Laser-induced alloying Au-Pd and Ag-Pd colloidal mixtures: the formation of dispersed Au/Pd and Ag/Pd nanoparticles

Laser irradiation of colloidal mixtures consisting of Au-Pd and Ag-Pd were conducted to synthesize Au/Pd and Ag/Pd alloy nanoparticles. Compositional ratios of 1 : 1 and 2 : 1 were prepared in both the Au/Pd and Ag/Pd systems. The compositions, the particle sizes, and the morphology were measured as a function of the laser irradiation period in order to monitor the changes from the two-component mixtures into the alloy colloids. The average particle sizes of the 1 : 1 and 2 : 1 metal ratios were 3.9 +/- 1.2 nm and 4.3 +/- 1.1 nm, respectively, for Au/Pd and 7.3 +/- 2.0 nm and 5.4 +/- 2.0 nm, respectively, for Ag/Pd. However, Ag/Pd with a 2 : 1 ratio had difficult in forming dispersed spherical particles and the expected compositions. In addition to EDX analysis, X-ray diffraction measurements were carried out to confirm the formation of the alloy nanoparticles.