非均匀电场的电堆积理论研究

基于样品区非均匀电场电势分布的测试结果并利用异性双点电荷电场的理论模型,研究了非均匀电场电堆积效应,提出了非均匀电场电堆积作用的理论模型.采用一种改进的非均匀电场电堆积系统,以矿泉水中痕量Cr(Ⅵ)和Pb(Ⅱ)为考察对象,同时对其进行分离富集和测定,为理论模型提供了实验依据.     

电场响应光子晶体

光子晶体是一种介电常数周期变化、具有光子带隙、对光路可控的新型功能材料。将对外界刺激敏感性材料引入光子晶体空隙就得到可响应光子晶体。电场响应光子晶体是由电活性材料与光子晶体结构相结合所得,可以应用于反射型彩色显示并表现出其他显示技术所没有的独特优点。本文重点介绍了电场响应光子晶体器件的结构和响应机理,并按照引入电活性材料的不同将电场响应光子晶体分为基于液晶、聚电解质水凝胶、金属有机聚合物凝胶、导电聚合物以及核壳式电场响应光子晶体,总结了近几年各类电场响应光子晶体的研究进展,提出了在反射型彩色显示器件方面的应用以及存在的问题和展望。     

电流变液中悬浮颗粒的体积与形状的变化

基于偶极近似,运用电极化方法,定量研究了电流变液中悬浮颗粒在外电场作用下其体积和形状的变化,并计算了其体积和形状的相对变化率.研究结果表明:悬浮颗粒的体积和形状的相对变化率均与电场强度的平方成正比,并与ER本身的性质有关.一般情况下,颗粒的体积和形状的相对变化率分别为8.4%和12.5%,对总体积变化率的贡献为1.68%.这种变化对于ER系统的电涨和电热都作出了贡献,仅当将颗粒当作刚性球时,其自由能才与电场强度的平方成正比.     

外电场作用下甲基乙烯基硅酮分子结构和电子光谱

采用密度泛函B3P86方法在6-311++G(d, p)基组水平上优化得到了沿分子轴方向不同外电场(0-0.04 a.u.)作用下, 甲基乙烯基硅酮分子的基态电子状态、几何结构、电偶极矩和分子总能量. 在优化构型下利用杂化CIS-DFT方法(CIS-B3P86)研究了同样外电场条件下对甲基乙烯基硅酮的激发能和振子强度的影响. 计算结果表明, 分子几何构型与电场大小呈现强烈的依赖关系, 分子偶极矩μ随电场的增加先减小后急剧增大. 电场为零时, 分子总能量为-483.5532137 a.u., 随着电场增加, 能量升高, 在F=0.02 a.u.时达到最大值-483.5393952 a.u., 此后, 继续增大电场系统总能量则开始降低. 激发能随电场增加急剧减小, 表明在电场作用下, 分子易于激发和离解.     

非水介质中明胶水凝胶电场驱动行为的研究

研究了明胶水凝胶在绝缘硅油中的电场响应行为。结果表明,在硅油中,明胶水凝胶在外加高压直流电场作用下可发生运动,其运动由转动和平动两部分组成。存在一个运动所需的最小阈值电场,只有外加电场在此阈值以上时,才可观察到水凝胶明显的运动。水凝胶的运动速度随外加电场的增大而增大,其运动可通过外加电场的大小来调控。由硅油很稳定且在电场中会电解,因此避免了传统电场驱动水凝胶在水介质中响应时不可避免的电解缺点,为建立一种新的电响应凝毅然驱动方式提供了可能。     

离子色谱电渗析技术的研究进展

电渗析器件通常定义为在电场作用下操纵离子从一种溶液穿过离子交换膜迁移到另外一种溶液的一种设备。它可以通过电解水产生氢离子或氢氧根离子,从而用于离子色谱系统的淋洗液在线制备、抑制或检测。相较于人工配制淋洗液或再生液,电渗析技术具有绿色、高效、纯度高、自动化程度高等优势。因此基于电渗析器件的离子色谱系统应用范围越来越大。该文简要评述了近几年该器件的研究进展,具体包括电致淋洗液发生器、电致膜抑制器和电渗析样品前处理器。     

