利用Matlab模拟布朗运动测量实验

利用matlab工具模拟了布朗运动测量的实验。通过一正态随机数产生函数模拟从而产生布朗运动步距。在假定粒子所受拖曳力满足斯托克斯关系的情况下,通过拟合多个粒子的均方位移随时间的变化曲线得到斜率,从而进一步可得出扩散系数和波尔兹曼常数。同时,根据模拟结果也对如何减小实验误差作了分析。     

非水纳米分散系的冷冻蚀刻电镜原位观测

研究了冷冻蚀刻电镜技术原位观测合成的纳米分散系的制样步骤、制样方法 ,并利用冷冻蚀刻电镜技术原位观测了四种纳米分散系中分散相的粒度、粒度分布和聚集状态 .研究结果表明 :蚀刻时间对电镜照片图像质量有较大影响 ,蚀刻时间应根据分散系中分散相含量、粒度大小来选 ;冷冻蚀刻电镜用于原位观测非水纳米分散系 ,具有准确、直观、清晰、立体的特点 ,并且可同时采集多种信息 .     

Metal–Polymer Hybrid Nanoparticles for Correlative High‐Resolution Light and Electron Microscopy

The combination of fluorescence microscopy and electron microscopy promises a deeper insight into the ultrastructural features of cell organelles, e.g., after drug administration. Both methods complement each other and provide, as a correlative approach, a keen insight into the fate of nanoparticles within the cell. Moreover, it represents a promising tool to determine alterations of the cellular environment as a response to particle uptake. However, the availability of suitable correlative markers is mandatory for such correlative approaches. In this contribution, the utilization of poly(ethylene imine) based metal–polymer hybrid particles labeled with small gold nanoparticles and Rhodamine B facilitating the observation of the particles by means of fluorescence as well as by transmission electron microscopy is suggested. Correlative light and electron microscopy is used to study uptake and intracellular fusion processes of endosomal/lysosomal structures.     

Material Discrimination in Nanoparticle Hetero-Aggregates by Analysis of Scanning Transmission Electron Microscopy Images

Hetero-contacts are interfaces between different materials at the nanoscale leading to novel functional properties. In hetero-aggregates, primary particles of at least two different materials are mixed at primary particle or cluster level. Double flame spray pyrolysis (DFSP) is a versatile technique for the controlled synthesis of such materials. Characterization of hetero-aggregates by scanning transmission electron microscopy (STEM) requires acquisition and evaluation of many aggregate images in order to derive statistically significant results. Usually, STEM energy dispersive X-ray spectroscopy (EDXS) is used to acquire elemental maps providing the material distribution of the primary particles within hetero-aggregates. However, the acquisition of a single EDXS map takes up to several minutes. For this reason, determination of material types of primary particles from the intensity in high-angle annular dark field STEM images alone is desirable. These images can be acquired within a couple of seconds. In the present work, a method is suggested which allows for achieving this objective. It can be applied to distinguish materials with a significant difference in their atomic number and hence sufficient material contrast in the STEM images.     

Electron Density of Polymeric Nanoparticles Determined by Image Processing of Transmission Electron Micrographs: Insights into Heavy Metal Staining Processes

A crucial parameter for the investigation of in particular low electron scattering materials by transmission electron microscopy is their ability to attenuate the electron beam and by this to generate appropriate contrast. Surprisingly little attempts have been devoted to at least qualitatively judge on this property of materials. Here an automated imaging analysis algorithm is introduced for the determination of a characteristic electron attenuation factor for homo‐ and (co)polymer nanoparticles which provides a means to access a measure for the contrast in a systematic study of the inherent contrast as well as of the contrast of the nanoparticles after staining procedures. The determination is based on similar imaging conditions for different nanoparticle systems, which enables a comparative approach. Additionally, based on the importance and versatility of osmium tetroxide staining, experiments are conducted elucidating the staining process of model nanoparticle systems bearing olefinic groups. The binding of osmium tetroxide in the environment of the nanoparticle is investigated by means of high‐resolution electrospray mass spectrometry.     

