Transmission electron microscopy of fine aromatic hydrocarbon particles

Fine perylene and pyrene particles were produced by evaporation in helium gas. The particles were sensitive to electron beam radiation. The pyrene particles sublimed under observation. These difficulties were cleared up by reducing electron beam exposure and sandwiching a specimen between two Formvar films. The fine perylene particles were rectangular or hexagonal plates about 50nm thick. The size was about 200-2000nm. The fine pyrene particles were polymorphic with a size of about 300-2000nm. The crystal forms of the perylene and pyrene particles were determined from the electron diffraction patterns to be alpha-perylene and pyrene I, respectively.