Deoxyribonucleic acid sample preparation in scanning probe microscope

The process of deoxyribonucleio acid (DNA) sample preparation in scanning tunneling microscope (STM) and atomic force microscope (AFM) is reviewed. The main discussions are devoted to the methods, advantages or drawbacks and improvement of the DNA sample's immobilization and spreading.

Simple preparation method of multilayer polymer films containing Pd nanoparticles

A simple route to the fabrication of multilayer films containing Pd nanoparticles is described. Following layer-by-layer assembly of PdCl42- and polycation, QPVP-Os (a quaternized poly(4-vinylpyridine) complexed with [Os(bpy)(2)Cl](2+/+)), on 4-aminobenzoic acid-modified glassy carbon electrodes, the three-dimensional Pd nanoparticle multilayer films are directly formed on electrode surfaces via electrochemical reduction of PdCl42- sandwiched between polymers. The growth of PdCl42- is easy on electrode surfaces by electrostatic interaction, and the assembly processes are monitored by cyclic voltammetry and UV-vis spectroscopy. The depth profile analyses by X-ray photoelectron spectroscopy verify the constant composition of the Pd nanoparticle multilayer films. Atomic force microscopy proves that the as-prepared Pd nanoparticles are uniformly distributed with an average particle diameter of 3-7 mn. The resulting Pd nanoparticle multilayer-modified electrode possesses high catalytic activity for the reduction of dissolved oxygen and oxidation of hydrazine compounds in aqueous solution.

Shear-induced spiral-like morphology of a main-chain liquid crystalline poly(aryl ether ketone)

The shear-induced spiral-like morphology of a main-chain thermotropic liquid crystalline poly(aryl ether ketone) is observed and characterized by means of polarizing light microscopy, atomic force microscopy, transmission electron microscopy and electron diffraction techniques. The spiral-like texture is formed during shearing in the temperature range of liquid crystalline to isotropic transition (335-340 degreesC), and dispersed discontinuously in the mosaic matrix. Electron diffraction results indicate that the spiral exhibits orthorhombic lateral packing of the crystals and homeotropic alignment of the molecules. The spiral formation process and possible affecting factors are discussed.

Controlled nucleation and growth of surface-confined gold nanoparticles on a (3-aminopropyl)trimethoxysilane-modified class slide: A strategy for SPR substrates

The thickness of the gold film and its morphology, including the surface roughness, are very important for getting a good, reproducible response in the SPR technique. Here, we report a novel alternative approach for preparing SPR-active substrates that is completely solution-based. Our strategy is based on self-assembly of the gold colloid monolayer on a (3-aminopropyl)trimethoxysilane-modified glass slide, followed by electroless gold plating. Using this method, the thickness of films can be easily controlled at the nanometer scale by setting the plating time in the same conditions. Surface roughness and morphology of gold films can be modified by both tuning the size of gold nanoparticles and agitation during the plating. Surface evolution of the Au film was followed in real time by UV-vis spectroscopy and in situ SPRS. To assess the surface roughness and electrochemical stability of the Au films, atomic force microscopy and cyclic voltammetry were used. In addition, the stability of the gold adhesion is demonstrated by three methods. The as-prepared Au films on substrates are reproducible and stable, which allows them to be used as electrodes for electrochemical experiments and as platforms for studying SAMs.

Langmuir-Blodgett film formation from surfactant-capped zinc sulfide nanoparticles spread on water surface

The surfactant-capped ZnS nanoparticulate multilayer film has been fabricated by Langmuir-Blodgett(LB) technique. ZnS LB firm was investigated by the small-angle x-ray diffraction(XRD), atomic force microscopy(AFM) and transmission electron microscopy(TEM). The results indicate that ZnS nanoparticulate LB film is one-dimensional superlattice.

