硅和锗纳米线的原子排布和电荷分布的密度泛函紧束缚方法研究

低维硅锗材料是制备纳米电子器件的重要候选材料，是研发高效率、低能耗和超高速新一代纳米电子器件的基础材料之一，有着潜在的应用价值。采用密度泛函紧束缚方法分别对厚度相同、宽度在0.272 nm~0.554 nm之间的硅纳米线和宽度在0.283 nm~0.567 nm之间的锗纳米线的原子排布和电荷分布进行了计算研究。硅、锗纳米线宽度的改变使原子排布，纳米线的原子间键长和键角发生明显改变。纳米线表层结构的改变对各层内的电荷分布产生重要影响。纳米线中各原子的电荷转移量与该原子在表层内的位置相关。纳米线的尺寸和表层内原子排列结构对体系的稳定性产生重要影响。     

Strategies for Improving the Catalytic Performance of 2D Covalent Organic Frameworks for Hydrogen Evolution and Oxygen Evolution Reactions

Hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) have been deemed as clean and sustainable strategies to solve the energy crisis and environmental problems. Various catalysts have been developed to promote the process of HER and OER. Among them, two-dimensional covalent organic frameworks (2D COFs) have received great attention due to their diverse and designable structure. In this minireview, we mainly summarize the diverse linkages of 2D COFs and strategies for enhancing the catalytic performance of 2D COFs for HER and OER, such as introducing active building blocks, metal ions and tailored linkages. Furthermore, a brief outlook for the development directions of COFs in the field of HER and OER is provided, expecting to stimulate new opportunities in future research.     

Interface-related effects on confined excitons in GaAs/AlxGa1−xAs single quantum wells

Confined excitons in non-abrupt GaAs/Al_xGa_1−xAs single quantum wells are studied. The graded interfaces are described taking into account fluctuations in their thickness a and positioning with respect to the abrupt interface picture. Numerical results for confined (0,0),(1,1) and (0,2) excitons in GaAs/Al_0.3Ga_0.7As quantum wells show that while the interfacial fluctuations produce small changes (<0.5 meV) in the exciton binding energies, the confined exciton energies can be red- or blue-shifted as much as 25 meV for wells with mean width of 50 Å and 2 ML wide interfaces.     

Exciton energy broadening due to interface fluctuations in ZnSe/ZnSxSe1−x strained quantum wells

The excitonic properties of a ZnSe/ZnS_xSe_1−x strained quantum well (QW) are calculated taking into account interface effects. Numerical results obtained with ZnS_0.18Se_0.82/ZnSe QWs show that graded interfaces can be responsible for a strong broadening of excitonic spectra.     

Discovery of a new long-lived isomeric state in 125Ce

A new long-lived isomeric state in the near proton dripline nucleus ¹²⁵Ce has been identified with Schottky mass spectrometry at GSI. The excitation energy E ^* = 103(12)keV and the decay time of 193(1)s have been obtained from a single stored fully ionized ^125m Ce⁵⁸⁺ ion. The data implies an E3 transition and a 1/2⁺ assignment for the spin of the isomer.     

Spectroscopy on very neutron-rich nuclei beyond N = 20

Recent studies on nuclear structure by using radioactive isotope beams available at the RIKEN projectile-fragment separator (RIPS) are introduced. Special emphasis is given to two selected experiments from recent programs that highlight studies on the magicity loss observed for very neutron-rich nuclei beyond N = 20 in the “island-of-inversion” region; the particle stability of ³¹F, and the low-lying excited states of ³⁴Mg. Received: 1 May 2001 / Accepted: 4 December 2001     

氯化钠团簇的形成规律与结合能计算

当离子蒸气冷凝形成团簇时，其结构表现出特定的规律。文中对不同大小不同形状的氯化钠团簇结构与结合能进行了计算，以求揭示离子蒸气冷凝形成团簇的一些规律，并与实验结果进行对照。     

Studies on the Spectral Behavior between Protein with Poniacyl Carmine 2B and its Analytical Application

In this paper, the spectral behavior of protein and Poniacyl Carmine 2B (PC 2B) has been studied by spectrophotometric method. The conditional constants, apparent combination constant K and maximum binding number n, were used to express the combination ability of the reactions between PC 2B and protein under a set of given conditions. The Sandell index s was used to express the sensitivity of the determination of protein. The factors, acidity, PC 2B concentration and the ionic strength, were discussed by the change of apparent combination constant and maximum binding number. It was found that acidity of the solution, PC 2B concentration and ionic strength had a significant effect on the sensitivity of the assay of protein. Under the optimal conditions, the apparent combination constant K and the maximum binding number n were 2.36 × 10⁶ L mol^?1 and 95, respectively. With further investigation, it was found that the Scatchard model was suitable in treating the data obtained in the experiments. In the buffer medium of HCl‐KCl at 1.87, the addition of protein made the maximum absorption of the system move from 527 nm to 513 nm. Its apparent molar absorptivity is 4.46 × 10⁵ Lmol^?1 cm^?1 at 513 nm. Beer's law is obeyed in the range of 0 ? 55 μg mL^?1. The system developed in this paper has been used for the determination of protein in milk powder successfully.     

牛血清白蛋白与十二烷基硫酸钠作用的机理

利用电动势法得到了牛血清白蛋白(BSA)与十二烷基硫酸钠(SDS)相互作用的结合等温线. 通过四阶导数紫外光谱法和荧光光谱法研究了相互作用过程中芳香族氨基酸残基微环境极性的变化. 通过研究发现, 随着SDS浓度的逐渐增大, SDS在BSA上的平均结合数(v)逐渐增大, 色氨酸(Trp)残基所处微环境的极性在减弱后保持基本不变, 酪氨酸残基所处微环境的极性在明显增强后稍有减弱, 苯丙氨酸残基所处微环境的极性略有增强. 结果表明, 当v由0增大到14时, SDS主要结合在BSA的Trp-213附近并逐渐形成聚集体, 从而诱导BSA由结构域ⅡA 开始逐渐展开. 此后, SDS呈正协同作用的特点与BSA 结合, v急剧增大. 当v约为302 时, SDS在BSA上的结合基本达到饱和, BSA的构象趋于稳定.     

A novel phosphoramidite method for automated synthesis of oligonucleotides on glass supports for biosensor development

Two protocols for functionalization of glass supports with hexaethylene glycol (HEG)-linked oligonucleotides were developed. The first method (standard amidite protocol) made use of the 2-cyanoethyl-phosphoramidite derivative of 4,4′-dimethoxytrityl-protected HEG. This was first coupled to the support by standard solid-phase phosphoramidite chemistry followed by extension with a thymidylic acid icosanucleotide. Stepwise addition of the linker phosphoramidite graduated at 1% (relative to the total sites available) perstep at 50°C resulted in an optimal yield of immobilized oligonucleotides at a density of 2.24 × 10¹⁰ strands/mm². This observed loading maximum lies well below the theoretical maximum loading owing to nonspecific adsorption of HEG on the glass and subsequent blocking of reactive sites. Surface loadings as high as 3.73 × 10¹⁰/mm² and of excellent sequence quality were achieved with a reverse amidite protocol. The support was first modified into a 2-cyanoethyl-N,N-diisopropylphosphoramidite analog followed by coupling with 4,4′-dimethoxytrityl-protected HEG. This protocol is conveniently available when using a conventional DNA synthesizer. The reverse amidite protocol allowed for control of the surface loading at values suitable for subsequent analytical applications that make use of immobilized oligonucleotides as probes for selective hybridization of sample nucleic acids of unknown sequence and concentration.