Self‐Assembly of Bowlic Supramolecules on Graphene Imaged at the Individual Molecular Level using Heavy Atom Tagging. Issue 39 (1st September 2020)

• Record Type: Journal Article
• Authors: Kengmana, Everett S.; Lee, Ja Kyung; Li, Xiang; Warner, Jamie H.; Han, Grace G. D.
• Is Part Of: Small. Volume 16:Issue 39(2020)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2020-09-01
• Subjects: annular dark‐field scanning transmission electron microscopy -- calix[4]arenes -- heavy atom markers -- self‐assembly -- supramolecules; Nanotechnology -- Periodicals; Nanoparticles -- Periodicals; Microtechnology -- Periodicals; 620.5
• DOI: 10.1002/smll.202002860
• Languages: English
• ISSNs: 1613-6810

Abstract

Abstract: The self‐assembly of bowlic supramolecules on graphene surface is studied with single molecular sensitivity. This is achieved by incorporating a heavy metal tag in the form of a single W atom into the tip of the molecular structure, which enables the direct imaging of molecular distribution using annular dark‐field scanning transmission electron microscopy (ADF‐STEM) along with graphene as an electron transparent support. The bowlic molecules have nonplanar geometry, and their orientations with respect to their graphene substrate and with each other result in various packing configurations. Statistical data on intermolecular distances is obtained from numerous measurements of the bright contrast from the single metal atom tags. The analysis shows that the bowlic molecules lie sideways on the graphene surface with favorable head‐to‐tail stacking, rather than sitting vertically with the bowl facing toward the graphene surface. In thicker film regions, nanoscale lamellar fringes are observed, demonstrating that large‐scale aligned packing extends into 3D. Image simulations and various molecular packing schemes are discussed to help interpret the ADF‐STEM images and the possible range of molecular interactions occurring. These results aid the understanding of nonplanar supramolecular assemblies on van der Waals surfaces for potential applications in molecular recognition by porous films. Abstract : Calix[4]arenes tagged with single W atom markers self‐assemble on a graphene monolayer, which is directly imaged by annular dark field scanning transmission electron microscopy. Various intermolecular interactions are monitored from head‐to‐head, side‐by‐side, and head‐to‐tail packings between the bowlic supramolecules. At high concentrations, the W‐tagged molecules self‐assemble into lamellar structures, confirming the favored head‐to‐tail stacking.