Synthesis of Complex Nanoparticle Geometries via pH-Controlled Overgrowth of Gold Nanorods

We show that many complex gold nanostructures such as the water chestnut, dog bone, nanobar, and octahedron, which are not easily accessible via a direct seed-growth synthesis approach, can be prepared via overgrowth of the same gold nanorods by varying pH and Ag concentrations in the growth solution. Overgrown nanostructures' shapes were determined by the rate of gold atom deposition, which is faster at higher pH. In the presence of AgNO<inf>3</inf>, codeposition of gold and silver atoms affects the shapes of overgrown nanostructures, particularly at high pH.