Organic light-emitting diodes (OLEDs) based on thermally activated delayed fluorescence (TADF) materials are promising for the realization of highly efficient light emitters. However, such devices ...have so far suffered from efficiency roll-off at high luminance. Here, we report the design and synthesis of two diboron-based molecules, CzDBA and tBuCzDBA, which show excellent TADF properties and yield efficient OLEDs with very low efficiency roll-off. These donor–acceptor–donor (D–A–D) type and rod-like compounds concurrently generate TADF with a photoluminescence quantum yield of ~100% and an 84% horizontal dipole ratio in the thin film. A green OLED based on CzDBA exhibits a high external quantum efficiency of 37.8 ± 0.6%, a current efficiency of 139.6 ± 2.8 cd A−1 and a power efficiency of 121.6 ± 3.1 lm W−1 with an efficiency roll-off of only 0.3% at 1,000 cd m−2. The device has a peak emission wavelength of 528 nm and colour coordinates of the Commission International de l´Eclairage (CIE) of (0.31, 0.61), making it attractive for colour-display applications.
Owing to the high technology maturity of thermally activated delayed fluorescence (TADF) emitter design with a specific molecular shape, extremely high-performance organic light-emitting diodes ...(OLEDs) have recently been achieved
via
various doping techniques. Recently, undoped OLEDs have drawn immense attention because of their manufacturing cost reduction and procedure simplification. However, capable materials as host emitters are rare and precious because general fluorophores in high-concentration states suffer from serious aggregation-caused quenching (ACQ) and undergo exciton quenching. In this work, a series of diboron materials, CzDBA, iCzDBA, and
t
BuCzDBA, is introduced to realize the effect of steric hindrance and the molecular aspect ratio
via
experimental and theoretical studies. We computed transition electric dipole moment (TEDM) and molecular dynamics (MD) simulations as a proof-of-concept model to investigate the molecular stacking in neat films. It is worth noting that the pure
t
BuCzDBA film with a high horizontal ratio of 92% is employed to achieve a nondoped OLED with an excellent external quantum efficiency of 26.9%. In addition, we demonstrated the first ultrathin emitting layer (1 nm) TADF device, which exhibited outstanding power efficiency. This molecular design and high-performance devices show the potential of power-saving and economical fabrication for advanced OLEDs.
A strategy of substituent engineering of DBA-based molecules is investigated
via
experimental and theoretical methods. A 1 nm-thick emitting layer OLED has been developed.
Recently, thermally activated delayed fluorescence (TADF) materials have become the most promising hosts for realizing high-performance phosphorescent and fluorescent organic light-emitting diodes ...(OLEDs) because of their ability to upconvert triplet excitons to singlet excitons. However, despite a few TADF hosts having been introduced for low energy phosphorescent and fluorescent dopants, developing host materials with TADF properties for blue phosphorescent and TADF OLEDs is still a great challenge to date. In this study, bipolar hosts exhibiting TADF behavior and high triplet energy, consisting of the carbazole group as the donor, diphenylsulphone moiety as the acceptor, and m-bitolyl as the π-conjugated bridge, are synthesized and applied for the first time to blue devices. The ΔE ST value of the TADF host is tuned via the introduction of a cyano group in the carbazole moiety due to the increase of the LE contribution in the CT excited state. Detailed photophysical studies confirm the efficient TADF properties of bipolar hosts. The blue phosphorescent and TADF devices using BT-01 as the host give external quantum efficiencies of 31.8% and 25.5%, respectively. The blue devices based on the BT-01 host exhibit superior electroluminescence performance and more reduced efficiency roll-off compared with those hosted by BT-02, ascribed to the faster reverse intersystem crossing process on the BT-01 host. These excellent results manifest that the use of the bipolar host with TADF behavior is a promising approach for the realization of highly efficient blue phosphorescent and TADF devices in the future.
