Template synthesis of hollow silver hexapods using hexapod-shaped silver oxide mesoparticles

One powerful method to make nanoparticles is template-based approach. Because such templates confine the size and shape of nanoparticles, diverse nanoparticles can be prepared through such method. For example, hollow gold (Au) nanoparticles are easily fabricated using silver (Ag) nanoparticles as templates. Ag nanoparticles in a solution containing Au(3+) are readily oxidized to Ag(+) and dissolved into the solution, while Au(3+) are reduced and deposited near Ag nanoparticles. Because the reactivity of Au(3+) is lower than that of Ag(+), this exchange reaction readily occurs, resulting in hollow Au nanoparticles. In this paper, we use morphology-controlled silver oxide (Ag2O) mesoparticles as a sacrificial template to make well-defined Ag mesoparticles. The hexapod-shaped Ag2O mesoparticles are synthesized by retarding its reaction rate using bis (p-sulfonatophenyl) phenylphosphine dehydrate dipotassium as a ligand, and reduced into Ag hexapods by sodium borohydride. Complete conversion of Ag2O into Ag is confirmed by a series of characterization procedure, and the shape and size of Ag2O hexapods are retained during the reduction process. Reduced Ag hexapods have hollow inner structure, and interestingly show single crystalline phase, which is contrary to the previous report. A new mechanism is introduced to explain formation of hollow structure and its single crystalline phase.