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41.
用苝四酸酐为反应物,在酸酐位置上引入天冬氨酸,合成了水溶性的含4个羧基的荧光苝二酰亚胺衍生物:N,N'-二天冬氨酸铵盐-3,4,91,0-苝四羧酸二酰亚胺(PTCDA).在水溶液中与Fe3+、Al3+、Pb2+和Cu2+等金属离子反应,吸收光谱发生红移,荧光淬灭.当加入等量Hg2+、Zn2+、Ni2+、Co2+、Mn2+和Mg2+等金属离子后不干扰荧光反应,有选择性好、灵敏度高等特点.并探讨了衍生物的荧光反应机理,表明有好的应用价值和广阔发展前景。 相似文献
42.
The constant elasticity of variance(CEV) model was constructed to study a defined contribution pension plan where benefits were paid by annuity. It also presents the process that the Legendre transform and dual theory can be applied to find an optimal investment policy during a participant's whole life in the pension plan. Finally, two explicit solutions to exponential utility function in the two different periods (before and after retirement) are revealed. Hence, the optimal investment strategies in the two periods are obtained. 相似文献
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本文对采用双坩埚提拉法(DCCZ)生长的化学计量比LiNbO3晶体中出现的机械双晶、组分过冷、包裹体等宏观生长缺陷进行了观察和分析.结果表明机械双晶通常以{102}和{104}面族为双晶面,而不是以前文献报道的{102}和{012}面族;化学计量比LiNbO3晶体双坩埚提拉法生长与同成份晶体生长不同,前者是助熔剂生长体系,生长速度稍快或温度较小的波动就会导致组分过冷,而后者属于纯熔体生长体系,不容易产生组分过冷;包裹体是由于组分过冷生长时界面失稳夹入熔体所造成的.由于这些缺陷的存在都会严重影响单晶的获得率和质量,为此,我们通过大量实验研究后提出了可以减少和避免这些生长缺陷提高晶体质量的方法. 相似文献
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以Ti(OBu)4为原料,采用溶胶-凝胶法制备了固体超强酸SO4^2-/TiO2,其结构经XRD,DRS及IR表征。以SO4^2-/TiO2为催化剂,通过乙酸与戊醇反应合成了乙酸戊酯。讨论了影响酯化率的主要因素。实验结果表明,当催化剂用量为0.6g,乙酸87.3mmol,醇酸摩尔比为1.4:1.0,于115℃反应6h时,平行实验的平均酯化率可达94.2%。 相似文献
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Jun-jie Shi Barry C. Sanders Shao-hua Pan E. M. Goldys 《Physica E: Low-dimensional Systems and Nanostructures》2001,10(4)
Based on the global coherent tunneling model, we present a self-consistent calculation and show that structural asymmetry of double barrier resonant tunneling structures (DBRTSs) significantly modifies the current–voltage characteristics compared to the symmetric structures. Within the framework of the dielectric continuum model, we further investigate the phonon-assisted tunneling (PAT) current in symmetric and asymmetric DBRTSs. Both the interface modes and the confined bulk-like longitudinal-optical phonons are considered. The results indicate that the four higher-frequency interface phonon modes (especially the one which has the largest electron–phonon interaction at either interface of the emitter barrier) dominate the PAT processes. We show that a suitably designed asymmetric structure can produce much larger peak current and absolute value of the negative differential conductivity than its commonly used symmetric counterpart. 相似文献
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利用UV-Vis吸收光谱、荧光光谱及半经验ZINDO/S方法,研究了4种可溶性镍酞菁(FPcNi、MePcNi、iBPcNi、iPPcNi)的电子吸收光谱和荧光光谱.研究结果表明:随着取代基的供电子能力增加,酞菁的最大吸收波长(λmax)和发射波长(λem)发生红移,摩尔消光系数变小;随着溶液浓度增大,酞菁聚集体浓度增大,λmax发生蓝移,但浓度对λem影响较小,同时荧光相对强度随浓度增大,出现最大值;随着溶剂配合能力的增加,λmax、λem都发生红移. 相似文献
50.
The reaction kinetics of cyanomethylidyne radical, CCN( eX2Π), with a series of primary alcohols were studied at about 1.33 kPa total pressure and room temperature using pulsed laser photolysis/laser-induced fluorescence (LP/LIF) technique. The CCN radical was produced via laser photolysis of CCl3CN with the fourth harmonic output of a Nd: YAG laser (266 nm). The relative concentration of the CCN( eX2Π) radical was monitored by LIF in the (0, 0) band of the CCN( ~ A2¢? eX2Π) transition at 470.9 nm. Under pseudofirst-order conditions, the reaction rate constants of CCN( eX2Π) with a series of primary alcohol molecules (n-CnH2n+1OH, n=1-6) were determined by measuring the time evolution of the relative concentration of CCN( eX2Πi). The measured rate constants increased monotonously with the number of carbon atoms in the alcohols, and the values for reactions of CCN( eX2Π) with alcohols were larger than those for reactions of CCN( eX2Π) with alkanes (C1-C5). Based on the bond dissociation energies and linear free energy correlations, it was believed that the reactions of CCN( eX2Π) with alcohols proceeded via a hydrogen abstraction mechanism that was analogous to CCN( eX2Π) with alkanes. The experimental results indicated that the H atoms on the C-H bonds were activated at the presence of the OH group in alcohol molecules and the hydrogen abstraction from the C-H bonds in the alcohol molecules was the dominant reaction pathway. The relation between the rate constants and the long-distance attractive potentials between the CCN radical and the alcohol molecules was discussed. 相似文献