| Abstract
| - We report the shape transformation of gold nanorods to spherical nanoparticles, assisted by cupric ions. The reactionproceeds through a series of structures and could be arrested at any stage to produce particles of desired shape. Inthe presence of a larger concentration of cetyltrimethylammonium bromide (CTAB), selective etching of the tips ofthe nanorods occurs to a greater extent. The subsequent transformation is driven by the surface reconstruction ofnanorods to generate more stable surfaces. As the stability of various surfaces depends on the protecting agent used,the reactivity is modified by controlling its presence at the surface. We show that the body of the rods is moresusceptible for reaction at reduced CTAB concentrations. During the conversion to particles, several anisotropictransient structures were observed and were imaged using high-resolution transmission electron microscopy (HRTEM).The transformation occurs due to the hydroxyl radicals produced by Cu2+ in the presence of ascorbic acid (AA). Amechanism has been proposed and several control experiments were conducted to test it. The cupric ion induced shapetransformations can be extended to other ions, and knowing the mechanism allows the control of the process to stabilizevarious anisotropic structures.
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