CdSe在高压下的电学性质及相变

 利用在金刚石压砧上集成的微电路,原位测量了CdSe多晶粉末在温度为300~450 K、压力达到23 GPa时电阻率随温度和压力的变化关系。实验结果表明：在加压过程中,电阻率在2.6 GPa压力时出现的异常改变,对应着CdSe从纤锌矿向岩盐矿结构的转变,而在6.0、9.8、17.0 GPa等压力处出现的电阻率异常,则是由CdSe中的电子结构的变化所引起的;在卸压过程中,只在约14.0和3.0 GPa压力下观察到了两个电阻率异常点。通过对电阻率随压力变化曲线的模拟,得出了CdSe高压相的带隙随压力的变化关系,据此预测CdSe金属化的压力应在70~100 GPa之间。变温实验结果表明,在实验的温度和压力范围内,CdSe的电阻率均随温度的增加而升高。     

Electrophoretic measurement of water charge density and ion hydration

Water exchange between bulk water and water-ion complexes will be at equilibrium when the charge density of the complex surface equals the charge density of bulk water, producing a constant radius water-ion complex. This complex will migrate in an electric field at a velocity proportional to the complex radius. CE velocity is the sum of the complex charge-dependent velocity and the buffer electro-osmotic flow. Simultaneous use of both a base (1.07 mM imidazole) and an acid (1.5 mM MOPS) buffer negates EOF at pH 7.4. Electric fields below 300 V/cm (potassium, calcium) and 400 V/cm (magnesium) yield migration velocities with no dehydration of the water-ion complexes. The number of waters per complex increase with the ion charge density: K⁺ 1.90, Ca⁺⁺ 5.90, Mg⁺⁺ 6.59 waters/ion. The charge densities of the complexes are similar: K⁺ 1.24, Ca⁺⁺ 1.43, Mg⁺⁺ 1.21 e/nm², for an average bulk water charge density of 1.29 ± 0.11 (SD) e/nm². The addition of 0.1% Triton increases the number of waters for Mg⁺⁺ to 25.33 and lowers the charge density to 0.497 e/nm². High electric field dehydration shows that calcium will be fully dehydrated at 638.3 V/cm and magnesium fully dehydrated at 925.5 V/cm, which occur at 6.15 and 5.78 nm from the membrane. Dehydrated magnesium will then bind to calcium channels leading to decreased smooth muscle activation.     

电四极矩对高次谐波产生的贡献

通过数值求解强场近似下单电子原子的含时薛定谔方程,研究了在强线偏振激光场下,氢原子电四极矩对高次谐波产生的贡献.研究结果表明,在强激光场的作用下,在偶极矩的影响下氢原子能够产生奇次谐波,当激光场强度增加到一定值时,氢原子在电四极矩的作用下产生了偶次谐波.根据谐波功率谱和时频分析图并结合半经典"三步模型"分析了偶次高次谐波产生机制,并对产生的物理现象做出了合理的解释.     

Electro-optical enhancement of nonporous Zn2SnO4-based dye-sensitized solar cell by electric field assisted sintering

Third generation nanostructure-based solar cells such as dye-sensitized solar cells (DSSCs) are green and low-cost future substitute for silicon-based solar cells. Zinc Stannate-based DSSCs are attractive due to their interesting properties, but aggregated Zn₂SnO₄ nanoparticles are large in comparison to TiO₂ nanoparticles which deteriorate DSSC performance. Electric field assisted sintering (EFAS) due to its outstanding impacts on optical and electrical characteristics is favorable. To this aim, we try to study the enhancement effect of EFAS on the performance of Zn₂SnO₄-based DSSCs. EFAS could manipulate nanostructure matrix remarkably to develop the effective surface area to gather higher amounts of dye molecules resulting enhanced light harvesting and improved current density further; this method helps to improve electron transportation by decreasing recombination probability. The reported strategy is applicable in numerous electro-optical devices including nanoporous medium such as perovskite solar cells.     

Electric and optical properties modulations of armchair silicene nanoribbons by transverse electric fields

Under the influence of the external transverse electric fields, the effective mass and optical properties of armchair-edge silicene nanoribbons (ASiNRs) are investigated using the first-principles based on density functional theory (DFT). The results show that, comparing without the external transverse electric fields, the band gaps decrease monotonously, and the effective masses of the electrons and holes change non-monotonously with the absolute value of the electric fields, respectively. The total density of states (DOS) shows that, under the external electric fields, 9-ASiNR exhibits p-type semiconductor characters. Because of the obvious difference of the imaginary parts between the//x and//y directions, 9-ASiNR shows an optical anisotropy. In//x direction, the peaks of the dielectric function have evident red shift which are all associated with the electrons transition between Si 3p orbit and Si 3p, 3s orbits.     

