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Reactions of polyaromatic molecules in crystals under electron beam of the transmission electron microscope

Fung, Kayleigh L.Y.; Weare, Benjamin L.; Fay, Michael W.; Argent, Stephen P.; Khlobystov, Andrei N.


Kayleigh L.Y. Fung

Benjamin L. Weare


Reactivity of a series of related molecules under the 80 keV electron beam have been investigated and correlated with their structures and chemical composition. Hydrogenated and halogenated derivatives of hexaazatrinaphthylene, coronene, and phthalocyanine were prepared by sublimation in vacuum to form solventless crystals then deposited onto transmission electron microscopy (TEM) grids. The transformation of the molecules in the microcrystals were triggered by an 80 keV electron beam in the TEM and studied using correlated selected area electron diffraction, conventional bright field imaging, and energy dispersive X-ray spectroscopy. The critical fluence (ē nm-2) required to cause a disappearance of the diffraction pattern was recorded and used as a measure of the reactivity of the molecules. The same electron flux (102 ē nm-2 s-1) was used throughout. Fully halogenated molecules were found to be the most stable and did not change significantly under our experimental conditions, followed by fully hydrogenated molecules with critical fluences of 104 ē nm-2. Surprisingly, semi-halogenated molecules that contained an equal number of hydrogen and halogen atoms were found to be the least stable, with critical fluences an order of magnitude lower at 103 ē nm-2. This is attributed to elimination of H-X (where X = F or Cl), followed by polymerisation of aryne / aryl radicals within the crystal. The critical fluence for the semi-fluorinated hexaazatrinaphthylene is the lowest as the presence of water molecules in its crystal lattice significantly decreased the stability of the organic molecules under the electron beam. Semi-halogenation reduces the beam stability of organic molecules compared to the parent hydrogenated molecule, thus providing the chemical guidance for design of electron beam stable materials. Understanding of molecular reactivity in the electron beam is necessary for advancement of molecular imaging and analysis methods by the TEM, molecular materials processing, and electron beam-driven synthesis of novel materials.


Fung, K. L., Weare, B. L., Fay, M. W., Argent, S. P., & Khlobystov, A. N. (2023). Reactions of polyaromatic molecules in crystals under electron beam of the transmission electron microscope. Micron, 165, Article 103395.

Journal Article Type Article
Acceptance Date Dec 1, 2022
Online Publication Date Dec 7, 2022
Publication Date 2023-02
Deposit Date Jan 1, 2023
Publicly Available Date Dec 8, 2023
Journal Micron
Print ISSN 0968-4328
Publisher Elsevier
Peer Reviewed Peer Reviewed
Volume 165
Article Number 103395
Keywords Cell Biology; Structural Biology; General Physics and Astronomy; General Materials Science
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