Introducing Chirality into Graphene Oxide Layers through a Facile Amino Acid-Based Covalent Functionalization

Abstract

Graphene-based materials, including graphene oxide (GO), intrinsically lack stereocenters, limiting their usefulness in applications where chirality plays a crucial role. Covalent attachment of chiral molecules offers a promising strategy to introduce stereogenic elements into layers of GO. In this work, we report a one-pot method for the covalent functionalization of GO with lysine, exploiting the reactivity of the aminic groups of the amino acid toward epoxy groups located on the basal plane of the layers. Chirally functionalized layers of GO were prepared using d- and l-lysine and extensively purified to remove unreacted amino acid residuals. A comprehensive spectroscopic characterization confirms the successful functionalization, resulting in ∼3% N content. The chirality of the molecules bound to the resulting GO layers (relying on a rigorous purification by dialysis) was demonstrated through their interaction with a water-soluble porphyrin, which yielded chiral J-aggregates. The corresponding circular dichroism spectra confirmed that the porphyrin assemblies adopt distinct chiral configurations when templated by d- or l-GO. These findings highlight a straightforward route to impart chiral features to GO, expanding its applicability to several relevant fields, such as asymmetric catalysis, nanofiltration, and chiral sensing.