We report on photocatalytic activity of new homogeneously Fe(III)-doped TiO2 nanocoatings. The material is prepared in a two-stage process including (1) oxo-TiO2 nanoparticles nucleation, doping by iron(acetylacetonate)3 and reactive deposition on glass substrates in a sot-gel micromixing reactor and (2) thermal treatment. The photocatalytic test of the nanocoatings is conducted on ethylene degradation in a continuous-flow fixed bead reactor. The catalyst shows the best performance at Fe/Ti molar ratio of 0.005 at.%, which is explained by a competition between VB-hole localisation on Fe3+ and its annihilation on Fe2+. The proposed model permits an estimation of the localisation distance of the CB-electron in anatase TiO2 after a photoexcitation and defines the optimal size for the nanoparticulate TiO2 photocatalyst to be similar to 8 nm. (C) 2011 Elsevier B.V. All rights reserved.