Atomic Force Microscope

Arrays of atomic force microscope (AFM) probes were developed for applications of dip-pen nanolithography (DPN), which is capable of surface patterning with functionalized bio-molecules and can be used to construct biological and chemical ...

The atomic force microscope ( AFM) ' is able to image the surfaces of conducting and nonconducting materials with very high vertical and lateral resolution. It is cur-rently being used in a variety of scientific and technological applications.2 The AFM works by bringing a cantilever in ...

The present study was based on assessments of the anti-parasitic activities of the hematophagous (blood feeding) larvae of malaria vector, Anopheles subpictus Grassi, filariasis vector, Culex quinquefasciatus, Say (Diptera: Culicidae), and the larvae of cattle tick Rhipicephalus (Boophilus) microplus, Canestrini (Acari: Ixodidae). The metallic copper nanoparticles (Cu NPs) synthesized by polyol process from copper acetate as precursor and Tween 80 were used as both the medium and the stabilizing reagent. The efficacy of synthesized Cu NPs was tested against the larvae of blood-sucking parasites. UV-vis spectra characterization was performed, and peak was observed at 575 nm, which is the characteristic to the surface plasmon bond of Cu NPs. The strong surface plasmon absorption band observed at 575 nm may be due to the formation of non-oxidized Cu NPs. X-ray diffraction (XRD) spectral data showed concentric rings corresponding to the 26.79 (111), 34.52 (200), and 70.40 (220) reflections. XRD spectrum of the copper nanoparticles exhibited 2θ values corresponding to the copper nanocrystal. No peaks of impurities are observed in XRD data. The scanning electron micrograph (SEM) showed structures of irregular polygonal, cylindrical shape, and the size range was found to be 35–80 nm. The size of the Cu NPs was measured by atomic force microscope (AFM) in non-contact mode. For imaging by AFM, the sample was suspended in acetone and spins coated on a silicon wafer. The line profile image was drawn by the XEI software and the horizontal line at 6 μm on a 2D AFM image. Research has demonstrated that metallic nanoparticles produce toxicity in aquatic organisms that is due largely to effects of particulates as opposed to release of dissolved ions. Copper acetate solution tested against the parasite larvae exposed to varying concentrations and the larval mortality was observed for 24 h. The larval percent mortality observed in synthesized Cu NPs were 36, 49, 75, 93,100; 32, 53, 63, 73, and 100 and 36, 47, 69, 88, 100 at 0.5, 1.0, 2.0, 4.0, and 8.0 mg/L against A. subpictus, C. quinquefasciatus and R. microplus, respectively. The larval percent mortality shown in copper acetate solution were 16, 45, 57, 66 and 100, 37, 58, 83, 87, and 100 and 41, 59, 79, 100, and 100 at 10, 20, 30, 40, and 50 mg/L against A. subpictus, C. quinquefasciatus, and R. microplus, respectively. The maximum efficacy was observed in Cu NPs and copper acetate solution against the larvae of A. subpictus, C. quinquefasciatus, and R. microplus with LC50 and r 2 values of 0.95 and 23.47, 1.01 and 15.24, and 1.06 and 14.14 mg/L with r 2 = 0.766; 0.957 and 0.908; 0.946; and 0.816 and 0.945, respectively. The control (distilled water) showed nil mortality in the concurrent assay. The chi-square value was significant at p ≤ 0.05 level. This is the first report on anti-parasitic activity of the synthesized Cu NPs and copper acetate solution.

Hollow fiber membranes for hemodialysis were prepared from polyethersulfone (PES) and poly(vinyl pyrrolidone) (PVP) (PES/PVP=18/3 and 18/6 by weight) solution in N,N-dimethylacetamide by the dry wet spinning method. Hollow fibers were then heated either in hot water (95 °C for 30 min) or in air (150 °C for 5 min). These membranes were characterized by ultrafiltering dextrans of different molecular weights (200 ppm in water) at room temperature and an operating pressure of 5 psig. It was observed that the water flux of the hollow fiber increased significantly when heat-treated in water, while decreased when heat-treated in air. On the other hand, molecular weight cut-off (MWCO) of the hollow fiber increased slightly when heat-treated in water, while decreased drastically when heat-treated in air. The morphology of the surfaces of the hollow fibers was studied by atomic force microscope (AFM) in terms of surface roughness. The roughness of both inner and outer surface decreased upon heat-treatment, either heated in water or in air. The membrane heat-treated in air exhibited the lowest roughness parameter. SEM images also showed that the surface morphology of membranes was different before and after heat-treatment. Discussions are made on the basis of MWCO and AFM results. The performance data of the hollow fiber heated in air at 150 °C was found to be the most appropriate for hemodialysis application. The hollow fiber membrane prepared from the blend ratio of PES/PVP=18/3 showed slightly higher flux than the hollow fiber membrane prepared from a solution with PES/PVP ratio of 18/6.

This thesis reports on electron transport and the magnetization dynamics of crystalline multilayers grown on Fe-whiskers(001) and clean GaAs(001) wafers by means of molecular beam epitaxy (MBE). The high quality magnetic multilayers with well defined interfaces are required to allow one to compare quantitatively the experimental results with the theoretical predictions. The electrical properties of crystalline Fe/MgO/Fe-whisker structures were characterized by in-situ scanning tunneling spectroscopy. Far mast of the scanned area, the tunneling I-V characteristics have revealed a tunneling barrier of 3.6 V which corresponds to the perfect MgO layer. At negative bias voltages, the localized spikes in the tunneling current have been observed indicating ballistic transport in crystalline tunnel junctions. Kerr microscopy has shown, that the magnetization of Fe-whisker and Fe film are coupled via stray field of the Fe-whisker domain wall. Atom force microscope (AFM) operating in an exter...

It is well known that functional surfaces in microelectronics and optics can be inspected very fast with scatterometers or scatter sensors. However, there is an increasing interest in looking at specific sample areas in more detail, i.e., the micro topography of the surface has to be measured. Since far-field optical profilers are diffraction limited, the means of choice are very often Scanning Probem Microscopes (SPMs), and namely, Atomic Force Microscopes (AFMs). Various methods for processing data obtained by AFMs will be discussed. An AFM measurement should deliver the surface micro topography to enable the determination of characteristic values, in particular rms roughness. Normally, a superposition of the surface characteristics and artifacts due to the AFM is obtained.

Atomic force microscope images show that self-assembled monolayers of octadecyltrichlorosilane form on mica by nucleating isolated, self-similar domains. With increasing coverage, the fractal dimension of the growing domains evolves from 1.6 to 1.8. At higher coverage, continued growth is limited by adsorption from solution. Monte Carlo simulations that include, for the first time, adsorption as well as surface diffusion qualitatively