Enhanced Aggregation-Induced Delayed Electrochemiluminescence Triggered by Spatial Perturbation of Organic Dots.

Development of highly efficient, heavy-metal-free electrochemiluminescence (ECL) materials is attractive but still challenging. Herein, we report an aggregation-induced delayed ECL (AIDECL) active organic dot (OD) composed of a tert-butoxy-group-substituted benzophenone-dimethylacridine compound, which shows high ECL efficiency. The resultant ODs exhibit 2.1-fold higher ECL efficiency compared to control AIDECL-active ODs. Molecular stacking combined with theoretical calculations suggests that tert-butoxy groups effectively participate in the intermolecular interactions, further inhibiting the molecular motions in the aggregated states and thus accelerating radiative decay. On the basis of these ODs exhibiting excellent ECL performance, a proof-of-concept biosensor is constructed for the detection of miR-16 associated with Alzheimer's disease, which demonstrates excellent detection ability with the limit of detection of 1.7 fM. This work provides a new approach to improve the ECL efficiency and enriches the fundamental understanding of the structure-property relationship.

Stretchable phosphorescent polymers by multiphase engineering.

Stretchable phosphorescence materials potentially enable applications in diverse advanced fields in wearable electronics. However, achieving room-temperature phosphorescence materials simultaneously featuring long-lived emission and good stretchability is challenging because it is hard to balance the rigidity and flexibility in the same polymer. Here we present a multiphase engineering for obtaining stretchable phosphorescent materials by combining stiffness and softness simultaneously in well-designed block copolymers. Due to the microphase separation, copolymers demonstrate an intrinsic stretchability of 712%, maintaining an ultralong phosphorescence lifetime of up to 981.11 ms. This multiphase engineering is generally applicable to a series of binary and ternary initiator systems with color-tunable phosphorescence in the visible range. Moreover, these copolymers enable multi-level volumetric data encryption and stretchable afterglow display. This work provides a fundamental understanding of the nanostructures and material properties for designing stretchable materials and extends the potential of phosphorescence polymers.

Boosting organic phosphorescence in adaptive host-guest materials by hyperconjugation.

Phosphorescence is ubiquitous in heavy atom-containing organic phosphors, which attracts considerable attention in optoelectronics and bioelectronics. However, heavy atom-free organic materials with efficient phosphorescence are rare under ambient conditions. Herein, we report a series of adaptive host-guest materials derived from dibenzo-heterocyclic analogues, showing host-dependent color-tunable phosphorescence with phosphorescence efficiency of up to 98.9%. The adaptive structural deformation of the guests arises from the hyperconjugation, namely the n→π* interaction, enabling them to inhabit the cavity of host crystals in synergy with steric effects. Consequently, a perfect conformation match between host and guest molecules facilitates the suppression of triplet exciton dissipation, thereby boosting the phosphorescence of these adaptive materials. Moreover, we extend this strategy to a ternary host-guest system, yielding both excitation- and time-dependent phosphorescence with a phosphorescence efficiency of 92.0%. This principle provides a concise way for obtaining efficient and color-tunable phosphorescence, making a major step toward potential applications in optoelectronics.

Abnormal thermally-stimulated dynamic organic phosphorescence.

Dynamic luminescence behavior by external stimuli, such as light, thermal field, electricity, mechanical force, etc., endows the materials with great promise in optoelectronic applications. Upon thermal stimulus, the emission is inevitably quenched due to intensive non-radiative transition, especially for phosphorescence at high temperature. Herein, we report an abnormal thermally-stimulated phosphorescence behavior in a series of organic phosphors. As temperature changes from 198 to 343 K, the phosphorescence at around 479 nm gradually enhances for the model phosphor, of which the phosphorescent colors are tuned from yellow to cyan-blue. Furthermore, we demonstrate the potential applications of such dynamic emission for smart dyes and colorful afterglow displays. Our results would initiate the exploration of dynamic high-temperature phosphorescence for applications in smart optoelectronics. This finding not only contributes to an in-depth understanding of the thermally-stimulated phosphorescence, but also paves the way toward the development of smart materials for applications in optoelectronics.

