Scanning electron microscopy interface structures

Modern surface analytical tools make it possible to probe the physical structure as well as the chemical composition and reactivity of interfacial supramolecular assemblies with unprecedented precision and sensitivity. Therefore, Chapter 3 discusses the modern instrumental techniques used to probe the structure and reactivity of interfacial supramolecular assemblies. The discussion here is focused on techniques traditionally applied to the interrogation of interfaces, such as electrochemistry and scanning electron microscopy, as well as various microprobe techniques. In addition, some less common techniques, which will make an increasing contribution to supramolecular interfacial chemistry over the coming years, are considered. 

This review covers the formation, composition, structure, function and properties of the acquired pellicle. Specifically, the formation of pellicle is considered in terms of thermodynamic and kinetic aspects. The composition of the pellicle is reviewed in terms of the proteins, carbohydrates and lipids that have been identified using a range of analytical techniques. The ultrastructure of the pellicle is described in some detail from studies involving enamel slabs carried in the mouth, in which the subsequent pellicle was analysed by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and confocal laser scanning microscopy (CLSM). The function of the pellicle is outlined in terms of its lubrication properties, its ability to act as a semi-permeable membrane and its overall protection of the underlying enamel surfaces. Since pellicle is formed at the interface between the enamel surface and the oral environment, the important process of bacterial attachment to the pellicle surface is described and the specific bacterial binding sites found in the pellicle are summarised. The influence of diet and nutrition on the pellicle layer is considered. The formation of extrinsic stain is discussed in particular, the role that chlorhexidine... 

Analysis methods, used for the investigation of modified surfaces and interfaces, are briefiy reviewed. Emphasis is on the combination of chemical, structural/ morphological, electronic, and optical characterization. Many techniques such as transmission electron microscopy (TEM), standard X-ray photoelectron spectroscopy (XPS) using A1 or Mg K radiation, high-resolution scanning electron microscopy (HRSEM), and standard scanning probe microscopies (AEM in contact... 

Both transmission electron microscopy (TEM) and scanning electron microscopy (SEM) have been used to determine structural features of various polymer-silica systems. Electron microscopic techniques generally provides information on the nature of the filler, average particle size, or the distribution of particle sizes, smoothness of the interfaces, and the degree of agglomeration of particles. 

Some diffusion studies have also been undertaken for compatible systems. Two-phase systems have been annealed and the disappearance of structure observed by microscopy. In another experiment, layers of PVC and poly-caprolactone were contacted and heated at 90 °C. Scanning electron microscopy with chlorine analysis was used to measure diffusion at the interface. Perhaps surprisingly, the results suggest a dependence on (molecular weight). More commonly the diffusion constant scales as (molecular weight)" ... 

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