Germanane synthesis with simultaneous covalent functionalization: towards highly functionalized fluorescent germananes†
Monoelemental 2D-materials beyond graphene are attracting great attention. Although monolayer graphene or phosphorene can be prepared from its layered 3D form, graphite or black phosphorus, by exfoliation of a large van der Waals crystal, this route is not suitable for the preparation of 2D-germanene based materials due to the crystal structure and chemical properties of germanium. Unlike graphene or phosphorene, these materials are prepared by chemical exfoliation from bulk Zintl phases – here represented by calcium germanide. We describe the exfoliation and subsequent modification of calcium germanide, which yields layered germanium materials with alkyl or aryl groups. Different organic functional groups covalently attached to layered germanane exhibit a very intense fluorescence in the blue region, which makes them prospective materials for further application in optoelectronic devices. The described procedure for covalently functionalized germananes represents the way for the production of these materials.