Phase transfer identification of core-shell structures in Ag-Au bimetallic nanoparticles

The difference between the transfer of poly(vinylpyrrolidone)-protected Au and Ag nanoparticles from an aqueous solution to toluene was used to develop a simple experimental procedure that can positively identify the formation of bimetallic Ag-Au nanoparticles with the core-shell structure. The method was validated by UV-visible spectroscopy, EDX, and TEM measurements. Using this technique, we have found that core-shell nanoparticles of Ag-Au were formed by the seed-mediated growth method using Ag nanoparticles as the seeds. The reversed order of using Au nanoparticles as the seeds, on the contrary, could only produce a physical mixture of Ag-Au core-shell nanoparticles and isolated Ag nanoparticles.