Chirality generation on carbon nanosheets by chemical modification

Chirality is an intriguing property of molecules, and an exciting area of study involves the generation of chirality in nanographenes (NGs), also known as graphene quantum dots. Unlike those synthesized through stepwise carbon-carbon bond formation by organic reactions (bottom-up method), NGs obtained by cutting parent carbons (top-down method) pose challenges in precisely regulating their three-dimensional structures by post-synthesis. This includes the incorporation of non-hexagonal rings and helicene-like structures in carbon frameworks. Currently, edge functionalization is the only method for generating chirality in NGs produced by the top-down method. While various chiral NGs have been synthesized through organic methods, examples of chemical modification remain rare due to limited structural information and the substantial size of NGs. However, these problems can be mitigated by disclosing the structures of NGs, particularly their edge structures. This mini-review focuses on recently published papers that have addressed the structural characterization of NGs and their chirality generation by edge modification. Comparing these NGs with those synthesized by organic synthesis will help to develop reasonable strategies for creating sophisticated chiral NGs. We hope this mini-review contributes to the advancement of NG-organic hybrid materials.