Structural and optical properties of distyrylbenzene derivative thin films

In order to understand the relationship between the molecular orientation and optical properties of oligophenylenevinylene film, oriented thin films of 1,4-di(p-methoxystyryl)benzene (DSB-1) and 1,4-di(p-methoxystyryl)-2,5-dimethoxybenzene (DSB-2) were fabricated on a potassium bromide (KBr) (001) surface by the vacuum-evaporation method. The structures and optical properties of DSB films have been investigated by transmission electron microscopy (TEM), atomic force microscopy (AFM) and polarized photoluminescence (PL) spectroscopy, respectively. DSB-1 molecules orient obliquely and/or parallel to the substrate surface depending on the substrate temperature. On the other hand, DSB-2 molecules tend to grow epitaxially with the molecular plane parallel to the substrate surface. The anisotropic molecular orientations represent the polarized PL. The epitaxial growth and molecular orientations observed by TEM and AFM at the local and microscopic scale are confirmed by polarized PL measurement on a macroscopic scale. (C) 1999 American Institute of Physics. [S0021-8979(99)01523-6].

Fabrication and characterization of heteropolyanion Langmuir-Blodgett films

The possibility of the formation of Langmuir-Blodgett (LB) films with dimethyldioctadecylammonium (DODA) after the addition of cobalt(II)-substituted Dawson-type tungstodiphosphate anion (briefed as (H2O)(CoP2W17O618-)-P-11) in the subphase has been explored. Marked modifications of the compression isotherms are observed when this anion is dissolved in the subphase, which demonstrates that the polyanions interact with the monolayers. LB films have been readily obtained from this system. The adsorption Fourier transform IR (FT IR) spectroscopy, atomic force microscopy (AFM), X-ray diffraction (XRD) and cyclic voltammetry (CV) have been used to investigate the morphological and molecular structure of the deposited film. The FT IR results showed the presence of the polyanion within the LB films, and the shift for its characteristic bands may be related to the presence of positively charged DODA. AFM measurement reveals that the LB films of DODA/(H2O)(CoP2W17O618)-P-II are regularly and uniformly deposited on the substrate. XRD experiments prove that the lamellar structure of the LB films of DODA/(H2O)(CoP2W17O618-)-P-II is well-defined. The LB films of DODA/(H2O)(CoP2W17O618-)-P-II immobilized onto an indium-oxide (ITO) glass, in aqueous solutions of pH 2.0-5.0, show quite facile redox reactions even for multilayers. All the experiments carried out in the present study suggest that the new materials of heteropolyanions can be formed by LB techniques and beneficial physicochemical properties of heteropolyanions can be maintained/enhanced through molecular-level design. (C) 1999 Elsevier Science S.A. All rights reserved.

IN-SITU AFM STUDY OF THE SURFACE-MORPHOLOGY OF POLYPYRROLE FILM

In this paper we focus on the surface morphology of polypyrrole film by using in situ atomic force microscopy (AFM). The formation process of polypyrrole film and the transformation process of the film from the oxidized to reduced state were clearly observed.

EPITAXIAL BEHAVIOR OF HDPE ON THE BOUNDARY OF HIGHLY ORIENTED IPP SUBSTRATES

The epitaxial crystallization behavior of high-density polyethylene on the boundary of highly oriented isotactic polypropylene (iPP) substrates has been investigated by means of atomic force microscopy (AFM) and transmission electron microscopy (TEM). The results obtained from AFM and TEM indicate that the epitaxial nucleation of HDPE on the highly oriented iPP substrates occurs earlier than that in the pure HDPE phase, i.e., homogeneous nucleation. Therefore the epitaxially grown HDPE lamellae can grow across the boundary of the iPP substrate into the HDPE spherulitic phase with the epitaxial orientation relationship remaining.

