GOLD NANOELECTRODES OF VARIED SIZE - TRANSITION TO MOLECULE-LIKE CHARGING

A transition from metal-like double-layer capacitive charging to redox -like charging was observed in electrochemical ensemble Coulomb stairc ase experiments on solutions of gold nanoparticles of varied core size . The monodisperse gold nanoparticles are stabilized by short-chain al kanethiolate monolayers and have 8 to 38 kilodaltons core mass (1.1 to 1.9 nanometers in diameter). Larger cores display Coulomb staircase r esponses consistent with double-layer charging of metal-electrolyte in terfaces, whereas smaller core nanoparticles exhibit redox chemical ch aracter, including a large central gap. The change in behavior is cons istent with new near-infrared spectroscopic data showing an emerging g ap between the highest occupied and lowest unoccupied orbitals of 0.4 to 0.9 electron volt.