扫描探针制备技术的研究现状及发展

探讨了近几年来探针制备技术的发展和趋势,分别就探针检测性能的改进、探针结构、探针检测功能拓展及多通道信息采集组合探针等几方面,对相关制备技术的方法、特点以及相应检测条件、适用环境展开讨论,这些方面反映探针制备技术正朝着尖锐化、多样化、功能化和组合方向发展。     

TbFe磁性薄膜的磁力显微镜成像研究

利用磁力显微镜（MFM）对TbFe磁性薄膜进行了不同抬举距离（分别为60～780nm）的磁力成像研究．在实验中，比较了低抬举距离（100nm以下）磁力像中样品-针尖的互相干扰；同时发现在高抬举距离磁力像中，随着抬举距离的增大，出现了与高凸起形貌对应的图像衬度特征，并随抬举距离的变化也改变着位置与强度，一直到抬举距离为仪器的极限值780nm时，形貌干扰仍未消失，对其形成机制进行了分析．     

Polyamide-6/vegetal fiber composite prepared by extrusion and injection molding

The interest for the use of vegetal fibers as polymers reinforcement has recently increased because of their unique environmental and technological advantages. This work evaluated the use of Curauá fibers in polyamide-6 composites aiming at glass fiber replacement. Fiber content of 20, 30 or 40 wt% and fiber lengths of 0.1 or 10 mm were studied. Fibers were treated with N₂ plasma or washed with NaOH solution, to improve their adhesion to PA-6. Samples with 20 wt% of short or long fibers, with or without pre-treatment, were compounded in two different co-rotating intermeshing twin-screw extruders. These samples were submitted to mechanical and thermal tests. In conclusion, non-dried raw materials improved fiber/matrix interfacial adhesion. Tensile and flexural properties of this composite are better than unfilled, but lower than glass fiber reinforced polyamide-6. However, its impact resistance and heat deflection temperature are similar to the glass fiber reinforced polyamide-6 and its lower density, enable it to replace this latter in specific non-critical applications.     

Investigation of the Correlation between Texture and Microstructure on a Submicrometer Scale in the TEM

In recent years the investigation of local texture and microstructure by analysis of electron backscatter diffraction patterns (EBSP) in the SEM has become a very powerful and popular method. With the introduction of SEM with field emission guns (FEG) the spatial resolution of EBSP measurements could be enhanced from 500 nm with a tungsten emitter to better than 50 nm. This evolution of SEM techniques raises the question whether transmission electron microscopy (TEM) still has fields of application in texture research. The present article answers this question with a clear “yes” and presents three examples of investigations where TEM is indispensable. The three examples comprise the investigation of the correlation between dislocation structure and deformation texture, a study on nucleation mechanisms of recrystallization in highly deformed metals and the investigation of microtexture and microstructure in nanocrystalline materials. Together with the presentation of these cases some of the necessary measurement techniques are described briefly. It is shown that TEM has to be applied when highest spatial resolution of orientation determination and imaging and high accuracy of orientation determination are to be reached, when the three‐dimensional and quantitative characterization of lattice defects is required or when materials with a high density of lattice defects are to be investigated.     

Young’s modulus of crystalline C60 nanotubes studied by in situ transmission electron microscopy

Bending tests of crystalline nanotubes composed of fullerene C₆₀ molecules are performed inside a high-resolution transmission electron microscope. We fixed one side of a C₆₀ nanotube with a body-centered tetragonal structure with typical inner and outer diameters, i.e., 180 nm and 510 nm, respectively, and then applied concentrated forces on the other side using piezomanipulation of a silicon nanotip. The bending process was observed in situ by transmission electron microscopy with simultaneous measurements of the forces by an optical deflection method. It was found that the Young’s modulus of the nanotube was estimated to be 62–107 GPa, which was 1.1–3.3 times larger than that of C₆₀ nanowhiskers. The result concerning the increase in the Young’s modulus of the C₆₀ nanotube provided an experimental evidence for the structural model composed of an inner core and a surface shell for C₆₀ nanowhiskers.     

Multiwalled Nanotubes: Their Formation by Irradiating Graphite with High Doses of Electrons

We report the production of carbon nanotubes by high dose of electron irradiation. The irradiation was performed with a 2 MeV Van de Graaff accelerator, while the irradiation conditions were the following: voltage 1.3 MeV, current 5 µA, dose rate 25 kGy/min, and total dosage 1000 kGy. The samples were analyzed in a high-resolution transmission electron microscope. The main features observed on the samples, were huge nanotubes of several nanometer long and few nanometer wide, which are capped at one end. It is good to point out, that at this level of irradiation, we were not able to find either onion-like or particle structures throughout the material, as it is usual in similar hexagonal structures. This behavior could be attributed to the level of irradiation used to create the nanotubes under investigation.     