碳纳米管探针的制作方法研究

碳纳米管的小直径、高纵横比、高强度和高弹性、优良的耐磨损性能以及独特的电学和化学特性,使其成为高分辨率原子力显微镜的理想探针针尖。本文根据制作工艺的特点,综述现有碳纳米管探针的代表性研究和制作方法:组装式和生长式。组装式是通过手工、电场或磁场的方式将制备好的碳纳米管粘附到常规硅探针的末端;而生长式是在常规硅探针末端或悬臂梁上定点催化生长出一定直径和长度的CNT。最后指出这些方法目前存在的主要问题。

面向可视化纳米操作的DNA分子运动学建模研究

利用原子力显微镜(AFM:Atomic Force Microscopy)对DNA进行单分子纳米操作对生命科学的发展具有特别重要的意义,但是AFM纳米操作缺乏实时视觉反馈的问题依然制约着生物操纵技术的发展.虚拟现实技术是解决该问题的有效方法之一,但是必须预先建立起被操作物体的运动学模型.目前面向可视化纳米操作的建模研究多针对纳米棒、纳米颗粒等刚性物体展开,很少涉及到柔性DNA分子的运动建模方法。针对该问题,本文以弹簧-质点模型为基础,借鉴统计力学在DNA机械特性上的研究成果,提出了一种具有较强物理意义和实际可信度的柔性DNA分子运动学建模方法,并进行了相关仿真实验研究,从而为实现DNA分子的可视化纳米操作提供了理论依据。

机器人化纳米操作中任务空间的实时反馈方法研究

纳米科技的最终目标是在原子、分子尺度上，制造具有新颖物理、化学和生物特性的器件和系统，而实现这个目标最为关键的使能技术便是纳米尺度下进行观测、操作和装配的科学方法与相关技术手段。原子力显微镜（AFM：Atomic Force Microscopy）的发明为实现这一目标提供了可行途径，AFM除了能够在常态下实现对原子、分子尺度大小物体的观测，并且由于其超高的分辨率和运动精度，可控、可重复的运动方式，独特的机械力作用机理，任意环境的可适应性而广泛应用于纳米操作。然而AFM的主要功能是进行纳米观测，应用于纳米操作时面临着许多挑战性的难题，尽管随着近十年的深入研究，一些问题已经得到了部分解决，但是缺乏高可信度的实时视觉反馈、无法实现任务空间内探针的精确定位依然阻碍着AFM纳米操作的效率。以目前最为先进的AFM纳米操作方法—增强现实技术为例，尽管该技术可以为操作者提供实时的视觉反馈，但是这种视觉反馈并不代表纳米操作场景的真实变化，而是根据离线模型计算得到的一种图形仿真，因而视觉反馈是否可信取决于模型的准确程度，然而受纳米尺度下各种非线性力的影响，如毛细力、范德华力、静电力等等，很难建立完全精确的物理模型，模型误差将导致错误的视觉反馈并引起纳米操作的失败。此外，受PZT非线性和温漂的影响，基于AFM的纳米操作还缺乏在任务空间内对探针进行精确定位的能力，导致操作过程中AFM探针无法有效接触到纳米物体，使得机器人学中“从A点运动到B点”最为基本的任务难以实现，这些缺点都严重阻碍着AFM纳米操作的效率和效果。本论文针对上述问题，以机器人学中的感知、决策、行为理论和监控方法为基础，具体开展了以下几方面的工作： 1、视觉反馈缺乏可信度是基于增强现实AFM纳米操作面临的主要问题，由于操作者无法对视觉反馈可信度作出评断，经常会在错误视觉反馈的指引下进行无效的纳米操作，从而浪费大量的时间，降低了AFM纳米操作的效率。为了克服上述问题，本文在研究信息诊断与反馈理论基础上，提出了基于Kalman滤波的视觉反馈可信度在线监控方法，实现了视觉反馈错误的实时检测，避免了无效纳米操作的发生，提高了AFM纳米操作的效率。 2、错误视觉反馈被检测出后，需要对其修正以保证纳米操作任务的成功完成。然而传统修正方法需要中断纳米操作进行重新扫描成像，这往往需要耗费几分钟的时间，严重降低了AFM纳米操作的效率。针对该问题，本文提出一种基于局部扫描的在线修正方法，通过扫描轨迹的优化，该方法能够对真实纳米操作结果进行实时感知，从而不需要中断纳米操作就能实现错误视觉反馈的修正，并使得整个修正过程对于操作者透明。这保证了实时可视监控信息的真实性，显著提升了AFM纳米操作的效率。 3、PZT非线性和随机漂移是影响AFM探针精确定位的主要因素，针对该问题本文提出了一种基于路标的探针定位方法，其核心思想是不再采用距离为测度方式进行探针位置描述，而是将作业区域的特定形貌特征定义为参考路标，通过探针对特征形貌的主动感知实现基于路标地图的探针定位，有效消除PZT非线性和随机漂移引起的定位误差，提高探针在任务空间内的定位精度。 4、研究了机器人化纳米操作系统任务空间实时反馈的构建技术，具体包括高灵敏度纳米操作力的感知方法，系统结构误差的产生原因和补偿策略，面向探针实时运动控制的系统结构设计，系统的软硬件实现方案等内容，并利用该实验平台开展了大量实验研究，验证了本论文所提出理论方法的正确性，同时演示性地组建了基于单根CNT和DNA的纳电子器件，实验结果表明AFM纳米操作的效率和效果得到了极大提升。本文的研究工作丰富了基于AFM的机器人化纳米操作理论，为基于AFM的纳米制造技术发展提供了具有一定指导意义的理论方法和研究途径。

