Electric potential distribution near nanocone arrays on metal substrates

Based on the nanostructured surface model,where conical nanoparticle arrays grow out symmetrically from a plane metal substrate,a theoretical model of the local electric potential near nanocones is built when a uniform external electric field is applied.In terms of this model,the electric potential distribution near the nanocone arrays is obtained and given by a curved surface using a numerical computation method.The computational results show that the electric potential distribution near the nanocone arrays exhibit an obvious geometrical symmetry.These results could serve as a basis for explaining many abnormal phenomena,such as the abnormal infrared effects(AIREs) which are found on nanostructured metal surfaces,as well as a reference for investigating the applications of nanomaterials,such as nanoelectrodes and nanosensors.     

纳米结构金属表面的近场电势分布

基于均匀外电场中金属纳米半球颗粒按一定对称性从平面衬底生长出的表面结构,建立纳米半球颗粒表面附近近场电势的理论模型.采用数值计算方法得到近场电势的空间分布,并以三维曲面的形式给出.结果表明:电势分布呈现明显的几何对称性.结果为解释与纳米结构薄膜表面有关的各种异常现象提供依据,为纳米结构薄膜材料的应用研究提供参考.     

Local electric field and configuration of CO molecules adsorbed on a nanostructured surface with nanocones

Based on the nanostructured surface model that the (platinum, Pt) nanocones grow out symmetrically from a plane substrate, the local electric field near the conical nanoparticle surface is computed and discussed. On the basis of these results, the adsorbed CO molecules are modelled as dipoles, and three kinds of interactions, i.e. interactions between dipoles and local electric field, between dipoles and dipoles, as well as between dipoles and nanostructured substrate, are taken into account. The spatial configuration of CO molecules adsorbed on the nanocone surface is then given by Monte-Carlo simulation. Our results show that the CO molecules adsorbed on the nanocone surface cause local agglomeration under the action of an external electric field, and this agglomeration becomes more compact with decreasing conical angle, which results in a stronger interaction among molecules. These results serve as a basis for explaining abnormal phenomena such as the abnormal infrared effect (AIRE), which was found when CO molecules were adsorbed on the nanostructured transition-metal surface.     

金属纳米椭球结构表面的局域电场和吸附分子分布

过渡金属纳米结构表面吸附CO分子时会出现异常红外效应,这一现象可以用纳米结构表面吸附分子在外电场作用下产生局部凝聚从而相互作用能增加来解释.在前期研究的基础上,给出金属基底表面生长出的纳米颗粒为椭球状颗粒的理论计算结果.基于均匀外电场中金属纳米椭球颗粒按一定对称性排列的表面结构模型,用经典电磁学理论计算了纳米椭球颗粒表面附近的局域电场.在此基础上,将吸附的CO分子等效为偶极子,在考虑了偶极子与局域电场、偶极子之间以及偶极子与金属基底三种相互作用的情况下,用Monte-Carlo方法进行数值模拟,最后给出纳 关键词： 金属纳米结构表面 纳米椭球 吸附分子 局域电场     

纳米结构Pt膜上CO吸附的异常红外效应机理研究

CO吸附在经方波电势处理后的纳米结构Pt金属膜电极上可观察到异常红外效应（AIREs）.在实验基础上用粒子间的相互作用和电子-空穴衰减机理分析、模拟了AIREs，表明Pt金属表面的纳米岛状结构增强了CO分子间及CO分子与纳米结构表面的相互作用，电子-空穴衰减引起的能量转移和粒子间相互作用的增强可以导致异常红外吸收谱线变化特征的出现. 关键词： 异常红外效应 粒子相互作用 电子-空穴衰减     

应用平行隔板增强纳米球表面电场

球形纳米粒子已经被广泛地应用于表面增强拉曼散射.为进一步提高纳米球表面电场,从而提高表面增强拉曼散射信号强度,本文设计了平行隔板纳米球结构.离散偶极子近似计算结果表明,应用平行隔板后,纳米球表面电场得到了大幅度增强,故平行隔板纳米球结构更适合作为表面增强拉曼散射衬底,用于生物分子探测.另外,本文还系统地研究了平行隔板结构参数对整个平行隔板纳米球结构光学性质的影响. 关键词： 银纳米球 平行隔板 表面等离子体 离散偶极子近似     

表面注入P-top区double RESURF功率器件表面电场模型

提出表面注入P-top区double RESURF功率器件表面电场和击穿电压解析模型. 基于分区求解二维Poisson方程, 获得double RESURF表面电场的解析式. 借助此模型, 研究了器件结构参数对表面电场和电势的影响; 计算了漂移区长度和厚度与击穿电压的关系, 给出了获得最大击穿电压和最小导通电阻的途径. 数值结果, 解析结果和试验结果符合较好.     

