Preparation of Ag/Au Bimetallic Nanodecahedra through Galvanic Displacement Method

In this work, Ag/Au bimetallic nanodecahedra was successfully synthesized using the reduction process and photochemical method. Polyvinylpyrrolidone was used as a shape-directing agent, AgNO3, HAuCl4 as precursor raw materials, sodium borohydride as a reducing agent for the growth of Ag metal. Ag+ ions were reduced to Ag nanoparticles (AgNPs) as seeds using sodium borohydride (NaBH4), and then Ag nanodecahedra (AgND) were prepared by a photochemical seeding growth method under the illumination of blue light emitting diode (BLED) with a wavelength of 480 nm. Next, an Au nanofilm was formed by chemical reduction on the surface of the Ag nanodecahedra from precursors of HAuCl4 and ascorbic acid (C6H8O6). At the same time, Ag was replaced by Au through a galvanic replacement reaction. As-prepared products have been characterized by X-ray diffraction, scanning electron microscope (SEM), transmission electron microscope (TEM), high-resolution transmission electron microscope (HRTEM), energy dispersive X-ray spectroscopy (EDS), EDX mapping, and ultraviolet-visible (UV-Vis) absorption spectroscopy. The intensity and position of UV-Vis peaks of AgND and Ag/Au changed as BLED illumination time and HAuCl4 amount changed. Keywords: Au/Ag bimetallic, galvanic replacement reaction, nanodecahedra, photochemical reduction.