Transmission electron microscopy adhesion

Many years have passed since the early days of AFM, when adhesion was seen as a hindrance, and it is now regarded as a useful parameter for identification of material as well as a key to understanding many important processes in biological function. In this area, the ability of AFM to map spatial variations of adhesion has not yet been fully exploited but in future could prove to be particularly useful. At present, the chemical nature and interaction area of the AFM probe are still rarely characterized to a desirable level. This may be improved dramatically by the use of nanotubes, carbon or otherwise, with functionalized end groups. However, reliance on other measurement techniques, such as transmission electron microscopy and field ion microscopy, will probably be essential in order to fully evaluate the tip-sample systems under investigation. 

The important role Transmission Electron Microscopy (TEM) can play in this process is demonstrated on the development of an oxidation catalyst for the production of acrylic acid. Acrylic acid is produced by BASF in quantities of several 100.000 tons per year in a two step gas phase oxidation process starting from propene, which is oxidised to acrolein in the first step and then further oxidised to acrylic acid in a second step, each step requiring a special developed catalyst. Acrylic acid is used as a base material for the production of superabsorbents for nappies, dispersions and emulsions for adhesives and construction materials. 

Mieroscopic visualization techniques have also been used to investigate mucus-polymer interactions [36-39]. Transmission electron microscopy was used by Fiebrig et al. [36], whereas different microscopical techniques were used by Lehr et al. [37] for the visualization of mucoadhesive interfaces. Transmission electron microscopy in combination with near-fleld Fourier transform infrared microscopy (FT-IR) has been shown to be suitable for investigating the adhesion-promoting effect of polyethyleneglycol added in a hydrogel [38]. Moreover, scanning force microscopy may be a valuable approaeh to obtain information on mueoadhesion and specific adhesion phenomena [39]. 

The adhesion protein FimH mediates the attachment of uropathogenic E. coli strains with the host cell glycocalyx and specifically recognizes mannosylated structures. In 2002, Lin et al. first demonstrated that the glyco-AuNP can be used as a probe for staining the binding protein on the cell surface through carbohydrate-receptor interactions [67], Man-AuNPs were used to visualize the FimH adhesins on the type I pili of E. coli via transmission electron microscopy. 

Transmission Electron Microscopy (TEM) has been used to characterize aluminum thin films thermally evaporated (vacuum around 10 4 Torr) on Polyethyleneterephtalate (Mylar) and to correlate the crystallographic structure of the system Al/Mylar and the adhesion of the aluminum films. The adhesion of these films has been measured by a Peel test technique. For the polymer, an amorphous layer (t=12 nm) followed by a crystalline film have been observed on a Corona treated film and the opposite configuration has been found on a bi-axially stretched film. Some spherical precipitation ana interdiffusion zones have also be observed in the Mylar for the films which have the lower coefficient of adhesion (100 g/inch). The main conclusion is the augmentation of the adhesion of the aluminum film as the size of the grains decreases and/or as the microroughness of the Al/Mylar interface increases. 

For example, glomerular microvascular endothelial cells in culture should maintain the characteristic fenestration, the presence of Weibel-Palade bodies (both observed by transmission electron microscopy), the basal expression of von Willebrand factor and CD 31 (plate-let-endothelial cell adhesion molecule-1) and the binding of lectin Ulex Europaeus (for human cells) [18,19]. 

Mondragon et al ° reported that unmodified and modified NR latex were used to prepare thermoplastic starch/NR/MMT nanoeomposites by twin-screw extrusion. After drying, the nanoeomposites were injection moulded to produce test specimens. SEM of fractured samples revealed that chemical modification of NR latex enhanced the interfacial adhesion between NR and thermoplastic starch (TPS), and improved their dispersion. X-ray diffraction (XRD) showed that the nanoeomposites exhibited partially intercalated/exfoKated structures. Surprisingly, transmission electron microscopy (TEM) showed that clay nanoparticles were preferentially intercalated into the rubber phase. Elastic modulus and tensile strength of TPS/NR blends were dramatically improved from 1.5 to 43 MPa and from 0.03 to 1.5 MPa, respectively, as a result of rubber modification. 

The morphology of the surface has been studied by transmission Electron microscopy Under optimum conditions, it consists of a cell structure with oxide whiskers protruding fi om the surface." It has been suggested that microscopic interlocking (see Mechanical theory of adhesion) appears to be a crucial factor in the adhesion." It may be that the sensitivity to processing conditions, mentioned above, is a result of the production of a morphology with less potential for interlocking. 

Surface analysis such as dynamic contact angle and surface tension are used to ensure proper wetting of epoxy and the substrate. Microscopic techniques, such as scanning electron microscopy (SEM), transmission electron microscopy (TEM), and atomic force microscopy (AFM), are widely used to study morphology, fracture, and adhesion issues of cured epoxy systems. Chemical analysis techniques, such as micro-IR, X-ray photoelectron spectrometry (XPS), and secondary ion mass... 

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