稀土配合物的NMR性质及在生物体系中应用的研究

本文从几个方面研究了稀土离子及稀土配合物的性质和在生物体系中的应用，并取得了如下结果。1)稀土离子具有良好的核磁特性。向外消旋丙－丝二肽溶液中加入顺磁性稀土离子，可使不同旋光异构体相同磁核的共振信号明显分开，便于指认和归属。指出外消旋丙－丝二肽顺磁稀土配合物不同异构体的诱导位移主要由接触位移决定；2)合成了几类Dy~(3+)配合物，并对其~(23)Na位移性质加以研究；3)稀土配合物Gd(DCBDA)、Gd(DBDA)、Gd(EDTMP)、Gd(DETPMP)、Gd_2(EDTMP)、Gd_2(DETPMP)具有很强的~(13)C弛豫增强作用，并不对~(13)C共振信号产生明显位移和增宽。Gd(DCBDA)、Gd(DBDA)弛豫能力最强，是很有应用前景的新型水溶性弛豫试剂；4)首次利用~(133)Cs NMR技术研究了稀土离子La~(3+)对人血红细胞金属离子迁移性质的影响。

杂多酸修饰电极的研究

杂多酸由于一系列有利于催化反应的特性在电催化和化学修饰电极的研究中引起了人们广泛的重视。本文重点研究了杂多酸掺杂聚吡咯薄膜修饰电极的制备及其电化学和电催化性质，研究了取代杂多酸的电化学行为，并着重讨论了取代杂多酸独特的电催化性质。分述如下：1、研究了稀土杂多配合物K_(10)H_3[Dy(SiMo_(11)_2] xH_2O在酸性水溶液中的电化学过程，采用一步法制备了该杂多酸掺杂聚吡咯薄膜修饰电极，讨论了膜内微环境对杂多酸电化学行为的影响。该修饰电极具有非常好的稳定性，并且对ClO_3~-、BrO_3~-的还原具有催化作用。2、在水溶液中以Dawson结构磷钨酸(P_2W_(18))为支持电解质，通过电化学聚合吡咯，制备出P_2W_(18)掺杂聚吡咯薄膜修饰电极，研究了该修饰电极的电化学和电催化行为。同文献相比，本实验制备的修饰电极具有较好的稳定性和电化学行为。该电极能催化氧的还原，使氧的还原电位正移150 ～ 200mV。3、通过电化学聚合的方法，在电极表面制备出聚(N，N-二甲基苯胺)膜(PDMA)，并用Fe(CN)_6~(4-)研究了该膜的阴离子交换性能。实验表明，磷钼杂多酸能够被交换到PDMA膜内，从而固定在电极表面。固定在PDMA膜内的磷钼酸的电子传递受扩散控制，与固定在聚乙烯基吡啶膜内杂多酸的快速电子传递不同。首次观察到膜内磷钼酸的自催化现象。4、研究了铁取代Dawson结构磷钨酸(P_2W_(17)Fe)的电化学行为，检验了P_2W_(17)Fe对H_2O_2、NO_2~-还原的催化作用，用微电极测定了P_2W_(17)Fe催化还原H_2O_2反应的速率常数，并对催化反应机理进行了研究。

Rashba electron's ballistic transport in two-dimensional quantum waveguide

The ballistic transport of Rashba electrons in a straight structure in two-dimensional electron gas is studied. It is found that there is no mixing between the wave functions of spin up and spin down states, and the transfer matrix is independent for the spin in every interface. The influence of the structure and Rashba coefficient on the electron transport is investigated. Our results indicate that the transmission probabilities are independent of the sign and magnitude of the Rashba coefficient and it depends on the shape of the structure, especially the stub width. The antiresonance is found, where the quasiconfined state is formed in the center part of the structure.

Photoluminescence characterization of 1.3 mu m In(Ga)As/GaAs islands grown by molecular beam epitaxy

1.3 mum wavelength In(Ga)As/GaAs nanometer scale islands grown by molecular beam epitaxy (MBE) were characterized by photoluminescence (PL) and atomic force microscopy (AFM) measurements. It is shown that inhomogeneous broadening of optical emission due to fluctuation of the In0.5Ga0.5As islands both in size and in compositions can be effectively suppressed by introducing a AlAs layer and a strain reduction In0.2Ga0.8As layer overgrown on top of the islands, 1.3mum emission wavelength with narrower line-width less than 20meV at room temperature was obtained.

Surface morphology and optical property of 1.3 mu m In0.5Ga0.5As/GaAs self-organized quantum dots grown by MBE

Surface morphology and optical properties of 1.3 mum self-organized InGaAs/GaAs quantum dots structure grown by molecular beam epitaxy have been investigated by atomic force microscopy and photoluminescence measurements. It has been shown that the surface morphology evolution and emission wavelengths of InGaAs/GaAs QDs can be controlled effectively via cycled monolayer deposition methods due to the reduction of the surface strain. Our results provide important information for optimizing the epitaxial parameters for obtaining 1.3 mum long wavelength emission quantum dots structures. (C) 2002 Elsevier Science B.V. All rights reserved.

