Plasmon Induced Photovoltage and Charge Separation in Citrate-Stabilized Gold Nanoparticles

The photoelectrochemistry of citrate-stabilized gold nanoparticles on an ITO electrode is studied at low light intensity. Weak cathodic photovoltage develops under visible gold plasmon irradiation. Photovoltage results from adsorbed citrate oxidation by hot holes in the irradiated Au. Under identical conditions, Ag nanocrystals give a stronger photovoltage than Au nanocrystals. The photocurrent is linear in light intensity, and a complete citrate monolayer forms on the Au particles above 10(-6) M aqueous concentration. At strongly oxidizing potentials, a photocurrent peak occurs which may be related to electron photoinjection from Au into the ITO substrate.