White Light from a Light-Emitting Electrochemical Cell: Controlling the Energy-Transfer in a Conjugated Polymer/Triplet-Emitter Blend

We report on the attainment of broadband white light emission from a host–guest light-emitting electrochemical cell, comprising a blue-emitting conjugated polymer as the majority host and a red-emitting small-molecule triplet emitter as the minority guest. An analysis of the energy structure reveals that host-to-guest energy transfer can be effectuated by both Förster and Dexter processes, and through a careful optimization of the active material composition partial energy transfer and white emission is accomplished at a low guest concentration of 0.5%. By adding a small amount of a yellow-emitting conjugated polymer to the active material, white light emission with a high color rendering index of 79, and an efficiency of 4.3 cd/A at significant luminance (>200 cd/m²), is realized

Simple Preparation Process of <i>syn</i> Phenylpropanolamines from Racemic <i>O</i>-TBDPS Cyanohydrins

<div><p></p><p>In this article, a practically interesting route for the diastereoselective synthesis of phenylpropanolamines has been demonstrated for the first time. Using racemic <i>O-tert</i>-butyldiphenylsilyl (TBDPS) cyanohydrins as the starting materials, various <i>syn</i> phenylpropanolamines and derivatives (e.g., norpseudophedrine) have been successfully prepared in exellent diastereoselectivity via a practically interesting process.</p> </div

Combining an Ionic Transition Metal Complex with a Conjugated Polymer for Wide-Range Voltage-Controlled Light-Emission Color

We report on voltage-controlled electroluminescence (EL) over a broad range of colors from a “two-luminophor” (2L) light-emitting electrochemical cell (LEC), comprising a blend of a majority blue-emitting conjugated polymer (blue-CP), a minority red-emitting ionic transition metal complex (red-iTMC), and an ion-transporting compound as the active layer. The EL color is reversibly shifted from red, over orange, pink, and white, to blue by simply changing the applied voltage from 3 to 7 V. An analysis of our results suggests that the low concentration of immobile cations intrinsic to this particular device configuration controls the electron injection and thereby the EL color: at low voltage, electrons are selectively injected into the low-barrier minority red-iTMC, but with increasing voltage the injection into the high-barrier majority blue-CP is gradually improved

A Solution-Processed Trilayer Electrochemical Device: Localizing the Light Emission for Optimized Performance

We present a solution-processed trilayer light-emitting device architecture, comprising two hydrophobic and mobile-ion-containing “transport layers” sandwiching a hydrophilic and ion-free “intermediate layer”, which allows for lowered self-absorption, minimized electrode quenching, and tunable light emission. Our results reveal that the transport layers can be doped in situ when a voltage is applied, that the intermediate layer as desired can contribute significantly to the light emission, and that the key to a successful operation is the employment of a porous and (∼5–10 nm) thin intermediate layer allowing for facile ion transport. We report that such a solution-processed device, comprising a thick trilayer material (∼250 nm) and air-stable electrodes, emits blue light (λ_peak = 450, 484 nm) with high efficiency (5.3 cd/A) at a low drive voltage of 5 V

Hydrogen-Borrowing Reduction/Dehydrogenative Aromatization of Nitroarenes through Visible-Light-Induced Energy Transfer: An Entry to Pyrimidoindazoles and Carbazoles

Herein, we describe a novel visible-light-induced protocol for hydrogen-borrowing reduction/dehydrogenation aromatization/cyclization of nitroarenes by energy transfer. The present protocol does not require additional oxidants, hydrogen acceptors, and hydrogen evolution metal catalysts. The mechanistic studies demonstrated that the hydrogen-borrowing reduction/dehydrogenative aromatization process was initiated by the formation of active singlet species through efficient energy transfer of excited Ir[dF(CF3)ppy]2(dtbpy)PF6 to nitroarenes

Intense and Stable Near-Infrared Emission from Light-Emitting Electrochemical Cells Comprising a Metal-Free Indacenodithieno[3,2‑<i>b</i>]thiophene-Based Copolymer as the Single Emitter

We report on the synthesis, characterization, and application of a series of metal-free near-infrared (NIR) emitting alternating donor/acceptor copolymers based on indacenodithieno­[3,2-<i>b</i>]­thiophene (IDTT) as the donor unit. A light-emitting electrochemical cell (LEC), comprising a blend of the copolymer poly­[indacenodithieno­[3,2-<i>b</i>]­thiophene-2,8-diyl-<i>alt</i>-2,3-diphenyl-5,8-di­(thiophen-2-yl)­quinoxaline-5,5′-diyl] and an ionic liquid as the single-layer active material sandwiched between two air-stable electrodes, delivered NIR emission (λ_peak = 705 nm) with a high radiance of 129 μW/cm² when driven by a low voltage of 3.4 V. The NIR-LEC also featured good stress stability, as manifested in that the peak NIR output from a nonencapsulated device after 24 h of continuous operation only had dropped by 3% under N₂ atmosphere and by 27% under ambient air. This work accordingly introduces IDTT-based donor/acceptor copolymers as functional metal-free electroluminescent materials in NIR-emitting devices and also provides guidelines for how future NIR emitters should be designed for further improved performance

