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981.
982.
在1000 ℃用活性炭把二氧化锡粉末还原成单质锡, 锡作为催化剂, 硅片作为硅源同时作为收集衬底, 在硅片上制备出了非晶SiO2纳米灯笼. 灯笼的一端连在硅片上, 另一端为一个锡球, 中间是一些圆弧状的SiO2纳米线把两端相连. 纳米灯笼具有良好的对称性. 利用扫描电子显微镜(SEM)、高分辨透射电子显微镜(HRTEM)、选区电子衍射(SAED) 和HRTEM自带的能谱分析仪(EDS)对样品的表面形貌、微观结构和成分进行了分析研究. 结果表明, 灯笼中SiO2纳米线为非晶态, 结点是晶态锡, 结点表面覆盖一层非晶态的硅的氧化物. 结合实验条件对纳米灯笼的生长机理进行了讨论, 提出了纳米灯笼生长的一个模型. 相似文献
983.
Quan Xiang WE Xia LIU Yan Ping SHI 《中国化学快报》2005,16(11):1477-1480
A novel dimeric eremophilane, ligulolide B, was isolated from the alcoholic extract of the whole plant of Ligularia virgaurea spp. oligocephala. The structure was elucidated by various spectroscopic methods including intensive 2D NMR techniques (^1H-^1H COSY, gHMQC, gHMBC and ^1H-^1H NOESY) and HR-ESI-MS. 相似文献
984.
Horseradish peroxidase catalyzed grafting of acrylamide (AM) onto Kevlar fibers has been studied. The modified fiber has been characterized with scanning electron microscopy (SEM), elemental analysis and the grafting yield. From the SEM micrographs, the surface of the grafted Kevlar fiber is rougher than that of the untreated fiber, and the elemental analysis indicated that the nitrogen content of the treated fibers is higher than that of the untreated fiber. All the results suggested that AM must have been grafted onto the Kevlar surface through HRP-mediated radical initiated grafting reaction. The probably mechanism of HRP catalyzed grafting of AM onto Kevlar surface is proposed. 相似文献
985.
An ionic liquid-type carbon paste electrode and its polyoxometalate-modified properties 总被引:1,自引:0,他引:1
Hongtao Liu Ping He Zhiying Li Chunyan Sun Lihong Shi Yang Liu Guoyi Zhu Jinghong Li 《Electrochemistry communications》2005,7(12):1357-1363
The replacement of a non-conductive organic binder with a conductive room temperature ionic liquid in fabricating carbon paste electrode has been made. This new electrode due to its enhanced conductivity presented very large current response from electroactive substrates. The novel carbon paste electrode was bulk-modified via the uniform dispersion of Keggin-type phospho polyoxomolybdate (PMo12) in bulky carbons, which possessed excellent electrocatalytic activity for the reduction of nitrite. The pronounced multi-electron catalytic ability was ascribed to the used hydrophobic ionic liquid which constructed an excellent charge-transfer bridge in the bulk of carbon paste electrode, thus facilitated the intake of electrons from reduced PMo12 mediators. In view of their prominent properties, the carbon paste electrode using ionic liquid binder and its bulk-modified electrode take on good prospects of the application in physical chemistry and electroanalytical chemistry fields. 相似文献
986.
2-Azido-3,5-dichloropyridine and 2-azido-5-chloro-3-fluoropyridine were given by reaction of sodium azide with 2,3,5-trichloropyridine, 3,5-dichloro-2-fluoropyridine or 5-chloro-2,3-difluoropyridine in ionic liquids. 1,3-Dipolar cycloaddition of 2-azido-3,5-dichloropyridine or 2-azido-5-chloro-3-fluoropyridine to alkynes in ionic liquids afforded the corresponding 1,4,5-trisubstituted [1,2,3]-triazoles in good yields and regioselectivities. 相似文献
987.
Liu JF Ye P Zhang B Bi G Sargent K Yu L Yohannes D Baldino CM 《The Journal of organic chemistry》2005,70(16):6339-6345
A microwave-promoted three-component one-pot reaction has been developed to provide access to the core pyrazino[2,1-b]quinazoline-3,6-dione (1) scaffold, which is common to several families of alkaloids with significant biological activities. By adapting this synthetic strategy through the use of selected Boc-amino acids and amino acid esters, we have accomplished highly efficient and concise total syntheses of glyantrypine (2), fumiquinazoline F (3), and fiscalin B (5), achieving overall yields of 55, 39, and 20%, respectively. 相似文献
988.
在三乙胺的作用下,利用(S)-3-羟甲基-1,2,3,4-四氢异喹啉((S)-TicOL)和Ph2PCl缩合,得到六元N-杂环配体(S)-TIAMPP.研究了(S)-TIAMPP与Rh(I)形成的手性催化剂[Rh((S)-TIAMPP)(COD)]BF。在脱氢氨基酸的衍生物中不对称催化加氢的对映选择性和适应性,以及该催化剂对N-苯甲酰基脱氢肉桂酸甲酯加氢过程中温度、压力、反应溶剂、底物与催化剂比例(S/C)对光学收率的影响.结果表明,在S/C=100,15℃,1.0MPa的甲醇溶液中,反应24h,[Rh((S)-TIAMPP)(COD)]BF。对N-苯甲酰基脱氢肉桂酸甲酯加氢的光学收率可达到96%. 相似文献
989.
990.
A sensitive and selective method is described for the determination of neodymium in mixed rare earths using fourth-derivative spectrophotometry. The method is based on the absorption spectra of 4f electron transitions of the complex of neodymium with methyl thymol blue and cetylpyridinium chloride. The influence of various instrumental parameters and reaction conditions for maximum colour development are investigated. The calibration curve is linear over the range 0–3.5 g ml–1 neodymium. The relative standard deviation for determination of 1.4 g ml–1 neodymium (n = 7) is 1.6%. The detection limit (signal-to-noise ratio = 3) is 0.2 g ml–1. 相似文献