Our sample is now ready for imaging in a transmission electron microscope (TEM). But how do TEMs work? Why do we use them? Lets start with some basic microscopy.
If you think back to high school or undergrad biology, you’ll probably recall using handheld microscopes that look something like this
These are called light microscopes - because the illumination source is light (typically from a lamp).
In microscopy, resolution is defined as the smallest distance between two points in a sample that can be discerned by an observer/camera as two seperate entities. Optical resolution is calculated to be approximately half of the wavelength of the source used. In light microscopes, the wavelength used is ~400nm, therefore the smallest resolution is ~200nm (nanometres).
If you recall, my nanoparticles are between 3-60nm big, therefore light microscopes don’t have a high enough resolution to even tell two of my nanoparticles apart, let alone discern the individual atoms making them up! So, we use electron microscopes!
Electron microscopes, as you can probably guess, use electrons as an illumination source. This is possible because electrons display a wave-particle duality, and so these microscopes can have resolution as high as 0.05nm!
Ill tell you a bit more on thurs! But here I’ve posted photos of the three microscopes I used in my honours! They are all transmission electron microscopes, but vary in the resolution they can achieve, image is a Tecnai G20, a Philips CM200 and a Jeol F200. They’re listed from lowest to high resolution, and this variation in resolution is primarily due to the specific source used to generate electrons (if you want to know, more flick me a dm )
If you have any questions, let me know!
Tune in next time to learn more about transmission electron microscopy (TEM) and imaging our nanoparticles to see what they actually look like!
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