How Electron Microscopy Samples Are Prepared
1. Projection method
Under vacuum conditions, the surface of the sample is sprayed with heavy metal atoms with strong electron scattering ability, so that a strong contrast is formed between the sample and the unsprayed area, and the unsprayed part becomes the projection of the sample. According to the projection, we The three-dimensional shape and height of the sample can be understood, and this method is usually used to observe the flagella of bacteria or particles of viruses.
2. Negative staining method
Because this method stains the background of the sample to highlight the sample, it is called negative staining. Generally, the sample is surrounded by a substance that has a high electron density, does not show any structure itself, and does not react with the sample, such as the sodium salt of phosphotungstic acid. The shape can also reflect the internal structure of the sample to a certain extent. In this way, bacterial cells, viruses, etc. can be observed.
3. Ultrathin section method
This is the most commonly used method because it allows the observation of fine structures inside cells or other samples. Usually it is necessary to fix the sample according to a certain procedure, dehydrate it, then embed it in resin as a support, and cut it into very thin slices with an ultra-thin microtome. Because only slices with a thickness of 20 to 100 nanometers can be observed with a transmission electron microscope, in general bacterial samples, one cell should be divided into 10 to 50 slices.
To choose an electron microscope, first of all, check whether the scanning electron microscope manufacturer has complete certificates; secondly, look at the contract of the scanning electron microscope manufacturer; secondly, understand the services of the scanning electron microscope manufacturer; in addition, look at the technical parameters of the scanning electron microscope.
In addition to the selection of scanning electron microscope manufacturers, when purchasing the corresponding scanning electron microscope, it is also necessary to consider the performance and technical indicators of the scanning electron microscope, whether it can meet our daily analysis needs, and also need to consider various aspects when purchasing. Only in this way can we meet our testing and analysis requirements.