Three pyridine-carbonitrile–carbazole-based thermally activated delayed fluorescence (TADF) materials with highly sterically congested structures have been synthesized. The donor–acceptor-type TADF ...emitters (26-, 246-, and 35tCzPPC) consist of a 2,6-diphenylpyridine-3,5-dicarbonitrile core (PPC) as the acceptor and a di(t-butyl)carbazole-substituted phenyl group attached to C4 of the PC core as the donor. The molecules show a unique structure containing two consecutive large twisted angles along the donor and acceptor groups. The structure leads to a nearly complete space separation of the highest occupied molecular orbital and lowest unoccupied molecular orbital, a small ΔE ST value, and excellent TADF property. Moreover, the 26- and 246tCzPPC dopants favor a horizontal alignment enhancing the light outcoupling of the device. In contrast, 35tCzPPC favors a perpendicular alignment reducing the light outcoupling efficiency of the device. The 246tCzPPC-based devices show external quantum efficiency as high as 29.6% because of excellent TADF property, very high photoluminescence quantum yield, and high Θ value in the thin films. The device performance is the best among the pyridine-carbonitrile-based TADF emitters.
In contrast to the lipid droplets (LDs) in the cytoplasm, nuclear lipid droplets (nLDs), generated from the metabolically active inner nuclear membrane, contribute to the nuclear lipid homeostasis, ...locally regulate the availability of signaling lipids, and exchange the proteins between LDs and nuclei. Since the currently available fluorescence tools for imaging and tracking nLDs are limited, exploring a new nLD probe would be highly beneficial for studying the biogenesis and functional significance of nLDs. Herein, we developed a near-infrared probe, namely
DTZ-TPA-DCN
, which possessed the aggregation-induced emission (AIE) property with good biocompatibility for cytoplasm LD and nLD imaging.
DTZ-TPA-DCN
could be used for the super-resolution imaging of LDs with the structured illumination microscopy. By labelling nLDs, we could monitor the nLD formation under an ER stress, and for the first time, we observed that the signaling lipid, namely diacylglycerol (DAG), enhanced the formation of the nLDs. Together,
DTZ-TPA-DCN
provided a promising imaging tool for nLD studies, which contributed to a better understanding of the physiological significance of nLDs.
A near-infrared AIE probe was developed for super-resolution imaging and nuclear lipid droplets dynamic study with good biocompatibility and high photostability.
We designed and synthesized a novel nano-thermometer using aggregation-induced-emission (AIE) dye as the reporter and household butter as the matrix. This temperature nanosensor showed decreased ...fluorescence intensities (∼2%/°C) and shorter fluorescence lifetimes (∼0.11 ns/°C) upon increasing the environmental temperature in the physiological temperature range. Such fluorescence responses were reversible and independent of the environmental pH and ionic strength. The application of these nano-thermometers in temperature sensing in living cells using fluorescence lifetime imaging microscopy (FLIM) was also demonstrated. To the best of our knowledge, this is the first example of AIE-based nano-thermometer for temperature sensing in living cells. This work also provides us with a simple and low-cost method for rapid fabrication of an effective nanosensor based on AIE mechanism.
A novel nano-thermometer composed of butter and AIE molecules can be used for intracellular temperature mapping using fluorescence lifetime imaging.
Photosensitizers (PSs), a critical drug administered for successful photodynamic therapy (PDT), have been well researched regarding their anticancer or bactericidal capability with high precision and ...low invasiveness. Although traditional PSs have been explored either in photodynamic anticancer or in antibiosis, they usually require synthesis with multiple steps, harsh synthetic conditions, and a complicated purification process for a single targeted product. Therefore, developing new multifunctional PSs with a simple synthesis and reactant flexibility which combine mitochondrial and bacterial imaging, efficient photodynamic anticancer and antibacterial effects is of the utmost urgency and of great importance for clinical applications. Herein, a large structural investigation of isoquinolinium-based PSs synthesized by a simple Rh-catalysed annulation reaction with high yields is presented. These lipophilic cationic PSs have a tunable photophysical property.
LIQ-6
was found to perform not only as an ideal mitochondria targeting probe but also an effective cancer cell killing PS, and moreover, a tracker for bacterial imaging and ablation.
