The first thermally activated delayed fluorescence (TADF) emitter and organic light-emitting diodes (OLEDs) in the near-infrared (NIR) II region (
λ
EL,max
= 1010 nm) were realized
via
intermolecular ...charge-transfer aggregates. This work provides a promising strategy for achieving TADF in the NIR-II region.
The first thermally activated delayed fluorescence emitter and organic light-emitting diodes in the near-infrared II region were realized
via
intermolecular charge-transfer aggregates.
Organic light‐emitting diodes (OLEDs) have attracted great attention because of their potential applications in full‐color displays and solid‐state lights. In the continual effort to search for ideal ...materials for OLEDs, small molecules with bipolar transporting character are extremely attractive as they offer the possibility to achieve efficient and stable OLEDs even in a simple single‐layer device. In this Research News, we review the two design strategies of bipolar materials for OLEDs: molecules with or without donor‐acceptor structures. The correlation between the experimental results and theoretical calculations of some of the materials is also discussed.
Small molecules with bipolar transporting characters are extremely attractive as they offer the possibility to achieve efficient and stable organic light‐emitting diodes (OLEDs). In this article we review the two design strategies for bipolar materials for OLEDs: with or without donor‐acceptor structure. The correlation between the experimental results and theoretical calculations of some of the materials is also discussed.
Multiple resonance (MR) emitters are promising for highly efficient organic light‐emitting diodes (OLEDs) with narrowband emission; however, they still face intractable challenges with ...concentration‐caused emission quenching, exciton annihilation, and spectral broadening. In this study, sterically wrapped MR dopants with a fluorescent MR core sandwiched by bulk substituents were developed to address the intractable challenges by reducing intermolecular interactions. Consequently, high photo‐luminance quantum yields of ≥90 % and small full width at half maximums (FWHMs) of ≤25 nm over a wide range of dopant concentrations (1–20 wt %) were recorded. In addition, we demonstrated that the sandwiched MR emitter can effectively suppress Dexter interaction when doped in a thermally activated delayed fluorescence sensitizer, eliminating exciton loss through dopant triplet. Within the above dopant concentration range, the optimal emitter realizes remarkably high maximum external quantum efficiencies of 36.3–37.2 %, identical small FWHMs of 24 nm, and alleviated efficiency roll‐offs in OLEDs.
Sterically wrapped multiple resonance (MR) dopants with the MR‐core sandwiched by bulk substituents have been developed to suppress molecular interactions, realizing organic light‐emitting diodes with remarkably high maximum external quantum efficiencies of 36.3–37.2 %, identical small FWHMs of 24 nm and alleviated efficiency roll‐offs over a wide range of dopant concentrations (1–20 wt %).
Organic light-emitting diodes (OLEDs) have become popular displays from small screens of wearables to large screens of televisions. In those active-matrix OLED displays, phosphorescent iridium(III) ...complexes serve as the indispensable green and red emitters because of their high luminous efficiency, excellent color tunability, and high durability. However, in contrast to their brilliant success in the visible region, iridium complexes are still underperforming in the near-infrared (NIR) region, particular in poor luminous efficiency according to the energy gap law. In this review, we first recall the basic theory of phosphorescent iridium complexes and explore their full potential for NIR emission. Next, the recent advances in NIR-emitting iridium complexes are summarized by highlighting design strategies and the structure-properties relationship. Some important implications for controlling photophysical properties are revealed. Moreover, as promising applications, NIR-OLEDs and bio-imaging based on NIR Ir(III) complexes are also presented. Finally, challenges and opportunities for NIR-emitting iridium complexes are envisioned.
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•Basic theory of phosphorescent Ir complexes and useful implications for NIR emission•Recent advances and design strategies of NIR-emitting Ir complexes for OLEDs•Recent advances of NIR probes based on Ir complexes for bioimaging•Challenges and opportunities for the development and applications of NIR Ir complexes
Organic chemistry; Optical materials; Photonics
Despite the great potential for applications spanning from military night-vision displays and information-secured devices to civilian medical diagnostics and phototherapy, the development of highly ...efficient, stable, and low-cost near-infrared (NIR) emitting lumophores is still a formidable challenge. Herein, we report two novel NIR-emitting homoleptic facial Ir(III) complexes based on extended π-conjugated benzogphthalazine ligands, namely, tris1,4-di(thiophen-2-yl)benzogphthalazine iridium(III) (Ir(dtbpa)3, 1) and tris1-(2,4-bis(trifluoromethyl)phenyl)-4-(thiophen-2-yl)benzogphthalazine iridium(III) (Ir(Ftbpa)3, 2). Actually, these two ligands not only enable simple one-pot synthesis of homoleptic Ir(III) complexes without any catalyst under mild conditions, but also contribute to intense NIR-emission with high photoluminescence quantum yield up to 5.2% at 824 nm for 1 and 17.3% at 765 nm for 2, respectively. Single-crystal structure of 1 demonstrates desired facial form with short Ir–N and Ir–C bonds because of strong coordination and small steric hindrance of those highly conjugated C^NN ligands. Importantly, the incorporation of CF3 groups in 2 further leads to high thermal stability and a good ability to sublime, thus resulting in ultrapurity for highly efficient NIR-organic light-emitting diodes (NIR-OLEDs) with a high maximum external quantum efficiency of 4.5% at 760 nm and small efficiency roll-off remaining of 3.5% at 100 mA cm–2, values which rank with those of the most efficient NIR-OLEDs with small roll-off and peak emission over 750 nm. Notably, the content percentages of the noble metal in these two complexes (∼10% Ir) are markedly lower by about two-thirds than that of typical green-emitting tris(2-phenylpyridine)iridium (∼30% Ir). The findings may provide a new strategy to develop robust NIR emitters and achieve high efficiency, small roll-off, and low cost simultaneously in NIR-OLEDs for practical applications.
