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91.
Phosphorescent OLEDs: Sky‐Blue Phosphorescent OLEDs with 34.1% External Quantum Efficiency Using a Low Refractive Index Electron Transporting Layer (Adv. Mater. 24/2016) 下载免费PDF全文
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93.
Wonsang Kwon Yecheol Rho Kensuke Kamoshida Kyung Ho Kwon Youn Cheol Jeong Jonghyun Kim Hideki Misaka Tae Joo Shin Jehan Kim Kwang‐Woo Kim Kyeong Sik Jin Taihyun Chang Heesoo Kim Toshifumi Satoh Toyoji Kakuchi Moonhor Ree 《Advanced functional materials》2012,22(24):5194-5208
Low‐temperature anionic ring‐opening homopolymerizations and copolymerizations of two glycidol derivatives (allyl glycidyl ether (AGE) and ethoxyethyl glycidyl ether (EEGE)) are studied using a metal‐free catalyst system, 3‐phenyl‐1‐propanol (PPA) (an initiator) and 1‐tert‐butyl‐4,4,4‐tris(dimethylamino)‐2,2‐bis[tris‐(dimethylamino)phosphoranylidenamino]‐2Λ5,4Λ5‐catenadi(phosphazene) (t‐Bu‐P4) (a promoter) in order to obtain well‐defined functional linear polyethers and diblock copolymers. With the aid of the catalyst system, AGE is found to successfully undergo anionic ring‐opening polymerization (ROP) even at room temperature (low reaction temperature) without any side reactions, producing well‐defined linear AGE‐homopolymer in a unimodal narrow molecular weight distribution. Under the same conditions, EEGE also undergoes polymerization, producing a linear EEGE‐homopolymer in a unimodal narrow molecular‐weight distribution. In this case, however, a side reaction (i.e., chain‐transfer reaction) is found to occur at low levels during the early stages of polymerization. The chemical properties of the monomers in the context of the homopolymerization reactions are considered in the design of a protocol used to synthesize well‐defined linear diblock copolyethers with a variety of compositions. The approach, anionic polymerization via the sequential step feed of AGE and EEGE as the first and second monomers, is found to be free from side reactions at room temperature. Each block of the obtained linear diblock copolymers undergoes selective deprotection to permit further chemical modification for selective functionalization. In addition, thermal properties and structures of the polymers and their post‐modification products are examined. Overall, this study demonstrates that a low‐temperature metal‐free anionic ROP using the PPA/t‐Bu‐P4 catalyst system is suitable for the production of well‐defined linear AGE‐homopolymers and their diblock copolymers with the EEGE monomer, which are versatile and selectively functionalizable linear aliphatic polyether platforms for a variety of post‐modifications, nanostructures, and their applications. 相似文献
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95.
The effects of light emitting diode (LED) irradiation on maintaining freshness and nutrition in cabbage during low temperature storage were investigated. Cabbage, ‘Dongdori’ was stored at 4–5°C for 18 days under white, green, blue, and red LED light. On day 15 of storage, the total chlorophyll content of cabbage was highest for green, followed by white, red, blue, and a nonirradiated control group. The vitamin C content was highest for blue, followed by white, green, red, and the control. On day 18 of storage, the total polyphenolic content in cabbage was highest for blue followed by white, red, green, and the control. LED irradiation is effective for enriching the chlorophyll, vitamin C, and polyphenol contents of cabbage stored at a low temperature and results suggest that LED colors have different effects. 相似文献
96.
