Imaging, interfacial

The SECM technique can image interfacial supramolecular assemblies so as to identify heterogeneities in their conductivity values. Information of this type is... 

A. Imaging Interfacial Aggregates by Atomic Force Microscopy... 

Briefly, AFM is a technique that maps the topography of a surface by plotting (on a color scale) the measured force between the surface and a small tip attached to a sensitive cantilever spring. In most applications, the tip is in direct contact with the surface, and the AFM performs as a sensitive contact profilometer. For imaging interfacial surfactant structures, however, contact forces disrupt the liquid crystalline aggregates. Therefore the repulsive colloidal stabilization forces between the surfactant layers adsorbed to the tip and sample are used as the contrast mechanism during imaging. 

Atomic force microscopy (AFM) [20] has recently been used to image interfacial aggregates directly, in situ and at nanometer resolution [21, 22], The key to this application lies in an unusual contrast mechanism, namely a pre-contact repulsive force ( colloidal stabilization force ) between the adsorbed surfactant layers on the tip and sample. In contrast to previous adsorbate models of flat monolayers and bilayers, AFM images have shown a striking variety of interfacial aggregates - spheres, cylinders, half-cylinders and bilayers - depending on the surface chemistry and surfactant geometry. I review the AFM evidence for these structures and discuss the possible inter-molecular and molecule-surface interactions involved. 

Fig. 4.29. EDXS line-profile analysis across the interfacial region of a C-fiber reinforced SiC composite and corresponding TEM bright-field image.

Visually, failure was mostly eohesive within the adhesive (see Figs. 34 and 46). However, there was a small area of apparent interfacial failure ( initiation zone ) located at one end of each substrate. Line scans were eondueted aeross the initiation zone, from the edge of the substrate to the area of cohesive failure within the adhesive. From the line scans, it was apparent that there were patehes of polymer present in the initiation zone, even when failure appeared to be interfaeial (see Fig. 46). SIMS images of the initiation zone were constructed for various mass numbers (see Figs. 47-49). The images showed well-defined cation-rieh... 

The spinning drop technique measures the shape of the oil drop in the flooding solution in a capillary tube. An automatic measuring system has been developed by combining a video-image analysis, an automatic recording system, and a computer for calculation of the interfacial tension [1865]. 

Fig. 6-22. Effect of interfadal excess charge, om, on the effective image plane, Xi , the shift of the plane of closest approach of water molecules, the inverse interfacial capadty on the metal side, 1 /Cm and the interfadal capacity on the solution side, Cs. M/vac = metaWacuum interface M/sol = metal/solution interface.

FIG. 28. The formation of upd layers often involves complex interactions between the anion, upd metal, and substrate. An example is provided by the (Vs X vVs) R30° STM image of the copper/sulfate upd layer formed on Au(lll) and the SXS of the interfacial structure. (Adapted from Refs. 148, 351, 353.)... 

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