Facile preparation of Au/Ag bimetallic hollow nanospheres and its application in surface-enhanced Raman scattering

In this paper, an Au/Ag bimetallic hollow nanostructure was obtained by using SiO₂ nanospheres as sacrificial templates. The nanostructure was fabricated via a three steps method. SiO₂@Au nanospheres were first synthesized by the layer-by-layer technique, and then they were coated with a layer of Ag particles, finally, the Au/Ag bimetallic hollow nanospheres were obtained by dissolution of the SiO₂ core by exposure in HF solution. Several characterizations, such as transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX) and UV visible absorption spectroscopy were used to investigate the prepared nanostructures. The effectiveness of these Au/Ag bimetallic hollow nanospheres as substrates toward surface-enhanced Raman scattering (SERS) detection was evaluated by using rhodamine 6G (R6G) as a probe molecule. We show that such Au/Ag bimetallic hollow nanospheres structure films which consisting of larger interconnected aggregates are highly desirable as SERS substrates in terms of high Raman intensity enhancement. The Au/Ag bimetallic hollow nanostructured aggregate, interconnected nanostructured aggregate and nanoscale roughness are important factors responsible for this large SERS enhancement ability.     

电子辐照下聚合物介质深层充电现象研究

空间辐射环境中,聚合物介质的深层充放电效应是威胁航天器安全的重要因素之一.文中在Chudleigh和von Berlepsch所发展的电位衰减模型基础上引入传输电流项,考虑了电子入射引起的感应电导率和感应电场的影响,提出了新的分析研究介质材料深层充电规律和特征的模型.通过该模型,分析了不同辐射条件下介质的表面电位、内部电荷与电场分布的变化,并设计实验及援引其他实验数据对模型分析结果进行验证.分析和实验结果表明,聚合物介质在深层充电过程中的平衡电位随着入射电子束流强度和介质电阻率的增加而增大,决定深层充电平 关键词： 深层充电 电荷传输模型 电子束 聚合物     

Study of electrical field distribution of gold-capped nanoparticle for excitation of localized surface plasmon resonance

The specific optical characteristics which can be observed from noble metal nanostructured materials such as nanoparticles and nanoislands have wide variety of applications such as biosensors, solar cells, and optical circuit. Because, these noble metal nanostructures induce the increment of light absorption efficiency by the enhancing effect of electrical field from localized surface plasmon resonance (LSPR) excitation. However, the enhancing effects of electrical field from LSPR using simple structured noble metal nanostructures for several applications are not satisfactory. To realize the more effective light absorption efficiency by the enhancing effect of electrical field, quite different noble metal nanostructures have been desired for applying to several applications using LSPR. In this study, to obtain the more effective enhancing effect of electrical field, conditions for LSPR excitation using a gold-capped nanoparticle layer substrate are computationally analyzed using finite-difference time-domain (FDTD) method. From the previous research, LSPR excitation using such gold-capped nanoparticle layer substrates has a great potential for application to high-sensitive label-free monitoring of biomolecular interactions. For understanding of detailed LSPR excitation mechanism, LSPR excitation conditions were investigated by analyzing the electrical field distribution using simulation software and comparing the results obtained with experimental results. As a result of computational analysis, LSPR excitation was found to depend on the particle alignment, interparticle distance, and excitation wavelength. Furthermore, the LSPR optical characteristics obtained from the simulation analysis were consistent with experimentally approximated LSPR optical characteristics. Using this gold-capped nanoparticle layer substrate, LSPR can be excited easily more than conventional noble metal nanoparticle-based LSPR excitation without noble metal nanoparticle synthesis. Hence, this structure is detectable a small change of refractive index such as biomolecular interactions for biosensing applications.     

