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.

Aggregative Luminescence from CsPbBr3 Perovskite Precursors.

Understanding the properties of the precursor can provide deeper insight into the crystallization and nucleation mechanisms of perovskites, which is vital for the solution-process device performance. Herein, we conducted a detailed investigation into the photophysics properties of CsPbBr3 precursors in a broad concentration and various solvents. The precursor transformed from the solution state into the colloidal state and exhibited aggregation-induced emission character as the concentration increased. The aggregative luminescence from the precursors originates from the polybromide plumbous that is formed through the coordination of solvent molecules to the lead metal center. Two adducts with monodentate (PbBr2 ⋅ solvent) and bidentate (PbBr2 ⋅ 2solvent) ligands can be obtained, accompanied by emission with photoluminescence at 610 and 565 nm, respectively. Furthermore, the aggregative luminescence intensity and color could be regulated by changing the solvent and precursor ratio. Besides, we discussed the difference between the molecular aggregate in the organic system and the ionic aggregate in the inorganic system: the ionic aggregate is composed of solvated ions rather than individual molecules as in organic systems, which could possess properties that ions do not have. The fluorescence that is sensitive to Pb2+ coordination reported here could be applied to screen perovskite additives and judge the precursor aging.

Multi-Stimuli-Responsive and Cell Membrane Camouflaged Aggregation-Induced Emission Nanogels for Precise Chemo-photothermal Synergistic Therapy of Tumors.

Targeted and controllable drug release at lesion sites with the aid of visual navigation in real-time is of great significance for precise theranostics of cancers. Benefiting from the marvelous features (e.g., bright emission and phototheranostic effects in aggregates) of aggregation-induced emission (AIE) materials, constructing AIE-based multifunctional nanocarriers that act as all-arounders to integrate multimodalities for precise theranostics is highly desirable. Here, an intelligent nanoplatform (P-TN-Dox@CM) with homologous targeting, controllable drug release, and in vivo dual-modal imaging for precise chemo-photothermal synergistic therapy is proposed. AIE photothermic agent (TN) and anticancer drug (Dox) are encapsulated in thermo-/pH-responsive nanogels (PNA), and the tumor cell membranes are camouflaged onto the surface of nanogels. Active targeting can be realized through homologous effects derived from source tumor cell membranes, which advantageously elevates the specific drug delivery to tumor sites. After being engulfed into tumor cells, the nanogels exhibit a burst drug release at low pH. The near-infrared (NIR) photoinduced local hyperthermia can activate severe cytotoxicity and further accelerate drug release, thus generating enhanced synergistic chemo-photothermal therapy to thoroughly eradicate tumors. Moreover, P-TN-Dox@CM nanogels could achieve NIR-fluorescence/photothermal dual-modal imaging to monitor the dynamic distribution of therapeutics in real-time. This work highlights the great potential of smart P-TN-Dox@CM nanogels as a versatile nanoplatform to integrate multimodalities for precise chemo-photothermal synergistic therapy in combating cancers.

A New Strategy to Improve the Toughness of Epoxy Thermosets-By Introducing Poly(ether nitrile ketone)s Containing Phthalazinone Structures.

As high brittleness limits the application of all epoxy resins (EP), here, it can be modified by high-performance thermoplastic poly(ether nitrile ketone) containing phthalazinone structures (PPENK). Therefore, the influence of different PPENK contents on the mechanical, thermal, and low-temperature properties of EP was comprehensively investigated in this paper. The binary blend of PPENK/EP exhibited excellent properties due to homogeneous mixing and good interaction. The presence of PPENK significantly improved the mechanical properties of EP, showing 131.0%, 14.2%, and 10.0% increases in impact, tensile, and flexural strength, respectively. Morphological studies revealed that the crack deflection and bridging in PPENK were the main toughening mechanism in the blend systems. In addition, the PPENK/EP blends showed excellent thermal and low-temperature properties (-183 °C). The glass transition temperatures of the PPENK/EP blends were enhanced by approximately 50 °C. The 15 phr of the PPENK/EP blends had a low-temperature flexural strength of up to 230 MPa, which was 46.5% higher than EP. Furthermore, all blends exhibited better thermal stability.

Study on the Pressure Regulation Method of New Automatic Pressure Regulating Valve in the Electronically Controlled Pneumatic Brake Systems in Commercial Vehicles.