Soon-Jong Jeong Min-Soo Kim In-Sung Kim Hyeon-Kyu Joo Dae-Su Lee 《Journal of Electroceramics》2011,26(1-4):162-169
In this study, a process was proposed which allows a base metal electrode to be burnt-out in an oxidative atmosphere for fabrication of multilayer ceramic device. To protect Cu in an oxidative atmosphere, the Cu powder was coated with borosilicate glass via a sol-gel process. The oxidation resistance and shrinkage of the glass-coated Cu were investigated. When a 10% glass-coated Cu was heated up to 500°C under an oxidative atmosphere, the Cu could survive without formation of copper oxide. The oxidation of the Cu was observed when heating at temperatures above 700°C. This might be due to exposure of Cu to oxidative atmosphere related to softening behavior of glass. The glass-coated Cu exhibited a shrinkage behavior which follows the shrinkage behavior of glass in the low temperature range and the shrinkage of pure Cu in the high temperature range. To measure the electrical conductivity of the glass-coated Cu electrode, the Cu pastes were prepared and printed onto alumina substrate. The binder-burn-out process of the glass-coated Cu was carried out at 550°C under an air atmosphere, and was then sintered at 1000°C under a nitrogen atmosphere. The electrical conductivity of the Cu electrode measured was above 104 /Ωcm which means that it can be used as the internal electrode of a multilayer device. 相似文献
97.
98.
We applied high-pressure torsion (HPT) for consolidation of gas-atomized metallic glass Cu54Zr22Ti18Ni6 powders into high-density bulk disks. The effects of the number of revolutions (N = 1–5 turns), applied pressure (2.5–10 GPa), and temperature (298–473 K) on densification and structural changes were investigated. The consolidated glassy disks showed an excellent hardness of ~5.2 GPa although a mechanical softening effect along with fragmentation in the center of HPT disks occurred at N > 3 by a couple of branching cracks. The HPT process at higher applied pressures improved the bulk density and inter-particulate bonding, resulting in higher hardness. Increasing the temperature of HPT processing enhanced the densification and deep drawability of the consolidated metallic glass. Although the HPT process did not change the crystallization temperature of the metallic glass powders, it increased the crystallization enthalpy, suggesting the free volume increase and inhibition of a significant nanocrystallization during the HPT process. 相似文献
99.
ε‐Branched Flexible Side Chain Substituted Diketopyrrolopyrrole‐Containing Polymers Designed for High Hole and Electron Mobilities 下载免费PDF全文
A‐Reum Han Gitish K. Dutta Junghoon Lee Hae Rang Lee Sang Myeon Lee Hyungju Ahn Tae Joo Shin Joon Hak Oh Changduk Yang 《Advanced functional materials》2015,25(2):247-254
Based on the integrated consideration and engineering of both conjugated backbones and flexible side chains, solution‐processable polymeric semiconductors consisting of a diketopyrrolopyrrole (DPP) backbone and a finely modulated branching side chain (ε‐branched chain) are reported. The subtle change in the branching point from the backbone alters the π?π stacking and the lamellar distances between polymer backbones, which has a significant influence on the charge‐transport properties and in turn the performances of field‐effect transistors (FETs). In addition to their excellent electron mobilities (up to 2.25 cm2 V?1 s?1), ultra‐high hole mobilities (up to 12.25 cm2 V?1 s?1) with an on/off ratio (Ion/Ioff) of at least 106 are achieved in the FETs fabricated using the polymers. The developed polymers exhibit extraordinarily high electrical performance with both hole and electron mobilities superior to that of unipolar amorphous silicon. 相似文献
100.
Gramicidin A Mutants with Antibiotic Activity against Both Gram‐Positive and Gram‐Negative Bacteria 下载免费PDF全文
Antimicrobial peptides (AMPs) have shown potential as alternatives to traditional antibiotics for fighting infections caused by antibiotic‐resistant bacteria. One promising example of this is gramicidin A (gA). In its wild‐type sequence, gA is active by permeating the plasma membrane of Gram‐positive bacteria. However, gA is toxic to human red blood cells at similar concentrations to those required for it to exert its antimicrobial effects. Installing cationic side chains into gA has been shown to lower its hemolytic activity while maintaining the antimicrobial potency. In this study, we present the synthesis and the antibiotic activity of a new series of gA mutants that display cationic side chains. Specifically, by synthesizing alkylated lysine derivatives through reductive amination, we were able to create a broad selection of structures with varied activities towards Staphylococcus aureus and methicillin‐resistant S. aureus (MRSA). Importantly, some of the new mutants were observed to have an unprecedented activity towards important Gram‐negative pathogens, including Escherichia coli, Klebsiella pneumoniae and Psuedomonas aeruginosa. 相似文献