Identifying Key Properties of Electrolytes for Light-Emitting Electrochemical Cells

The electrolyte is a key component in light-emitting electrochemical cells (LECs), as it facilitates <i>in situ</i> electrochemical doping and associated attractive device features. LiCF₃SO₃ dissolved in hydroxyl-capped trimethylolpropane ethoxylate (TMPE-OH) constitutes an electrolyte with which we have attained high stability and efficiency for polymer LECs, but the turn-on time of such devices is unfortunately slow. By replacing hydroxyl with methoxy as the TMPE end-group, we produced LECs with a desired combination of high efficiency, good stability, and fast turn-on time. Specifically, we showed that the turn-on time to high luminance (300 cd/m²) at a current density of 7.7 mA/cm² is lowered from 1740 to 16 s, that the efficiency is improved by ∼20%, and that the other device properties are either maintained or improved. In a parallel modeling and experimental effort, we demonstrated that the faster kinetics following the shift in the TMPE end-group is attributed to a marked decrease in the level of both inter- and intramolecular interactions of the electrolyte, as manifested in a lowered electrolyte viscosity, faster ion transport, and more facile ion release during doping

High-Performance Light-Emitting Electrochemical Cells by Electrolyte Design

Polymer light-emitting electrochemical cells (LECs) are inherently dependent on a suitable electrolyte for proper function. Here, we design and synthesize a series of alkyl carbonate-capped star-branched oligoether-based electrolytes with large electrochemical stability windows, facile ion release, and high compatibility with common light-emitting materials. LECs based on such designed electrolytes feature fast turn-on, a long operational lifetime of 1400 h at >100 cd m^–2 and a record-high power conversion efficiency of 18.1 lm W^–1, when equipped with an external outcoupling film

MicroRNA-497 Induces Apoptosis and Suppresses Proliferation via the Bcl-2/Bax-Caspase9-Caspase3 Pathway and Cyclin D2 Protein in HUVECs

<div><p>Introduction</p><p>MicroRNAs play crucial roles in various types of diseases. However, to date, no information about the role of miR-497 in the development of atherosclerosis has been reported. This study investigated the possible role of miR-497 in vascular endothelial cell injury during the early stage of atherosclerosis.</p><p>Materials and Methods</p><p>The expression level of miR-497 in human umbilical vein endothelial cells (HUVECs) exposed to ox-LDL was detected using qRT-PCR. To perform gain of function and loss of function analyses, miR-497 mimics were transfected into HUVECs, and miR-497 inhibitors were transfected into HUVECs stimulated with ox-LDL. Flow cytometry was used to analyze cell cycle progression and apoptosis. EdU and CCK-8 assays were employed to detect DNA synthesis and cell proliferation, respectively. After bioinformatics prediction, a dual Luciferase Reporter assay was used to analyze the direct target genes of miR-497. The mRNA and protein levels of the target genes were detected using qRT-PCR and western blot analyses, respectively. Caspase-9/3 activity was analyzed to determine the mechanism of endothelial dysfunction.</p><p>Results</p><p>We showed that miR-497 was significantly upregulated in HUVECs stimulated with ox-LDL. Ectopic expression of miR-497 suppressed cell proliferation, induced apoptosis and increased the activity of caspase-9/3. After verification, Bcl2 and CCND2 were shown to be direct target genes of miR-497 in HUVECs. MiR-497 significantly suppressed cell proliferation by arresting the cell cycle through the CCND2 protein and induced apoptosis through the Bcl2/Bax-caspase9-caspase3 pathway.</p><p>Conclusion</p><p>Overall, our study shows that miR-497 might play a role in the development of atherosclerosis by inducing apoptosis and suppressing the proliferation of vascular endothelial cells. Therefore, miR-497 could be a potential therapeutic target for the treatment of atherosclerosis.</p></div

QRT-PCR analysis was used to analyze the levels of miR-497 in HUVECs stimulated with ox-LDL.

<p>HUVECs were exposed to 100 μg/ml ox-LDL for 3, 6, 12, 24, 36, or 48 h. The miR-497 levels were significantly upregulated after 36 h of stimulation with 100 μg/ml ox-LDL; **P<0.01.</p