Red phosphorescent organic light-emitting diodes based on a novel host material with thermally activated delayed fluorescent properties

High cost of phosphors and significant efficiency roll-off at high brightness are the two main factors that limit the wide application of phosphorescent organic light-emitting diodes (PHOLEDs). Efforts have been paid to find ways to reduce the phosphors’ concentration and efficiency roll-off of PHOLEDs. In this work, we reported red emission PHOLEDs with low dopant concentration and low efficiency roll-off based on a novel host material 2,4-biscyanophenyl-6-(12-phenylindole[2,3-a]carbazole-11-yl)-1,3,5-triazine (BCPICT), with thermally activated delayed fluorescent(TADF) properties. The device with 1.0% dopant concentration displayed a maximum external quantum efficiency of 10.7%.When the dopant concentration was increased to 2.0%, the device displayed a maximum external quantum efficiency of 10.5% and a low efficiency roll-off of 5.7% at 1000 cd/m2.     

In Situ Pyrolysis Tracking and Real-Time Phase Evolution: From a Binary Zinc Cluster to Supercapacitive Porous Carbon

The in situ tracking of the pyrolysis of a binary molecular cluster [Zn₇(μ₃-CH₃O)₆(L)₆][ZnLCl₂]₂ is presented with one brucite disk and two mononuclear fragments (L=mmimp: 2-methoxy-6-((methylimino)-methyl)phenolate) to porous carbon using TG-MS from 30 to 900 °C. Following up the spilled gas product during the decomposed reaction of zinc cluster along the temperature rising, and in conjunction with XRD, SEM, BET and other materials characterization, where three key steps were observed: 1) cleavage of the bulky external ligand; 2) reduction of ZnO and 3) volatilization of Zn. The real-time-dependent phase-sequential evolution of the remaining products and the processing of pore forming template transformation are proposed simultaneously. The porous carbon structure featuring a uniform nano-sized pore distribution synthesized at 900 °C with the highest surface area of 1644 m² g⁻¹ and pore volume of 0.926 cm³ g⁻¹ exhibits the best known capacitance of 662 F g⁻¹ at 0.5 A g⁻¹.     

A Smart Photochromic Semiconductor: Breaking the Intrinsic Positive Relation Between Conductance and Temperature

Breaking the intrinsic rule of semiconductors that conductivity increases with increase of temperature and realizing a dramatic dropping of conductivity at high temperature may arouse new intriguing applications, such as circuit overload or over‐temperature protecting. This goal has now been achieved through T‐type electron‐transfer photochromism of one organic semiconductor assembled by intermolecular cation???π interactions. Conductivity of the viologen‐based model semiconductor (H₂bipy)(Hox)₂ (H₂bipy=4,4′‐bipyridin‐1,1′‐dium; ox=oxalate) increased by 2 orders of magnitude after photoinduced electron transfer (a record for photoswitchable organic semiconductors) and generation of radical cation???π interactions, and fell by approximately 81 % at 100 °C through reverse electron transfer and degeneration of the radical cation???π interactions. The model semiconductor has at least two different electron transfer pathways in the decoloration process.     

Modulation versus Templating: Fine‐Tuning of Hierarchally Porous PCN‐250 Using Fatty Acids To Engineer Guest Adsorption

Modulation and templating are two synthetic techniques that have garnered significant attention over the last several years for the preparation of hierarchically porous metal–organic frameworks (HP‐MOFs). In this study, by using fatty acids with different lengths and concentrations as dual‐functional modulators/templates, we were able to obtain HP‐MOFs with tunable mesopores that exhibit different pore diameters and locations. We found that the length and concentration of the fatty acids can determine if micelle formation occurs, which in turn dictates the porosity of the resulting HP‐MOFs. The HP‐MOFs with different mesopores differed in their performance in gas uptake and dye adsorption, and the structure–performance relationships were ascribed to the pore diameters and locations. This approach could provide a potentially universal method to efficiently introduce hierarchal mesopores into existing microporous MOF adsorbents with tunable properties.     

Hydrothermal synthesis method of 5-(4'-methylbiphenyl-2-yl)-1H-tetrazole

A clean and safe synthesis method of 5-(4’-methylbiphenyl-2-yl)-1H-tetrazole was found:under hydrothermal conditions,1.2 equiv.of 4’-methylbiphenyl-2-carbonitrile react with 1 equiv.of sodium azide in a mixed solvent of propane-1,2-diol/H2O,with 1.5 equiv.of ammonium chloride and 0.2 equiv.of ammonium fluoride as catalyst.After simple post-processing,the yield can be improved to 95%,and the purity of the product is 99%without further recrystallization.     