•90 plant resources were investigated for the distribution of protease activities.•Proteases of various types may be developed from kiwifruit, broccoli, ginger and leek.•Novel proteases may be ...discovered from red pepper.
In this study, a comparative analysis on the distribution of protease activities among 90 plant resources, including fruits and vegetables, has been performed. Protease activities of plant extracts were assayed at different pH values (pH 3.0, pH 7.5 and pH 10.5) using casein as a substrate. Ten fruits and thirteen vegetables show protease activities above 10U/g. Pineapple, fig and papaya, which are used for commercial protease production, exhibited high protease activities. Additionally, high protease activities were detected in kiwifruit (28.8U/g), broccoli (16.9U/g), ginger (16.6U/g), leek (32.7U/g) and red pepper (15.8U/g) at different pH values. SDS-PAGE and zymograms confirmed that various types of proteases existed in the five plant extracts and might be explored. Furthermore, five plant extracts were treated by different protease inhibitors. These results show that there are still many plant resources unexplored, which may be promising candidates for plant-derived protease production.
Summary
This work investigated gelling properties and structural characteristics of fish gelatin (FG) modified by four different molecular weights of γ‐polyglutamic acid (γ‐PGA) with 700, 1000, 2000 ...and 3000 kDa, respectively. Gelation‐melting transition temperature and gel strength increased with the increase of molecular weight in γ‐PGA. Especially, γ‐PGA in 3000 kDa made gel strength, gelation and melting temperatures reaching to 628.08 g (
P
< 0.05), 22.30 °C and 30.17 °C (
P
< 0.05), respectively. Non‐covalent interactions existed in FG and γ‐PGA. Such as, new hydrogen bonds were generated between them. Moreover, γ‐PGA with increased molecular weight enhanced three‐stranded helical structure and microscopic meshwork of FG. Finally, a schematic model was described to illustrate the interaction between FG and γ‐PGA in different molecular weights. On the whole, γ‐PGA with high molecular weight significantly improved gelling properties of FG, and could be a potential modifier of FG in the future.
Multitudinous biochemical reactions occur in living cells, creating and releasing free energy to impel numerous cellular activities. Surplus energy is expelled as heat and resulted in elevated ...temperature, which induce control of gene expression, tumour metabolism and etc. Sensitive measurement of temperature on nanoscale in cells with ideal fluorescent probes is a great challenge in many areas. By taking the advantages of polymers in tunable critical solution temperature range and good biocompatibility, fluorescent polymeric thermometers (FPT) have drawn extensive attention because they are capable of accurate monitoring temperature with high spatial resolution at cellular level. This review offers a general overview of recent examples of FPT working in cells. The strategy for design and synthesis of the FPT has been highlighted. Furthermore, the applications of the constructed FPT for intracellular temperature variations under normal and external stimuli conditions have been discussed. Deep understanding of these aspects would lead to improvement in designing of unique FPT with real function and applications for intracellular temperature sensing. It will pave a new way not only for the study of intrinsic relationship between temperature and organelle function, but also provide the possibility for deep understanding of intracellular biological processes.
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•Design and synthesis of fluorescent polymeric thermometers are summarized.•Polymeric thermometers for intracellular temperature sensing are introduced.•Advantages of these polymeric thermometers for temperature sensing in cells are highlighted.
Chemical stability of organic materials on service toward excitons and charge carriers is intrinsically associated with the operational stability and economics of state-of-the-art organic ...light-emitting devices. Here we conducted comprehensive experiments and theoretical calculations to comparatively investigate the intrinsic chemical stability of organic materials, which contain typical electron-accepting moieties of sulfonyl, phosphine-oxide, and carbonyl group. The materials with a diphenylsulfonyl moiety suffered a fatal chemical instability originating from the cleavage of C–S single bond whether under UV irradiation or in electrical-stressed devices. The material with a dibenzothiophene-S,S-dioxide moiety exhibited significantly improved chemical stability because of effective shielding of the weak C–S single bond in a ring. In contrast, the commercially used carbonyl-containing compound demonstrated the highest chemical stability with negligible degradation under the same condition. Quantum chemical calculations fully supported the experimental results and suggested that the bond strength of the weak chemical bonds of the molecules would determine the intrinsic chemical stability of the organic materials in their excited and charged states, which might be a plausible origin of the limited stability of high-energy blue-emitting materials and devices. Several implications have been drawn for the design of new blue-emitting materials.
Bacteria biofilm plays a key role in current generation of microbial fuel cells (MFCs), especially for the start-up stage. However, the detailed mechanism of the biofilm promoting the power ...generation is not very clear so far, especially for those exoelectrogens who rely on the self-excreted electron mediators for extracellular electron transfer. In this work, a biofilm formation inhibitor—sodium houttuyfonate (SH) is used to build a “non-biofilm” anode of Pseudomonas aeruginosa (P. aeruginosa) without affecting the bacteria growth during the MFC operation. According to the comparison results of the “non-biofilm” anode and biofilm-covered anode on current generation, phenazines concentration variation and anodic electrocatalysis, the biofilm on the anode not only provides plenty of bacterial cells for catalysis but also promotes the interfacial phenazine redox reaction through accumulating the self-generated mediators on anode for fast interfacial electron transfer. This work proves that the biofilm assisted electron mediator accumulation will benefit such kind of exoelectrogens to sustain sufficient electron mediators for extracellular electron transfer.
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•Biofilm formation promotes the current generation of P. aeruginosa anode.•Biofilm assists phenazines accumulation on anode for fast electron transfer.•Phenazines on anode rather than suspended ones determine the anode performance.
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