Pure anatase nano-TiO2 powders were synthesized by solvothermal method using titanium butoxide as the precursor and were subjected to a rapid quenching in various media such as H2O, H2O2, air, and liquid N-2 as a post-synthesis treatment. By creating a thermal shock effect, quenching process has shown to be an easy novel route for modifying surface defects of the nano-TiO2 and its photocatalytic activity. In this study, the TiO2 sample quenched in air at 77 K contained the highest amount of Ti3+ surface defect with the highest Ti3+/OH and was found to exhibit the highest photocatalytic activity for ethylene decomposition. (C) 2007 Elsevier B.V. All rights reserved.