抄録
It is known that nano-size metal particles have different functions from bulk-size metal. Sonochemically prepared metal particles such as Pd, Au, and Pt are of nanometer size with a fairly narrow distribution. For example, Pd particles obtained from a 1.0mM Pd(II) in polyethylene glycol monostearate(PEG-MS) solution were about 5 nm sizes. We have suggested three different reduction pathways of metal ions under sonication: (i)reduction by H atoms, (ii)reduction by secondary reducing radicals formed by hydrogen abstraction from organic additives with OH radicals and H atoms, (iii)reduction by radicals formed from pyrolysis of the additives at the interfacial region between cavitation bubbles and the bulk solution. With these processes, the solution composed of PdCl_2・2NaCl(1.0mM), CuSO_4(3.0mM), and PEG-MS(0.4mM) was sonicated for 24 hours. Products were Cu-Pd bimetal particles. By X-rays analyses, it was found that the particles consisted of Cu-core and Pd-shell.
