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961.
The application of polyfluorenes in polymeric light-emitting diodes has been hampered because of the charge injection difficulties and the troublesome formation of a tailed emission band at long wavelengths (>500 nm) during device fabrication and operation, leading to both a color instability and reduced efficiency. The incorporation of the phenothiazine units has been proven to significantly enhance the hole injection and charge carrier balance and at the same time efficiently suppress the keto defect emission. In this contribution, we apply quantum-chemical techniques to investigate poly[10-(N-(2'-methyl)phenothiazine-3,7-diyl) and its fluorene copolymer poly[10-(N-(2'-methyl)phenothiazine-3,7-diyl)-co-alt-2,7-(9,9-dimethylfluorene)] (PFPTZ) and gain a detailed understanding the influence of phenothiazine units on the electronic and optical properties of fluorene derivatives. Density functional theory (DFT) and time-dependent DFT approaches are employed to study the neutral molecules, HOMO-LUMO gaps (Delta(H-L)), the lowest excitation energies (E(g)'s), positive and negative ions, as well as the IPs and EAs, focusing on the superiority of the electronic and optical properties attributed to the introduction of electron-donating moiety phenothiazine (PTZ) through comparing with pristine polyfluorene. The outcomes show that the highly nonplanar conformation of phenothiazine ring in the ground state preclude sufficiently close intermolecular interactions essential to forming aggregates or excimers. Furthermore, the HOMO energies lift about 0.4 eV, and thus, the IPs decrease about 0.3 eV in PFPTZ, suggesting the significant improved hole-accepting and transporting abilities, due to the electron-donating properties of phenothiazine ring by the presence of electron-rich sulfur and nitrogen heteroatoms and highly nonplanar characters, resulting in the enhanced performances in both efficiency and brightness compared with pristine polyfluorene. In addition, even though the introduction of electron-donating moiety PTZ onto fluorene leads to a slight bathochromic shift in absorption and emission spectra, the copolymer still exhibited strong blue emission. 相似文献
962.
Fabrication and characterization of miniature, flexible, planar biosensors for monitoring l-lactate accumulation in an ischemic myocardium are described. Three configurations of Au-based electrodes were fabricated by a photolithographic technique on flexible polyimide Kapton((R)) foil. All sensors are based on an immobilized lactate oxidase with amperometric detection of the enzymatically produced hydrogen peroxide at a platinum-electroplated-gold base electrode polarized at 0.5 V versus Ag/AgCl. An inner electropolymeric layer is used to prevent electrode fouling and to reject the interference effects of easily oxidizable molecules. In addition, a diffusion controlling outer layer that greatly enhances the linear dynamic range of the sensor, is obtained by casting a polyurethane external film. The developed sensor was evaluated in vitro and proved to have high selectivity, good operational stability, good accuracy and precision (average recovery = 102.3 +/- 0.4% for control sera), fast response time (t(95) = 20 s) and high upper limit of the linear dynamic range (25-80 mM, with sensitivity of 1.7-0.4 nA mM(-1) respectively at PO(2) = 15 mmHg). Subsequently, the sensor was brought into direct contact with the surface of the rabbit papillary muscle and used for continuous quantitative monitoring of extracellular lactate accumulation during no-flow ischemia. 相似文献
963.
3类手性配体d-10-樟脑磺酸及其衍生物,α-(-)-羟蒎酮及其衍生物,又恶唑啉6衍生物分别与铜(Ⅱ)形成手性铜配合物,催化重氮乙酸酯与1,1-二苯乙烯或异丁烯的环丙烷化加成反应,得到光学活性环丙羧酸酯,不对称诱导最高可达95%e.e.。 相似文献
964.
965.
966.
967.
Sm(NO_3)_3·6H_2O热分解过程的研究工作虽有文献报道,但结果不尽相同。文献[2]不同于文献[1,3],认为分解过程中存在无水盐阶段;文献[3]不同于文献[1,2],认为分解过程中存在低水合物。而且文献尚缺低水合物热分解机理的报道。我们也曾做过一些工作,但脱水阶段也不详尽。为此,我们详细地研究了Sm(NO_3)_3·nH_2O(n= 相似文献
968.
聚合条件对N-羧基-L-丙氨酸-环内酸酐开环聚合产物分子量的影响 总被引:3,自引:0,他引:3
用光气法制备了N-羧基-L-丙氨酸-环内酸酐(L-Alanine NCA).系统研究了L-Alanine NCA开环聚合反应过程中引发剂、溶剂、温度对聚合物分子量的影响.用硝基苯作溶剂,三乙胺作引发剂,所得聚合物特性粘度[η]=1.18.实验中发现,L-Alanine NCA可以顺利地进行热聚合反应。反应具有速率快,转化率高,分子量大的特点。甲苯溶剂中反应5小时所得聚合物[η]=2.35,高于采用引发剂的聚合体系产物的相应值。 相似文献
969.
高效液相色谱法测定蜂王浆中特有成分10—羟基—2—癸烯酸的研究 总被引:3,自引:0,他引:3
本文报道反相高效液相色谱法测定蜂王浆和蜂王浆制剂中的10-羟基-2-癸烯酸(10-HDA)的方法,用二氯甲烷从蜂王浆或蜂王浆制课题占萃取10-HDA,而后用HPLC测定,实验采用YWG-C18柱,35%乙醇水溶液为流动相,己二酸为内标,紫外检测器波长为212nm,加入法测回收率在95%以上。用此法测定了鲜蜂王浆和蜂王浆制剂中的10-HDA的含量。该法简单、快速,优于气相色谱法和薄层色谱法。 相似文献
970.
Keum SR Roh HJ Choi YK Lim SS Kim SH Koh K 《Magnetic resonance in chemistry : MRC》2005,43(10):873-876
(1)H and (13)C NMR spectra of symmetric and asymmetric bis-spiropyrans, Series 1-3, were completely assigned. Especially, the (1)H assignment of asymmetric spiropyrans was achieved by utilizing (1)H-(1)H COSY and nOe experiments. All of the carbons in the dye molecules were investigated through a combination of heteronuclear 2D-shift correlation spectroscopy (HETCOR), together with an attached proton test (APT). 相似文献