Scanning Electron Microscopy

Biological Samples
•Biological samples are not conductive and are particularly vulnerable to beam damage and
other heating effects when examined in an Electron Microscope.
•The level of exposure is referred to as ‘Electron Dose’ and is a measure of the number of
electrons per unit area (e/nm 2 ).
•Samples are either stained with conductive materials (e.g. OsO 4 ) or coated with Au or C.
•Samples are viewed under vacuum, so they are dried to remove all water.
a) b)
•a) SEM image of Pneumonia, and b) SEM image of Diatom (Pictures from University of Iowa)
•Preparing the samples ‘fixes’, and alters them – need a way to look at samples whilst they are
still ‘wet’.
Analytical
Workshop 2012