In order to adapt the development of vehicle driving automation technology for driving conditions under different levels of automation and based on the independently invented LF automatic pressure regulating valve (LF-APRV) for electronically controlled pneumatic brake systems (ECPBS), the dynamic PWM coupling pressure regulation method is proposed. This method realizes pressure regulation by adjusting the duty cycle of the control signal of the LF-APRV at different stages in the pressure regulation cycle. A co-simulation model was established to verify the feasibility of the method, and a test system was built to verify the correctness of the co-simulation model. Through the test, the pressure regulation performance of dynamic PWM coupling pressure regulation method and conventional on/off pressure regulation method was compared. The results show that the new method can improve the stability of pressure regulation, although the response time increases; under the new method, the overshoot of the pressure rising from 0 to 0.5 MPa was reduced by 69%, and the overshoot of the pressure decreasing from 0.5 MPa to 0.2 MPa was basically 0. Finally, tests and simulations showed that the dynamic PWM coupling pressure regulation method can meet the continuous graded braking requirements of vehicles, and the pressure response has good tracking performance on the target pressure.

Evoking Highly Immunogenic Ferroptosis Aided by Intramolecular Motion-Induced Photo-Hyperthermia for Cancer Therapy.

Immunogenic cell death (ICD) through apoptosis or necroptosis is widely adopted to improve the therapeutic effect in cancer treatment by triggering a specific antitumor immunity. However, the tumor resistance to apoptosis/necroptosis seriously impedes the therapeutic effect. Recently, ferroptosis featured with excessive lipid peroxidation is demonstrated capable of bypassing the apoptosis/necroptosis resistance to kill cancer cells. To date, numerous efficient ferroptosis inducers are developed and successfully utilized for sensitizing cancer cells to ferroptosis. Unfortunately, these inducers can hardly generate adequate immunogenicity during induction of ferroptotic cancer cell death, which distinctly attenuates the efficacy of triggering antitumor immune response, therefore leads to unsatisfactory therapeutic effect. Herein, a novel high-performance photothermal nanoparticle (TPA-NDTA NP) is designed by exploiting energy via excited-state intramolecular motion and employed for immensely assisting ferroptosis inducer to evoke highly efficient ICD through ferroptosis pathway. Tumor models with poor immunogenicity are used to demonstrate the tremendously enhanced therapeutic effect endowed by highly enhanced immunogenic ferroptosis in vitro and in vivo by virtue of the NPs. This study sheds new light on a previously unrecognized facet of boosting the immunogenicity of ferroptosis for achieving satisfactory therapeutic effect in cancer therapy.

Autonomous Visualization of Damage in Polymers by Metal-Free Polymerizations of Microencapsulated Activated Alkynes.

The development of autonomous materials with desired performance and built-in visualizable sensing units is of great academic and industrial significance. Although a wide range of damage indication methods have been reported, the "turn-on" sensing mechanism by damaging events based on microcapsule systems, especially those relying on chemical reactions to elicit a chromogenic response, are still very limited. Herein, a facile and metal-free polymerization route with an interesting reaction-induced coloration effect is demonstrated. Under the catalysis of 1,4-diazabicyclo[2.2.2]octane (DABCO), the polymerizations of difunctional or trifunctional activated alkynes proceed very quickly at 0 °C in air. A series of polymers composed of stereoregular enyne structure (major unit) and divinyl ether structure (minor unit) are obtained. Both the catalyst and monomers are colorless while the polymerized products are deep-colored. This process can be applied for the damage visualization of polymers using the microencapsulation technique. Microcapsules containing the reactive alkyne monomer are prepared and mixed in a DABCO-dispersed polymer film. Both the external and internal damage regions of this composite film can be readily visualized once the reaction is initiated from the ruptured microcapsules. Moreover, the newly formed polymer automatically seals the cracks with an additional protection function.

Highly efficient photothermal nanoparticles for the rapid eradication of bacterial biofilms.

Biofilm-related infections, such as dental plaque, chronic sinusitis, native valve endocarditis, and chronic airway infections in cystic fibrosis have brought serious suffering to patients and financial burden to society. Materials that can eliminate mature biofilms without developing drug resistance are promising tools to treat biofilm-related infections, and thus they are in urgent demand. Herein, we designed and readily prepared organic nanoparticles (NPs) with highly efficient photothermal conversion by harvesting energy via excited-state intramolecular motions and enlarging molar absorptivity. The photothermal NPs can sufficiently eliminate mature bacterial biofilms upon low-power near-infrared laser irradiation. NPs hold great promise for the rapid eradication of bacterial biofilms by photothermal therapy.

