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11.
It is well known that porphyrin derivatives play a key role in the primary process of photo-synthesis[1], in which porphyrins directly absorb the sunlight or indirectly acquire excitation en-ergy from light-harvesting antenna system to reach their excited state, and then donate electrons to quinone acceptors to yield a series of charge-separated species. In general, only first singlet ex-cited state of porphyrins is involved in energy transfer process[2]. However, highly excited state (S2 stat… 相似文献
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HF与SiO2的反应是一种亲核取代反应,但高温下此反应不能发生.当涂覆在SiO2表面的聚合物膜中含有某些特殊的有机化合物或超强酸时,可以促进该反应的发生,这些化合物被称为诱蚀剂.诱蚀剂分三类:(1)三级胺与HF形成季铵盐得到浓度很高的氟阴离子使该反应很容易发生;(2)强的偶极非质子官能团化合物与HF中的氢形成氢键使氟的亲核活性增加,有助于该反应发生;(3)超强酸因其质子对SiO2骨架中氧的牢固结合能力活化了反应的离去基团,对HF与SiO2的亲核反应起到催化作用.聚合物膜对添加在其中的小分子诱蚀剂起到阻止逃逸的栅栏作用,而本身带有诱蚀官能团的聚合物可以同时充当成膜物及诱蚀剂的作用.通过光化学反应可以选择性地实现聚合物膜下HF与SiO2的刻蚀反应. 相似文献
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α-异丙基、β-异丁基丙烯酸希土配合物的合成和配位性质研究 总被引:3,自引:0,他引:3
本文制备了α-异丙基、β-异丁基丙烯酸的15种希土配合物RE(C9H17COO)3,用X射线多晶粉末衍射、电子光谱、红外光谱和热重差热分析方法研究了配合物中RE-O键的成键性能以及羧基的配位性质.配合物中存在两种不同的羧基配位形式,轻中希土配合物(La,Ce,Pr,Nd,Sm,Eu)中羧基具有不对称桥式双齿配位形式,而重希土配合物(Gd,Tb,Dy,Ho,Er,Tm,Yb,Lu,Y)中羧基具有对称螯合双齿配位形式,配位形式的不同使得希土配合物呈现两种不同的多晶衍射图和热分解过程. 相似文献
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GRAFT COPOLYMERIZATION OF VINYL MONOMERS ONTO STARCH INITIATED BY TRANSITION METAL-THIOUREA REDOX SYSTEMS 总被引:5,自引:0,他引:5
In this paper, the capabilities of grafting acrylonitrile (AN) onto starch initiatedby Fe(III)-TU, V(V)-TU, Cr(VI)-TU, Mn(VII)-TU redox systems were compared in thepresence of sulfuric acid of different concentrations. It was shown that the grafting capabili-ty of Mn(VII)-TU is the highest in these initiating systems. Using Mn (VII-TU as initia-tor, the effects of various acids (HClO_4, H_2SO_4, HNO_3, HCl) on the graft copolymerizationof acrylonitrile onto starch were discussed, and the capabilities of graft copolymerizationof methyl methacrylate (MMA), acrylamide (AM), acrylic acid (AA) onto starch wereinvestigated. The experimental results show that the order of the influences of differentacids is HClO_4>H_2SO_4>HNO_3>HCl, and the order of grafting capabilities of differentmonomers grafted onto starch is MMA>AN>AM>AA. The structure and morphology ofgraft copolymers were studied with infrared spectroscopy and scanning electron microscopy.The size, shape and roughness of surface of the grafted starch granules are changed aftergrafting. 相似文献
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A facile and environment friendly approach was developed to graft vinyl acetate (VAc) onto plastic articles in an aqueous solution using tert‐butyl alcohol (TBA) as a compatiblizer and benzoyl peroxide (BPO) as an initiator. In a novel setup, excessive monomer suspended in a water phase, VAc could be conveniently grafted on the model substrate of low‐density polyethylene (LDPE) film and the graft percentage (GP) could be developed up to 7.3%. Reaction temperature could increase GP significantly, while adding monomer over a critical volume did not influence GP. By adding some paradioxybenzene, i.e. 0.06–0.08% in VAc phase, homopolymer PVAc could be avoided practically, while graft polymerization proceeded favorably in aqueous solutions. It was proved by attenuated total reflection‐infrared (ATR‐IR) spectroscopy that grafted VAc was located mainly at the surface of the LDPE film and hydrophilic nature of both grafted and alcoholyzed films were improved via contact angle measurements. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
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在 pH 4.5 HAc-NaAc缓冲溶液中,钍试剂分别于- 0.36 V、- 0.60 V产生两个灵敏的极谱波。基于钒对溴酸钾氧化钍试剂的催化作用,建立了双极谱波测量的催化动力学极谱法。钒浓度在0.7~15μg/L与△I(△I1+ I2)呈线性关系,检测限为0.5μg/L。研究了极谱波性质及电极反应机理。本法简便、灵敏、准确,已用于直接测定水中痕量钒。 相似文献
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Jianping X Jiyou Z Jiaqin L Jianniao T Xingguo C Zhide H 《Biomedical chromatography : BMC》2005,19(1):9-14
A rapid, sensitive and reproducible micellar electrokinetic chromatographic method using hexamethyldisilazane as on-line regenerating covalent coating was developed for the quantification of ephedrine (E) and pseudoephedrine (PE). E and PE were derivatized with 4-chloro-7-nitrobenzo-2-oxa-1,3-diazol for laser-induced fluorescence detection. The on-line regenerating covalent coating formed a combinative double coating with the subsequently produced dynamic SDS coating. The total coating can be easily removed and conveniently regenerated on-line. The simple coating procedure was described. By a series of optimization, a running buffer of 20 mm Na(2)B(4)O(7) + 16 mm SDS was applied for the separation of the derivatives. Linear relationships for E and PE were obtained in the range of 0.044-6.60 microg mL(-1) (correlation coefficients: 0.9975 for E, 0.9981 for PE), and the detection limits for E and PE were 1.71 and 0.67 ng mL(-1), respectively. The separation speed, the reproducibility and the sensitivity were much improved over those of other capillary electrophoresis methods more recently reported. The method was applied to the analysis of the two alkaloids in traditional herbal preparations with recoveries in the range 92.8-104.8%. 相似文献