Sonolytical preparation of various types of metal nanoparticles in aqueous solution

Composite nanoparticles of Au, Pd and Pt, and nanoparticles of transition metal oxides, MnO₂, were prepared by the sonochemical reduction of corresponding ions (Au(III), Pd(II), Pt(II), Pt(IV) and Mn(VII)) in an aqueous system in the presence of surfactants. The prepared noble metal particles were stable and the sizes were of the order of nanometer with narrow distribution. Surfactants were found to be stabilizers for the noble metal nanoparticles as well as important sources of reducing species for the metal ions. In binary metallic particles, which were prepared from aqueous mixed solutions of noble metal ions, three possible constitutional forms were obtained. MnO₂ particles were reduce to water soluble Mn(II) ions by further sonication.