BioAIEgens derived from rosin: how does molecular motion affect their photophysical processes in solid state?

The exploration of artificial luminogens with bright emission has been fully developed with the advancement of synthetic chemistry. However, many of them face problems like weakened emission in the aggregated state as well as poor renewability and sustainability. Therefore, the development of renewable and sustainable luminogens with anti-quenching function in the solid state, as well as to unveil the key factors that influence their luminescence behavior become highly significant. Herein, a new class of natural rosin-derived luminogens with aggregation-induced emission property (AIEgens) have been facilely obtained with good biocompatibility and targeted organelle imaging capability as well as photochromic behavior in the solid state. Mechanistic study indicates that the introduction of the alicyclic moiety helps suppress the excited-state molecular motion to enhance the solid-state emission. The current work fundamentally elucidates the role of alicyclic moiety in luminogen design and practically demonstrates a new source to large-scalely obtain biocompatible AIEgens.

The coupling and competition of crystallization and phase separation, correlating thermodynamics and kinetics in OPV morphology and performances.

The active layer morphology transition of organic photovoltaics under non-equilibrium conditions are of vital importance in determining the device power conversion efficiency and stability; however, a general and unified picture on this issue has not been well addressed. Using combined in situ and ex situ morphology characterizations, morphological parameters relating to kinetics and thermodynamics of morphology evolution are extracted and studied in model systems under thermal annealing. The coupling and competition of crystallization and demixing are found to be critical in morphology evolution, phase purification and interfacial orientation. A unified model summarizing different phase diagrams and all possible kinetic routes is proposed. The current observations address the fundamental issues underlying the formation of the complex multi-length scale morphology in bulk heterojunction blends and provide useful morphology optimization guidelines for processing devices with higher efficiency and stability.

Molecular Motions in AIEgen Crystals: Turning on Photoluminescence by Force-Induced Filament Sliding.

Life process is amazing, and it proceeds against the eternal law of entropy increase through molecular motion and takes energy from the environment to build high-order complexity from chaos to achieve evolution with more sophisticated architectures. Inspired from the elegance of life process and also to effectively exploit the undeveloped solid-state molecular motion, two unique chiral Au(I) complexes were elaborately developed in this study, in which their powders could realize a dramatic transformation from nonemissive isolated crystallites to emissive well-defined microcrystals under the stimulation of mechanical force. Such an unusual crystallization was presumed to be caused by molecular motions driven by the formation of strong aurophilic interactions as well as multiple C-H···F and π-π interactions. Such a prominent macroscopic off/on luminescent switching could also be achieved through extremely subtle molecular motions in the crystal state and presented a filament sliding that occurred in a layer-by-layer molecular stacking fashion with no involvement of any crystal phase transition. Additionally, it had been demonstrated that the manipulation of the solid-state molecular motions could result in the generation of circularly polarized luminescence.

Less is more: Silver-AIE core@shell nanoparticles for multimodality cancer imaging and synergistic therapy.

Nanomaterials with integrated multiple imaging and therapeutic modalities possess great potentials in accurate cancer diagnostics and enhanced therapeutic efficacy. Traditional strategies for achieving multimodality nanoplatform through one by one combination of different modalities are challenged by the complicated structural design and fabrication as well as inherent incompatibility between different modalities. Herein, a novel strategy is presented to realize multimodal imaging and synergistic therapy using a class of simple silver core/AIE (aggregation-induced emission) shell nanoparticles. In addition to the intrinsic AIE fluorescence (FL) and metal-based computed tomography (CT) and radiation therapy (RT) properties, an extra functionality at the core/shell interface was identified to enable excellent photothermal (PT) and photoacoustic (PA) performance. As a result, five imaging and therapy modalities (FL, CT, PA, photothermal therapy (PTT), and RT) were achieved with a single structural unit for sensitive tumor imaging and effective therapy.

A Conjugated Polymeric Supramolecular Network with Aggregation-Induced Emission Enhancement: An Efficient Light-Harvesting System with an Ultrahigh Antenna Effect.

