An improved fabrication method for carbon nanotube probe

An improved arc discharge method is developed to fabricate the carbon nanotube probe. In this method, the silicon probe and the carbon nanotube were manipulated under an optical microscope. When the silicon probe and the carbon nanotube were very close, 30-60 V dc or ae was applied between them, and the carbon nanotube was divided and attached to the end of the silicon probe. Comparing with the arc discharge method, the new method need not coat the silicon probe with metal in advance, which can greatly reduce the fabrication difficulty and cost. The fabricated carbon nanotube probe exhibits the good property of high aspect ratio and can reflect the true topography more accurately than the silicon probe.     

Nanowear pretreatment of AFM tips for reasonable friction force

In a nanoscale friction test, wear of an atomic force microscope (AFM) tip is inevitable. The shape of the worn tip influences the friction force measured. In order to eliminate the influence, nanowear pretreatment should be conducted for the AFM tip. In our study, pretreatment of three kinds of tips, i.e. Si₃N₄ tip, Si tip and silica colloidal tip, was performed using AFM. The results show that the shape of the tips changes with the increase of sliding distance, which leads to the variety of friction force. Whereas, when the tip gets blunt, the shape of tip tends to become stable and the friction force becomes stable correspondingly. To a certain degree, it reveals that the pretreated tips can be applied to study the friction force of samples.     

DNA原子力显微镜成象条件的研究

原子力显微镜（AFM）在空气中对DNA进行观察时，针尖很容易对其造成损伤，从而影响图象质量，为探索此问题的解决办法，本研究在空气、水和无水乙醇中对DNA进行成象，同时对针尖的结构进行了扫描电镜观察，取100μg/ml质粒pQE30水溶液20μl滴加在新鲜剥离的云母基底上，吸附1min，用滤纸吸去基底上的多余残液，氮气吹干后在空气中成像；pQE30分别溶于去离子水和无水乙醇，质量浓度为100μg/ml,各取100μl加入液体池中成象，成象时均采用MultiMode AFM(NanoscopeⅢa）的敲击模式，并记录力曲线，结果发现：在液体中DNA的图象分辨率优于在空气中，在无水乙醇中优于在水中；针尖与DNA样品间的相互作用力越大，成象的分辨率越低，多次使用后针磨损，分辨率降低，这一结果为选择DNA的理想AFM成象环境，研究生理条件下DNA的结构和功能提供了实验基础。     

热台原子力显微镜研究PVDF/PBA共混物的表面结晶形态

制备了低温结晶的聚偏氟乙烯（PVDF）/聚己二酸丁二酯（PBA）共混物薄膜.使用热台原子力显微镜跟踪研究PVDF/PBA共混物薄膜样品的原位熔融过程,从片晶尺度上考察不同的共混比例对相分离形态结构的影响规律.结果表明,当PVDF/PBA共混体系在低温下结晶时,PBA组分主要在PVDF的片晶间的区域内分布;共混比例影响两组分都结晶后的片晶排列方式;PBA组分含量较低时,两组分片晶的排列方式主要为＂ABABABAB＂,PBA中等含量时,两组分片晶的排列方式主要为＂ABBBABBB＂;片晶间分相结构对PBA的结晶扩散有抑制作用,PBA组分要充分结晶需要较高的过冷度或者足够长的结晶时间.     

有机物对聚酰胺复合纳滤膜硫酸钙结垢的影响

为揭示不同有机物形成的污染层对硫酸钙在纳滤膜面结垢行为的影响,选用牛血清蛋白(BSA)、腐殖酸(HA)、海藻酸(SA)作为典型有机污染物对聚酰胺复合纳滤膜进行污染,之后进行硫酸钙结垢实验.利用扫描电镜(SEM)观察不同污染条件下的硫酸钙形态,采用原子力显微镜(AFM)结合自制的硫酸钙探针测定不同污染条件下膜-硫酸钙及硫酸钙-硫酸钙之间的作用力.结果表明:与新膜结垢相比,有机物吸附在纳滤膜上改变了膜面性质,影响硫酸钙晶体成核机理.3种有机污染条件下硫酸钙结垢污染程度为SAHABSA.这是因为SA与Ca~(2+)的相互作用可缩短硫酸钙晶体成核时间,增大晶体尺寸,导致纳滤膜通量迅速下降;HA与Ca~(2+)络合增大了结垢层的厚度和密实度,导致纳滤膜通量衰减较大;而BSA与Ca~(2+)的结合能力较弱,加上其特殊的心形分子结构,导致该情况下硫酸钙结垢程度弱于其他两种有机物条件.     