Photoluminescence of nanocrystalline SiC films prepared by rf magnetron sputtering

Amorphous Sic films are deposited on Si (111) substrates by rf magnetron sputtering and then annealed at 1200 degreesC for different times by a dc self-heating method in a vacuum annealing system. The crystallization of the amorphous Sic is determined by Raman scattering at room temperature and X-ray diffraction. The experimental result indicates that the Sic nanocrystals have formed in the films. The topography of the as-annealed films is characterized by atomic force microscopy. Measurements of photoluminescence of the as-annealed films show blue or violet light emission from the nanocrystalline Sic films and photoluminescence peak shifts to short wavelength side as the annealing time decreases.

Strain relaxation of GeSi alloy with low dislocation density grown on low-temperature Si buffers

We have developed a low-temperature (LT) growth technique. Even with Ge fraction x upto 90%, the total thickness of fully relaxed GexSi1-x buffers can he reduced to 1.7 mu m with dislocation density lower than 5 x 10(6) cm(-2). The surface roughness is no more than 6 nm. The strain relaxation is quite inhomogeneous From the beginning. Stacking faults generate and form the mismatch dislocations in the interface of GeSi/LT-Si. (C) 1999 Elsevier Science B.V. All rights reserved.

Sequential coupling transport for the dark current of quantum dots-in-well infrared photodetectors

The dark current characteristics and temperature dependence for quantum dot infrared photodetectors have been investigated by comparing the dark current activation energies between two samples with identical structure of the dots-in-well in nanoscale but different microscale n-i-n environments. A sequential coupling transport mechanism for the dark current between the nanoscale and the microscale processes is proposed. The dark current is determined by the additive mode of two activation energies: E-a,E-micro from the built-in potential in the microscale and E-a,E-nano related to the thermally assisted tunneling in nanoscale. The activation energies E-a,E-micro and E-a,E-nano decrease exponentially and linearly with increasing applied electric field, respectively.

镉、铅对东北典型地区不同品种大白菜胁迫效应研究

随着工农业的快速发展，土壤重金属污染问题日益严重，在我国东北，大面积的蔬菜种植地受到Cd、Pb的污染。大白菜在东北地区一直得到广泛种植，然而，Cd、Pb单一及复合污染对这一地区大白菜的胁迫效应仍然缺乏系统的研究。本研究以辽宁省普遍种植的四种大白菜（抗病金春KB、东洋春夏DY、青绿王QL、强势QS）为对象，用发芽实验、砂培实验和盆栽实验，研究了Cd、Pb单一及复合胁迫下大白菜的生理生化变化。 在发芽阶段，Cd、Pb单一及复合胁迫下，重金属浓度与根长、芽长和生物量抑制率间呈极显著线性相关，根伸长对Cd、Pb的毒害最敏感。KB对Cd毒害的抗性最强，DY对Pb单一和Cd、Pb复合胁迫的抗性最强，而QS对Cd、Pb单一及复合胁迫的抗性最弱。Cd、Pb复合胁迫时，对根伸长、芽伸长和生物量抑制的联合作用类型都为相加作用。 砂培实验中，在Cd、Pb浓度较低时，4种大白菜超氧化物歧化酶（SOD）、过氧化物酶（POD）和过氧化氢酶（CAT）活性及丙二醛（MDA）、可溶性蛋白（SP）、脯氨酸（PRO）含量都不同程度提高，但是随Cd、Pb浓度的提高，各生理过程受到抑制。KB和QS中PRO的含量约是DY和QL中的2-3倍，高PRO累积量很可能是Cd、Pb耐性大白菜品种所具有的特点。 盆栽实验中，在各生长时期，抗氧化酶活性、抗坏血酸（AsA）和还原型谷胱甘肽（GSH），及可溶性糖和SP的含量随Cd、Pb浓度的提高先升高后下降。硝态氮的含量基本随Cd、Pb浓度的提高而上升。在整个实验期间，KB和QS中MDA都保持较低的水平，KB对Cd、Pb的耐性主要是由于其体内PRO及AsA、GSH等抗氧化剂的累积；而GSH和可溶性糖对QS的Cd、Pb耐性起重要作用。QL和DY中MDA的含量要高于KB和QS，它们体内的抗氧化酶活性，及PRO、AsA和GSH含量在某个生长时期会达到较高的水平，但是与KB和QS相比，这些变化并不稳定，所以比KB和QS对Cd、Pb的耐性要弱。