​Gold nanorods have received tremendous attention in recent years due to their exciting potential applications in chemical sensing, biological imaging, drug delivery and phototherapeutics. A seed-mediated growth procedure in aqueous solution has been developed to produce these colloidal materials in reasonable quantities, with tunable shape. Details of the reaction chemistry, role of impurity ions, and their influence on the final product shape are still under debate. Subsequent chemistry on preformed nanorods can yield a variety of new shapes and functionalities for numerous applications.​