Charge Distribution between UV-Irradiated TiO₂ and Gold Nanoparticles:  Determination of Shift in the Fermi Level

Abstract

TiO 2 nanoparticles when subjected to UV irradiation exhibit blue coloration as electrons are stored within the particles. Upon contact with gold nanoparticles, a partial disappearance of the blue color is seen as the stored electrons are transferred from TiO 2 to Au nanoparticles. The charge distribution between the semiconductor and metal nanoparticles causes the Fermi level to shift to more negative potentials. By employing C 60 /C 60 •- as a probe−redox couple, we were able to estimate the apparent Fermi levels of TiO 2 and TiO 2 /Au nanoparticles. A Fermi level shift of −22 mV observed for the Au−TiO 2 nanocomposite is indicative of improved charge separation in semiconductor−metal systems and demonstrates its usefulness for improving the efficiency of photocatalytic reactions.