An AIE Controlled "Off-On" Cu2+-Sensitive Probe for Early Detection of Renal Fibrosis.

Early detection of renal fibrosis (RF) is very important given that it is irreversible when it progresses to the terminal stage. A key marker of RF pathogenesis is activation of myomyofibroblasts, and its targeted imaging may be a promising approach for early detection of RF, but no study has directly imaged activation of renal myomyofibroblasts. Cu2+ plays a major role in the fibrotic activity of myofibroblasts. Herein, inspired by that Cu2+ can complex with bovine serum albumin (BSA), BSA-Ag2S quantum dots (QDs) with aggregation-induced emission (AIE) property are synthesized. Then BSA-Ag2S QDs are modified by chitosan (CS) with renal targeting and hyaluronic acid (HA) with myofibroblast targeting to obtain the AIE assay system (QDs@CS@HA). The system is simple to synthesize, and produces a rapid NIR fluorescence signal turn-on response and a low detection limit of 75 × 10-9 m to Cu2+. In addition, cellular and animal experiments have shown that QDs@CS@HA has good biosafety and cell-targeted imaging capability for RF. Based on the successful application of QDs@CS@HA and the mechanism of RF progression in early RF detection, it is expected that QDs@CS@HA may detect RF before the appearance of clinical symptoms.

HLCT-Type Acceptor Molecule-Based Exciplex System for Highly Efficient Solution-Processable OLEDs with Suppressed Efficiency Roll-Offs.

Exciplex systems are promising candidates for thermally activated delayed fluorescence (TADF) molecules because of the small energy difference between the lowest singlet and triplet excited states (ΔEST). However, realizing high-efficiency and low-external-quantum-efficiency (EQE) roll-off in solution-processed organic light-emitting diodes (OLEDs) using an exciplex system remains a formidable challenge. In this study, two (HLCT)-type isomers with a spiro skeleton, 2-tBuspoCz-TRZ and 10-tBuspoCz-TRZ, are designed and synthesized as acceptors of exciplexes, where tert-butylspirofluorene indole is regarded as a donor and the triazine unit as an acceptor. Green exciplex emissions are observed for the 2-tBuspoCz-TRZ:TAPC and 10-tBuspoCz-TRZ:TAPC exciplexes, indicating distinct TADF characteristics with a very small ΔEST of 35 ± 5 meV. By using the TADF exciplex system based on the HLCT acceptor as an emitter, solution-processable OLEDs achieve a maximum external quantum efficiency (EQEmax) of 20.8%. Furthermore, a high EQEmax > 25% with a very low-efficiency roll-off (≈3.5% at 1000 cd m-2) is obtained for solution-processable phosphorescent devices using HLCT-based exciplexes as the host matrix of phosphors. This study paves the way for a novel strategy for designing acceptor exciplex molecules for effective TADF molecules and host matrices in solution-processable OLEDs.

Achieving High-Temperature Phosphorescence by Organic Cocrystal Engineering.

Organic phosphors offer a promising alternative in optoelectronics, but their temperature-sensitive feature has restricted their applications in high-temperature scenarios, and the attainment of high-temperature phosphorescence (HTP) is still challenging. Herein, a series of organic cocrystal phosphors are constructed by supramolecular assembly with an ultralong emission lifetime of up to 2.16 s. Intriguingly, remarkable stabilization of triplet excitons can also be realized at elevated temperature, and green phosphorescence is still exhibited in solid state even up to 150 °C. From special molecular packing within the crystal lattice, it has been observed that the orientation of isolated water cluster and well-controlled molecular organization via multiple interactions can favor the structural rigidity of cocrystals more effectively to suppress the nonradiative transition, thus resulting in efficient room-temperature phosphorescence and unprecedented survival of HTP.

One Stone, Two Birds: High-Brightness Aggregation-Induced Emission Photosensitizers for Super-Resolution Imaging and Photodynamic Therapy.

