization.

Design and Construction of Highly Luminescent Transparent Woody Materials Exhibiting Unique Fluorescence-Enhanced Staining Effects for Visualization of Intrinsic Microporous Networks.

Luminescent wood materials are an emerging class of biomass hybrid host materials owing to the hierarchical porous structure and functionalization versatility. The fluorescence properties are largely dependent on exogenous fluorophores, which are, however, often plagued by notorious aggregation effects. In this work, an efficient strategy for the preparation of luminescent transparent wood materials is developed by incorporating tetraphenylethylene-derived aggregation-induced emission (AIE)-active fluorophores during a delignification-backfill transparency process. These wood hybrids showed unexpected luminescence enhancement that significantly increased the fluorescence quantum yield of the fluorophores up to 99%, much higher than that of the fluorophores in other states such as crystalline solids or doped in a polymer substrate. Mechanistic investigations reveal that in situ polymerization of prepolymerized methyl methacrylate in delignified microporous wood frames produces high molecular weight ordered PMMA polymers, resulting in a rigid molecular environment that improves the luminescence efficiency of TPE-based fluorophores at the interfaces of PMMA polymer and cell walls. By confocal laser scanning microscopy (CLSM), this excellent fluorescence staining capability was furthermore utilized to visualize the intrinsic porous network of wood in three dimensions over a large volume with submicrometer resolution, thus providing an alternative approach to the study of structure-function relationships in such wood hybrids.

Tandem Solid-Solution Post-Synthetic Modification of Porous Molecular Crystals for In-situ Generation of Fluorophores.

Conventional synthetic methods of organic luminescent molecules often involve labor-intensive solution-phase organic synthesis, which violate the principles of atom-economic transformation. Post-synthetic modification (PSM) offers a promising alternative, allowing direct transformation from one fluorophore to another. Although PSM is commonly implemented in extended frameworks, its application in porous molecular crystals remains challenging. Herein, we focus on utilizing porous molecular crystals, specifically tetraphenylethylene-cored frameworks, as versatile platforms for tandem PSM reactions to customize organic fluorophores. The tailored skeleton design ensures both the formation of porous structures and the occurrence of tandem solid-solution reactions while maintaining the solid state of reactants and products in each step. The inherent non-covalent bonding nature of the frameworks facilitates processing and characterization, offering unparalleled advantages for porous networks. The accompanying solid-state fluorescence transition from green to blue and then to green (or yellow) enables real-time monitoring of tandem reactions and provides intuitive mechanistic insights. This phenomenon is exploited for the facile construction of a dynamic information encryption system using fluorescent quick response codes.

Structural modulation of aggregation-induced emission luminogens for NIR-II fluorescence imaging/photoacoustic imaging of tumors.

Concurrent near-infrared-II (NIR-II) fluorescence imaging (FLI) and photoacoustic imaging (PAI) holds tremendous potential for effective disease diagnosis owing to their combined benefits and complementary features, in particular on the basis of a single molecule. However, the simultaneous guarantee of high-quality NIR-II FLI and PAI is recognized to be challenging impeded by the competitive photophysical processes at the molecular level. Herein, a simple organic fluorophore, namely T-NSD, is finely engineered with facile synthetic procedures through delicately modulating the rigidity and electron-withdrawing ability of the molecular acceptor. The notable advantages of fabricated T-NSD nanoparticles include a large Stokes shift, intense fluorescence emission in the NIR-II region, and anti-quenching properties in the aggregated states, which eventually enable the implementation of dual-modal NIR-II FLI/PAI in a 4T1 tumor-xenografted mouse model with reliable performance and good biocompatibility. Overall, these findings present a simple strategy for the construction of NIR-II optical agents to allow multimodal disease diagnosis.

Molecular Engineering Towards Efficient Aggregation-Induced Delayed Fluorescence Luminogens as Emitters and Sensitizers for High-Performance Organic Light-Emitting Diodes.

