Epitaxial Growth of Hollow Gold Nanotetrakaidecahedrons on Hollow Gold Nanocubes: A Method for Modifying the Morphology of Hollow Nanoparticles

Abstract

The morphology of hollow noble metal nanoparticles is one of the most critical factors that determine their unique properties and applications. However, hollow nanoparticles typically take on the shape of the template, of which few types exist. In this study, a galvanic replacement reaction was used to synthesize hollow gold nanocubes on solid silver nanocubes, which served as the template. Conventionally, galvanic replacement reactions were only suitable to synthesize hollow gold nanoparticles with the same shape as the silver template particles. Here, ascorbic acid was introduced as a weak reducing agent to reduce the gold ions to gold atoms and cetyltrimethylammonium bromide (CTAB) as a surfactant to fabricate hollow gold nanotetrakaidecahedrons by epitaxially depositing gold atoms on the hollow gold nanocubes. The surfactant CTAB is selectively and preferentially adsorbed on the {110} and {100} facets of the hollow nanocubes because of their higher free energies than the {111} facet, which inhibits the growth of the {110} and {100} facets. Consequently, the {111} facet grew the fastest and eventually occupied the largest area, whereas the area of the {100} facets was slightly smaller, and the {110} facets disappeared during the formation of the hollow gold nanotetrakaidecahedrons. The calculated optical absorption spectra provided further evidence for the mechanism of formation and growth of the hollow gold nanotetrakaidecahedrons. This indicates that by adjusting the experimental conditions, hollow nanoparticles with the desired shapes can be fabricated by subsequent oriented and epitaxial growth on the surfaces of hollow nanoparticles synthesized by the galvanic replacement reaction.