Electron Microscopy for Chemists
In 1956, Soviet scientists claimed the development of a new form of electron microscope that enabled atoms to be seen for the first time. Today, advances in imaging are allowing chemists to probe materials with extraordinary resolution using transmission electron microscopy.
Cruising at about half the speed of light, tightly focused beams of electrons pass through thin slices of materials and carry away subtle information about the substance’s structure and composition. Commonly known as transmission electron microscopy (TEM), this high-energy method has been used for decades to deduce the positions of rows of atoms in solids, often with angstrom-level resolution.
Traditionally, TEM’s strong suit has been spotting the odd men out—out-of-place atoms and other types of crystal lattice defects. But scientists are increasingly pushing the limits of TEM to extract chemical information from microscopy samples, and they are doing so with ever finer spatial resolution.
“Angstrom by angstrom, TEM is moving toward imaging individual lightweight atoms,” such as those making up organic molecules, says Laurence D. Marks, a microscopist and professor of materials science at Northwestern University. At the same time, the field is progressing toward atomic-scale chemical analysis of lightweight atoms, as new instrument designs enable microscopy and spectroscopy to be carried out simultaneously.
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Excerpted with permission, Chemical & Engineering News
Copyright © 2009 American Chemical Society