Most aggregation-induced emission (AIE) luminogens exhibit high brightness, excellent photostability, and good biocompatibility, but these AIE-active agents, which kill two birds with one stone to result in applications in both stimulated emission depletion (STED) super-resolution imaging and photodynamic therapy (PDT), have not been reported yet but are urgently needed. To meet the requirements of STED nanoscopy and PDT, D-A-π-A-D type DTPABT-HP is designed by tuning conjugated π spacers. It exhibits red-shifted emission, high PLQY of 32.04%, and impressive 1O2 generation (9.24 fold compared to RB) in nanoparticles (NPs). Then, DTPABT-HP NPs are applied in cell imaging via STED nanoscopy, especially visualizing the dynamic changes of lysosomes in the PDT process at ultrahigh resolution. After that, in vivo PDT was also conducted by DTPABT-HP NPs, resulting in significantly inhibited tumor growth, with an inhibition rate of 86%. The work here is beneficial to the design of multifunctional agents and the deep understanding of their phototheranostic mechanism in biological research.

Hybridized local and charge transfer dendrimers with near-unity exciton utilization for enabling high-efficiency solution-processed hyperfluorescent OLEDs.

Achieving both high emission efficiency and exciton utilization efficiency (ηS) in hot exciton materials is still a formidable task. Herein, a proof-of-concept design for improving ηS in hot exciton materials is proposed via elaborate regulation of singlet-triplet energy difference, leading to an additional thermally activated delayed fluorescence (TADF) process. Two novel dendrimers, named D-TTT-H and D-TTT-tBu, were prepared and characterized, in which diphenylamine derivatives were used as a donor moiety and tri(triazolo)triazine (TTT) as an acceptor fragment. Compounds D-TTT-H and D-TTT-tBu showed an intense green color with an emission efficiency of approximately 80% in solution. Impressively, both dendrimers simultaneously exhibited a hot exciton process and TADF characteristic in the solid state, as was demonstrated via theoretical calculation, transient photoluminescence, magneto-electroluminescence and transient electroluminescence measurements, thus achieving almost unity ηS. A solution processable organic light-emitting diode (OLED) employing the dendrimer as a dopant represents the best performance with the highest luminance of 15090 cd m-2 and a maximum external quantum efficiency (EQEmax) of 11.96%. Moreover, using D-TTT-H as a sensitizer, an EQEmax of 30.88%, 24.08% and 14.33% were achieved for green, orange and red solution-processed OLEDs, respectively. This research paves a new avenue to construct a fluorescent molecule with high ηS for efficient and stable OLEDs.

Organic Phosphorescent Hopper-Shaped Microstructures.

Hopper-shaped microcrystals, an unusual type of crystal with a large specific surface area, are promising for use in catalysis, drug delivery, and gas sensors. In contrast to well-studied inorganic hopper-shaped crystals, organic phosphorescent concave hopper-shaped microstructures are rarely reported. This study reports the synthesis of two types of organic stepped indented hopper-shaped microstructures with efficient room temperature phosphorescence (RTP) using a liquid phase self-assembly strategy. The formation mechanism is attributed to the interfacial instability induced by the concentration gradient and selective etching. Compared with flat microstructures, the stepped indented hopper-like RTP microstructures exhibit high sensitivity to oxygen. This work also demonstrates that packing the photochromic material into the concave hopper "vessel" effectively controls the switch of phosphorescence from energy transfer, expanding the potential applications of phosphorescent materials.

Polymorphism-Dependent Organic Room Temperature Phosphorescent Scintillation for X-Ray Imaging.

Organic phosphorescent scintillating materials have shown great potential for applications in radiography and radiation detection due to their efficient utilization of excitons. However, revealing the relationship between molecule stacking and the phosphorescent radioluminescence of scintillators is still challenging. This study reports on two phenothiazine derivatives with polymorphism-dependent phosphorescence radioluminescence. The experiments reveal that molecule stacking significantly affects the non-radiation decay of the triplet excitons of scintillators, which further determines the phosphorescence scintillation performance under X-ray irradiation. These phosphorescent scintillators exhibit high radio stability and have a low detection limit of 278 nGys-1. Additionally, the potential application of these scintillators in X-ray radiography, based on their X-ray excited radioluminescence properties, is demonstrated. These findings provide a guideline for obtaining high-performance phosphorescent scintillating materials by shedding light on the effect of crystal packing on the radioluminescence of organic molecules.

