Recent Progress in Blue Thermally Activated Delayed Fluorescence Emitters and Their Applications in OLEDs: Beyond Pure Organic Molecules with Twist D-π-A Structures.

Thermally activated delayed fluorescence (TADF) materials, which can harvest all excitons and emit light without the use of noble metals, are an appealing class of functional materials emerging as next-generation organic electroluminescent materials. Triplet excitons can be upconverted to the singlet state with the aid of ambient thermal energy under the reverse inter-system crossing owing to the small singlet-triplet splitting energy (ΔEST). This results from a specific molecular design consisting of minimal overlap between the highest occupied molecular orbital and the lowest unoccupied molecular orbital, due to the spatial separation of the electron-donating and electron-releasing part. When a well-designed device structure is applied, high-performance blue-emitting TADF organic light-emitting diodes can be realized with an appropriate molecular design. Unlike the previous literature that has reviewed general blue-emitting TADF materials, in this paper, we focus on materials other than pure organic molecules with twist D-π-A structures, including multi-resonance TADF, through-space charge transfer TADF, and metal-TADF materials. Cutting-edge molecules with extremely small and even negative ΔEST values are also introduced as candidates for next-generation TADF materials. In addition, OLED structures used to exploit the merits of the abovementioned TADF emitters are also described in this review.

Conformational Engineering of Two-Coordinate Gold(I) Complexes: Regulation of Excited-State Dynamics for Efficient Delayed Fluorescence.

Carbene-Au-amide (CMA) type complexes, in which the amide and carbene ligands act as an electron donor (D) and acceptor (A), respectively, can exhibit strong delayed fluorescence (DF) from a ligand to ligand charge transfer (LLCT) excited state. Although the coplanar donor-acceptor (D-A) conformation has been suggested to be a crucial factor favoring radiative decay of the charge-transfer excited state, the geometric structural factor underpinning the excited-state mechanism of CMA complexes remains an open question. We herein develop a new class of carbene-Au-carbazolate complexes by introducing large aromatic substituents onto the carbazolate ligand, the presence of which are conceived to restrict the rotation of the Au-N bond and thus confine a twisted D-A conformation in both ground and excited states. A highly twisted D-A orientation is found for the complexes in their crystal structures. Photophysical studies reveal that the twisted conformation induces a decrease in the gap (ΔEST) between the lowest singlet excited state (S1) and the triplet manifold (T1) and thus a faster reverse intersystem crossing (RISC) from T1 to S1 at the expense of oscillator strength for an S1 radiative transition. In comparison with the coplanar analogue, the twisted complexes exhibit comparable or improved DF with quantum yields of up to 94% and short emission lifetimes down to sub-microseconds. The tuning of excited-state dynamics has been well interpreted by density functional theory (DFT) and time-dependent DFT (TDDFT) calculations, which unveil much faster RISC rates for twisted complexes. Solution-processed organic light-emitting diodes (OLEDs) based on the new CMA complexes show promising performances with almost negligible efficiency rolloff at a brightness of 1000 cd m-2. This work implies that neither a coplanar ground-state D-A conformation nor a dynamic rotation of the M-N bond is the key to the realization of efficient DF for CMA complexes.

Electroacupuncture for women with stress urinary incontinence: Protocol for a systematic review and meta-analysis.

BACKGROUND: Stress urinary incontinence (SUI) is a widespread complaint in the adult women. Electroacupuncture has been widely applied in the treatment of SUI. But its efficacy has not been evaluated scientifically and systematically. Therefore, we provide a protocol of systematic evaluation to assess the effectiveness and safety of electroacupuncture treatment on women with SUI. METHODS: The retrieved databases include 3 English literature databases, namely PubMed, Embase, and Cochrane Library, and 3 Chinese literature databases, namely Chinese Biomedical Literature Database (CBM), China National Knowledge Infrastructure (CNKI), and Wanfang Database. The randomized controlled trials (RCTs) of the electroacupuncture treatment on women with SUI will be searched in the above-mentioned databases from the time when the respective databases were established to December 2017. The change from baseline in the amount of urine leakage measured by the 1-hour pad test will be accepted as the primary outcomes. We will use RevMan V.5.3 software as well to compute the data synthesis carefully when a meta-analysis is allowed. RESULTS: This study will provide a high-quality synthesis to assess the effectiveness and safety of electroacupuncture treatment on women with SUI. CONCLUSION: The conclusion of our systematic review will provide evidence to judge whether electroacupuncture is an effective intervention for women with SUI. PROSPERO REGISTRATION NUMBER: PROSPERO CRD42017070947.

High Sensitivity Polymer Visible-Near Infrared Photodetectors via an Inverted Device Structure and Manipulation of Injection Barrier Height.

Visible-near infrared photodetectors are reported with excellent overall device parameters from conjugated polymers with different optical bandgaps by optimal design in device structure and optimizing the thickness of the photoactive layer in nanoscale. The best visible-near infrared photodetectors show high detectivity (D*) of 1.7 × 10(13) Jones at a wavelength of 710 nm, which is among one of the best results of polymer photodetectors reported to date.

n-Type Water/Alcohol-Soluble Naphthalene Diimide-Based Conjugated Polymers for High-Performance Polymer Solar Cells.

