Platinum nanoparticles have been prepared by radiolytic and chemical methods in the presence of stabilizer gelatin and SiO2 nanoparticles. The formation of Pt nanoparticles was confirmed using UV-vis absorption spectroscopy and transmission electron microscopy (TEM). The prepared particles were coated on the inner walls of the tubular pyrex reactor and tested for their catalytic activity for oxidation of CO. It was observed that Pt nanoparticles prepared in the presence of a stabilizer (gelatin) showed a higher tendency to adhere to the inner walls of the pyrex reactor as compared to that prepared in the presence of silica nanoparticles. The catalyst was found to be active at >= 150 degrees C giving CO2. Chemically reduced Pt nanoparticles stabilized on silica nanoparticles gave similar to 7% CO conversion per hour. However, radiolytically prepared Pt nanoparticles stabilized by gelatin gave similar to 10% conversion per hour. Catalytic activity of radiolytically prepared platinum catalyst, coated on the inner walls of the reactor, was evaluated as a function of CO concentration and reaction temperature. The rate of reaction increased with increase in reaction temperature and the activation energy for the reaction was found to be similar to 108.8 kJ mol(-1). The rate Of CO2 formation was almost constant (similar to 1.5 x 10(-4) mol dm(-3) h(-1)) at constant 02 concentration (6.5 x 10(-3) mol dm(-3)) with increase in CO concentration from 2 x 10(-4) mol dm(-3) to 3.25 x 10(-3) mol dm(-3). The data indicate that catalytic oxidation of CO takes place by Eley-Rideal mechanism. (C) 2005 Elsevier Ltd. All rights reserved.