Ultrathin case studies

Transmission electron microscopy of ultrathin sections and confocal laser scanning microscopy were used to study the distribution of proteins within polyelectrolyte microcapsules. Since obtaining quality images using transmission electron microscopy is possible in case studies of electron dense objects, the iron containing protein, ferritin, with a value of p/ 4.7, was selected for encapsulation. Polyelectrolytes polyallylamine (PAA) and polystyrene (PSS) that were used have values of ioniza-... 

Mitochondria are present in all eukaryotic cells that use oxygen in respiration, but the number per cell and the form and size vary. Certain tiny trypanosomes have just one mitochondrion but some oocytes have as many as 3 x 10 . Mammalian cells typically contain several hundred mitochondria and liver cells more than 1000. Mammalian sperm cells may contain 50-75 mitochondria, but in some organisms only one very large helical mitochondrion, formed by the fusion of many individual mitochondria, wraps aroimd the base of the tail. Typical mitochondria appear to be about the size of cells of E. coU. However, study of ultrathin serial sections of a single yeast cell by electron microscopy has shown that, under some growth conditions, all of the mitochondria are interconnected. In every case a mitochondrion is enclosed by two... 

As shown in Chapter 2, to optimize the contrast in the IR spectrum of an ultrathin film, it is necessary in many cases to use nonnormal angles of incidence and p-polarized radiation, which creates specific difficulties in the interpretation of the spectrum. The problems stem from the appearance of additional bands in the spectra of samples that are small relative to the wavelength these bands are due to the surface charges resulting from the polarization of the samples. The dependence of the transverse vibrational frequency of a polar crystal on the crystal size, called the size effect, was discovered by Frohlich [2]. A convincing explanation of this effect in the IR spectra of thin films was presented in 1963 by Berreman [3] while studying the transmission of 325-348-nm LiF layers. Consequently, this size effect in the IR spectra of ultrathin films became known as the Berreman effect by Harbecke et al. [4]. 

Enhancement of absorption bands in the IR spectra of ultrathin films in the presence of discontinnons (islandlike) nnder- and ovemanolayers of Ag and An was discovered by Hartstein et al. [356] in the early 1980s. Although these researchers believed that they observed an increase in the vCH band intensities for p-nitro-benzoic acid (p-NBA), benzoic acid, and 4-pyridine-COOH films, it was recently shown [350] that the spectra reported are in actual fact due to fully saturated hydrocarbons (possibly vacuum pump oil). In any case, this discovery has stimulated various research activities and led to the development of surface-enhanced IR absorption (SEIRA) spectroscopy. To date, the SEIRA phenomenon has been exploited in chemical [357] and biochemical IR sensors (see [357-360] and literature therein), in studying electrode-electrolyte interfaces [171, 361-365], and in LB films and SAMs [364, 366-370]. Other metals that demonstrate this effect are In [371] and Cu, Pd, Sn, and Pt [372-375]. The metal films can be prepared by conventional metal deposition procedures such as condensation of small amounts of metal vapor on the substrate, spin coating of a colloidal solution, electrochemical [388], or reactive deposition [299] (see also Section 4.10.2). 

The important information that can be provided by IR spectra is the molecular orientation in/on polymer films, which include SAMs as the specific case (Section 3.11). In the case of self-supporting anisotropic films, the linear dichro-ism is usually calculated from normal-incidence transmission spectra measured at two mutually perpendicular positions of the polarizer [684], Obviously, this approach is insensitive to the modes perpendicular to the film surface. This problem is circumvented by using a combination of the normal-incidence transmission with metallic IRRAS [727], since these methods have complimentary selection rules — the modes whose TDMs are parallel or perpendicular to the surface are active in transmission or IRRAS, respectively. This technique was used to study the MO in ultrathin n-aUcylacrylamide LB films [727, 728]. A strong biaxial distribution was found in these LB films in which the carbon-hydrogen chains are inclined in the dipping direction [727]. 

To study the linear FME coupling in ferroelectrics-ferromagnets we consider the model case of one-dimensional distributions of the single-component polarization and magnetization inside an ultrathin nanotube with inner R, and outer radius Ro, where the tube thickness h = Ro —Ri is very small in comparison with the average tube radius R = 0.5(Ro + Ri), see Fig. 4.29a. This simple model can be useful as it allows analytical calculations of the average quantities, which are measured by majority of conventional experimental methods. 

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