Transmission electron microscopy background

Recently two different disciplines, chemical structural elucidation and transmission electron microscopy, were utilized in the study of pectin, with particular emphasis on tobacco pectin. The goal was to help bridge the gap between knowledge of their chemical structures to understanding the complex physical structures revealed by microscopy. To provide background on chemical structure, a study established that tobacco pectin was present as a series of related rhamnogalacturonans. 

The size and shape of dendrimers have been estimated using transmission electron microscopy [14]. Producing better images of dendrimers may supply answers to fundamental questions such as whether dendrimers have truly uniform sizes, spherical shapes, and dense cores. The visualization of dendrimer assemblies would also be helpful to confirm the structure and morphology for many applications of dendrimers. The positively stained PAMAM dendrimers are shown in Fig. 2 for G10 to G5, respectively. The dendrimer molecules appear as dark objects on a light background of the amorphous carbon substrate and they are well separated from each other. The shapes of the stained molecules are spherical to a first approximation for G10 to G7, with some molecules showing... 

The size and morphology of nanoparticles were examined by transmission electron microscopy (TEM) which provides maximum resolution of 0.7 nm. In the image shown in Fig. 1 the semiconductor nanoparticles appear as dark spots on the light background of the polymer matrix. 

In order to prepare oxide model systems well-suited for characterization by high-resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED), AFM or X-ray photoemission spectroscopy (XPS), as well as for kinetic studies by gas chromatography (GC), oxide films and oxide nanoparticles were vacuum-grown on a crystalline soluble substrate (e.g., NaCl(OOl)) via oxide (or metal) evaporation in a low background pressure ( 10" Pa) of oxygen. 

Nanoscopic Investigations of Dealloyed Surfaces Erom the background of competitive models of selective alloy dissolution as described above, a closer microscopic examination of this process with the ultimate objective of atomic resolution and chemical information on an atomic scale appears mandatory. Ex situ transmission electron microscopy (TEM) of thin, corroded alloy films provides lateral resolution at the nanometer scale, but suffers from poor depth resolution and from structural relaxation processes that may occur after termination of the anodic polarization and transferring the samples into high vacuum. Classical TEM investigations in this field were performed under open circuit conditions in oxidizing environments (that is, at > Eq) [51,... 

The background of the idea was our findings in previous work that conductive polymers are composed of more or less globular primary particles (Figure 1.3). We first found [6] that polyacetylene, even though apparently in a fibrillar morphology (as concluded from transmission electron microscopy), clearly showed a particle substructure with a particle size of 100 nm (Figure 1.4). 

Figure 5.70. A phase contrast optical micrograph (A) of an impact modified nylon shows the fine dispersion of modifier in the matrix. Transmission electron microscopy micrographs of a cryosection, stained with ruthenium tetroxide (B and C), show more detail and finely dispersed subinclusions (arrows) within the elastomeric phase. Scanning transmission electron microscopy (D) of an unstained cryosection shows less dense regions in a darker background due to mass loss of the rubber phase during exposure to the electron beam, resulting in contrast enhancement.

Fig. 3.4.8a-c. Transmission electron microscopy of a crocidol-ite asbestos fiber recovered from the lung tissue of an asbestos cement worker (a) with chemical composition spectrum (b) and selected area electron diffraction pattern (c). Copper peaks in the chemical spectrum are instrumental background... 

Figure C2.17.1. Transmission electron micrograph of a Ti02 (anatase) nanocrystal. The mottled and unstmctured background is an amorjihous carbon support film. The nanocrystal is centred in die middle of die image. This microscopy allows for die direct imaging of die crystal stmcture, as well as the overall nanocrystal shape. This titania nanocrystal was syndiesized using die nonhydrolytic niediod outlined in [79].

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