Atomically precise noble metal nanoclusters for engineering self-assembled two-dimensional materials

Two-dimensional nanomaterials derived from noble metals exhibit unique optoelectronic properties with potential applications in advanced nanodevices, catalysis, imaging, biomedicine, and sensing. Over the years, atomically precise noble metal nanoclusters have emerged as promising building blocks for self-assembled discrete and hierarchical colloidal superstructures. Various approaches, including templated growth, air-water interfaces, and non-covalent interactions between surface ligand functional groups, have been utilized to promote the self-assembly of nanoclusters. However, until recently, the self-assembly of nanoclusters into ultrathin, free-standing, two-dimensional materials across length scales has remained challenging. In this perspective article, approaches for the fabrication of self-assembled gold and silver nanocluster-based films, 2D nanosheets, colloidal crystals and macroscopic membranes are discussed. We present the self-assembly principles and insights into how such assemblies enable altered optoelectronic properties, mechanical performance, catalytic activities, enhanced sensing, and device performance. Finally, we highlight how nanocluster-based two-dimensional assemblies offer the emergence of new optoelectronic properties, still retaining the intrinsic properties of individual building blocks.