LAUSR

Abstract Using surface photovoltaic and electric-field-induced surface photovoltaic techniques, as well as a CASTEP simulation method, we have studied the photo-excited and field-induced charge transfer (CT) behaviors of anatase nano-TiO2 particles adsorbed by O2, N2, and water vapor. Our results suggest that the photo-generated carriers transport process is strongly influenced by the adsorbates on the TiO2 nanoparticles. Oxygen molecules enhance the main-band-gap CT transition at 345 nm and inhibit the sub-band-gap CT transition at 419 nm. This can be explained by the 1 π g electrons in adsorbed O2 and the widened bandgap after adsorbing O2. Nitrogen molecules inhibit the main-band-gap and the sub-band-gap CT transitions differently. This can be explained by the 3 σ g and 1 π g electrons of adsorbed N2, which may cause more new surface states in between the bandgap and decrease the valence band edge of nano-TiO2, as suggested by the CASTEP simulation. The influence of adsorbed water molecule on the main-band-gap CT transition is much stronger than that on the sub-band-gap CT transition.