介电弹性体致动器的结构设计及应用

介电弹性体作为一种新型的电活性高分子聚合物,当受到电场的激励时会产生变形,撤销电场后能够恢复原状,具有将电能直接转换为机械能的特点。通过将其设计成具有不同结构的致动器,能够提高变形能力,并且满足不同的应用需求。本文介绍了介电弹性体致动器的致动机理,阐明了它们是能够以直线方式产生运动的线性致动器,在此基础上可设计出不同结构的致动器,主要归纳了各种介电弹性体致动器,从它们的性能特征、加工技术和潜在应用等方面进行了讨论。     

电场敏感性聚(丙烯酸-co-丙烯酸甲酯)凝胶的合成和性能

以丙烯酸、丙烯酸甲酯为单体,亚甲基双丙烯酰胺为交联剂,过硫酸铵为引发剂,N,N-四甲基乙二胺为促进剂,合成了一系列电场敏感性凝胶.研究了氯化钠溶液,pH缓冲溶液对凝胶平衡溶胀度的影响,并测定了所得电场敏感性凝胶在电场作用下的脱水行为.研究结果表明,所得凝胶具有很好的电场敏感性.此外,初步讨论了该类电场敏感性凝胶的电致收缩机理.     

罐底外侧深井阳极阴极保护电位分布规律研究

依据电磁场基本定律和罐底阴极保护系统的几何特征推导深井阳极电场在罐底外侧的电位分布.根据电场叠加原理,综合考虑阳极电场和阴极电场的作用,研究了单侧深井阳极保护下罐底外侧的阴极保护电位分布,并将计算结果与实测数据作对比,吻合较好.     

用光学方法研究玻璃微珠电流变液颗粒间的相互作用

运用一套适合研究颗粒间相互作用的双光镊系统,通过对颗粒聚集时间的测量,得出颗粒聚集时间和电场的平方成反比.这是第一次用电流变液颗粒在动态情况下直接验证电偶极子对间的相互作用.发展了一套使用高速CCD摄像机进行扩散波谱(DWS)测量的方法,首次实时测量具有颗粒结构的非各态历经体系的自相关函数,以研究电流变液机理,得到了玻璃微珠电流变液的结构响应时间和力的响应时间;测量了不同电场下体系相关函数的特征衰减时间随时间的变化.在不同电场下测量扩散系数可以反映出相互作用力与电场的平方成正比.     

Periodic electro-optical characteristics of ion-doped Smectic A phase liquid crystals driven by a low-frequency electric field

Functional liquid crystal (LC)-based electro-optical materials are promising candidates in a wide range of smart fields due to their excellent external stimuli-responsive characteristics. Herein, ion-doped Smectic A (SmA)-phase LCs gradually change from a transparent to a scattering state and then return to the transparent state via a circularly driven low-frequency electric field. All optical states can be maintained after removing the electric field. This phenomenon is due to charge transport and convection effects that appear and disappear periodically in SmA LCs doped with suitable ionic liquids. Diverse periodic characteristics were observed upon applying electric fields with different waveforms (e.g. square, sawtooth, and sine). Furthermore, the optical contrast of the periodic feature was abated by increasing the frequency of the electric field. These ion-doped SmA LCs can be widely used in multi-stable optical devices, optical switches, and timers, etc.     

Numerical simulation of deformation behavior of droplet in gas under the electric field and flow field coupling

The water droplets in the process of electrostatic coalescence are important when studying electrohydrodynamics. In the present study, the electric field and flow field are coupled through the phase field method based on the Cahn–Hilliard formulation. A numerical simulation model of single droplet deformation under the coupling field was established. It simulated the deformation behavior of the movement of a droplet in the continuous phase and took the impact of droplet deformation into consideration which is affected by two-phase flow velocity, electric field strength, the droplet diameter, and the interfacial tension. The results indicated that under the single action of the flow field, when the flow velocity was lower, the droplet diameter was greater as was the droplet deformation degree. When the flow velocity was increased, the droplet deformation degree of a small-diameter droplet was at its maximum size, the large-diameter droplet had a smaller deformation degree, and the middle-diameter droplet was at a minimum deformation degree. When the flow velocity was further increased, the droplet diameter was smaller, and the droplet deformation degree was greater. Under the coupled effect of the electric field and flow field, the two-phase flow velocity and the electric field strength were greater, and the degree of droplet deformation was greater. While the droplet diameter and interfacial tension were smaller, the degree of droplet deformation was greater. Droplet deformation degree increased along with the two-phase flow velocity. The research results provided a theoretical basis for gas–liquid separation with electrostatic coalescence technology.     

