Sample processing of electron microscope

Biological samples must be pretreated before being observed by perspective electron microscope. With the needs of different research requirements, scientists have adopted different treatment methods. Fixation: In order to preserve the original sample as much as possible, the sample was hardened with glutaraldehyde and the fat was dyed with osmium acid. Cold fixation: put the sample into liquid ethane for quick freezing, so that water will not crystallize to form amorphous ice. The samples stored in this way are less damaged, but the contrast of the image is very low. Dehydration: Use ethanol and acetone instead of water. Filling: The sample can be divided after being filled. Segmentation: Slice the sample with a diamond blade. Dyeing: Heavy atoms such as lead or uranium have higher electron scattering ability than light atoms, so they can be used to improve contrast. Before observing the metal with a perspective electron microscope, the sample shall

It is cut into very thin slices (about 0. 1 mm), and then the metal is thinned by electrolytic polishing. Finally, a hole is usually formed in the center of the sample, and electrons can pass through the very thin metal near this hole. Metals that cannot be polished by electrolysis or non-conductive or poorly conductive substances (such as silicon) are usually thinned by mechanical methods first, and then treated by ion impact. In order to prevent non-conductive samples from accumulating static electricity in scanning electron microscope, it is necessary to cover their surfaces with a conductive layer.