The paper reports the application of supersonic thermal plasma expansion technique for controlled chemical synthesis of non-agglomerated, mono-dispersed nanoparticles of TiO2 and also deposition of a nanocrystalline porous coating in a single-step. continuous process. The phase transformation of the nanoparticles was investigated as a function of feed rates of the basic reactants. The possibility of the particle charging and its consequences are also discussed. The grain structure of the coating was found to retain the characteristics of the seed nanoparticles. Optical Emission Spectroscopy performed at the injection section of the reactor identified the presence of TiO and TiCl molecules, which are suspected to be intermediates in this chemical route. (C) 2009 Elsevier B.V. All rights reserved.