Exploring efficient thermally-activated delayed fluorescence materials having maximum external quantum efficiencies (ηext,maxs) exceeding 30% for organic light-emitting diodes (OLEDs) still remains challenging because it generally requires efficient reverse intersystem crossing (RISC), high photoluminescence quantum yield (ΦPL), and large optical out-coupling efficiency (Φout) simultaneously. Herein, two green aggregation-induced delayed fluorescence (AIDF) luminogens, named XTCz-2 and XTCz-3, are designed and constructed by using xanthone (XT) as electron acceptor and phenylcarbazole-substituted carbazole as donors. XTCz-2 and XTCz-3 exhibit distinguished advantages of high thermal stability (439‒560 oC), excellent ΦPLs (84‒88%) and fast RISC rates (1.9 × 105‒4.2 × 105 s-1), and prefer horizontal dipole orientation and thus have high Φouts. Consequently, they can achieve the state-of-the-art electroluminescence (EL) performances with ηext,maxs of up to 35.0%. Moreover, XTCz-3 is selected as a sensitizer for sky-blue multi-resonance delayed fluorescence emitter in hyperfluorescence OLEDs, providing narrow EL spectra and excellent ηext,maxs of up to 33.8% with low efficiency roll-offs. The splendid comprehensive performances demonstrate the significant application potential of these AIDF luminogens as both light-emitting materials and sensitizers for OLEDs.

Unconventional Luminescence Polymer with Color-Tunability based on Solvent-induced Electrostatic Potential Distribution of Fluorophore.

Tuning the full-color emission of polymers holds significant promise. However, preparing unconventional luminescence polymers with color-tunability in dilute solution and understanding the relationship between non-covalent interactions and luminescent behavior remains a great challenge. We report two emitters (P1 and P2) incorporating tetracoordinate boron. The P1 with non-conjugated D-π-A structure, exhibited red delayed fluorescence at 645 nm with quantum yield of 9.15% in aggregates. Notably, the emission wavelength of P1 can be tuned from 418 to 588 nm at different solvent. Similarly, the emission wavelength of P2 can also be adjusted by manipulating the interactions between the solvent and fluorophore. Experimental characterization and theoretical calculations indicate that the B←N bond and electronic interactions between solvent and fluorophore significantly regulate the equilibrium the electrostatic potential (ESP) and the intramolecular O···O interactions of P1, thereby modulating its emission wavelength. Additionally, these polymers showed excellent potential in fluoride ions detection. This work provides new insights into the complex effects of intermolecular interactions on luminescent properties.

Interstitial Optical Fiber-Mediated Multimodal Phototheranostics Based on an Aggregation-Induced NIR-II Emission Luminogen for Orthotopic Breast Cancer Treatment.

One-for-all phototheranostics based on a single molecule is recognized as a convenient approach for cancer treatment, whose efficacy relies on precise lesion localization through multimodal imaging, coupled with the efficient exertion of phototherapy. To unleash the full potential of phototheranostics, advancement in both phototheranostic agents and light delivery methods is essential. Herein, an integrated strategy combining a versatile molecule featuring aggregation-induced emission, namely tBuTTBD, with a modified optical fiber to realize comprehensive tumor diagnosis and "inside-out" irradiation in the orthotopic breast tumor, is proposed for the first time. Attributed to the intense donor-acceptor interaction, highly distorted conformation, abundant molecular rotors, and loose intermolecular packing upon aggregation, tBuTTBD can synchronously undergo second near-infrared (NIR-II) fluorescence emission, photothermal and photodynamic generation under laser irradiation, contributing to a trimodal NIR-II fluorescence-photoacoustic (PA)-photothermal imaging-guided phototherapy. The tumor treatment is further carried out following the insertion of a modified optical fiber, which is fabricated by splicing a flat-end fiber with an air-core fiber. This configuration aims to enable effective in situ phototherapy by maximizing energy utilization for therapeutic benefits. This work not only enriches the palette of NIR-II phototheranostic agents but also provides valuable insight for exploring an integrated phototheranostic protocol for practical cancer treatment.

Study of transient absorption spectroscopy of a D-π-A structure aggregation-induced emission luminogen and its photodynamic therapy application.

