Direct Imaging of Tunable Crystal Surface Structures of MOF MIL-101 Using High-Resolution Electron Microscopy

2019 ◽  
Vol 141 (30) ◽  
pp. 12021-12028 ◽  
Author(s):  
Xinghua Li ◽  
Jianjian Wang ◽  
Xin Liu ◽  
Lingmei Liu ◽  
Dongkyu Cha ◽  
...  

The value of high-resolution electron microscopy as a technique in coal science and technology is illustrated by reference to the study of the onset, on heating, of the crystallinity of relatively unstructured coals and carbonaceous solids; by the detection of changes, upon use, that occur in hydrodesulphurization catalysts; and by the direct imaging of structural features in ( a ) metal catalysts supported on graphitic carbons and ( b ) graphite intercalates of the kind known to be potentially useful in Fischer-Tropsch and related syntheses, which are commercially viable in the conversion of coal to petrols and chemicals. The technique is also capable of imaging directly the structure of a range of zeolites, including the A, X and Y types, and the ZSM-5 zeolitic catalysts, which figure eminently in the conversion of methanol to petrol. The advantages of high-resolution microscopy, compared with X-ray based methods for the problems peculiar to coal science, are stressed.


Author(s):  
W. H. Wu ◽  
R. M. Glaeser

Spirillum serpens possesses a surface layer protein which exhibits a regular hexagonal packing of the morphological subunits. A morphological model of the structure of the protein has been proposed at a resolution of about 25 Å, in which the morphological unit might be described as having the appearance of a flared-out, hollow cylinder with six ÅspokesÅ at the flared end. In order to understand the detailed association of the macromolecules, it is necessary to do a high resolution structural analysis. Large, single layered arrays of the surface layer protein have been obtained for this purpose by means of extensive heating in high CaCl2, a procedure derived from that of Buckmire and Murray. Low dose, low temperature electron microscopy has been applied to the large arrays.As a first step, the samples were negatively stained with neutralized phosphotungstic acid, and the specimens were imaged at 40,000 magnification by use of a high resolution cold stage on a JE0L 100B. Low dose images were recorded with exposures of 7-9 electrons/Å2. The micrographs obtained (Fig. 1) were examined by use of optical diffraction (Fig. 2) to tell what areas were especially well ordered.


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