Dark scanning transmission microscopy

High-Angular Annular Dark-Field Scanning Transmission Electron Microscopy... 

Figures 2a, 2b, 2c, and 2d represent the morphology of the 25/75 (PC-PST) blend. PST forms the continuous phase and the dispersed spherical PC particles show some aggregation (Figure 2a). From the transmission electron micrographs (Figures 2b and 2c) it can be seen that small PST particles are present in the dispersed PC phase. Examination of the etched fracture surface by scanning electron microscopy reveals depressions of completely removed PC particles as well as spheres with dark periphery because of partial hydrolysis of PC (Figure 2d).

Improved annular dark field detectors for the scanning transmission electron microscopes may assist in detecting lnm crystallites. For tailoring a catalyst to a specific reaction, one must be able to relate the structure of the site to catalytic activity and selectivity. Possibly future developments in high resolution electron microscopy will address this problem. 

Figure 4 (a) Low-resolution scanning transmission electron microscopy (STEM) image of a thin sol-gel film (1 -2 layers) containing 5 nm CdSe NCs. The NCs appear in white, and the dark areas are pores, (h) Linear absorption (solid line) and PL (dashed line) spectra of as-prepared CdSe NCs (r = 2.5 nm) in a hexane solution (the arrow marks the lowest IS absorption resonance), (c) Absorption and PL spectra of the same NCs after their incorporation into titania... 

FIG. 9 Dark-field scanning transmission electron microscopy image of an unstained cytochrome b6f complexed with the amphiphilic short poly anions A8-75 (a C8 modified poly(acrylic acid) of 8000). Dark bar tobacco mosaic virus added as an internal standard of diameter 18 nm. Dots complexes of diameter ca. 10-15 nm. Reprinted from Ref. 71. Copyright 1998 with permission from Elsevier.)... 

The electron microscopes can be divided into two types (166) scanning electron microscopes (SEM), which use a 10-nm electron beam at the specimen surface, and transmission electron microscopes (TEM). With current TEMs, resolution of about 0.2 nm can be achieved, provided very thin (<20 nm) samples are available. With conventional inorganic oxide-supported metal catalysts, particles of approximately 1 nm can be detected. Scanning transmission electron microscopes (STEM) use a high brightness dark-field emission gun to produce a probe about 0.3 nm in diameter and combine the techniques of SEM and TEM. Further experimental and theoretical aspects of electron microscopy applied to catalysis have been reviewed recently (113, 167-169). 

Menard, L. D., Gao,S. P, et al. Sub-Nanometer Au Monolayer-Protected Clusters Exhibiting Molecule-like Electronic Behavior Quantitative High-Angle Annular Dark-Field Scanning Transmission Electron Microscopy and Electrochemical Characterization of Clusters with Precise Atomic Stoichiometry."The Journal of Physical Chemistry B,110(26), 12874-12883 (2006). 

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