Photodynamic therapy (PDT) represents an emerging and noninvasive modality that has gained clinical approval for the treatment of cancers, leveraging photosensitizers for optimal therapeutic efficacy. In this study, we synthesized a photosensitizer (denoted as DTCSPP) exhibiting a donor-π-acceptor (D-π-A) structural motif. The DTCSPP manifests aggregation-induced emission (AIE) characteristics, along with good biocompatibility and mitochondrial targeting capabilities attributed to its intrinsic charge and D-π-A architecture. The excited-state intramolecular charge transfer of DTCSPP was systematically investigated in both solution and aggregate states using femtosecond transient absorption spectroscopy (fs-TA). The fs-TA results revealed that DTCSPP exhibited a more rapid and facile excited-state molecular motion in the solution state compared to the aggregate state, implying the predominance of nonradiative decay in its photophysical processes within the solution. Given its ability to simultaneously generate type I and type II reactive oxygen species and induce ferroptosis and autophagy in cancer cells, DTCSPP demonstrates effectiveness in PDT at both cellular and in vivo levels. This study contributes a comprehensive understanding of the excited-state intramolecular charge transfer dynamics of charged D-π-A type AIE photosensitizers, shedding light on their potential application in PDT. The multifaceted capabilities of DTCSPP underscore its promise in advancing the field of anticancer therapeutics, providing valuable insights for the identification of anticancer targets and the development of novel drugs.

Room Temperature Phosphorescent Nanofiber Membranes by Bio-Fermentation.

Stimuli-responsive materials exhibiting exceptional room temperature phosphorescence (RTP) hold promise for emerging technologies. However, constructing such systems in a sustainable, scalable, and processable manner remains challenging. This work reports a bio-inspired strategy to develop RTP nanofiber materials using bacterial cellulose (BC) via bio-fermentation. The green fabrication process, high biocompatibility, non-toxicity, and abundant hydroxyl groups make BC an ideal biopolymer for constructing durable and stimuli-responsive RTP materials. Remarkable RTP performance is observed with long lifetimes of up to 1636.79 ms at room temperature. Moreover, moisture can repeatedly quench and activate phosphorescence in a dynamic and tunable fashion by disrupting cellulose rigidity and permeability. With capabilities for repeatable moisture-sensitive phosphorescence, these materials are highly suitable for applications such as anti-counterfeiting and information encryption. This pioneering bio-derived approach provides a reliable and sustainable blueprint for constructing dynamic, scalable, and processable RTP materials beyond synthetic polymers.

Spontaneous aggregation-enhanced electrochemiluminescence via galvanic strategy.

Researchers unremittingly strive to develop innovative luminophores to enhance intrinsic electrochemiluminescence (ECL) performance. However, the potential to harness facile strategies, such as manipulating the physical properties of luminophores while retaining functional chemical properties to fabricate cost-effective ECL complexes, remains underexplored. Herein, we reported a novel and efficient one-step galvanic technique to actualize aggregation-enhanced ECL (AEECL) of ruthenium complexes. It marked the first instance of the galvanic process being employed to synthesize aggregate luminophores through electrostatic attraction. The ECL intensity and efficiency of the prepared ruthenium complexes with AEECL properties surpassed traditional ruthenium complexes by 8.9 and 13.6 times, respectively, outperforming most reported luminophores. Remarkably, the target luminophore exhibited high stability across varied scan rates and temperatures. Furthermore, a binder-free and carbon paper-based AEECL analytical device for lidocaine detection was fabricated, achieving a satisfactory detection limit (0.34 nM) and selectivity. The convenient modulation strategy of aggregate structure, along with the transformative leap from insufficient ECL to AEECL, bring forth a new revenue in aggregate science. This research also promises a universally applicable and versatile protocol for future biological analysis and bioimaging applications.

A Near-Infrared-II Excitable Pyridinium Probe with 1000-Fold ON/OFF Ratio for γ-Glutamyltranspeptidase and Cancer Detection.

Activity-based detection of γ-Glutamyltranspeptidase (GGT) using near-infrared (NIR) fluorescent probes is a promising strategy for early cancer diagnosis. Although NIR pyridinium probes show high performance in biochemical analysis, the aggregation of both the probes and parental fluorochromes in biological environments is prone to result in a low signal-to-noise ratio (SBR), thus affecting their clinical applications. Here, we develop a GGT-activatable aggregate probe called OTBP-G for two-photon fluorescence imaging in various biological environments under 1040 nm excitation. By rationally tunning the hydrophilicity and donor-acceptor strength, we enable a synergistic effect between twisted intramolecular charge transfer and intersystem crossing processes and realize a perfect dark state for OTBP-G before activation. After the enzymatic reaction, the parental fluorochrome exhibits bright aggregation-induced emission peaking at 670 nm. The fluorochrome-to-probe transformation can induce 1000-fold fluorescence ON/OFF ratio, realizing in vitro GGT detection with an SBR > 900. Activation of OTBP-G occurs within 1 min in vivo, showing an SBR > 400 in mouse ear blood vessels. OTBP-G can further enable the early detection of pulmonary metastasis in breast cancer by topically spraying, outperforming the clinical standard hematoxylin and eosin staining. We anticipate that the in-depth study of OTBP-G can prompt the development of early cancer diagnosis and tumor-related physiological research. Moreover, this work highlights the crucial role of hydrophilicity and donor-acceptor strength in maximizing the ON/OFF ratio of the TICT probes and showcases the potential of OTBP as a versatile platform for activity-based sensing.