Ground-State Orbital Descriptors for Accelerated Development of Organic Room-Temperature Phosphorescent Materials.

Organic materials with room-temperature phosphorescence (RTP) are in high demand for optoelectronics and bioelectronics. Developing RTP materials highly relies on expert experience and costly excited-state calculations. It is a challenge to find a tool for effectively screening RTP materials. Herein we first establish ground-state orbital descriptors (πFMOs ) derived from the π-electron component of the frontier molecular orbitals to characterize the RTP lifetime (τp ), achieving a balance in screening efficiency and accuracy. Using the πFMOs , a data-driven machine learning model gains a high accuracy in classifying long τp , filtering out 836 candidates with long-lived RTP from a virtual library of 19,295 molecules. With the aid of the excited-state calculations, 287 compounds are predicted with high RTP efficiency. Impressively, experiments further confirm the reliability of this workflow, opening a novel avenue for designing high-performance RTP materials for potential applications.

Organic Excitonic State Management by Surface Metallic Coupling of Inorganic Lanthanide Nanocrystals.

The ability to harness charges and spins for control of organic excitonic states is critical in developing high-performance organic luminophores and optoelectronic devices. Here we report a facile strategy to efficiently manipulate the electronic energy states of various organic phosphors by coupling them with inorganic lanthanide nanocrystals. We show that the metallic atoms exposed on the nanocrystal surface can introduce strong coupling effects to 9-(4-ethoxy-6-phenyl-1,3,5-triazin-2-yl)-9H-carbazole (OCzT) and some organic chromophores with carbazole functional groups when the organics are approaching the nanocrystals. This unconventional organic-inorganic hybridization enables a nearly 100 % conversion of the singlet excitation to fast charge transfer luminescence that does not exist in pristine organics, which broadens the utility of organic phosphors in hybrid systems.

Efficient Visible-Light-Activated Ultra-Long Room-Temperature Phosphorescence Triggered by Multi-Esterification.

The development of ultra-long room-temperature phosphorescence (UL-RTP) in processable amorphous organic materials is highly desirable for applications in flexible displays, anti-counterfeiting, and bio-imaging. However, achieving efficient UL-RTP from amorphous materials remains a challenging task, especially with activation by visible light and a bright afterglow. Here we report a general and rational molecular-design strategy to enable efficient visible-light-excited UL-RTP by multi-esterification of a rigid large-plane phosphorescence core. Notably, multi-esterification minimizes the aggregation-induced quenching and accomplishes a 'four birds with one stone' possibility in the generation and radiation process of UL-RTP: i) shifting the excitation from ultraviolet light to blue-light through enhancing the transition dipole moment of low-lying singlet-states, ii) facilitating the intersystem crossing process through the incorporation of lone-pair electrons, iii) boosting the decay process of long-lived triplet excitons resulting from a significantly increased transition dipole moment, and iv) reducing the intrinsic triplet nonradiative decay by substitution of high-frequency vibrating hydrogen atoms. All these factors synergistically contribute to the most efficient and stable visible-light-stimulated UL-RTP (lifetime up to 2.01 s and efficiency up to 35.4 % upon excitation at 450 nm) in flexible films using multi-esterified coronene, which allows high-tech applications in single-component time-delayed white light-emitting diodes and information technology based on flashlight-activated afterglow encryption.

Activating Molecular Room-Temperature Phosphorescence by Manipulating Excited-State Energy Levels in Poly(vinyl alcohol) Matrix.

