Nanometer to micrometer sized particles containing platinum and having selected morphologies are prepared by a sonochemical process. A compound of platinum is dissolved, suspended, or diluted in a suitable liquid medium at a predetermined concentration and the liquid is maintained at a predetermined temperature from sub-ambient temperatures to above ambient temperatures. A reducing gas is bubbled through the liquid as it is subjected to cavitation at a controlled power to affect the reductive decomposition of the platinum compound. The morphology of the precipitated platinum particles can be varied widely by varying the described concentration, temperature and power parameters.