Biomimetic Nanosystem Loading Aggregation-Induced Emission Luminogens and SO2 Prodrug for Inhibiting Insufficient Photothermal Therapy-Induced Breast Cancer Recurrence and Metastasis.

Photothermal therapy (PTT) holds considerable clinical promise. However, insufficient PTT-induced tumor recurrence and metastasis is an urgent practical problem that needs to be solved. Herein, a biomimetic mesoporous organosilicon nano-system called PSAB is designed to precisely deplete cancer stem cells (CSCs) and prevent tumor recurrence and metastasis after PTT. The PSAB system is made up of Aggregation-induced emission (AIE)-active photothermal agent, 2TT-oC26B, and SO2 prodrug, benzothiazole sulfinate (BTS), within mesoporous organosilicon nanoparticles (MON) enclosed by an exterior platelet membrane. PSAB effectively targets CSCs both in vitro and in vivo by P-selectin/CD44 interaction. The degradation of MON and subsequent release of BTS and AIE molecules are facilitated by intracellular glutathione (GSH). Subsequently, the acidic tumor environment triggers the SO2 gas therapy from BTS. This process leads to the depletion of GSH and CSCs elimination. After combining PSAB with photothermal therapy, there is no significant tumor recurrence or metastasis. These results indicate that SO2 gas therapy and AIE-mediated PTT act synergistically to offer a unique approach for preventing tumor recurrence and metastasis after PTT, thus holding significant promise for clinical applications in cancer PTT.

Stimuli-Responsive Hydrogels Potentiating Photothermal Therapy against Cancer Stem Cell-Induced Breast Cancer Metastasis.

The self-renewal and differentiation properties of cancer stem cells (CSCs) result in chemoresistance in breast cancer. Even though numerous drugs have been developed to target CSCs, they have suffered from inefficient delivery and accumulation at the focal site. Here, a thermoresponsive hydrogel is developed by coencapsulating aggregation-induced emission (AIE)-active photothermal agent and thioridazine (THZ), demonstrating a controllable delivery system triggered by the AIE agent to augment THZ-mediated CSC ablation. Upon near-infrared laser stimuli, the photothermal effect from the AIE agent induces hydrogel deformation for burst drug release. The precise in situ tumor administration of the hydrogel accelerates drug diffusion and accumulation in deep breast cancer lesions. Thus, THZ can invade tumors and provoke massive CSC apoptosis via dopamine receptor blockage and oxidative stress induction. Consequently, effective CSC inhibition and significant suppression of tumor recurrence and metastasis are demonstrated in mice with breast cancer. We believe that this intelligent hydrogel-based delivery system represents a promising treatment strategy for metastatic breast cancer with clinical potential.

Mesoscale Acid-Base Complexes Display Size-Associated Photophysical Property and Photochemical Activity.

The properties of single molecules and molecular aggregates can differ dramatically, leading to a long-standing interest in mesoscale aggregation processes. Herein, a series of acid-base molecular complexes is developed by using a tetraphenylethylene-backboned fluorophore, and investigated the photophysical properties and photochemical activities at different aggregation length scales. This fluorophore, with two basic diethylamine groups and two acidic tetrazole groups, exhibits sparse solubility due to multivalent interactions that cause infinite aggregation. The addition of a third acid leads to the formation of fluorophore/acid complexes with good dispersibility and colloidal stability. This assembly process can be controlled by the use of different acids and their stoichiometry, resulting in aggregates ranging in size from a few to hundreds of nanometers. A crystalline structure is obtained to illustrate the complex properties of the acid-base network. Unlike the single molecule, these complexes show a trend of size-related properties for photoluminescence efficiency and photochemical activity. As the amount of acid added increases, the size of the complexes decreases, the aggregation effect of the complexes on fluorescence emission increases, and the rates of the oxidative photocyclization and photodecomposition slow down. This work may help to understand size-controlled molecular materials at the mesoscale for functional design.