原子力显微镜"突跳"研究

“突跳”现象严重影响着原子力显微镜(AFM)的性能．根据Hamaker微观连续介质理论,建立了AFM针尖同试样面接触力包含斥力的数学模型;分析了AFM悬臂梁弹性力同针尖接触力的关系,发现了引起AFM“突跳”的本质是弹性力同接触力的不稳定平衡问题;通过增加AFM悬臂梁刚度,提出了一种避免“突跳”现象发生的方法,并给出了仿真结果。     

石英表面阳离子吸附膜结构的AFM研究

为了研究阳离子表面活性剂对固体表面的润湿性的影响,了解表面活性剂在石英表面的吸附机制,利用原子力显微镜(AFM)技术,考察了不同结构阳离子改性石英片与不同基团改性AFM探针间的拉脱力,从分子角度探索石英表面双层膜的结构特性.研究发现:直链烷基季铵盐CI6PC改性石英片与阴离子改性探针间的拉脱力随浓度增大在临界胶束浓度附...     

Development of XY scanner with minimized coupling motions for high-speed atomic force microscope

The design and fabrication processes of a novel scanner withminimized coupling motions for a high-speed atomic force microscope (AFM) were addressed.An appropriate design modification was proposed through the analyses of the dynamic characteristics of existing linear motion stages using a dynamic analysis program,Recurdyn.Because the scanning speed of each direction may differ,the linear motion stage for a high-speed scanner was designed to have different resonance frequencies for the modes,with one dominan...     

轻敲模式下原子力显微镜的能量耗散机理研究

为研究原子力显微镜(AFM)在轻敲工作模式下的能量耗散机理,基于Hamaker假设和Lennard-Jones势能定律得到了原子与球体间的作用力．通过将球体与平面原子间的作用力等效为球体与平面间的粘着分布力,并结合经典弹性理论建立了一种新型的球体与平面粘着接触的弹性模型,根据所建模型得到了AFM针尖与样品表面间的粘着力随其间距的变化规律．仿真结果表明,粘着力随间距的变化曲线在AFM针尖趋近和撤离样品表面,即加载和卸载的两个过程中并不完全相同,产生了粘着滞后现象,而粘着滞后现象的出现表明AFM在轻敲工作模式中将耗散能量,因而,所建模型从理论上证实了AFM在轻敲工作模式下存在能量耗散现象．     

Development of XY scanner with minimized coupling motions for high-speed atomic force microscope

The design and fabrication processes of a novel scanner with minimized coupling motions for a high-speed atomic force microscope (AFM) were addressed. An appropriate design modification was proposed through the analyses of the dynamic characteristics of existing linear motion stages using a dynamic analysis program, Recurdyn. Because the scanning speed of each direction may differ, the linear motion stage for a high-speed scanner was designed to have different resonance frequencies for the modes, with one dominant displacement in the desired directions. This objective was achieved by using one-direction flexure mechanisms for each direction and mounting one stage for fast motion on the other stage for slow motion. This unsymmetrical configuration separated the frequencies of two vibration modes with one dominant displacement in each desired direction, and hence suppressed the coupling between motions in two directions. A pair of actuators was used for each axis to decrease the crosstalk between the two motions and give a sufficient force to actuate the slow motion stage, which carried the fast motion stage. A lossy material, such as grease, was inserted into the flexure hinge to suppress vibration problems that occurred when using an input triangular waveform. With these design modifications and the vibration suppression method, a novel scanner with a scanning speed greater than 20 Hz is achieved.     

纳米碳管葡萄糖生物传感器的研究

基于纳米碳管的特殊物理结构和电化学特性，利用多壁纳米碳管（MWCN）修饰酶电极葡萄糖生物传感器，分析传感器性能的改变并探索酶和电子中间体在纳米碳管表面的作用机制。在碳糊电极表面纳米碳管修饰能够加快铁氰化钾/亚铁氰化钾的氧化还原速度，提高响应电流水平，但没有发现纳米碳管有直接电子传递作用；同时纳米碳管提高了葡萄糖氧化酶（GOD）分子在反应过程中的相对活性。经纳米碳管修饰后，葡萄糖生物传感器表现出良好的线性和分辨率，检测灵敏度、检测范围、检测速度有所提高；尤其在人体血糖浓度范围内，响应电流幅度提高了50%，分辨率提高了两倍。     

Aggregation of gold nanoparticles and DNA damage by atomic force microscopy

The plasmid DNA binding and cleavage activities with gold nanoparticles (Au-NPs) were investigated by the integrated tools of UV-vis spectroscopy, atomic force microscopy (AFM), and DNA electrophoresis. The results showed that the absorbance of Au-NPs decreased at 520 nm and a new absorption peak at 570 nm was found, as the DNA concentration increased, which indicated the particle aggregation. AFM experiments showed that DNA-induced particle aggregation originated from the strong interactions between DNA and Au-NPs, that is, the adsorption of DNA onto the Au-NPs surface would result in particle aggregation. After a short period of time, the Au-NPs were easier to aggregate in the presence of the higher concentration of DNA. At the early stage of incubation, the DNA double helix conformation was substantially changed by particles. The electrophoresis manifested the absorption and damage appeared on the native DNA molecules. With a longer treating time, the molecules were broken into fragments. The DNA damage was deemed to be a gradual process. The nonspecific interactions between DNA and Au-NPs resulted in the binding of DNA to the Au-NPs surface. Consequently, not only Au-NPs were aggregated but also DNA was damaged.     

