High PL quantum efficiency of poly(phenylene vinylene) systems through exciton confinement

Photoluminescence (PL) quantum efficiency is a key issue in designing successful light-emitting polymer systems. Exciton relaxation is strongly affected by exciton quenching at nonradiative trapping centers and the formation of excimers. These factors reduce the PL quantum yield of light-emitting polymers. In this work, we have systematically investigated the effects of exciton confinement on the PL quantum yield of an oligomer, polymer, and alternating block copolymer (ABC) PPV system. Time-resolved and temperature-dependent luminescence studies have been performed. The ABC design effectively confine photoexcitations within the chromophores, preventing exciton migration and excimer formation. An unusually high (PL) quantum yield (above 90%) in the solid state is reported for the alternating block copolymer PPV, as compared to that of similar to 30% of the polymer and oligomer model compounds. (C) 2000 Elsevier Science S.A. All rights reserved.

1.54 mu m infrared photoluminescence and electroluminescence from an erbium organic compound

Infrared emission at 1.54 mu m excited optically and electrically from an erbium organic compound tris(acetylacetonato)(1,10-phenanthroline) erbium [Er(acac)(3)(phen)] is observed. The rare-earth complex is dispersed into a polymer matrix of poly(N-vinylcarbazole) (PVK) to fabricate an electroluminescent (EL) device with an ITO/PVK:Er(acac)(3)(phen)/Al:Li/Ag structure, where ITO represents indium-tin-oxide-coated glass. The device shows infrared EL emission at 1.54 mu m, which suggests a simple and cheap method to obtain a light source for 1.54-mu m-wavelength devices in optical communications. (C) 2000 American Institute of Physics. [S0021-8979(00)00301-7].

珊瑚姜精油的超临界萃取及其抗真菌和细菌活性

珊瑚姜(Zin~ r corMlinum}IaI )为姜科姜属植物，产于贵州、广西、广东，贵州主要分布在南、北盘江下游河谷地带，为贵州苗族习用药材，称Jab hn hna／b diel(加榜海丢)或阴姜，少数民族常以珊瑚姜块茎人药，具有消肿解毒、抗菌的功能，用于治疗感冒、咳嗽、腰痛、腹泻⋯1。其挥发油的药理研究表明，有抑制离体肠肌引起的痉挛性收缩的自发运动、拮抗组织胺引起的胃肠收缩反应和解除毛果芸香碱、乙酰胆碱、氯化钠等引起的肠痉挛性收缩 2。挥发油还具有显著的抗真菌作用 3，用于治疗皮癣[制。超临界co2萃取是一项新兴的提取分离技术，在中药有效成分提取方面有其显著特点 J，我们用超临界co2进行了珊瑚姜精油的提取工艺研究，并进行了不同提取工艺参数及所得提取物化学组成的比较 ．7J，对以上工艺得到精油的主要活性一抑制真菌和细菌进行了初步试验研究