In this work, we developed a facile and efficient route to deposit ultra. ne Pt particles onto multi-walled carbon nanotubes (MWNTs) with the aid of tip sonication. The loading of Pt on the MWNTs could attain the very high level of 50 wt% and the size of the Pt particles could be controllably tuned in the range 1.9-3.5 nm with narrow size distributions. The resultant nanocomposites were applied to catalyze the hydrogenation of nitrobenzene under solvent-free conditions. It was demonstrated that the Pt/MWNT catalysts showed excellent activity with a high turnover frequency (e. g., 69 900 h(-1)) as well as superior selectivity to aniline (e. g., >99%) in this reaction.