Understanding CeO2‐Based Nanostructures through Advanced Electron Microscopy in 2D and 3D

Engineering morphology and size of CeO₂‐based nanostructures on a (sub)nanometer scale will greatly influence their performance; this is because of their high oxygen storage capacity and unique redox properties, which allow faster switching of the oxidation state between Ce⁴⁺ and Ce³⁺. Although tremendous research has been carried out on the shape‐controlled synthesis of CeO₂, the characterization of these nanostructures at the atomic scale remains a major challenge and the origin of debate. The rapid developments of aberration‐corrected transmission electron microscopy (AC‐TEM) have pushed the resolution below 1 Å, both in TEM and in scanning transmission electron microscopy (STEM) mode. At present, not only morphology and structure, but also composition and electronic structure can be analyzed at an atomic scale, even in 3D. This review summarizes recent significant achievements using TEM/STEM and associated spectroscopic techniques to study CeO₂‐based nanostructures and related catalytic phenomena. Recent results have shed light on the understanding of the different mechanisms. The potential and limitations, including future needs of various techniques, are discussed with recommendations to facilitate further developments of new and highly efficient CeO₂‐based nanostructures.     

Laser-Scanning Microscopy for Electrophoretic Mobility Characterization of Single Nanoparticles

To enable detailed studies of interactions between nanoparticles and their environment and the correlations between various nanoparticle properties, one must go beyond ensemble averages and toward single-particle measurements. However, current methodologies for the single-nanoparticle analysis of charge and size either lack the flexibility to study dynamic processes on the single-particle level or are highly specific and require complex microfluidic devices. In addition, accurate measurements of the electrophoretic mobility (or zeta-potential) based on the optical detection of single nanoparticles remain challenging due to the low photon budget, the required sampling frequency, and the fact that electroosmosis in typical microfluidic devices must be analyzed carefully. In this study, a method is investigated to accurately characterize the electrophoretic mobility of individual nanoparticles and estimate their size by simultaneously analyzing the electrokinetic- and Brownian motion in a simple microfluidic channel. Fast laser scanning excitation and sensitive detection of fluorescent photons enable single-nanoparticle velocimetry experiments in an oscillating electric field at high frame rates.     

Recent Notable Approaches to Study Self-Assembly of Nanoparticles with X-Ray Scattering and Electron Microscopy

Self-assembly of nanoparticles (NPs) has evolved into a powerful tool for the synthesis of superstructures with tailored properties. The quality, diversity, and complexity of synthesized structures are continuously improving and fascinating new collective properties are demonstrated. At the same time, the rapid development of electron microscopy and synchrotron sources for X-rays has enabled new exciting experimental approaches to study structure and structure formation in the context of NP self-assembly. In this review, some recent studies and what can be learned from them are highlighted and discussed. It is started with a general introduction covering important concepts, experimental approaches, commonly obtained structures, the ideas of artificial atoms, and emerging properties are discussed. Recent experimental in situ and ex situ approaches with state-of-the-art electron microscopy and X-ray diffraction and scattering that helped to obtain a detailed picture of NP self-assembly processes and resulting structures are then presented.     

Direct Synthesis of ZIF-8 on Transmission Electron Microscopy Grids Allows Structure Analysis and 3D Reconstruction

The first example of layer-by-layer growth of a metal–organic framework (MOF) directly on transmission electron microscopy (TEM) grids is described. ZIF-8 is deposited on thin amorphous carbon films and subjected to a structure analysis by (scanning) TEM ((S)TEM). This method serves as a two-in-one synthesis and TEM sample-preparation technique and allows straightforward analysis of ZIF-8 crystallites. Artifacts resulting from sample preparation are completely avoided by this approach. The morphological properties, crystal structure, and the chemical composition of the material are investigated with high spatial resolution by a variety of methods of (analytical) electron microscopy. Furthermore, the incorporation of metallic nanoparticles in ZIF-8 by integrating a corresponding step into the layer-by-layer deposition process is examined. The formation of ZIF-8 crystals on the film proceeds as under the absence of nanoparticle-forming synthesis steps. However, the nanoparticles rather cover the supporting amorphous carbon film than being incorporated in the ZIF-8 material. This information cannot be obtained from standard characterization techniques but requires the application of analytical (S)TEM techniques.     

