Generation of mixed metallic nanoparticles from immiscible metals by spark discharge

Using a spark discharge system, we synthesized Ag-Cu, Pt-Au and Cu-W mixed particles a few nanometers in size. These combinations have miscibility gaps in the bulk form. The microsecond sparks between electrodes consisting of the respective materials, form a vapour cloud. Very fast quenching of the mixed vapour results in the formation of nanoparticles. To investigate the morphology, size, composition and structure of the particles, TEM, XRD analyses and EDS elemental mapping were performed on the samples. The average compositions were measured by ICP and the specific surface areas were determined by the BET. Our method produces Ag-Cu and Au-Pt mixed crystalline phases that do not exist in macroscopic samples. For Cu-W, alloying is not observed, and the metals are mixed on a scale of about 1 nm.