Molecular scanning transmission electron

Powdered, particulate MCM-41 molecular sieves (Si/Al = 37) with varied pore diameters (1.80, 2.18, 2.54 and 3.04 nm) were synthesized following the conventional procedure using sodium silicate, sodium aluminate and C TMAB (n = 12, 14, 16 and 18) as the source materials for Si, A1 and quaternary ammonium surfactants, respectively [13]. Each sample was subjected to calcination in air at 560 °C for 6 h to remove the organic templates. The structure of the synthesized material was confirmed by powder X-ray diffraction (XRD) and by scanning/transmission electron microscopy. Their average pore sizes were deduced from the adsorption curve of the N2 adsorption-desorption isotherm obtained at 77 K by means of the BJH method (Table 1). 

Tribet C., Mills D., Haider M., Popot J.-L. Scanning transmission electron microscopy study of the molecular mass of amphipol/cytochrome b6f complexes. Biochimie 1998 80 475-482. 

As the pH of a suspension increases further, the potential decreases again, revealing another point of potential reversal at PZR 3. A careful analysis of the data indicated that the surface-induced adsorption of the molecular Al(OH)3 and the subsequent formation of the hydroxylated aluminum surface sites are responsible for the PZR 3 [44], Figure 11a is a scanning transmission electron micrograph of the cordierite core coated with the aluminum hydroxide layer of approximately 15 nm thickness. The uniform surface-induced coating of ultra-fine scale aluminum hydroxide was achieved by an excess addition of aluminum salt [e.g., A1(N03)3] to the suspension at a pH below the PZR 2 and... 

Engel A. (1978), Molecular weight determination by scanning transmission electron microscopy. 

Hamilton, M. G., Herskovits, T. H., Furcinitti, P. S., and Wall, J. S. (1989). Scanning transmission electron microscopic study of molluscan hemocyanins in various aggregation states. Comparison with light scattering molecular weights. J. UltrastrucL MoL Struct. Res. 102,221-228. ... 

In the author s opinion, the better approach to experimentally study the morphology of the silica surface is with the help of physical adsorption (see Chapter 6). Then, with the obtained, adsorption data, some well-defined parameters can be calculated, such as surface area, pore volume, and pore size distribution. This line of attack (see Chapter 4) should be complemented with a study of the morphology of these materials by scanning electron microscopy (SEM), transmission electron microscopy (TEM), scanning probe microscopy (SPM), or atomic force microscopy (AFM), and the characterization of their molecular and supramolecular structure by Fourier transform infrared (FTIR) spectrometry, nuclear magnetic resonance (NMR) spectrometry, thermal methods, and possibly with other methodologies. 

Electron microscopy, with its high spatial resolution, plays an important role in the physical characterization of these catalysts. Scanning electron microscopy (SEM) is used to characterize the molecular sieve particle sizes and morphologies as a function of preparation conditions. Transmission electron microscopy (TEM) is used to follow the changes in the microstructure of the iron silicates caused by different growth conditions and subsequent thermal and hydrothermal treatments. 

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