Poly(vinyl alcohol) (PVA) has been found as a wonderful matrix for chromophores to boost their room-temperature phosphorescence (RTP) character by forming abundant hydrogen bonding. Despite the well-utilized protective effect, the constructive role in accelerating the intersystem crossing is less investigated. Here, we focus on its role in manipulating the excited-state energy level to facilitate multiple intersystem crossing channels. Six benzoyl carbazole derivatives do not emit RTP in their solutions, powders, or crystals but exhibit significantly persistent RTP signals when embedded into the PVA matrix. Charge-transfer excited states were trapped by cofacial stacking in crystal, which blocks the intersystem crossing channels. In the PVA matrix, the allowed broad distribution of charge-transfer states covers the locally excited states, offering multiple intersystem crossing pathways via spin-vibronic orbit coupling. Consequently, efficient and persistent heavy-atom-free phosphors have been developed with the highest quantum yields of 7.7% and the longest lifetime of 2.3 s.

Identification of Floral Volatile Components and Expression Analysis of Controlling Gene in Paeonia ostii 'Fengdan' under Different Cultivation Conditions.

In order to explore the release rule of floral volatile substances and the diurnal variation of different flower development stages of Paeonia ostii 'Fengdan' in potted and ground-planted conditions, dynamic headspace adsorption combined with gas chromatography-mass spectrometry(GC-MS) was used to analyze the dynamic changes in floral volatile components and contents. Quantitative real-time PCR (qRT-PCR) was used to analyze changes in flower fragrance-regulating genes PsPAL, PsTPSs, and PsbHLH at different flower development stages and a daily change process at the full-blooming stage. The results show that there were differences in aroma components and contents of Paeonia ostii 'Fengdan' at different flower development stages and different time quantum of every day. There were 25 and 28 aroma components identified in 7 flower development stages of tree peonies planted in pots and in the field, respectively, and 23 and 22 aroma components identified at different time quantum of the day, of which the largest and highest content was alkanes. The main characteristic aroma substances were (E)-ß-ocimene, 1,3,5-trimethoxybenzene, 2,4-di-tert-butylphenol, methyl jasmonate, nerol, and cinnamyl alcohol; released amounts of the abovementioned substances varied depending on the development stage and the time of the day. The expression of flower fragrance-controlling genes (PsPAL, PsTPSs, and PsbHLH) in tree peonies varied greatly in different conditions. The results of this study provide a valuable resource to investigate floral fragrance formation in tree peonies.

Narrowband Organic Afterglow via Phosphorescence Förster Resonance Energy Transfer for Multifunctional Applications.

Achieving multicolor organic afterglow materials with narrowband emission and high color purity is important in various optoelectronic fields but remains a great challenge. Here, an efficient strategy is presented to obtain narrowband organic afterglow materials via Förster resonance energy transfer from long-lived phosphorescence donors to narrowband fluorescence acceptors in a polyvinyl alcohol matrix. The resulting materials exhibit narrowband emission with a full width at half maximum (FWHM) as small as 23 nm and the longest lifetime of 721.22 ms. Meanwhile, by pairing the appropriate donors and acceptors, multicolor and high color purity afterglow ranging from green to red with the maximum photoluminescence quantum yield of 67.1% are achieved. Moreover, given their long luminescence lifetime, high color purity, and flexibility, the potential applications are demonstrated in high-resolution afterglow displays and dynamic and quick information identification in low-light conditions. This work provides a facile approach for developing multicolor and narrowband afterglow materials as well as expands the features of organic afterglow.

A nano-delivery system based on preventing degradation and promoting absorption to improve the oral bioavailability of insulin.

