This paper describes the relation between the size of synthesized nanoparticles and the temperature variation of the surrounding plasma in TiO2 nanoparticle synthesis using pulse-modulated induction thermal plasmas (PMITP). The Ar-O-2 PMITP at 20 kW was used to obtain repetitional temperature fields at pressure of 200 Torr. The TiO2 nanoparticles were synthesized by direct injection of Ti powder with mean diameter of 45 mu m. Dependence of the nanoparticle size on modulation parameters such as the duty factor and the shimmer current level of the PMITP were investigated experimentally. Instantaneous temperature evolution was evaluated through spectroscopic observation. Experimental results show that the temperature decay rate in the PMITP reached 10(5)10(6) K/s, and that the mean diameter of synthesized particles decreased with the temperature decay rate. (C) 2010 Elsevier B.V. All rights reserved.