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 O-2, N-2, 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 pi g electrons in adsorbed O-2 and the widened bandgap after adsorbing O-2. Nitrogen molecules inhibit the main-band-gap and the sub-band gap CT transitions differently. This can be explained by the 3 sigma g and 1 pi g electrons of adsorbed N-2, 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 Cr transition is much stronger than that on the sub-band-gap Cr transition. (C) 2018 Elsevier B.V. All rights reserved.