Perspectives on noble metallenes: from synthesis to application

Abstract Metallenes are presented for a new class of single-atom-thick two-dimensional (2D) metal sheets. It is motivated by a recent (2024) discovery of 2D gold, dubbed goldene, by selectively etching off Ti 3 C 2 slabs from a Ti 3 AuC 2 nanolaminate. This synthesis-derivative method bypasses the natural tendency for metals to form three-dimensional forms. Thus, 2D-materials’ research goes beyond ceramics with graphene as the most-known example. A range of noble and non-noble metals are now proposed for metallene preparation. Their exploration is motivated by the unique properties offered by 2D and nanostructured materials. Metallene’s ultimate high surface-to-volume ratio with abundant uncoordinated metal atoms makes them attractive for high-end applications, like in catalysis, sensing, electronics, and biomedicine. Challenges for scientific research and practical use, however, lie in scalable synthetic processes, sheet integrity, and transfer methods. Here, we review state-of-the-art for processes to prepare atomic and few-atomic layer-thick noble metals, as well as their characterization and properties.