Accelerator irradiations of minerals: Implications for track formation mechanisms and for studies of lunar and meteoritic materials

Abstract

Natural crystals of feldspars, pyroxenes, quartz and apatite have been irradiated in the Berkeley HILAC with neon and argon ions of up to 10.2 MeV/amu with maximum doses of 1.6 × 10¹³ argon ions/cm² and 4.0 × 10¹³ neon ions/cm² respectively. The samples were thinned to thicknesses near 30 microns, stacked to form the target and then bathed completely in the ion beams. X-ray and optical observations revealed: (a) a crystal distortion and curvature with the argon irradiation similar to that produced in mica; (b) a lesser effect from neon bombardment; (c) a fracturing of the crystal samples which depended on the total dose and energy of the incident ion; (d) polygonized structures produced when either neon or argon ions (with sufficiently high concentration) were trapped within the crystals. The interpretation of the measurements, their correlation with the mechanism of track formation and implications concerning the alteration of the lunar surface due to solar particles and the exposure of lunar and meteoritic material in the ancient solar flare cosmic rays are discussed.     

Enhancement of ablation rate and production of colloidal nanoparticles by irradiation of metals with nanosecond pulsed laser in presence of external electric field

This paper presents the results of experimental study on the effect of electric field on the ablation rate during the nanosecond pulsed laser ablation of aluminum and copper in deionized water. The effect of electric field strength on the material removal rate and its mechanisms were investigated both in the electric field parallel and perpendicular to the laser beam path schemes. The ablation rate was estimated by measuring the dimensions of craters on the target induced by laser. The crater dimensions and optical properties of the produced colloidal nanoparticles were characterized by means of optical microscopy and UV–Vis absorption spectroscopy, respectively. The results indicate that pulsed laser ablation in the presence of an electric field significantly leads to higher material removal rate. The experimental results also confirm that the crater geometry extremely depends on the direction of the electric field with respect to the laser beam direction. The UV–Vis spectra show that the nanoparticles production efficiency increases with increasing the electric field strength.     

Mechanism of proton transport in water clusters and the effect of electric fields: A DFT study

Proton transport inside metal organics frameworks (MOFs) plays an important role to understand and develop a new type of material for a high conductivity application. One of the possible pathways of this process is via water cluster which is confined inside the MOFs structure. In this work, the mechanism of proton transport is investigated within the Density Functional Theory (DFT) calculations. Different water clusters from dimer to pentamer and octamer, which are equivalent to water structures inside the tetrahedral and cubic cavities of MOF-801, respectively, were systematically considered. The results show that proton transfer inside the pentamer cluster has the lowest barrier around 16 kJ/mol. Moreover, the presence of electric fields has a strong effect on the mechanism and energy profile of the proton transfer in both pentamer and octamer cluster. Our DFT prediction of proton migration energies is supported by experimental data of high conducting MOFs such as MOF-801.     

Preparation of poly(3, 4‐ethylenedioxythiophene)/poly(styrene sulfonate) (PEDT/PSS) composite and its applications in anti‐static coating

Poly(3, 4‐ethylenedioxythiophene)/poly(styrene sulfonate) (PEDT/PSS) composite is prepared by solution polymerization at room temperature in the presence of 3, 4‐ethylenedioxythiophene as the monomer, PSS as the doping agent, potassium supersulfate (KPS) as the oxidant, and deionized water as the solvent. The color of the PEDT/PSS solution is dark blue and its solid content is 2.2%, its pH value is 1.5. By mixing alcohols, polar organic solvents, adhesives, and so on into PEDT/PSS solution, the anti‐static coating solution is prepared. The coating is conducted by bar‐coating (20 µm) at 40% relative humidity and 20°C. The influence of the content of each component on the coating surface resistivity is discussed, and a reasonable volume content of each component is obtained. The obtained coating has low surface resistivity (1 × 10⁶ Ω), excellent water resistance, and high transmittance of visible light together with a wide range of potential applications. Copyright © 2009 John Wiley & Sons, Ltd.