Fabrication of 3D structure by combining AFM and chemical etching on crystalline silicon surface

Anisotropic etching of monocrystalline silicon inalkaline solution has been researched for more than 40years, which is one of the key techniques in fabricationof different types of micromechanical structures such asdiaphragms and cantilevers on a silicon wafer[1]. Al-though having a lot of applications, it has many aca-demic and technical problems. Wet chemical etching,mostly performed using KOHsolution, is in general usefor microstructure[2 -4], which is based on the fact thatthe etching rat…     

利用AFM对单晶硅表面加工化学反应理论分析

以原子力显微镜为工具,在空气条件下对单晶硅片表面加工得到下凹的三维微结构。给出了AFM金刚石针尖在对单晶硅的微加工中的化学反应和加工模型。对加工条件下发生的化学反应及其原理进行了理论分析。用化学热力学定律、化学动力学原理和相关的热力学数据自由能、生成热、化学键能、活化能等分析加工过程中发生的反应是空气中O2与单晶硅Si反应生成二氧化硅的过程;金刚石针尖磨损发生的反应主要是空气中O2与金刚石针尖C反应生成CO2的过程。     

Atomic force microscope study of WC-10Co cemented carbide sintered from nanocrystalline composite powders

In order to compare the spark plasma sintedng （SPS） process plus hot isostatic press （HIP） with vacuum sintedng plus HIP, an investigation was carried out on the topography, microstructure and gain size distribution of nanocrystalline WC-10Co composite powder and the sintered specimens prepared by SPS plus HIP and by vacuum sintering plus HIP by means of atomic force microscopy （AFM）. The mechanical properties of the sintered specimens were also investigated. It is very easy to find cobalt lakes in the specimen prepared by vacuum sintering plus HIP process. But the microstructure of the specimen prepared by SPS plus HIP is more homogeneous, and the grain size is smaller than that prepared by vacuum sintering plus HIP. The WC-10Co ultrafine cemented carbide consolidated by SPS plus HIP can reach a relative density of 99.4%, and the transverse rupture strength （TRS） is higher than 3540 MPa, the Rockwell A hardness （HRA） is higher than 92.8, the average grain size is smaller than 300 nm, and the WC-10Co ultrafine cemented carbide with excellent properties is achieved. The specimen prepared by SPS with HIP has better properties and microstructure than that prepared by vacuum sintering with HIP.     

Effect of hydration film on scanning images of atomic force microscope

A standard calibration grating was used for image scanning to investigate the effect of hydration films on imaging resolution by Atomic Force Microscope （AFM）. The results showed that the hydration films greatly affect the imaging resolution for the tapping mode, but no evident effect on the contact mode, The possible reasons for the effect of hydration films on scanning images of AFM are also brought forward here.     

基于最小二乘拟合的不同探针测量线宽的比较

AFM探针的形貌和尺寸对纳米尺度线宽的测量有较大影响．首先建立了一个基于最小二乘的应用于AFM测量技术的线宽计量模型，并使用三种不同探针在NanoScopeⅢa型AFM上对设计线宽尺寸为1000nm的样本进行了测量．应用该模型和算法对线宽进行计算，揭示出探针尺寸对线宽测量结果的影响以及该模型对探针尺寸的依赖性．     

扫描探针显微镜系列及其应用综述

扫描探针显微镜将人类带入原子世界,使人类不仅能够观察到物质表面原子的排布情况,而且能够按照人类的意图实现原子操纵.回顾了扫描探针显微镜的历史,介绍了目前国际上各种系列的扫描探针显微镜基本原理、主要特点、研究现状和最新应用情况,重点介绍了原子操纵和生命科学、信息科学领域的应用,提出了扫描探针显微镜目前的研究方向.     

Evaluation and Characterization of Mechanical, Electrical, and Thermal Properties of Polymer Nanocomposites Reinforced with Different Allotropes of Carbon

The present work aims to present the results based on the processing of nanocomposites, which consist of matrix materials like epoxy and filler materials such as conjugated nanomaterials/allotropes of carbon, namely, carbon black, graphite, and multiwalled carbon nanotube (MWCNT) used for targeted applications. To improve the physical and chemical properties and to facilitate a better interfacial interface between the polymer and nanotube, functional MWCNT is used during the preparation of the composite. The prime objective of the study is to establish the thermal, mechanical, and electrical properties of nanocomposites using experimental methods. It has been observed from the experimental results that carbon nanotube (CNT) based composite exhibits higher mechanical (tensile and hardness) and thermal properties as compared with the others. The electrical properties are found to be better in a graphite-based composite. Although CNT has superior mechanical and thermal properties, the exorbitant price limits its use. Hence, the allotropes of carbon may be used judiciously considering both the cost and property requirements of the targeted application. The work also studies the dispersion state of nanofibers through scanning electron microscopy (SEM).