Ligand-Mediated Highly Ordered Aggregation of 5-Mercapto-2-Nitrobenzoic Acid Protected Atomically Precise Silver Nanocluster.

Understanding self-assembly of atomically precise nanoclusters is of paramount interest in designing various aggregated super-structures. Here pH-mediated self-assembly is reported of atomically precise Ag44(MNBA)30 (MNBA = 5-mercapto-2-nitrobenzoic acid) nanoclusters in aqueous solution. These nanoclusters formed hexagonal close-packed (hcp) structures when the pH of the solution is reduced from basic to neutral. High-resolution transmission microscopy result confirms bilayer and multilayer assembly at neutral pH. X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR) analysis, and molecular dynamics simulation delineate ligand-mediated inter-cluster interactions such as ligand to metal core coordination, H─bonding and π-π interactions playing a crucial role in the formation of the hexagonal close-packed self-assembled structure.