Quantification of the layer dispersion degree in polymer layered silicate nanocomposites by transmission electron microscopy

As the performance of polymer layered silicate nanocomposites strongly depends on their interior layer dispersion, quantification of the layer dispersion degree is needed. In this work, a new methodology was developed to determine the dispersion parameter D_0.1, based on the measurement of the free-path spacing distance between the single clay sheets from the transmission electron microscopy (TEM) images. Several examples of exfoliated, intercalated, and immiscible composites were studied. It was found that the exfoliated composites had D_0.1 over 8%, while that of intercalated composites were between 4 and 8%. In the case of intercalation, a high frequency peak appeared at a short spacing distance in the histogram, which was a characteristic of the intercalation, distinct from the exfoliation. The main utility of this TEM methodology is for the quantification of exfoliated or intercalated samples with small number of layers with stacks. The dispersion parameter D_0.1 below 4% was suggested to classify as immiscible. A unique advantage of the TEM measurement is that the dispersion degree of different fillers can be counted individually.     

Focal adhesion interactions with topographical structures: a novel method for immuno-SEM labelling of focal adhesions in S-phase cells

Current understanding of the mechanisms involved in osseointegration following implantation of a biomaterial has led to adhesion quantification being implemented as an assay of cytocompatibility. Such measurement can be hindered by intra-sample variation owing to morphological changes associated with the cell cycle. Here we report on a new scanning electron microscopical method for the simultaneous immunogold labelling of cellular focal adhesions and S-phase nuclei identified by BrdU incorporation. Prior to labelling, cellular membranes are removed by tritonization and antigens of non-interest blocked by serum incubation. Adhesion plaque–associated vinculin and S-phase nuclei were both separately labelled with a 1.4 nm gold colloid and visualized by subsequent colloid enhancement via silver deposition. This study is specifically concerned with the effects microgroove topographies have on adhesion formation in S-phase osteoblasts. By combining backscattered electron (BSE) imaging with secondary electron (SE) imaging it was possible to visualize S-phase nuclei and the immunogold-labelled adhesion sites in one energy 'plane' and the underlying nanotopography in another. Osteoblast adhesion to these nanotopographies was ascertained by quantification of adhesion complex formation.     

In vivo confocal microscopy of human skin: A new design for cosmetology and dermatology

In-depth exploration of cellular structures in living human skin in situ is possible with the tandem scanning microscope (TSM). However, the rigid design of the microscope limited observations to the arms, hands, and fingers. A mobile version allowing the investigation of any parts of the body has been designed. The head containing the Nipkow disk and the optical path were the only part saved from the original TSM. This prototype can be used to observe, in real time, the different skin structures down to a depth of 200 μm and to measure the thickness of the different layers with micron precision level. The hydration of the stratum corneum (SC) could be assessed. For example, lengthy immersion of the hand in water led to an increase in SC thickness without affecting that of the living epidermis. Occlusive patch tests also showed that water and, even more so, propylene glycol, led to transient swelling of the SC. In dermatology, the example of psoriasis illustrated the value of the TSM for describing, measuring, and assessing pathologic skin changes. The availability of this noninvasive method for observing changes with time in a given skin site should prove useful for monitoring treatment efficacy. This tool opens up new insight for the investigation of cutaneous pathophysiology.     

Vitrification of aqueous suspensions from a controlled environment for electron microscopy: An improved plunge-cooling device

In the process of vitrifying aqueous suspensions for cryotransmission electron microscopy, water is solidified without crystallization. Vitrification can be achieved by rapidly plunging an aqueous thin film into a liquid cryogen. The preparation of aqueous thin films prior to vitrification must be performed in an environmental cabinet at controlled temperature and humidity in order to prevent evaporation and temperature-induced phase changes in the thin film. The device described here incorporates several important features which make the apparatus simpler and more convenient to use than similar devices described in the literature. One of these features includes the use of a totally enclosed environmental cabinet in which the grid, sample, micropipette and absorbent paper are equilibrated before thin-film preparation. Other features include a cryogen dewar on a swing arm for easy refilling, a guillotine shutter which is used to trigger the plunger electrically and a semiautomatic system which facilitates rapid transfer of the vitrified specimen from liquid propane to liquid nitrogen for storage and reduces handling of the specimen. To demonstrate the utility of the device, results showing the influence of temperature on the morphology of phospholipid vesicles are presented. A commercial cryotransfer apparatus (which is used for transportation of the vitrified specimen to the electron microscope cold-stage) has been modified to reduce the possibility of reversion of the vitreous phase to the crystalline ice phases.