osmium staining

In the backscattered electron imaging of high polymers and biological specimens using SEM, it is difficult to acquire a high contrast image because the atomic numbers of the constituent elements are close to each other. In such cases, a technique of Osmium (a heavy metal) staining of the specific components or tissues is used to obtain their high contrast images.
The staining is performed by immersing a specimen in a solution of osmium tetroxide or is placed in a vapor environment of the solution. By staining, osmium breaks the double bond of carbon in butadiene (high polymer material) or in phospholipid (biological specimen) and binds to the sites. As a result, the number of backscattered electrons from the sites stained by osmium of high atomic number increases and the specific components or tissues are clearly observed.
Osmium is highly toxic and it is very dangerous if an operator breathes the vapor of osmium tetroxide or contacts the solution on their skin. So when using osmium, it is requisite to wear gloves in a draft chamber under the guide of the Safety Data Sheet (SDS) issued by reagent manufacturers.

Related Term(s)