Superior artificial light-harvesting systems (ALHSs) require exceptional capacity in harvesting light and transferring energy. In this work, we report a novel strategy to build ALHSs with an unprecedented antenna effect (35.9 in solution and 90.4 in solid film). The ALHSs made use of a conjugated polymeric supramolecular network (CPSN), a crosslinked network obtained from the self-assembly of a pillar[5]arene-based conjugated polymeric host (CPH) and conjugated ditopic guests (Gs). The excellent performance of the CPSN could be attributed to the following factors: 1) The "molecular wire effect" of the conjugated polymeric structure, 2) aggregation-induced enhanced emission (AEE) moieties in the CPH backbone, and 3) high capacity of donor-acceptor energy transfer, and 4) crosslinked structures triggered by the host-guest binding between Gs and CPH. Moreover, the emission of the CPSN could be tuned by using different Gs or varying the host/guest ratio, thus reaching a 96 % sRGB area.

AIE-based theranostic systems for detection and killing of pathogens.

Pathogenic bacteria, fungi and viruses pose serious threats to the human health under appropriate conditions. There are many rapid and sensitive approaches have been developed for identification and quantification of specific pathogens, but many challenges still exist. Culture/colony counting and polymerase chain reaction are the classical methods used for pathogen detection, but their operations are time-consuming and laborious. On the other hand, the emergence and rapid spread of multidrug-resistant pathogens is another global threat. It is thus of utmost urgency to develop new therapeutic agents or strategies. Luminogens with aggregation-induced emission (AIEgens) and their derived supramolecular systems with unique optical properties have been developed as fluorescent probes for turn-on sensing of pathogens with high sensitivity and specificity. In addition, AIE-based supramolecular nanostructures exhibit excellent photodynamic inactivation (PDI) activity in aggregate, offering great potential for not only light-up diagnosis of pathogen, but also image-guided PDI therapy for pathogenic infection.

Panchromatic Ternary Organic Solar Cells with Porphyrin Dimers and Absorption-Complementary Benzodithiophene-based Small Molecules.

Diketopyrrolopyrrole-ethynylene-bridged porphyrin dimers are capped with electron-deficient 3-ethylrhodanine (A2) via a π-bridge of phenylene ethynylene, affording two new acceptor-donor-acceptor structural porphyrin dimers (DPP-2TTP and DPP-2TP) with strong absorption in ranges of 400-550 nm (Soret bands) and 700-900 nm (Q bands). Their intrinsic absorption deficiency between the Soret and Q bands could be perfectly compensated by a wide-bandgap small molecule DR3TBDTTF (D*) with absorption at 500-700 nm. Impressively, the optimal ternary device based on the blend films of DPP-2TPP, DR3TBDTTF (20 wt %), and PC71BM shows a PCE of 11.15%, whereas the binary devices based on DPP-2TTP/PC71BM and DPP-2TP/PC71BM blend films exhibit PCEs of 9.30 and 8.23%, respectively. The high compatibility of the low bandgap porphyrin dimers with the wide-bandgap small molecule provides a new threesome with PC71BM for highly efficient panchromatic ternary organic solar cells.

Critical Role of Vertical Phase Separation in Small-Molecule Organic Solar Cells.

An inverted device structure is a more stable configuration than a regular device structure for solution-processed organic solar cells (OSCs). However, most of the solution-processed small-molecule OSCs (SM-OSCs) reported in the literature used the regular device structure, and a regular device normally exhibits a higher efficiency than an inverted device. Herein, a representative small-molecule DR3TBDTT was selected to figure out the reason for photovoltaic performance differences between regular and inverted devices. The mechanisms for a reduced open-circuit voltage ( Voc) and fill factor (FF) in the inverted device were studied. The reduced Voc and FF is due to the vertical phase separation with excess [6,6]-phenyl-C71-butyric acid methyl ester near the air/blend surface, which leads to a reduction in build-in voltage and unbalanced charge transport in the inverted device. Another reason for the reduced FF is the unfavorable DR3TBDTT crystallite orientation distribution along the film thickness, which is preferential edge-on crystallites in the top layer of the blend film and the increased population of face-on crystallites in the bottom layer of the blend film. This study illustrates that the morphology plays a key role in photovoltaic performance difference between regular and inverted devices and provides useful guidelines for further optimization of the morphology of solution-processed SM-OSCs.

From Alloy-Like to Cascade Blended Structure: Designing High-Performance All-Small-Molecule Ternary Solar Cells.

