By Isabelle Robinson, M.Sc.Feb 14 2019
Image Credits: Have a nice day Photo/shutterstock.com
The highest magnification image ever created shows a single molecule of pentacene. Pentacene is a hydrocarbon which consists of five linearly fused benzene rings and has a molar mass of 278 g.mol-1. It is approximately 1.4 nanometers in length and the space between the carbon atoms of the molecule is 0.14 nanometers, 500,000 times smaller than the diameter of a single human hair.
The photograph was taken by IBM scientists in Zurich in 2009 using non-contact atomic force microscopy in an ultrahigh vacuum at temperatures of 5K. The microscope uses a cantilever which has a nanoscale tip. The image is generated by registering the response of the cantilever tip, which moves up and down as the microscope scans due to the interactive forces of the sample's surface.
To put this into perspective, the closest a human eye can see without losing focus is 20cm and simply cannot see anything smaller than 0.05mm. A nanometer is 1,000,000 times smaller than a millimeter and therefore cannot be seen without an extremely powerful microscope.
The Zacharias Janssen first invented the microscope in 1590 which comprised of just two lenses and was capable of magnifying to 9 times the original size. This was later improved upon by celebrated 17th-century English scientist, Robert Hooke who used the device to explore the structure of snowflakes and cork, as well as publishing a book on fleas, lice, and plants named ‘Micrographia’ in 1665. Interestingly, he was the first person to use the word ‘cell’, which is still used today.
A decade later, the Dutch scientist Antony van Leeuwenhoek designed the first high-powered single lens microscope that could magnify an object approximately 200 times its true size without distorting the image. With this microscope, he was able to describe and study sperm cells, blood cells, yeast, and bacteria.
At the start of the 20th century, the absolute limit for observation using a conventional microscope was found to be the wavelength of light, approximately 200 nanometers in length. This is due to the fact that light waves move around the object which are smaller than this without being affected by it and therefore it cannot register. It was therefore obvious that a shorter wavelength must be used in order to detect smaller objects. In 1931, German scientists Ernst Ruska and Max Knoll were able to create the electron microscope for the first time.
The electron microscope uses electrons instead of light waves. Fast-moving electrons behave like waves and if excited to speed near the speed of light, electrons of a wavelength similar to that of an X-ray, approximately one million times shorter than light. The two main types of electron microscope are the transmission electron microscope and the scanning electron microscope. The former can produce magnified images up to 50million times the objects true size, however, it cannot see in 3D and can only be used on extremely thin specimen slices. Scanning electron microspores are the most popular as they can detect complex surfaces on objects. While they cannot reach the levels of magnification that the transmission electron microscope can, they are able to create an image of the object by scanning across the surface one layer at a time.
The highest magnification image is also the highest resolution image at such a high magnification. Researchers have used the technique to determine how charges move through molecules in the hops of building computing elements at an atomic scale.
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