Ultrasonic synthesis of silica-alumina nanomaterials with controlled mesopore distribution without using surfactants

A novel sol-gel process has been developed for the synthesis of amorphous silica-aluminas with controlled mesopore distribution without the use of organic templating agents, e.g., surfactant molecules. Ultrasonic treatment during the synthesis enables production of precursor sols with narrow particle size distribution. Atomic force microscopy analysis shows that these sol particles are spherical in shape with a narrow size distribution (i.e., 13-25 nm) and their aggregation during the gelation creates clusters containing similar sized interparticle mesopores. A nitrogen physiadsorption study indicates that the mesoporous materials containing different Si/Al ratios prepared by the new synthesis method has a large specific surface area (i.e., 587-692 m(2)/g) and similar pore sizes of 2-11 nm. Solid-state Al-27 magic angle spinning (MAS) NMR shows that most of the aluminum is located in the tetrahedral position. A transmission electron microscopy (TEM) image shows that the mesoporous silica-alumina consists of 12-25 nm spheres. Additionally, high-resolution TEM and electron diffraction indicate that some nanoparticles are characteristic of a crystal, although X-ray diffraction and Si-29 MAS NMR analysis show an amorphous material.

Internal structure of copper(II)-phthalocyanine thin films on SiO2/Si substrates investigated by grazing incidence x-ray reflectometry

Jenkins, Tudor; Brieva, A.C.; Jones, D.G.; Evans, D.A., (2006) 'Internal structure of copper(II)-phthalocyanine thin films on SiO2/Si substrates investigated by grazing incidence x-ray reflectometry', Journal of Applied Physics 99 pp.73504 RAE2008

Pressure induced anisotropy of electrical conductivity in polycrystalline molybdenum disulfide

Anisotropic specimens of MoS2 are obtained by pressing the microcrystalline powder into special die. This inelastic compression results in a rearrangement of the disulfide micro platelets observed by Atomic Force Microscopy and reflected in the macroscopic anisotropy in electrical conductivity in these samples. The conductivity measured parallel and perpendicular to the direction of applied pressure exhibits an anisotropy factor of ∼10 at 1 GPa. This behaviour of the conductivity as a function of applied pressure is explained as the result of the simultaneous influence of a rearrangement of the micro platelets in the solid and the change of the inter-grain distances.