| Abstract
| - This paper describes a simple and versatile method for growing highly anisotropic nanostructuresof Pd, single-crystal nanobars bounded by {100} facets and single-crystal nanorods with their side surfacesenclosed by {100} and {110} facets. According to thermodynamic arguments, Pd atoms should nucleateand grow in a solution phase to form cuboctahedrons of spherical shape with their surfaces bounded bya mix of {111} and {100} facets. Anisotropic nanostructures can only form under kinetically controlledconditions, while the cubic symmetry is broken. In the present system, we found that one-dimensionalgrowth could be induced and maintained through an interplay of the following processes: (i) speedy reductionof the precursor to ensure prompt addition of atoms to the seed; (ii) chemisorption of bromide on the seedto promote the formation of {100} and {110} facets; and (iii) localized oxidative etching on one specificface of the seed to initiate preferential growth on this face. Experimentally, the anisotropic growth can beachieved by varying the type and concentration of reducing agent, as well as by adjusting the reactiontemperature. This methodology developed for Pd has also been extended to both Au and Pt. As expectedfor a kinetically controlled product, the anisotropic nanostructure evolved into the thermodynamically favoredshape during an aging process.
|