A method to study the electric field distribution on sample surfaces in atom probe analysis

We report the development of a nondestructive method to estimate the electric field (EF) distribution on a nano-sized sample surface in atom probe (AP) analysis. The simulated EF distribution on an ideal hemisphere indicates that the largest EF exists on the geometrical top of the ideal hemisphere and that EF decreases as the emitting area getting away from the sample apex. To estimate the EF distribution on a real sample surface, the sample apex is determined via comparing the field ion microscopy (FIM) signal intensity of {113} planes on the symmetrical sample surface. A series of contour maps showing the intensity of the evaporated ions (eg, H⁺) was obtained by applying various EFs on the sample surface. A plot of relative EFs with respect to the emitting angle can thus be extracted.     

电场对TiO2纳米膜光催化性能的影响

 以泡沫镍为基材,采用溶胶-凝胶法制备了TiO2纳米膜光催化剂. 在自制外加电场光催化反应装置中,对催化剂施加一定的偏电压,研究了甲基橙溶液的光电催化降解反应,考察了偏压极性、阳极偏压和甲基橙初始溶液浓度等对降解效率的影响,并比较了光电催化与光催化、光解对甲基橙溶液降解的差异. 结果表明,外加阳极偏压形成的电场可以较大幅度提高甲基橙溶液的降解效率. 从半导体和量子力学理论出发探讨了电场促进光催化反应的作用机理.     

印刷线路板分压离子阱的离子单向出射性能研究

印刷线路板(Printed-Circuit-Board,PCB)分压离子阱是一种新型质量分析器,其突出优点在于内部电场可通过调节射频分压比进行优化.本实验在PCB分压离子阱离子出射方向的两组离散电极上配置了非对称的射频分压,以引入奇次阶场成分,使得射频电场的场中心(即离子运动中心)发生偏移,从而实现离子单向出射.通过数值计算软件SIMION和AXSIM分析了射频分压比差值与其内部电场分布的关系,并模拟离子运动轨迹,得到离子出射情况和模拟质谱峰.模拟结果表明,当两组离散电极的射频分压比差值为20％时,在合适的AC频率条件下,对于m/z=609 Th的离子,PCB分压离子阱的离子单向出射率可达90％以上,且质量分辨率大于2500.本研究可使PCB分压离子阱在基本不损失质量分辨率和使用单检测器模式下,大幅提高离子检测效率,因而在小型化质谱仪应用中具有显著优势.     

The effect of electric field and Al doping on the sensitivity of hexa‐peri‐hexabenzocoronene nanographene to chloropicrin

It has been previously reported that the recently synthesized hexa‐peri‐hexabenzocoronene (HBC) nanographene cannot detect toxic chloropicrin (CP) gas. To overcome this problem, we examined the effect of Al doping and applying an electric field on the sensitivity of HBC towards CP gas by means of density functional theory calculations. We found that the Al‐doping process significantly increases the adsorption energy of CP gas from ?7.1 to ?39.9 kcal mol^?1 but decreases the sensitivity of HBC. By applying an electric field, the HBC is polarized with two different electrostatic potentials on its different surfaces, which increases the adsorption energy. By increasing the electric field strength, the adsorption energy and electronic sensitivity of HBC are increased. We predicted that in the presence of an electric field of about ?0.025 au, HBC can act as an electronic senor or a work function‐type sensor with a short recovery time. At this field, the electrical conductivity of HBC is significantly increased on CP adsorption which generates an electrical signal. Increasing the electric field to higher intensities is not favourable because of increasing recovery times, and decreasing it to lower intensities reduces the sensitivity of HBC.     