Molecular tilting and its impact on frictional properties of n-alkane self-assembled monolayers

Hydrophobic, methyl-terminated self-assembled monolayer (SAM) surfaces can be used to reduce friction. Among methyl-terminated SAMs, the frictional properties of alkanethiol SAMs and silane SAMs have been well-studied. In this research, we investigated friction of methyl-terminated n-hexatriacontane (C36) SAM and compared its friction properties with the alkanethiol and silane SAMs. Alkane SAM does not have an anchoring group. The alkane molecules stand on the surface by physical adsorption, which leads to a higher surface mobility of alkane molecules. We found that C36 SAM has a higher coefficient of friction than that of octadecyltrichlorosilane (OTS) silane. When an atomic force microscope (AFM) tip was swiped across the alkane SAM with a loading force, we found that the alkane SAM can withstand the tip loading pressure up to 0.48 GPa. Between 0.48 and 0.49Ga, the AFM tip partially penetrated the SAM. When the tip moved away, the deformed SAM healed and maintained the structural integrity. When the loading pressure was higher than 0.49 GPa, the alkane SAM was shaved into small pieces by the tip. In addition, we found that the molecular tilting of C36 molecules interacted with the tribological properties of the alkane SAM surface. On one hand, a higher loading force can push the rod-like alkane molecules to a higher tilting angle; on the other hand, a higher molecular tilting leads to a lower friction surface.     

Steroidal saponins from rhizomes of Tupistra wattii Hook. f

Chemical examination of the fresh rhizomes of Tupistra wattii HOOK. f. led to the isolation of three new steroidal saponins, wattoside G (1), H (2), and I (3), together with one known steroidal saponin, (25S)-1beta,3beta,4beta-trihydroxyspirotan-5beta-yl-O-beta-D-glucopyranoside (4). The structures of 1-3 were established to be (25R)-1beta,2beta,3beta,5beta-tetrahydroxyspirostan-4beta-yl-O-beta-D-xylopyranoside (1), (24S,25S)-24-[(beta-D-glucopyranosyl)oxy]-1beta,2beta,3beta,4beta,5beta,7beta-hexahydroxyspirostan-6-one (2), and (24S,25S)-1beta,3beta-dihydroxy-5beta-spirostan-24-yl-O-beta-D-glucopyranosyl-(1-->6)-beta-D-glucopyranoside (3) on the basis of detailed analyses of physical, chemical, and spectral data. The isolated compounds were evaluated for cytotoxic activity against the cancer cell line K562 in vitro.     

Synthesis of Fluoro-Contained Bisazo Chromotropic Acid Derivants and studies on Their Color Reactions with Rare Earth Elements

In this paper, a series of f1uoro-contained bisazo chromotropic acid derivants has been designed and synthesized. They are easily soluble in water, alcohol and acetone but insoluble in benzene, ether and chloroform. Some regularities of the effects of their molecular structure on the color reaction have also been studied. The result shows that in this series of reagents, DCF-chlorophosphonazo and DBF-chlorophosphonazo are excellent color reagents for the determination of the total amount of rare earth elements. The molar absor-ptivities of light and heavy rare earth elements are approach to each other. The tolerant quantity of Bi (Ⅲ) and Pb (Ⅱ) , Sn(Ⅳ) are larger than that of the other arsenazo or chlorophosphonazo type of color reagents. We also discover that p-fluorochlorophosphonazo can form β-type complexes with heavy rare earth elements, and p -fluoro-carboxyazo with light rare earth elements. If the reaction time is controlled, p -fluoro-carboxyao can form β-type complex only with La, and the     

Ab initio study of the low-lying electronic states of the CH2NO2 radical

Ab initio electronic structures calculations are reported for the four low-lying electronic states X ²B₁, ²B₂, ²A₂, and ²A₁ of the CH₂NO₂ radical. The geometric parameters for the ground-state X ²B₁ are predicted by MRSDCI calculations with a double zeta plus polarization basis set. The vertical excitations energies for these electronic states are determined using MRSDCI /DZ +P calculations at the ground-state equilibrium geometry and in agreement with the recent experimental data obtained via PES of the CH₂NO anion. The oscillator strenghts and the radiative lifetimes for these electronic states and the spin properties for the ground state are calculated based on the MRSDCI wave functions, predicting results in good agreement with available experimental data. © 1994 John Wiley & Sons, Inc.     

羧甲基壳聚糖的取代度及保湿性

吸湿性;分子量;羧甲基壳聚糖的取代度及保湿性