Pure and doped nanocoatings were prepared of from chemically active TiO2 colloids. The colloids are generated in sol-gel reactor with turbulent mixing of two reactive fluids, containing titanium tetra-isopropoxide and water, in T-mixer. The particle size is measured by the light-scattering technique using optical-fibre probe. The TiO2 nanopartides doped with nitrogen are obtained by the injection of a doping agent into the reaction zone at the mixing stage. The mixing at the nucleation stage has a strong impact on the nanoparticles polydispersity and mean size. The prepared nanocoatings show photocatalytic activity under UV and visible light illumination. (C) 2009 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.