Charge transfer in nanocrystalline-Au/ZnO nanorods investigated by x-ray spectroscopy and scanning photoelectron microscopy

O Kand Zn and Au L3-edge x-ray absorption near-edge structure XANES , x-ray emission spectroscopy XES , and scanning photoelectron microscopy SPEM are performed to investigate the electronic structure of ZnO nanorods with nanocrystalline nc -Au particles grown on the surfaces. The XANES spectra of nc-Au/ZnO nanorods reveal the decrease of the number of both O 2p and Zn 4s /3d unoccupied states with the increase of the nc-Au particle size. The number of Au 6s /5d unoccupied states increases when the size of nc-Au particle decreases, indicating that the deposition of nc-Au particles on the surface of ZnO nanorods promotes charge transfer from the ZnO nanorods to nc-Au particles. Excitation energy dependent XES and SPEM spectra show that the number of electrons in the valence band of O 2p-Zn 4sp hybridized states decreases as the nc-Au particle size increases, revealing that more electrons are excited from the valence band to the conduction band of ZnO nanorods and the storage of electrons in nc-Au particles. © 2007 American Institute of Physics. DOI: 10.1063/1.2738369