扫描电镜图像去噪的研究与实现

扫描电镜能直观观察样品的表面结构,但其高分辨形貌成像图固有的噪声不利于图像分析。针对集成电路器件扫描电镜成像图的去噪声问题,采用了通过滑动条方式自适应设置图像二值化阈值,将数学形态学处理方法与图像二值化相结合,实现了对图像噪声的自动去除处理;同时还设计了通过手动勾勒图像中的多边形区域实现去除噪声的功能;为使图像达到更好的效果,系统还可允许针对自动去噪后的图像自行选择是否进行手动去噪,并设计实现了风格直观简洁,易于操作的交互式用户界面。对多幅集成电路器件扫描电镜成像图进行去噪声处理的结果和对去噪前后的图像进行无参考图像质量评价的数据表明,该方法有效地改善了扫描电镜图的信噪比,获得了突出前景等有用信息。     

A Comparative Study of the Determination of Ferrofluid Particle Size by Means of Rotational Brownian Motion and Translational Brownian Motion

Two methods, the Toroidal Technique and the Forced Rayleigh Scattering (FRS) method, were used in the determination of the size of magnetic particles and their aggregates in magnetic fluids. The toroidal technique was used in the determination of the complex, frequency dependent magnetic susceptibility, x(w)=x'(w) - ix"(w) of magnetic fluids consisting of two colloidal suspensions of cobalt ferrite in hexadecene and a colloidal suspension of magnetite in isopar m with corresponding saturation magnetisation of 45.5 mT, 20 mT and 90 mT, respectively. Plots of the susceptibility components against frequency f over the range 10 Hz to 1 MHz, are shown to have approximate Debye-type profiles with the presence of relaxation components being indicated by the frequency, f _max, of the maximum of the loss-peak in the x"(w) profiles. The FRS method (the interference of two intense laser beams in the thin film of magnetic fluid) was used to create the periodical structure of needle like clusters of magnetic particles. This creation is caused by a thermodiffusion effect known as the Soret effect. The obtained structures are indicative of as a self diffraction effect of the used primary laser beams. The relaxation phenomena arising from the switching off of the laser interference field is discussed in terms of a spectrum of relaxation times. This spectrum is proportional to the hydrodynamic particle size distribution. Corresponding calculations of particle hydrodynamic radius obtained by both mentioned methods indicate the presence of aggregates of magnetic particles.     

Recent advances in 3D SEM surface reconstruction

The scanning electron microscope (SEM), as one of the most commonly used instruments in biology and material sciences, employs electrons instead of light to determine the surface properties of specimens. However, the SEM micrographs still remain 2D images. To effectively measure and visualize the surface attributes, we need to restore the 3D shape model from the SEM images. 3D surface reconstruction is a longstanding topic in microscopy vision as it offers quantitative and visual information for a variety of applications consisting medicine, pharmacology, chemistry, and mechanics. In this paper, we attempt to explain the expanding body of the work in this area, including a discussion of recent techniques and algorithms. With the present work, we also enhance the reliability, accuracy, and speed of 3D SEM surface reconstruction by designing and developing an optimized multi-view framework. We then consider several real-world experiments as well as synthetic data to examine the qualitative and quantitative attributes of our proposed framework. Furthermore, we present a taxonomy of 3D SEM surface reconstruction approaches and address several challenging issues as part of our future work.     

