Fabrication of solid-solution gold–platinum nanoparticles with controllable compositions by high-intensity laser irradiation of solution

In the present study, solid-solution gold–platinum (Au–Pt) nanoparticles with controllable compositions were fabricated by high-intensity femtosecond laser irradiation of an aqueous solution of gold and platinum ions without any chemicals and complicated processes. Transmittance electron microscopy revealed that the single nanometer-sized particles were fabricated by femtosecond laser irradiation of mixed aqueous solutions of gold and platinum ions. The crystalline structure of nanoparticles was characterized by electron and X-ray diffractions. Contrary to the bulk Au–Pt binary systems, which commonly contain a pair of diffraction peaks between pure gold and platinum peaks because of its large miscibility gap in phase diagram, or mixture of Au and Pt, the diffraction peaks of Au–Pt nanoparticles fabricated in the experiment showed a characteristic of the fcc-type lattice. Moreover, the diffraction patterns shifted monotonically from the peak position of pure gold to that of pure platinum as the fractions of platinum ions in the solution were increased. These observations strongly imply that the Au–Pt nanoparticles were solid solution with intended compositions. This technique is not only simple and environmentally friendly, but also applicable to other binary and ternary systems.