Probing simultaneously the volume and surface structure of nanospheres adsorbed at a solid-liquid interface by GISANS

We demonstrate in this paper the possibilities offered by Grazing Incidence Small Angle Neutron Scattering (GISANS) for the study of solid/liquid interfaces. We present experimental results obtained by Specular Neutron Reflectivity (SNR) and GISANS on a model system made of silica nanospheres adsorbed on a silicon wafer by electrostatic interactions both at solid/air interface and solid/liquid interfaces. At the solid/liquid interface, we demonstrate that grazing incidence scattering enables to discriminate the surface and the bulk scattering. The surface structure factor derived from GISANS shows that the nanospheres are organized as a repulsive liquid system, with a surface fraction occupation consistent with values obtained by SNR. This original setup highlights a direct correlation between the structure of the silica nanospheres in solution and their organization on the surface: due to the strong electrostatic repulsions between spheres, their organization at the surface is close to the projection in 2D of the 3D organization of the nanospheres in solution.     

Evaluating the performance of Russia in the research in nanotechnology

Many toxicology studies on insoluble and poorly soluble nanoparticles point out surface area as an indicator of inhalation exposure. Measuring this criterion thus constitutes an important challenge. Instruments exist which can measure particle surface area concentration in real-time, but it is not known how well they perform when faced with polydisperse nanostructured aerosols. In this study, the response functions of three commercially available instruments based on diffusion charging (LQ1-DC, Matter Engineering; NSAM, TSI model 3550; AeroTrak? 9000, TSI) were measured for monodisperse aerosols of four different chemical natures with particles ranging in size from 15 to 520?nm. Our results show good agreement between the experimental and theoretical response functions for the three instruments studied. In addition, no significant effect of the chemical nature, density or particle morphology was revealed. Instrument response was also tested with polydisperse aerosols. For these aerosols, discrepancies were observed between measurements and calculated concentrations based on response function and particle number size distribution. Relative differences varied between ?60 and +55?% with an average value of ?20?%. These differences may be explained by different factors; among them, the existence of a distribution of electrical charges on particles can lead to identical signals measured, and differential diffusion charging performance might lead to concentration-dependent response.     

Thermodiffusion motion of electrically charged nanoparticles

The present work deals with experimental studies to examine the theoretical model of thermodiffusion of electrically charged nanoparticles. Three different ionic magnetic colloid samples have been synthesized and profoundly analyzed. The theoretical model is a classical one, based on the calculation of the temperature and the electric potential distribution around nanoparticles. The discrepancy between experimental data and theory turns out not to exceed 20%. We focus on applying different approximations between calculated electrical double layer in the theoretical model and experimental determination of the surface charge density of colloidal particles. We assume this is the main reason for obtained discrepancy.     

Preparation of Ni-doped carbon nanospheres with different surface chemistry and controlled pore structure

In classic carbon supports is very difficult to control pore size, pore size distribution, and surface chemical properties at the same time. In this work microporous carbons derived from furfuryl alcohol are used as support to prepare Ni-doped carbon materials. The N₂ flow rate used during the carbonisation process of the precursor influences on the size of the nanospheres obtained but not in their textural properties. Microporous carbon nanospheres have been synthesised with a narrow pore size distribution centred in 5.5 Å. The surface chemistry of these materials can be easily modified by different treatments without detriment of the pore structure of the doped carbon nanospheres.     

Synthesis and optoelectrical properties of SnO2 nanospheres derived by microwave-assisted hydrothermal method

SnO₂ nanospheres have been synthesized by microwave-assisted hydrothermal method from the starting materials of citric acid and tin metallic particles. From the results of SEM and TEM images, it can be found that the SnO₂ nanospheres are uniform with diameter of ~100 nm and aggregated by SnO₂ nanocrystals with size of 8–10 nm. The photoluminescence spectrum of the nanospheres shows a peak at ~330 nm and a cutoff wavelength of around 400 nm. The pronounced photocurrent was recoded from the as-prepared SnO₂ nanospheres assembled on a Mo thin sheet under the UV illumination, which is suggested for the potential application of UV photodetector.     

