Fermi level shifts of gold nanospheres on ZnO film upon UV irradiation.

Here, Fermi level shifts of gold nanospheres on zinc oxide (ZnO) film upon UV irradiation are studied. These Fermi level shifts are obtained by recording extinction spectra of gold nanospheres characterized by their plasmon resonance and are due to the presence of additional electrons stored in gold nanospheres and coming from ZnO film upon UV irradiation. It is demonstrated that the blueshift of the plasmon resonance of the Au nanospheres upon UV irradiation points out the transfer of electrons from ZnO film to Au nanospheres. Moreover, it is reported that the Fermi level shifts vary with UV irradiation time by approaching the conduction band of ZnO, and are estimated by an analogous model to the electronic structure of a semiconductor, which can be expressed as a function of the plasmon resonance blueshift of the Au nanospheres. Henceforward, these stored electrons and these Fermi level shifts can allow the improvement of the properties of photocatalytic reduction for the gold-semiconductor structures and can also be used for photo-induced enhanced Raman spectroscopy.