With the demonstration of small-area, single-junction polymer solar cells (PSCs) with power conversion efficiencies (PCEs) over the 10% performance milestone, the manufacturing of high-performance large-area PSC modules is becoming the most critical issue for commercial applications. However, materials and processes that are optimized for fabricating small-area devices may not be applicable for the production of high-performance large-area PSC modules. One of the challenges is to develop new conductive interfacial materials that can be easily processed with a wide range of thicknesses without significantly affecting the performance of the PSCs. Toward this goal, we report two novel naphthalene diimide-based, self-doped, n-type water/alcohol-soluble conjugated polymers (WSCPs) that can be processed with a broad thickness range of 5 to 100 nm as efficient electron transporting layers (ETLs) for high-performance PSCs. Space charge limited current and electron spin resonance spectroscopy studies confirm that the presence of amine or ammonium bromide groups on the side chains of the WSCP can n-dope PC71BM at the bulk heterojunction (BHJ)/ETL interface, which improves the electron extraction properties at the cathode. In addition, both amino functional groups can induce self-doping to the WSCPs, although by different doping mechanisms, which leads to highly conductive ETLs with reduced ohmic loss for electron transport and extraction. Ultimately, PSCs based on the self-doped WSCP ETLs exhibit significantly improved device performance, yielding PCEs as high as 9.7% and 10.11% for PTB7-Th/PC71BM and PffBT4T-2OD/PC71BM systems, respectively. More importantly, with PffBT4T-2OD/PC71BM BHJ as an active layer, a prominent PCE of over 8% was achieved even when a thick ETL of 100 nm was used. To the best of our knowledge, this is the highest efficiency demonstrated for PSCs with a thick interlayer and light-harvesting layer, which are important criteria for eventually making organic photovoltaic modules based on roll-to-roll coating processes.

Three-step biocatalytic reaction using whole cells for efficient production of tyramine from keratin acid hydrolysis wastewater.

Tyramine has been paid more attention in recent years as a significant metabolite of tyrosine and catecholamine drug and an intermediate of medicinal material and some drugs. In this study, an effective, green, and three-step biocatalytic synthesis method for production of tyramine starting from serine in keratin acid hydrolysis wastewater was developed and investigated. Serine deaminase from Escherichia coli was first combined with tyrosine phenol-lyase from Citrobacter koseri, to convert L-serine to L-tyrosine. L-Tyrosine can then be decarboxylated to tyramine by tyrosinede carboxylase from Lactobacillus brevis. All these enzymes originated from recombinant whole cells. Serine deaminaseand tyrosine phenol-lyase could efficiently convert L-serine in wastewater to L-tyrosine at pH 8.0, 37 °C, and Triton X-100 of 0.04% when tyrosine phenol-lyase and its corresponding substrates were sequentially added. Tyrosine conversion rate reached 98 % by L-tyrosine decarboxylase. In scale-up study, the conversion yield of L-serine in wastewater to tyrosine was up to 89 %. L-Tyrosine was decarboxylated to tyramine with a high yield 94 %. Tyramine hydrochloride was obtained with a total yield 84 %. This study has provided an efficient way of recycling keratin acid hydrolysis wastewater to produce tyramine.

Perylene Bisimide as a Promising Zinc Oxide Surface Modifier: Enhanced Interfacial Combination for Highly Efficient Inverted Polymer Solar Cells.

We report the application of a perylene bisimide (PBI-H) as zinc oxide (ZnO) surface modifier to afford an organic-inorganic co-interlayer for highly efficient inverted organic photovoltaics (i-OPV). By thermal annealing, a N-Zn chemical bond formed between PBI-H and ZnO, inducing close organic-inorganic combination. In addition, this co-interlayer shows decreased work function and increased electron transportation and conductivity, which are benefits for the cathode to enhance charge extraction efficiency and decrease recombination losses. As a result a highly efficient i-OPV was achieved with a power conversion efficiency (PCE) of 9.43% based on this co-interlayer with PTB7:PC71BM as the active layer, which shows over 35% enhancement compared to that of the device without the PBI-H layer. Moreover, this co-interlayer was widely applicable for i-OPVs based on various material systems, such as P3HT:PC61BM and PTB7-Th:PC71BM, resulting in PCE as high as 4.78% and 10.31%, respectively.

[Effect of "Jin three-needle therapy" on cognitive function and activity of daily living in patients of hemiplegia after stroke: a multi-central randomized controlled study].

OBJECTIVE: To provide reliable evidence of "J in three-needle therapy" for treatment of stroke. METHODS: Multi-central randomized controlled trials were adopted, 180 hemiplegia patients of ischemic stroke were randomly divided into a fin three-needle group (90 cases) and a routine acupuncture group (90 cases). Two groups were both treated with basic neurology therapies, and J in three-needle group was treated with J in three-needle therapy, three acupoints of tempora, hand and foot etc. were selected; the routine acupuncture group was treated with traditional acupuncture, Quchi (LI 11), Huantiao (GB 30), Futu (ST 32) etc. were selected. Both groups were treated with acupuncture for 5 weeks. The cognitive function score of functional comprehensive assessment scale (FCA), the scores of mini-mental state examination scale (MMSE) and modified Barthel index (BI) were compared before and after treatment between two groups. Results After treatment, the scores of FCA, MMSE and BI in both groups were significantly improved compared to those before treatment (P < 0.01, P < 0.05); the improvement of FCA score, MMSE score and BI score in the J in three-needle group were superior to those of the routine acupuncture group after treatment (P < 0.01, P < 0.05). The total effective rate of 85.4% in the J in three-needle group was superior to tohat of 70.0% in the routine acupuncture group (P < 0.05). CONCLUSION: J in three-needle acupuncture treatment can obviously improve the cognitive function and activity ability of daily life of hemiplegia patients after stroke, and the therapeutic effect of J in three-needle therapy is superior to that of traditional acupuncture treatment.