InAIAs／GaSbAs／InPDHBT与InP／GaSbAs／InPDHBT性能比较分析

双异质结双极晶体管（DHBT）的性能与发射区-基区（E．B）异质结和基区．集电区（B．C）异质结的能带突变类型关系密切,本文基于热场发射．扩散模型,对两类不同能带结构类型的新型DHBT的性能做了比较分析．结论表明：与作为当今研究热点的E．B和B．C异质结构均为全交错II型能带结构的InP／GaSbAs／InPDHBT的性能相比,E．B异质结采用传统I型、B．C异质结采用交错II型的一类新型能带结构的InAlAs／GaSbAs／InPDHBT虽然在开启电压上更高,但具有更好的电流驱动能力、直流增益和高频性能．     

BaTi2As2O电子结构的第一性原理研究

利用基于密度泛函理论的平面波赝势方法,研究BaTi2As2O的能带结构、费米面和态密度.发现:BaTi2As2O是一种非磁性金属,费米能级处的态密度主要来自Ti原子的3d电子,Ti 3d轨道和As 4p轨道有较强的杂化.没有发现其磁性基态,说明Ti原子上没有局域磁矩,与Pickett对Na2Ti2Sb2O的研究结论相吻合.     

微波消解-电感耦合等离子体-质谱法测定黑木耳中铅、镉、砷、铜、锌和铬

建立了微波消解法前处理,电感耦合等离子体-质谱法(ICP-MS)快速测定黑木耳中Zn、Cu、Pb、Cd、Cr、As等重金属元素的方法.该法采用内标法校正监测和校正信号的短期和长期漂移,提高仪器的稳定性,改善测定的精密度,校正一般样品的基体影响,建立了测定208pb、114Cd、75As的干扰方程以消除同质异位素重叠和多原子粒子的干扰.该方法能准确测定大米粉标准物质(GBW 10010)和茶叶标准物质(GBW 10016)中Pb、Cd、Cr、Zn、Cu、As的含量,黑木耳样品的加标回收率为94.0％-107.3％,RSD为2.5％-5.2％.     

ChemInform Abstract: Cd4Cu7As,the First Representative of a Fully Ordered,Orthorhombically Distorted MgCu2 Laves Phase.

The title compound, the first intermetallic compound in the Cu—Cd—As system, is synthesized by solid state reaction of a stoichiometric mixture of the elements (1000 °C, 63 h) and characterized by powder and single crystal XRD, DFT electronic structure calculations, and magnetic measurements.     

Successive Determination of Picogram Amounts of Phosphorus and Arsenic in Pure Water by Indirect Flameless Atomic Absorption (Mo) Spectroscopy

Abstract

The method involves the conversion of the P and As into the yellow 12-molybdo-phosphate or - arsenate complex, respectively, extraction into butyl acetate (in the case of As - with the preliminary addition of ethanol), the decomposition of the heteropoly-compounds with aqueous NH₃ and the back extraction of the liberated Mo into aqueous solution, for flameless AA determination. 10 pg P and 25 pg As in 0.4 ml samples of ultrapure water were determined with percentage errors below ±30%.     

Glassy Carbon Electrode Modified with Citrate Stabilized Gold Nanoparticles for Sensitive Arsenic (III) Detection

The electrochemical detection of As(III) was investigated on the novel citrate stabilized gold nanoparticle modified glassy carbon electrode (AuNPs/GCE) in 1 M HCl by square wave anodic stripping voltammetry. AuNPs/GCE was prepared by simply casting citrate stabilized gold nanoparticles onto the well-polished glassy carbon electrode. Gold modification was evaluated by cyclic voltammetry, while transmission electron microscopy and UV-vis Spectroscopy revealed the size and distribution of gold nanoparticles. Anodic stripping voltammetry was performed with the modified electrode in As(III) solution. Electrochemical experiments proved that AuNPS/GCE exhibited good performance for As(III) analysis, the linear range were obtained between 0.05 and 1 ppb for trace level of As(III) as well as 1 to 15 ppb, with a limit of detection of 0.025 ppb. In terms of reproducibility, the precision of the aforementioned method in %RSD was calculated at 7.78% (n = 10), and the repeatability of the proposed method was calculated to be 1.59%. The application of the method to analyze As(III) in tap water was investigated.     

The stabilities, electronic structures and elastic properties of Rb-As systems

The structural, electronic and elastic properties of Rb–As systems (RbAs in NaP, LiAs and AuCu structures, RbAs2 in the MgCu2 structure, Rb3 As in Na3As, Cu3 P and Li3Bi structures, and Rb5 As4 in the A5B4 structure) are investigated with the generalized gradient approximation in the frame of density functional theory. The lattice parameters, cohesive energies, formation energies, bulk moduli and the first derivatives of the bulk moduli (to fit Murnaghan’s equation of state) of the considered structures are calculated and reasonable agreement is obtained. In addition, the phase transition pressures are also predicted. The electronic band structures, the partial densities of states corresponding to the band structures and the charge density distributions are presented and analysed. The second-order elastic constants based on the stress-strain method and other related quantities such as Young’s modulus, the shear modulus, Poisson’s ratio, sound velocities, the Debye temperature and shear anisotropy factors are also estimated.     

应用激光诱导击穿光谱检测污水溶液中的砷

工业冶炼过程中产生的废水中含有As等重金属元素,对环境造成污染并对人类身体健康形成危害,有必要对其进行实时、在线的监测。激光诱导击穿光谱(LIBS)是一种新型的元素测量技术,具有快速检测等优点。文章作者搭建了一套激光诱导击穿光谱实验装置,采用Nd∶YAG激光器产生的脉冲激光击穿样品产生等离子体,其发射的光谱被中阶梯光栅光谱仪分光,并用ICCD进行光电探测。对从现场采集的含砷工业废水开展了LIBS探测实验,并定性分析出了As元素的特征谱线。根据一系列含As浓度不同的污水样品的LIBS实验结果,获得元素浓度与谱线强度的关系曲线(定标曲线)。采用定标曲线可以对未知含As浓度的工业废水进行定量分析。结果表明,采用LIBS方法能够实现对污水溶液中的As元素的快速检测,具有广泛的应用前景。     

电合成2,2-二羟甲基丙酸

制备Ti/SnO2+Sb2O4/PbO2电极,电极的组分及其价态由XRD和XPS表征;该电极可将2,2-二羟甲基丙醛直接电合成2,2-二羟甲基丙酸.应用高效液相色谱分析原料和产物,电化学方法研究电合成影响因素,包括:2,2-二羟甲基丙醛浓度、溶液pH值、反应温度和氧化电位等.在优化条件下(pH=1,C醛=0.10 mol.L-1,t=15℃,E=1.8 V)电合成2,2-二羟甲基丙酸的转化率为58%,选择性36%,电流效率28%.本法为该产物的合成提供了一种新的途径.     

Isochronous Mass Measurements of Hot Exotic Nuclei

A novel method for mass measurements of short-lived exotic nuclides is presented. Exotic nuclides were produced and separated in flight at relativistic energies with the fragment separator (FRS) and were injected into the experimental storage ring (ESR). Operating the ESR in the isochronous mode we performed mass measurements of neutron deficient fragments of ⁸⁴Kr with half-lives larger than 50 ms. However, this experimental technique is applicable in a half-life range down to a few μs. A mass resolving power of 110000 (FWHM) has been achieved. Results are presented for the masses of ⁶⁸As, ^70,71Se and ⁷³Br. This revised version was published online in July 2006 with corrections to the Cover Date.