Synthesis and Characterization of Multi-Pod-Shaped Gold/Silver Nanostructures

We describe here a novel method which shows that related large molecules, tannic acid, can control the morphology of silver/gold nanoparticles, resulting in the formation of multi-pod-shaped nanostructures. In this work, multi-pod-shaped gold/silver nanostructures have been synthesized using tannic acid as a reducing as well as a capping agent. The multi-pod-shaped Au/Ag nanostructures have been confirmed by transmission electron microscopy. The growth process of gold/silver nanostructures has been studied by UV/vis spectroscopy and extended X-ray absorption fine structure analysis. On the basis of these results, we propose a model explaining the role of tannic acid in the growth of gold/silver nanostructures. The reducing and capping properties of tannic acid favor the formation of unisotropic crystal growth. The growth of gold/silver nanostructures occurs as a consequence of the galvanic replacement reaction between Au3+ and Ag0 and subsequent reduction of both metal ions by tannic acid. Furthermore, it...