LIQ-6
can be used to image a wide range of cancer cells and to monitor the photo-induced cell apoptosis, and simultaneously, it can also image and be a photodynamic germicide for both Gram-positive and Gram-negative bacteria. Furthermore,
LIQ-6
shows great effectiveness in the wound healing process, showing its ability to be an ideal PS
in vivo
as well. This contribution is believed to offer a new platform for the construction of a theragnostic system for future practical applications in biology and biomedicine.
An isoquinolinium-based photosensitizer was developed for mitochondrial and bacterial imaging, and used in photodynamic anticancer and antibacterial therapy in a wound healing process
in vivo
.
Long-term plasma membrane (PM) tracking is important for studying the membrane function and diagnosis of membrane-related diseases. However, current PM probes can easily diffuse into the cytoplasm, ...which is undesirable. Here, we report an amphipathic aggregation-induced emission (AIE)-active far-red fluorescent probe, named DENPB, for long-term PM imaging. In live cancer cells, DENPB can be turned on after insertion into the PM and shows long-term membrane retention. It can be used for PM tracking for 6 h without obvious internalization. Interestingly, data show that it selectively stained the PM of live cancer cells (e.g., HeLa, HepG2, MDA-MB-231, MCF-7) but showed no signal in live non-cancer cells (e.g., RAW 264.7, NIH 3T3, HFF). It can also distinguish paraformaldehyde-fixed cancer cells from non-cancer cells by showing different signal patterns. This work provides a rational design strategy for a long-term PM-retention probe and a useful tool for cancer cell-specific staining that may greatly contribute to cancer diagnosis.
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An AIE-active amphipathic probe for plasma membrane imaging has been developedThe probe can be used for long-term plasma membrane trackingIt can distinguish live or PFA-fixed cancer cells from non-cancer cells
Wu et al. report an amphipathic AIE-active probe with a twisted, folded configuration, named DENPB, for long-term tracking of the plasma membrane. DENPB-stained cancer cells and non-cancer cells exhibited distinct signals, providing a potential tool for image-guided surgery.
Adult asthma is caused by interaction effects of multiple genetic and environmental factors. Some studies have suggested that antioxidant enzyme activity and gene polymorphisms may play important ...roles in the context of asthma. Therefore, our study objectives were to investigate the association between asthma, antioxidant activities and the polymorphisms of manganese superoxide dismutase (Mn-SOD) or catalase (CAT).
A case-control study, for which we recruited 250 asthmatic adults and 250 age- and sex-matched controls. All subjects completed a questionnaire. Waist and hip circumference measurements, a lung function test and DNA genotyping were performed. In total, 50 incident cases and 50 matched controls who were non-smokers or had quit smoking for at least 1 year were selected in order to investigate SOD and CAT activity levels.
In our study, we did not find a significant association between Mn-SOD Ala16Val, CAT C-262T and asthma. The level of SOD activity in new-onset asthma patients was significantly lower than in control subjects (p < 0.0005). The level of CAT activity in new-onset asthma patients was significantly higher than in control subjects (p < 0.0005).
The levels of SOD and CAT activity were significantly related to adult asthma. SOD and CAT activity may be good tools to differentiate potential asthma sufferers. This would enable us to further investigate the mechanism of defective antioxidant enzymes in the context of asthma pathogenesis.
Microviscosity is a fundamental parameter in the biophysics of life science and governs numerous cellular processes. Thus, the development of real-time quantitative monitoring of microviscosity ...inside cells is important. The traditional probes for detecting microviscosity via time-resolved luminescence imaging (TRLI) are generally disturbed by autofluorescence or surrounding oxygen in cells. Herein, we developed loose packing nanoaggregates with aggregation-induced delayed fluorescence (FKP-POA and FKP-PTA) and free from the effect of oxygen and autofluorescence for viscosity mapping via TRLI. The feasibility of FKP-PTA nanoparticles (NPs) for microviscosity mapping through TRLI was demonstrated by monitoring the variation of microviscosity inside HepG2 cancer cells, which demonstrated a value change from 14.9 cP to 216.9 cP during the apoptosis. This indicates that FKP-PTA NP can be used as a probe for cellular microviscosity mapping to help people to understand the physiologically dynamic microenvironment. The present results are expected to promote the advancement of diagnostic and therapeutic methods to cope with related diseases.
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