Counterion‐Assisted Shaping of Nanocluster Supracrystals

Ag₄₄(p‐MBA)₃₀^4? (p‐MBA=para‐mercaptobenzoic acid) nanocluster (NC) supracrystals (SCs) with customizable shapes can be obtained by simply altering the type and concentration of the counterions of the p‐MBA ligands in the dimethylsulfoxide (DMSO)/water crystallization system. Changing the counterion of the p‐MBA ligand from H⁺ to Cs⁺ eliminates the directional hydrogen bonds in the SCs, resulting in the packing of deprotonated Ag₄₄(p‐MBA)₃₀^4? NCs into octahedral SCs, which is in stark contrast to the rhombohedral SCs that were formed by the packing of protonated Ag₄₄(p‐MBA)₃₀^4? NCs in previous studies. Furthermore, the double layer of deprotonated Ag₄₄(p‐MBA)₃₀^4? NCs is sensitive to charge screening induced by increasing the Cs⁺ concentration, thereby providing a means to regulate the precipitation kinetics of the Ag₄₄(p‐MBA)₃₀^4? NCs for SC shape engineering. Slow precipitation kinetics was found to favor over‐growth at the corners and edges of the octahedral SC nuclei, shaping the SCs into concave octahedra.