Computational insights of two-dimensional infrared spectroscopy under electric fields in phosphorylcholine

Influence of static electric field in biological cells causes electroporation, which results in the increase of permeability of the cells and phospholipid bilayer. However, the precise mode of action of electric fields on phospholipid bilayer and their quantum mechanics are still unclear. Therefore, to understand the quantum-based biological effect, we aimed to study two-dimensional infrared (2D-IR) spectra-adopted quantum mechanics/molecular mechanics (QM/MM) simulations under the influence of static electric fields on Phosphorylcholine, an important component in phospholipid membrane. Initially, QM/MM studies were performed under the influence of electric field, ranging from −1.543 to 1.028 V/nm. A multilayer ONIOM model (in combination with DFT/B3LYP/6-31G [d, p] and DREIDING force fields) was used to obtain 2D-IR simulated spectra to calculate electrostatic interaction in the biological system. The results demonstrated that the phosphate group played an important role on α-rotation in LUMO and the chlorine atom had a major contribution in HOMO. In addition, decreased number of hydrogen bonds demonstrated that uncoupling reaction of the P-O stretching vibrations while the electric field was −1.542 V/nm. Moreover, we observed that the electric field is −1.028 V/nm, there is no rotational isomerization in phosphorylcholine. We concluded that the static electric fields significantly affect the anharmonic frequencies, vibration coupling and the structure of the phosphorylcholine.     

Surface electric field manipulation of the adsorption kinetics and biocatalytic properties of cytochrome c on a 3D macroporous Au electrode

Upon adsorbing on a solid-state substrate, water-soluble proteins are prone to denaturation and deterioration of their functions due to the conformation change. The surface electric field of a conductive substrate is one of the important factors that influence the character of adsorbed proteins. In this work, a 3D macroporous gold electrode has been prepared and served as the working electrode to study the influence of surface electric field on the adsorption kinetics and conformation of the adsorbed cytochrome c (cyt-c) with the help of electrochemical, in situ electrochemical IR spectroscopic, atomic force microscopic, and contact angle measurements. The external electric field creates excess surface charge which can manipulate the adsorption rate of proteins on the substrate by the enhanced electrostatic interactions between the electrode and protein patches by coupling with complementary charges. The amount of immobilized cyt-c with electrochemical activity on the 3D macroporous gold electrode showed a minimum at potential of zero charge (PZC) and it increased with increasing net excess surface charge. Higher electric field could influence the conformation and the corresponding properties such as direct electrochemistry, bioactivity, and surface character of the adsorbed cyt-c molecules. However, high external electric field leads to damage of the protein secondary structure. This study provides fundamentals for the fabrication of biomolecular devices, biosensors, and biofuel cells through electrostatic interactions. Figure Two cases are illustrated for the protein immobilized on electrode surfaces: a retention of protein structure under moderate excess surface charge, b denaturation and conformation change of proteins adsorbed at high excess surface charge, e.g., due to the higher external electric field.     

Theoretical investigation on the performance of DNA electrophoresis under programmed step electric field strength: Two‐step condition

Programmed step electric field strength is a simple‐to‐use technique that has already been reported to be effective to enhance the efficiency or speed of DNA electrophoresis. However, a global understanding and the details of this technique are still vague. In this paper, we investigated the influence of programmed step electric field strength by theoretical calculation and concentrated on a basic format named as two‐step electric field strength. Both subtypes of two‐step electric field strength conditions were considered. The important parameters, such as peak spacing, peak width, resolution, and migration time, were calculated in theory to understand the performance of DNA electrophoresis under programmed step electric field strength. The influence of two‐step electric field strength on DNA electrophoresis was clearly revealed on a diagram of resolution versus migration time. Both resolution and speed of DNA electrophoresis under two‐step electric field strength conditions are simply expressed by the shape of curves in the diagram. The possible shapes of curve were explored by calculation and shown in this paper. The subtype II of two‐step electric field strength brings drastic variation on the resolution. Its limitations of enhancement and deterioration of resolution were predicted in theory.     

表面电荷及外电场对液固界面热阻的影响

采用非平衡分子动力学方法模拟了外电场及固体表面电荷对水与固体间界面热阻的影响. 结果表明,外加电场平行于界面时, 其对界面热阻几乎没有影响, 而垂直于界面时, 界面热阻将随着电场强度的增大而减小. 壁面带正电荷或负电荷都将使得界面热阻减小. 界面热阻与表面电荷密度及电场强度均满足二次函数关系. 模拟结果表明施加外电场和表面电荷是控制液固界面热阻的有效方法.