Oral insulin delivery can improve patient compliance and simulate the portal-peripheral insulin concentration gradient produced by endogenous insulin, so oral insulin delivery has a broad prospect. However, some characteristics of the gastrointestinal tract, lead to low oral bioavailability. Therefore, a "ternary mutual-assist" nano-delivery system based on poly(lactide-co-glycolide) (PLGA) as the backbone combined with ionic liquids (IL) and vitamin B12-chitosan (VB12-CS) was constructed in this study, the protein protection performance of IL improves the room temperature stability of the loaded insulin during nanocarrier preparation, transportation and storage to a certain extent, and the protein protection function of IL combined with the slow degradation property of PLGA and the pH-responsive function of VB12-CS to prevent the degradation of insulin in the gastrointestinal tract. In addition, the mucosal adhesion function of VB12-CS, VB12 receptor- and clathrin-mediated transcellular transport involving VB12-CS and IL, and paracellular transport mediated by IL and CS can be combined to improve the intestinal epithelial transport efficiency of insulin, thus, the nanocarrier has stronger preventing degradation and promoting absorption effects. Pharmacodynamic studies showed that after oral administration of VB12-CS-PLGA@IL@INS NPs to diabetic mice, the blood glucose level decreased to about 13 mmol/L, below the critical point of 16.7 mmol/L, and the blood glucose reached a normal level, which was 0.4 times of the blood glucose value before administration, its relative pharmacological bioavailability was 31.8 %, higher than the general nanocarriers (10-20 %) and more beneficial to the clinical transformation of oral insulin.

Acceptor Engineering Produces Ultrafast Nonradiative Decay in NIR-II Aza-BODIPY Nanoparticles for Efficient Osteosarcoma Photothermal Therapy via Concurrent Apoptosis and Pyroptosis.

Small-molecule photothermal agents (PTAs) with intense second near-infrared (NIR-II, 1,000 to 1,700 nm) absorption and high photothermal conversion efficiencies (PCEs) are promising candidates for treating deep-seated tumors such as osteosarcoma. To date, the development of small-molecule NIR-II PTAs has largely relied on fabricating donor-acceptor-donor (D-A-D/D') structures and limited success has been achieved. Herein, through acceptor engineering, a donor-acceptor-acceptor (D-A-A')-structured NIR-II aza-boron-dipyrromethene (aza-BODIPY) PTA (SW8) was readily developed for the 1,064-nm laser-mediated phototheranostic treatment of osteosarcoma. Changing the donor groups to acceptor groups produced remarkable red-shifts of absorption maximums from first near-infrared (NIR-I) regions (~808 nm) to NIR-II ones (~1,064 nm) for aza-BODIPYs (SW1 to SW8). Furthermore, SW8 self-assembled into nanoparticles (SW8@NPs) with intense NIR-II absorption and an ultrahigh PCE (75%, 1,064 nm). This ultrahigh PCE primarily originated from an additional nonradiative decay pathway, which showed a 100-fold enhanced decay rate compared to that shown by conventional pathways such as internal conversion and vibrational relaxation. Eventually, SW8@NPs performed highly efficient 1,064-nm laser-mediated NIR-II photothermal therapy of osteosarcoma via concurrent apoptosis and pyroptosis. This work not only illustrates a remote approach for treating deep-seated tumors with high spatiotemporal control but also provides a new strategy for building high-performance small-molecule NIR-II PTAs.

Atomistic Insights into the Origin of High-Performance Thermoelectric Response in Hybrid Perovskites.

Due to their tantalizing prospect of heat-electricity interconversion, hybrid organic-inorganic perovskites have sparked considerable research interests recently. Nevertheless, understanding their complex interplay between the macroscopic properties, nonintuitive transport processes, and basic chemical structures still remains far from completion, although it plays a fundamental role in systematic materials development. On the basis of multiscale first-principles calculations, this understanding is herein advanced by establishing a comprehensive picture consisting of atomic and charge dynamics. It is unveiled that the ultralow room-temperature lattice thermal conductivity (≈0.20 W m-1 K-1 ) of hybrid perovskites is critical to their decent thermoelectric figure of merit (≈0.34), and such phonon-glass behavior stems from not only the inherent softness but also the strong anharmonicity. It is identified that the 3D electrostatic interaction and hydrogen-bonded networks between the PbI3- cage and embedded cations result in the strongly coupled motions of inorganic framework and cation, giving rise to their high degree of anharmonicity. Furthermore, such coupled motions bring about low-frequency optical vibrational modes, which leads to the dominant role of electron scattering with optical phonons in charge transport. It is expected that these new atomistic-level insights offer a standing point where the performance of thermoelectric perovskites can be further enhanced.