Self‐Assembly of Nanographenes

Supramolecular Assembly of Edge Functionalized Top-Down Chiral Graphene Quantum Dots

The construction of supramolecular assemblies of heterogeneous materials at the nanoscale is an open challenge in science. Herein, new chiral graphene quantum dots (GQDs) prepared by amidation reaction introducing chiral amide groups and pyrene moieties into the periphery of GQDs are described. The analytical and spectroscopic data show an efficient chemical functionalization and the morphological study of the supramolecular ensembles using SEM and AFM microscopies reveals the presence of highly ordered fibers of several micrometers length. Fluorescence studies, using emission spectroscopy and confocal microscopy, reveal that the fibers stem from the π-π stacking of both pyrenes and GQDs, together with the hydrogen bonding interactions of the amide groups. Circular dichroism analysis supports the chiral nature of the supramolecular aggregates.

Nanographene - A Scaffold of Two-Dimensional Materials

Substances can be divided into 0D to 3D species based on the number of repeating units (atom, ion, and molecule) and their arrangements in space (point, linear, layer, and solid). Discrete substances belong to 0D species, polymers are examples of 1D species, and molecular crystals are 3D species. Most of the substances belong to one of these species. On the other hand, those categorized into 2D species wherein the repeating units organize a layer are less explored. 2D species have a surface and edges. The incorporation of these structural features into a molecular design can realize multifunctionalized systems that are difficult to achieve by conventional organic synthesis. The development of 2D species is, therefore, the frontier of organic, inorganic, and polymer chemistry. Nanographenes (NGs) are suitable scaffolds for realizing 2D species due to several factors, such as chemical stability and oxygen-containing functional groups on the surface and on the edge, allowing postsynthetic modifications. Our group has utilized NGs with tens of nanometers in diameters for developing 2D species. Carboxy groups on the edge enable us to install various substituents into NGs, offering NG-based functional materials. These studies demonstrate that the integration of NGs with organic chemistry can widen the scope of their applications other than optical materials that are a main application of NGs. We introduce our recent studies on the development of NG-based functional materials realized by postsynthetic modifications. We hope that this account will contribute to the development of the chemistry of 2D species.