Electron Microscopy

• Electron microscopy is a type of microscopy that uses a beam of electrons to create an image of a specimen. It is used for extremely fine detail, much smaller than can be seen with a traditional light microscope.

• Two main types of electron microscopes exist. These are the transmission electron microscope (TEM) and the scanning electron microscope (SEM). TEM transmits electrons through an ultra-thin specimen, interacting with the specimen as it passes through. On the other hand, SEM creates images by detecting reflected or knocked-off electrons.

• In terms of resolution, electron microscopes surpass light microscopes. They can magnify objects up to two million times their actual size, while the maximum magnification of a light microscope is about 2000 times.

• The magnification and resolution power of electron microscopes is due to the wavelengths of electrons, which are shorter than those of light. Shorter wavelengths allow the microscope to distinguish between objects closer together.

• A key aspect of transmission electron microscopy (TEM) is the preparation of the specimen. It must be extremely thin, typically less than 200 nm, to allow electrons to pass through. This often requires an experienced technician to prepare the slide.

• While TEM gives a 2D projection or a 2D slice of the specimen, SEM produces 3D images by bouncing electrons off the surface of the specimen and detecting the emitted electrons.

• Electron microscopes need a vacuum to function effectively as electrons are deflected by molecules in the air. Therefore, specimens are placed inside a vacuum chamber.

• Drawbacks of electron microscopy include the complexity and cost of the microscopes themselves, the requirement for a vacuum, and the complex preparation of samples.

• Despite these challenges, electron microscopy has revolutionized many areas of science and technology, particularly in fields such as materials science, nanotechnology and biotechnology, by providing insights into the structure and function of materials and biological specimens at the nanometer scale.

Remember to familiarise yourself with basics like the difference between TEM and SEM, the benefits and drawbacks of electron microscopy, and how it compares to light microscopy.