Transmission Electron Microscopy ( TEM )

Abstract Transmission electron microscopy (TEM) is a powerful tool for imaging supermolecules on a nanometer scale. In TEM apparatus, the specimen is illuminated using electron beams in high‐vacuum conditions, and the transmitted beam makes the image magnified from about fifty to over one million times. In principle, contrast of the TEM image arises because of the differences in electron density of the elements constituting the specimen. Three types of specimen preparation techniques — negative staining, freeze‐fracture, and cryogenic TEM — are generally employed for imaging supermolecules. TEM tomography showing the three‐dimensional structure and the electron diffraction providing information on the periodic ordered structure of the specimen are described. In addition, two spectroscopic measurements performed by using the TEM apparatus, electron energy‐loss spectroscopy (EELS) and energy dispersive X‐ray spectroscopy (EDS), are effective for structural analysis of the specimen. Principles and protocols for these techniques and measurements are described, and potential of TEM for micro‐/nanoimaging in supramolecular chemistry is discussed with reference to the TEM imaging examples that have been reported recently.