Size and composition tunable Ag-Au alloy nanoparticles by replacement reactions

Ag - Au alloy nanoparticles with tunable size and composition were prepared by a replacement reaction between Ag nanoparticles and HAuCl4 at elevated temperatures. The formation of homogeneous alloy nanoparticles was confirmed by selected-area energy-dispersive x-ray spectroscopy (SAEDX), UV-visible absorption spectroscopy, high resolution transmission electron microscopy (HRTEM) and electron diffraction. This method leverages upon the rapid interdiffusion of Ag and Au atoms in the reduced dimension of a nanoparticle, elevated temperatures and the large number of vacancy defects created in the replacement reaction. This method of preparation has several notable advantages: ( 1) independent tuning of the size and composition of alloy nanoparticles; ( 2) production of alloy nanoparticles in high concentrations; ( 3) general utility in the synthesis of alloy nanoparticles that cannot be obtained by the co-reduction method.