Nanoscale Imaging and Stabilization of Silica Nanospheres in Liquid Phase Transmission Electron Microscopy

Liquid phase transmission electron microscopy (LP‐TEM) is a novel and highly promising technique for the in situ study of important nanoscale processes, in particular the synthesis and modification of various nanostructures in a liquid. Destabilization of the samples, including reduction, oxidation, or dissolution by interactions between electron beam, liquid, and sample, is still one of the main challenges of this technique. This work focuses on amorphous silica nanospheres and the phenomena behind their reshaping and dissolution in LP‐TEM. It is proposed that silica degradation is primarily the result of reducing radical formation in the liquid phase and the subsequent accelerated hydroxylation of the silica, while alterations in silica solid structure, pH, and oxidizing species formation had limited influence. Furthermore, the presence of water vapor instead of liquid water also results in degradation of silica. Most importantly however, it is shown that the addition of scavengers for reducing radicals significantly improved amorphous silica stability during LP‐TEM imaging. Devising such methods to overcome adverse effects in LP‐TEM is of the utmost importance for further development and implementation of this technique in studies of nanoscale processes in liquid.     

Artifact Reduction Based on Sinogram Interpolation for the 3D Reconstruction of Nanoparticles Using Electron Tomography

Electron tomography is a well‐known technique providing a 3D characterization of the morphology and chemical composition of nanoparticles. However, several reasons hamper the acquisition of tilt series with a large number of projection images, which deteriorate the quality of the 3D reconstruction. Here, an inpainting method that is based on sinogram interpolation is proposed, which enables one to reduce artifacts in the reconstruction related to a limited tilt series of projection images. The advantages of the approach will be demonstrated for the 3D characterization of nanoparticles using phantoms and several case studies.     

3DSEM++: Adaptive and intelligent 3D SEM surface reconstruction

Structural analysis of microscopic objects is a longstanding topic in several scientific disciplines, such as biological, mechanical, and materials sciences. The scanning electron microscope (SEM), as a promising imaging equipment has been around for decades to determine the surface properties (e.g., compositions or geometries) of specimens by achieving increased magnification, contrast, and resolution greater than one nanometer. Whereas SEM micrographs still remain two-dimensional (2D), many research and educational questions truly require knowledge and facts about their three-dimensional (3D) structures. 3D surface reconstruction from SEM images leads to remarkable understanding of microscopic surfaces, allowing informative and qualitative visualization of the samples being investigated. In this contribution, we integrate several computational technologies including machine learning, contrario methodology, and epipolar geometry to design and develop a novel and efficient method called 3DSEM++ for multi-view 3D SEM surface reconstruction in an adaptive and intelligent fashion. The experiments which have been performed on real and synthetic data assert the approach is able to reach a significant precision to both SEM extrinsic calibration and its 3D surface modeling.     

非球形颗粒布朗运动的涨落-格子Boltzmann数值研究

采用涨落-格子Boltzmann方法对非球形颗粒(二维)的布朗运动进行直接数值模拟.数值结果包括椭圆形、矩形颗粒的速度均方值及速度自相关函数等.研究发现,对于非球形颗粒,其方向性并没有影响能量均分原理的适用性,每个自由度的能量由其速度或角速度的均方值确定,而且计算的颗粒平动温度和转动温度一致.此外,颗粒的速度自相关函数在相对长的时间内以~ct^-1的规律衰减,其系数c与颗粒的形状无关.     

基于Simulink和VR技术的三维空间电子运动研究

以电子示波器中电子的运动模型为例,探讨了结合Simulink软件和虚拟现实编程语言在虚拟物理实验中应用问题。通过虚拟现实编程语言创建电子运动环境的三维模型,利用Simulink构建了较为完善的、严格遵循客观物理定律并且不以人的主观意识改变的仿真系统。给出了电子在三维空间运动的动画,和不同频率比的李萨如图形。体现出Simulink虚拟现实工具箱仿真物理实验的便捷性、可靠性和科学性。