Ternary blending strategy has been used to design and fabricate efficient organic solar cells by enhancing the short-circuit current density and the fill factor. In this manuscript, we report all-small-molecule ternary solar cells consisting of two compatible small molecules DR3TBDTT (M1) and DR3TBDTT-E (M2) as donors and PC71BM as acceptor. A transformation from an alloy-like model to a cascade model are first realized by designing a novel molecule M2. It is observed that after thermal and solvent vapor annealing M2 shifts from the mixed region to donor-acceptor (D-A) interfaces which ameliorates the charge transfer and recombination processes. The optimal ternary solar cells with 10% M2 exhibited a power conversion efficiency of 8.48% in the alloy-like model and 10.26% in the cascade model. The proposed working mechanisms are fully characterized and further supported by the density functional theory and atomistic molecular dynamics simulations. This provides an important strategy to design high-performance ternary solar cells which contains one molecule not only is compatible with the main donor molecule but also performs a preference to appear at the D-A interfaces hence builds cascade energy levels.

Enhancing Performance of Large-Area Organic Solar Cells with Thick Film via Ternary Strategy.

Large-scale fabrication of organic solar cells requires an active layer with high thickness tolerability and the use of environment-friendly solvents. Thick films with high-performance can be achieved via a ternary strategy studied herein. The ternary system consists of one polymer donor, one small molecule donor, and one fullerene acceptor. The small molecule enhances the crystallinity and face-on orientation of the active layer, leading to improved thickness tolerability compared with that of a polymer-fullerene binary system. An active layer with 270 nm thickness exhibits an average power conversion efficiency (PCE) of 10.78%, while the PCE is less than 8% with such thick film for binary system. Furthermore, large-area devices are successfully fabricated using polyethylene terephthalate (PET)/Silver gride or indium tin oxide (ITO)-based transparent flexible substrates. The product shows a high PCE of 8.28% with an area of 1.25 cm2 for a single cell and 5.18% for a 20 cm2 module. This study demonstrates that ternary organic solar cells exhibit great potential for large-scale fabrication and future applications.

High-Performance Ternary Organic Solar Cell Enabled by a Thick Active Layer Containing a Liquid Crystalline Small Molecule Donor.

Ternary organic solar cells (OSCs) have attracted much research attention in the past few years, as ternary organic blends can broaden the absorption range of OSCs without the use of complicated tandem cell structures. Despite their broadened absorption range, the light harvesting capability of ternary OSCs is still limited because most ternary OSCs use thin active layers of about 100 nm in thickness, which is not sufficient to absorb all photons in their spectral range and may also cause problems for future roll-to-roll mass production that requires thick active layers. In this paper, we report a highly efficient ternary OSC (11.40%) obtained by incorporating a nematic liquid crystalline small molecule (named benzodithiophene terthiophene rhodanine (BTR)) into a state-of-the-art PTB7-Th:PC71BM binary system. The addition of BTR into PTB7-Th:PC71BM was found to improve the morphology of the blend film with decreased π-π stacking distance, enlarged coherence length, and enhanced domain purity. This resulted in more efficient charge separation, faster charge transport, and less bimolecular recombination, which, when combined, led to better device performance even with thick active layers. Our results show that the introduction of highly crystalline small molecule donors into ternary OSCs is an effective means to enhance the charge transport and thus increase the active layer thickness of ternary OSCs to make them more suitable for roll-to-roll production than previous thinner devices.

Fluorination-enabled optimal morphology leads to over 11% efficiency for inverted small-molecule organic solar cells.

Solution-processable small molecules for organic solar cells have attracted intense attention for their advantages of definite molecular structures compared with their polymer counterparts. However, the device efficiencies based on small molecules are still lower than those of polymers, especially for inverted devices, the highest efficiency of which is <9%. Here we report three novel solution-processable small molecules, which contain π-bridges with gradient-decreased electron density and end acceptors substituted with various fluorine atoms (0F, 1F and 2F, respectively). Fluorination leads to an optimal active layer morphology, including an enhanced domain purity, the formation of hierarchical domain size and a directional vertical phase gradation. The optimal morphology balances charge separation and transfer, and facilitates charge collection. As a consequence, fluorinated molecules exhibit excellent inverted device performance, and an average power conversion efficiency of 11.08% is achieved for a two-fluorine atom substituted molecule.