Narrowband clusteroluminescence with 100% quantum yield enabled by through-space conjugation of asymmetric conformation.

Different from traditional organic luminescent materials based on covalent delocalization, clusteroluminescence from nonconjugated luminogens relies on noncovalent through-space conjugation of electrons. However, such spatial electron delocalization is usually weak, resulting in low luminescent efficiency and board emission peak due to multiple vibrational energy levels. Herein, several nonconjugated luminogens are constructed by employing biphenyl as the building unit to reveal the structure-property relationship and solve current challenges. The intramolecular through-space conjugation can be gradually strengthened by introducing building units and stabilized by rigid molecular skeleton and multiple intermolecular interactions. Surprisingly, narrowband clusteroluminescence with full width at half-maximum of 40 nm and 100% efficiency is successfully achieved via an asymmetric conformation, exhibiting comparable performance to the traditional conjugated luminogens. This work realizes highly efficient and narrowband clusteroluminescence from nonconjugated luminogens and highlights the essential role of structural conformation in manipulating the photophysical properties of unconventional luminescent materials.

White-light activatable organic NIR-II luminescence nanomaterials for imaging-guided surgery.

While second near-infrared (NIR-II) fluorescence imaging is a promising tool for real-time surveillance of surgical operations, the previously reported organic NIR-II luminescent materials for in vivo imaging are predominantly activated by expensive lasers or X-ray with high power and poor illumination homogeneity, which significantly limits their clinical applications. Here we report a white-light activatable NIR-II organic imaging agent by taking advantages of the strong intramolecular/intermolecular D-A interactions of conjugated Y6CT molecules in nanoparticles (Y6CT-NPs), with the brightness of as high as 13315.1, which is over two times that of the brightest laser-activated NIR-II organic contrast agents reported thus far. Upon white-light activation, Y6CT-NPs can achieve not only in vivo imaging of hepatic ischemia reperfusion, but also real-time monitoring of kidney transplantation surgery. During the surgery, identification of the renal vasculature, post-reconstruction assessment of renal allograft vascular integrity, and blood supply analysis of the ureter can be vividly depicted by using Y6CT-NPs with high signal-to-noise ratios upon clinical laparoscopic LED white-light activation. Our work provides efficient molecular design guidelines towards white-light activatable imaging agent and highlights an opportunity for precision imaging theranostics.

Advances in biomimetic AIE nanoparticles for diagnosis and phototherapy.

This minireview provides an overview of the recent advancements in the development of biomimetic Aggregation-Induced Emission (AIE) nanoparticles and their applications in disease diagnosis, phototherapy, and photoimmunotherapy. AIE nanoparticles can be engineered to enable efficient image-guided photodynamic and photothermal therapies, however, challenges related to immune defense and target specificity persist. To overcome these, coating biomimetic materials on the surface of AIE nanoparticles, which mimic the features and functions of native cells, have emerged as a promising solution. This minireview will highlight the synthesis strategies and discuss the biomedical application of biomimetic AIE nanoparticles.

Fluorescent Nanocable as a Biomedical Tool: Intracellular Self-Assembly Formed by a Natural Product Interconnects and Synchronizes Mitochondria.

Self-assembly processes commonly occur in various biological contexts to form functional biological structures. However, the self-assembly of nanofibers within cells by heterologous molecules showing a biological function is rare. In this work, we reported the intracellular formation of fluorescent nanofibers by a natural small molecule, lycobetaine (LBT), which facilitated the direct physical connection between mitochondria and synchronized their membrane potential oscillations. The luminescent properties of LBT enabled the real-time observation of nanofiber formation, while the semiconductive nature of the LBT nanofiber facilitated electrical signal transduction among the connected mitochondria. This study introduces an approach to modulate mitochondrial connectivity within cells using "nano-cables" which facilitate studies on synchronized mitochondrial operations and the underlying mechanisms of drug action.