漂移区表面阶梯掺杂LDMOS的击穿电压模型

提出表面阶梯掺杂(SD：Step Doping on surface)LDMOS的二维击穿电压模型.基于求解多区二维Poisson方程,获得SD结构表面电场的解析式.借助此模型,研究其结构参数对击穿电压的影响;计算优化漂移区浓度和厚度与结构参数的关系,给出获得最大击穿电压的途径.数值结果,解析结果和试验结果符合较好.漂移区各区和衬底电场相互调制,在漂移区中部产生新的峰值,改善电场分布;高掺杂区位于表面,降低了正向导通电阻.结果表明：SD结构较常规结构击穿电压从192V提高到242V,导通电阻下降33%. 关键词： 阶梯掺杂 模型 优化 调制     

Thermalization time of noble metal nanoparticles: effects of the electron density profile

The lack of d-electron screening in the s-electron spill-out region at the surface of Ag nanoparticles increases the electron-electron interaction in this region compared to the bulk. Therefore when comparing the electron-electron interaction contribution to the thermalization time of nanoparticles of varying radius, smaller particles thermalize faster due to the increased surface to bulk ratio. One aspect which has not been addressed is the effect of the spatial distribution of charge at the surface of the nanoparticle. In this work it is shown that the size dependence of the thermalization time is very sensitive to the surface density profile. The electron thermalization time of conduction electrons in noble metal nanoparticles as a function of the radius is calculated. The sensitivity of the scattering rate to the spatial distribution of charge at the surface of the nanostructure is analyzed using several model surface profiles. The change in surface charge distribution via charging or coating of the nanospheres is shown to be a tool for control and probing of the ultra-fast electron-electron dynamics in metallic nanoparticles.     

Wetting property of smooth and textured hydrophobic surfaces under condensation condition

Static and dynamic wetting behaviors of sessile droplet on smooth, microstructured and micro/nanostructured surface under condensation condition are systematically studied. In contrast to the conventional droplet wetting on such natural materials by dropping, we demonstrate here that when dropwise condensation occurs, the sessile droplet will transit from the Cassie-Baxter wetting state to the Wenzel wetting state or partial Cassie-Baxter wetting state on the microstructured surface or the micro/nanostructured surface, which leads to a strong adhesion between the droplet and the substrate. In contrast, the apparent contact angle and the sliding angle on the smooth surface changes a little before and after the condensation because of small roughness. Theoretical analysis shows that the roughness factor controls the adhesion force of the droplet during condensation, and a theoretical model is constructed which will be helpful for us to understand the relationship between the adhesion force and the geometry of the surface.     

铝纳米晶的低温导电特性研究

采用真空热压技术将电磁感应加热-自悬浮定向流法制备的铝纳米粉末压制成块体样品.通过X射线衍射、透射电子显微镜、扫描电子显微镜及X射线能谱分析了铝纳米晶的微观结构,并用四探针法测量了不同温度下(8—300 K)样品的电阻率,研究了铝纳米晶的电阻率(ρ)随温度的变化规律.结果表明:由于晶界(非晶氧化铝)对电子的散射以及晶界声子对电子的散射效应,低温(40 K)下,铝纳米晶的本征电阻率随温度变化关系明显不同于粗晶铝,不仅呈现出T~4变化,还表现出显著的T3变化规律.因晶界等缺陷和非晶氧化铝杂质对电子的散射,铝纳米晶残余电阻率比粗晶铝电阻率大5—6个数量级.     

A Method for Preparation of Ordered Porous Silicon Based on a 2D SiO_2 Template

A new method for fabricating ordered porous silicon is reported.A two-dimensional silica nanosphere array is used as a template with a hydrofluoric acid-hydrogen peroxide solution for etching the nanospheres.The initial diameter and distribution of the holes in the resulting porous silicon layer are determined by the size and distribution of the silica nanospheres.The corrosion time can be used to control the depths of the holes.It is found that the presence of a SiO_2 layer,formed by the oxidation of the rough internal surface of the hole,is the primary reason allowing the corrosion to proceed.Ultraviolet reflection and thermal conductivity measurements show that the diameter and distribution of the holes have a great influence on properties of the porous silicon.