Plasmonic Nanomolecules: Electrochemical Resolution of 22 Electronic States in Au₃₂₉(SR)₈₄

Gold nanomolecules are atomically precise gold thiolate nanoparticles. They show size-dependent optical and electrochemical properties due to the quantization effects. The optical properties are well explored. However, there is still a void in understanding their electrochemical properties and probing higher oxidation states. We report the 22 electronic states of a plasmonic nanocrystal molecule with 329 gold atoms and 84 phenylethanethiolate ligands in a wide electrochemical potential (∼4 V) window. We provide a comprehensive understanding of the electrochemical properties as a function of size and composition of gold nanomolecules. This report also demonstrates that they behave like quantum capacitors and their capacitance varies linearly with size. The effect of ligand monolayer and core composition on the electrochemical properties was demonstrated using a 144-metal atom system. These results would help us design applications using the gold and alloy nanomolecules in photovoltaics, catalysis, sensors, and energy storage devices.